Lecture 3: Muscular System

Biomedicine: Human Sciences

Lecture 3:

Muscular System

Learning Outcomes

In today’s topic you will learn:

⮚ The types of muscles in the human body;

how they differ in terms of structure and

function.

⮚ Be able to identify major skeletal muscles

of the body and recognise their functions.

⮚ The signs, symptoms, investigation

procedures and some orthodox treatments

of muscular system pathologies.

Functions

1. Movement — a result of muscular contraction. This relies on the integrated functioning of the muscles, bones and joints.

2. Maintaining posture — stabilising joints, posture and balance through continued partial muscle contraction.

3. Heat production — also known as thermogenesis. Helps maintain normal body temperature (36.5‒37.5°C). Shivering describes involuntary contractions of skeletal muscles.

thermo- = heat

genesis = creation 3

Functions ^sphincter^{= a}

circular muscle

4. Storage of substances — glycogen and oxygen.

5. Movement of substances:

- The heart muscle pumps blood around the body.

- Sphincters prevent out-flow from hollow organs.

- Smooth muscle in blood vessel walls helps

control blood flow.

- Smooth muscle moves food through the

digestive tract and urine through the urinary system.

- The diaphragm draws air into airways / lungs.

Muscle Properties

1. Contractility 🡪 ability to contract (shorten).

2. Excitability 🡪 ability to conduct an

electrical current. Nerve impulses

cause muscles to contract.

3. Extensibility 🡪 ability to stretch

without being damaged.

4. Elasticity 🡪 ability to return to

original length and shape after

contraction or extension (spring).

Striated and Non-Striated Muscle

Muscles in the body contain cells that are either striated or non-striated.

• Striated muscles contain cells that are aligned in parallel bundles, so that their different regions form stripes visible with a microscope.

• Non-striated muscles contain cells that are randomly arranged (no stripes visible).

• Skeletal and cardiac muscle is striated, whilst

Striated muscle: Non-striated:

smooth muscle is non-striated._striated_{= striped} 6

Muscle Types

There are three types of muscle in the body:

Muscle type:	Key features:
Skeletal muscle:	• Striated — attaches between bones and creates movement at joints. • Voluntary muscle.
Cardiac muscle:	• Striated — forms the heart muscle. • Involuntary muscle that generates its own rhythmic contraction (‘autorhythmic’).
Smooth muscle:	• Non-striated — found in the walls of blood vessels, walls of the gut and in the iris (coloured part of eye). • Involuntary muscle.

Striated Non-Striated Striated

Skeletal Muscle

There are 640 skeletal muscles in the body,

accounting for about 40% of body weight.

• All of these muscles are voluntary.

• Functions include: Motion and posture, speech

(larynx, lips, tongue) and breathing.

• Skeletal muscle is covered by fascia

— a dense sheet of connective tissue

that organises muscle, secures it to

skin, and provides stability. Collagen

is a major component.

Skeletal Muscle Cells

• The cell membrane of a skeletal muscle fibre is called the sarcolemma.

• The muscle cell cytoplasm is the sarcoplasm.

• Tubes called transverse tubules extend from the cell membrane into the muscle cells.

• Contain a sarcoplasmic reticulum, which stores calcium needed for

muscle contraction.

^{• Contain red coloured, iron and oxygen}binding protein called myoglobin.

• Contain many mitochondria for aerobic respiration — located close to myoglobin.

sarco- = flesh

plasm- = meaning fluid myo = muscle

globin = a sphere / protein fibril = relating to fibre

Skeletal Muscle Cells

Skeletal muscle is made up of long cells called

myocytes (also known as muscle fibres).

• Muscle fibres are formed from the fusion of cells

called myoblasts in the embryo. This is why

skeletal muscle cells contain many nuclei.

• Once mature muscle cells are formed (becoming

‘myocytes’), they can no longer undergo mitosis.

• However, there is limited regenerative capacity —

by satellite cells.

• This means that the number of skeletal muscle fibres each person has is set at birth.

myo- = muscle

cyt- = cell

blast = immature cell 11

Skeletal Muscle Cells

Myofibrils are cylindrical structures formed of bundles of protein filaments within the muscle fibre. They are contractile threads arranged in a striated pattern:

• Each myofibril is surrounded by a

network of sarcoplasmic reticulum.

• Myofibrils are made up of smaller filaments called myofilaments. There are two types: - Actin (thin filaments).

- Myosin (thick filaments) — shaped like golf clubs; the ‘myosin heads’ can bind to actin.

• The myofilaments overlap to form sarcomeres. © CNM: Human Sciences – Muscular System. BQ/MC

myo- = muscle

fibril = fibre/filament 12

Sarcomeres

A sarcomere is the basic unit of

striated muscle and contains the

following areas:

- H zone = myosin only.

- A band = dark area where actin

and myosin overlap.

- I band = light area of only actin

filaments.

- Z disc = filaments of actin that

are arranged at 90° angles,

where they separate sarcomeres.

sarco = flesh, muscle mere = ‘part’

epi = ‘upon’ or ‘over

Connective Tissue

Skeletal muscles consist of muscle fibres bound by connective tissue.

• Collagen fibres in connective tissue assist to tightly intermingle with other structures. — connections transfer force better.

• Individual muscle fibres are surrounded by a thin sheath called the endomysium.

• Bundles of between 10‒100 muscle fibres are bound together to form fascicles, which are surrounded by the perimysium.

• The entire muscle is surrounded by the epimysium that attaches it to fascia and tendons.

peri = ‘around’

endo = ‘within’

Skeletal Muscle Hierarchy

• Myocytes contain myofibrils that are

made up of smaller myofilaments

called actin and myosin.

• Myocytes are bundled together

and surrounded by the

perimysium to form fascicles.

• Fascicles accumulate together to

form the entire muscle, which is

surrounded by the epimysium.

• The epimysium provides an

attachment for the muscle to the

periosteum of bone. ₁₅ © CNM: Human Sciences – Muscular System. BQ/MC

Neuromuscular Junction (NMJ)

The neuromuscular junction is the meeting point (synapse) where motor neurons meet a muscle fibre.

• The neuron ending is the synaptic end bulb, which contains vesicles that store the neurotransmitter acetylcholine.

• Acetylcholine diffuses across the gap and causes the nerve impulse to continue along the sarcolemma.

neuro- = nerves

muscular = muscle

Synaptic end bulb

Muscle fibres

Neuromuscular Junction (NMJ)

• The motor end plate describes the

location where motor neurons terminate

in tiny pads on the muscle fibre.

• The strength of muscle contraction

depends on the number of motor

neurons that are conducting an

electrical impulse at one time, as

well as the frequency of impulses.

Sliding Filament: Contraction

1. Nerve impulse arrives at the neuromuscular junction.

2. The action potential spreads along the

sarcolemma and transverse tubules into the

muscle cell releasing calcium (Ca²⁺) from

storage in the sarcoplasmic reticulum.

3. Calcium and ATP cause the myosin head to

bind to the actin filament next to it. As

the actin and myosin bind, this movement causes the filaments to slide over each other, thereby shortening the fibre.

In a contracted state, the actin and myosin are bound together.

Sliding Filament: Relaxation

1. Nerve stimulation stops (no nerve impulse).

2. Using magnesium and ATP, calcium is actively

transported (pumped back) into storage,

breaking the actin and myosin bond.

3. Actin and myosin slide back into starting

positions, lengthening the fibre again

(relaxation).

• Magnesium makes muscle fibres less

excitable and prevents myosin binding with actin.

Sliding Filament Model

• As the image below highlights, muscle contraction is associated with the binding of actin and myosin. This causes the sarcomere (and muscle overall) to shorten.

• Muscle relaxation is associated with lengthening of the sarcomere and muscle overall.

a- = absence

Muscle Growth

Muscle growth is called muscle hypertrophy.

hyper- = increase

-trophy = growth in size

• Calcium, magnesium, sodium, potassium and iron are essential ingredients for effective muscle activity and athletic performance.

• The following hormones promote muscle hypertrophy:

⮚ Growth hormone ⮚ Testosterone ⮚ Thyroid hormones

Hence considerable muscle development occurs from puberty.

• During strength training, individuals experience

high levels of muscle tissue breakdown and

hence protein is required to support hypertrophy.

Muscle Metabolism

Muscles are highly energy-demanding and

require large quantities of ATP.

• The ability to produce ATP depends upon the

availability of nutrients such as glucose, fatty acids

and amino acids. More ATP is also generated in the presence of oxygen.

• To obtain these substances, muscles must receive a rich blood supply.

• There are two main pathways for ATP synthesis: • Aerobic respiration — with oxygen present.

This is how we transform the food we eat into energy.

• Anaerobic respiration — in the absence of oxygen.

Aerobic Respiration

Aerobic respiration requires oxygen to generate ATP.

• Requires a continual blood supply. The oxygen needed comes from breathing.

• Aerobic respiration occurs in the mitochondria.

• Each reaction produces 38 ATP molecules. However, as two ATP molecules are used up in the reaction, a net of 36 ATP molecules is produced.

• Aerobic respiration is used most of the time, as long as oxygen delivery is maintained.

ATP = adenosine triphosphate aerobic = with oxygen

Mitochondria perform aerobic respiration in cells. These are often located next to myoglobin.

Oxygen + (glucose) 🡪 carbon dioxide + water + energy 23

Anaerobic Respiration

Anaerobic respiration allows cells to produce ATP in the absence of oxygen.

• Utilised for intensive short-term activity.

• Anaerobic respiration takes place in the cytoplasm and occurs via glycolysis (breaking down of glucose). The reaction produces a net of two ATP molecules.

• Also produces lactic acid which lowers the muscle pH and can cause muscle fatigue.

Glucose 🡪 lactic acid + energy

an- = without

aerobic = with oxygen -lysis = breakdown

Creatine Phosphate

Creatine phosphate is a protein unique

to muscles and is an energy storage form.

• This is important because muscle cells have

very little energy within them that they can use up immediately.

• Creatine phosphate provides a small, but ready source of energy during the first 15 seconds of contraction.

• There is three to six times more creatine

phosphate in a muscle cell than ATP.

• Creatinine is a by-product from the

breakdown of creatine phosphate.

Types of Skeletal Muscle

Based on colour, skeletal muscle fibres can be categorised into two types: red and white.

myo- = muscle

globin = spherical protein

• The colour of the muscle reflects its content and functions.

White muscle fibres	Red muscle fibres
• White due to the low quantity of myoglobin.	• Red due to the large quantity of myoglobin.
• Large diameter fibres.	• Small diameter fibres.
• Anaerobic respiration.	• Aerobic respiration (hence lots of mitochondria).

• Fast and strenuous work, hence fatigue quickly.

• Designed for sustained activity with no fatigue.

Types of Skeletal Muscle

Skeletal muscle fibres can be categorised as one of three types:

Fibre type:	Slow oxidative (SO):	Fast oxidative glycolytic (FOG):	Fast glycolytic (FG):
Colour:	Dark red	White-pink	White
Respiration:	Aerobic	Aerobic / anaerobic	Anaerobic
Myoglobin and mitochondria:	Highest	Less	Least
Duration:	Longest	Resistant to fatigue	Fatigue quickly
Good for:	Endurance	Walking / sprinting	Weights
Diameter:	Small	Intermediate	Large

Types of Skeletal Muscle

Human muscles contain a genetically-determined mixture of fibres. About 50% of all fibres are SO.

• Most skeletal muscles are a mixture of muscle fibres: • Shoulders / arms: High amount of FG fibres.

• Legs and back (postural): FOG and SO fibres.

• Proportions also vary depending on individual training.

• Exercise can cause muscle fibres to change: • Endurance athletes often have more SO fibres. • Strength training increases the size

hyper = beyond normal trophy = development glyco - = sugar

-lytic = ‘to release’

(hypertrophy) and strength of fast glycolytic fibres.

Summary Quiz:

1. List THREE functions of the muscular system.

2. Name TWO types of muscle that are striated.

3. What does the endomysium surround?

4. Name the neurotransmitter at the neuromuscular junction. 5. Complete the sentence: ______ and ______ are needed for muscle contraction.

6. Name the TWO myofilaments.

7. Explain what is meant by muscle hypertrophy and atrophy. 8. Compare aerobic and anaerobic respiration.

9. Explain why some muscles appear red.

10. Indicate the type of cell respiration that slow oxidative muscle fibres use.

Skeletal Muscles: Face

The names of many skeletal muscles also describe some of their key features, e.g. size, shape, action, location, sites of attachment:

Name:	Function / Action:
Occipitofrontalis: occiput = back of head frontalis = front	Raises eyebrows.
Orbicularis oculi: orbi = circular, oculi = eyes	Closes eyes.
Orbicularis oris: orbi = circular, os- = mouth	Closes / pouts lips.
Masseter:	Mastication.
Temporalis:	Mastication.

Skeletal Muscles: Face

Orbicularis

oculi

Masseter

Skeletal Muscles: Neck

Name:

Function /

Action:

Sternocleidomastoid: sterno = sternum

cleido = clavicle

mastoid = mastoid process of the temporal bone

Turns and tilts head.

Trapezius:

trapeza = table

Pulls head

backwards.

Elevates (shrugs) and retracts

shoulders.

Skeletal Muscles: Back

Name:

Function / Action:

Supraspinatus:

(one of the rotator cuff muscles).

Initial abduction of shoulder.

Psoas:

(anterior to the lumbar spine).

Hip flexor (pulls thigh

towards trunk).

Latissimus dorsi:

latissimus = widest

dorsi = of the back.

Extends, adducts and

internally rotates arms.

Quadratus lumborum:

quad = four, lumbo = lumbar region attached to four of the five lumbar vertebrae.

Bending backwards or sideways (vertebral

extension or lateral flexion).

Erector spinae: (muscle group) erector = erect, spinae = spine.

Extension of the vertebral column. Keeps spine upright.

Skeletal Muscles: Back

Quadratus

_{lumborum Erector spinae}Latissimus dorsi

Psoas

Skeletal Muscles: Chest and Abdomen

Name:	Function / Action:
Pectoralis major: pector = chest, major = largest attaches from clavicle and sternum to humerus.	Draws arms forward: Shoulder flexion and medial rotation.
Rectus abdominis: rectus = fascicles parallel to midline abdominis = of the abdomen attaches from pubis to lower sternum and ribs.	Vertebral flexion: Bending forward (crunches).
Internal and external obliques: internal = inner, external = outside.	Rotation, bending sideways.

Skeletal Muscles: Chest and Abdomen _{Pectoralis major}Rectus

_abdominisAbdominal obliques

Respiratory Diaphragm

Name:

Function / Action:

Attaches to the lower six ribs,

sternum and

upper lumbar

spine.

When contracts, it descends into the abdominal cavity, increasing the

space for air to

enter the lungs.

Vital structures pass through the diaphragm, which further emphasises its importance in the body. These structures include the aorta, inferior vena cava, vagus nerve and oesophagus.

Skeletal Muscles: Arm

Name:	Function / Action:
Deltoid: Attaches from the scapula, acromion and clavicle to the humerus.	Flexion, abduction and extension of shoulder joint.
Biceps brachii: biceps = two heads, brachii = arm Attaches from the scapula to the radius.	Stabilises shoulder joint; flexion and supination of forearm.
Triceps brachii: triceps = three heads of origin brachii = arm.	Arm adduction; extends elbow.
Flexor carpi muscle: flexor = decrease angle, carpi = wrist.	Flexes the hand at the wrist joint.
Extensor carpi muscle: extensor = increase angle, carpi = wrist.	Extends the hand at the wrist joint.

Skeletal Muscles: Arm

^DeltoidBiceps brachii

Triceps brachii

Skeletal Muscles: Legs

Name:	Function / Action:
Gluteus maximus: glute = buttock, maximus = largest Attaches from the ilium (pelvis) to the femur.	External rotation, abduction and extension of the hip joint.
Piriformis: Attaches from the sacrum to the femur.	Externally rotates hips.
Hamstring: Three separate muscles in the posterior thigh.	Bends knee (flexes knee).
Rectus femoris: (One of four quadricep muscles) Attaches from the pelvis to the tibia.	Flexes hip and extends knee (e.g. kicking a football).

Skeletal Muscles: Legs

^{Gluteus maximus and piriformis: The Hamstrings:}Rectus femoris:

The sciatic nerve often runs

through the belly of the muscle

‘piriformis’. This makes the sciatic

nerve particularly vulnerable to

compression in this location.

Skeletal Muscles: Legs

Name:	Function / Action:
Thigh adductors: Attach from the pubis to the femur.	Squeeze the thighs together.
Tibialis anterior: ‘front of tibia’ Attaches from the tibia to the metatarsals.	Dorsiflexion and inversion of the foot (and supports medial arch of foot).
Soleus Attaches from the posterior tibia and fibula to the calcaneum (heel bone).	Plantar flexion of the foot at the ankle.
Gastrocnemius gastro = belly, knēmē = leg Attaches from the femur to the calcaneum (heel).	Flexes leg at the knee. Plantar flexion of foot.

Skeletal Muscles: Legs

Thigh

adductors:

Gastrocnemius:

Soleus (deep to the gastrocnemius):

Tibialis anterior:

Skeletal Muscle Mechanics

Tendons attach the skeletal muscles to the

periosteum of bone.

• The fleshy part of a muscle is called the muscle belly.

• When tendons span across a joint they can produce

movement (i.e. flex or extend the joint).

• When fibres contract, the muscle becomes thicker and shorter. This exerts a force on the tendons which pull on bones, producing movement at a joint.

• The location of muscle attachment points to bone are simply called muscle attachments.

Skeletal Muscle Mechanics

Muscles can be prime movers, antagonists,

synergists and fixators, depending on the movement.

• Most skeletal muscles are arranged in antagonistic

pairs over a joint, e.g. biceps brachii / triceps brachii.

• Depending on the movement, one muscle is the

prime mover, whilst the other is the antagonist.

• A synergist assists the prime mover in its action,

e.g. when flexing the elbow, brachialis helps the biceps

by pulling the ulna towards the humerus.

• A fixator is a muscle that keeps the origin bone stable

while a prime mover contracts, e.g. in the shoulder.

Cardiac Muscle

Cardiac muscle is a specialised muscle that is only found in the heart. It forms the myocardium.

• Cardiac muscle fibres are striated and involuntary.

• Cardiac muscle cells are joined end-to-end by specialised structures known as intercalated discs. These are unique to cardiac muscle and allow contraction to spread from cell to cell like a wave.

• Cardiac muscle cells are branching cells, so each cell is in contact with three to four other cells. This enables the wave of contraction to spread to more cells.

myo- = muscle

cardia- = heart

Cardiac Muscle

• Cardiac muscle is autorhythmic — it generates its own rhythm of contraction, which is approx. 75 times per minute at rest.

• Cardiac muscle stays contracted 10-15 times longer than skeletal muscle.

• Cardiac muscle depends highly on aerobic respiration and hence the cells contain lots of mitochondria. Cardiac muscle cells therefore require a constant blood supply and delivery of oxygen and nutrients like glucose.

• Can also use lactic acid to produce ATP.

auto = automatic

rhythmic = rhythm

Mitochondria

Smooth Muscle

Smooth muscle is found in the walls of blood vessels, airways, hollow organs (i.e. stomach, bladder), as well as the iris and arrector pili in the skin.

• Used to change diameter, shape

arrector = Latin for ‘to raise’

pili = Latin for hair

The iris:

or orientation of the tissue.

• Under autonomic nervous system control (involuntary).

• Also contracts in response to hormones, cell-to-cell signalling, and local chemical agents.

Stomach:

Smooth Muscle

• Smooth muscle cells are the smallest

type of muscle cell and contain a single

elongated, central nucleus.

• Smooth muscle fibres are non-striated:

giving it a smooth appearance.

• Filaments are attached to structures called

dense bodies (similar function to Z-discs in

skeletal muscle) that are not arranged in lines.

• During contraction the dense bodies are

pulled closer together by the filaments causing

the muscle to shorten and twist like a

corkscrew. ©_{CNM: Human Sciences – Muscular System. BQ/MC}

Smooth Muscle Properties

• Smooth muscle contraction is slower and

longer. It also shortens and stretches more

than skeletal muscle.

• Produces stress-relaxation response —

allows organs such as stomach and

bladder to expand when filled, causing

a contraction in order to carry contents.

• Smooth muscle maintains partial contraction

(important for blood pressure regulation).

• Smooth muscle contracts in response to

the autonomic nervous system,

hormones, stretch and blood gases.

Smooth Muscle Microscopy

Intestine cross-section:

Artery cross-section:

Arrector pili:

Muscle Regeneration

All muscle types can hypertrophy

(increase in size).

Muscle fibre

Skeletal muscle:

• Skeletal muscle cells can’t divide.

• Limited regeneration by satellite cells — when damage occurs, they divide slowly and fuse with existing fibres.

Smooth muscle:

• Can increase in number (hyperplasia) — often seen in the uterus and blood vessels. • Regeneration can occur from stem cells in blood vessels.

hyper = beyond normal trophy = development plasia = formation or development

Muscle Regeneration

Cardiac muscle:

• Post-heart attack, tissue remodeling

by fibroblasts (scarring).

• More recent evidence has identified

that stem cells in the endothelium

can undergo division.

• Hypertrophy can be physiological

(i.e. athletes) or pathological

(i.e. heart disease).

Homeostasis

Within all body systems, muscle tissue:

• Produces movement.

• Stabilises body position.

• Moves substances within the body.

• Produces heat to help maintain body temperature.

Integumentary system (skin):

– Facial expression.

– Muscle action increases blood flow to skin.

Skeletal system:

– Movement and joint stability.

Homeostasis

Nervous system

• Shivering — generates heat and raises body temperature.

Endocrine (glands and their secretions — hormones).

• Exercise can improve action of some hormones, e.g. insulin. • Muscle protects some endocrine glands.

Cardiovascular

• Cardiac muscle pumps blood.

• Smooth muscle in blood vessel walls controls blood flow. • Muscle contraction in legs helps return blood to the heart. • Exercise leads to hypertrophy of cardiac muscle.

• Lactic acid produced in skeletal muscle can be used to make ATP in the heart.

Homeostasis

Lymphatic (the interconnected system of spaces and vessels between body tissues and organs by which lymph circulates throughout the body).

• Muscle protects lymph nodes and vessels.

• Promotes lymph flow.

• Exercise can increase or decrease immune response.

Respiratory (concerned with breathing / respiration)

• Respiratory muscle facilitates airflow in and out of lungs. • Smooth muscle adjusts airway size.

• Skeletal muscle in larynx controls airflow

past vocal cords — changes voice.

• Coughing and sneezing — clears airways.

• Exercise improves breathing efficiency.

Homeostasis

^Digestive• Skeletal muscle protects and supports digestive

organs.

^{• Chewing and swallowing.}• Smooth muscle sphincters control flow. _{• Smooth muscle in intestinal wall helps mix}

contents (‘peristalsis’).

^Urinary• The bladder controls the release of urine.

^Reproductive• Skeletal and smooth muscle contractions eject

semen.

• Smooth muscle contractions propel egg along

uterine tubes, control menstrual flow and expel

baby from uterus in childbirth.

Activity

Identify the locations of the following muscles on the body surface:

1) Sternocleidomastoid.

2) Trapezius.

3) Pectoralis major.

4) Rectus abdominis.

5) Gluteus maximus.

6) Deltoid.

7) Triceps brachii.

8) Rectus femoris.

Muscular Pathologies:

Muscle Fatigue

Muscle fibres can fatigue if overused.

• Common in sports, occupational overuse and poor posture. This is now commonly seen in those who sit at desks with poor posture.

• Associated with a depletion of metabolic reserve. Cell respiration becomes anaerobic and by-products that can cause pain, such as lactic acid, are produced.

Ideal ergonomic setup:

• It is essential to prevent poor posture and provide

muscles with the time needed to rest. Meditation,

relaxation exercises, yoga, Pilates, essential oils,

manual therapy, acupuncture, nutrition (e.g.

magnesium), herbs and homeopathy can support this.

Muscle Shortening

If a muscle is continuously contracted, the

actin-myosin filaments remain attached.

• Chronic muscle contracture causes muscle

fatigue but also places a strain on the

skeletal muscle attachments.

• For example, a stressed individual

commonly sustains prolonged contraction of the upper trapezius muscle fibres. As this muscle attaches to the cervical

vertebrae, this may cause a strain of

these joints and possibly produce headaches.

• Recall that muscles require magnesium to break the actin-myosin bond.

Epsom salts

(magnesium)

Muscle Strain and Tear

Muscle strain:

• Over-stretching of muscle fibrils or the tendon, occurring when a joint is forced beyond its normal range (‘pulled muscle’).

• The muscle remains whole and blood supply intact to permit healing.

• Leg and back strains are common. Muscle tear:

Why do muscle tears often

cause bruising?

• More significant, where the muscle tears and is no longer whole. More likely to cause bruising.

• Prevents natural complete healing. Can lead to fibrosis. • A tear is suggested if movement is not possible.

Muscle Strain and Tear

TREATMENTS:

• Would you always RICE (rest, ice,

compression, elevation)?

• Herbal medicine (inflammation,

pain, connective tissue repair),

acupuncture, homeopathy (arnica),

Nutritional support (anti

inflammatory and tissue repair).

• If torn: Avoid heat, exercise,

massage, rest initially.

Impingement Syndrome

Impingement syndrome describes a shoulder condition in which movements of the shoulder can be painful and limited.

syndrome = a condition associated with a collection of signs or symptoms.

• In impingement syndrome, the rotator cuff tendons and / or bursa can become inflamed / damaged. This is most notable when compressing the space that they are both found within (the sub-acromial space).

• The sub-acromial space is the area

between the humeral head and acromion.

• The rotator cuff tendons connect the

humerus and scapula. Normally,

when moving the shoulder, the rotator

cuff has to manoeuvre intricately in order

to prevent impingement.

Impingement Syndrome

CAUSES:

• Overuse and working with the arms raised

overhead.

• More common with increasing age as blood

supply is poor and the tendons degenerate.

• Positional fault — when the head of the

humerus does not sit well in the socket.

• Bone spurs — can reduce the space

available for the bursa and tendons

to move under the acromion.

• Oddly-sized acromion resulting in reduced space.

Impingement Syndrome

SIGNS AND SYMPTOMS:

• Shoulder ache in early stages.

• Pain when abducting the shoulder or

rotating (i.e. reaching into back pocket).

• Painful arc of movement.

• A catching sensation is felt on

lowering the arm.

• Weakness and inability to raise the

arm may indicate rotator cuff tear.

Impingement Syndrome

ALLOPATHIC TREATMENT:

• Cortisone injection, NSAIDs, surgery.

NATURAL TREATMENT:

• Herbal medicine, acupuncture,

homeopathy (arnica), nutritional

support (anti-inflammatory).

• Osteopathy, chiropractic, exercise.

• Essential oils, i.e. peppermint, frankincense.

Fibromyalgia

fibro = fibrous tissue myalgia = muscle pain

Fibromyalgia is a chronic pain disorder, heavily associated with widespread musculoskeletal pain and fatigue.

• Often accompanied by multiple, unexplained

symptoms, anxiety, depression and functional

impairment of daily activities.

• Women are 10 times more commonly affected

than men; mostly occurring age 30‒50.

• Has a neurophysiologic basis, characterised by abnormalities in pain processing by the central nervous system (CNS).

• A form of central sensitisation: Pain perception to sensory stimuli that would not normally be painful.

Fibromyalgia: Pain Processing

Fibromyalgia is associated with central

sensitisation — a central disturbance in pain

processing.

• Normally, sensory input such as light touch and

temperature is sent as nerve signals to the brain /

spinal cord where it synapses with nerves.

• In fibromyalgia, alterations occur in pain processing

in the spinal cord and brain (centrally).

• High levels of substance P are found in synapses; this makes nerves more sensitised to pain.

• Excess post-synaptic nitric oxide production also causes the synapses to amplify pain signals.

We must try to understand why pain processing is faulty.

Fibromyalgia: Causes and Triggers

Biological, environmental and possibly genetic

factors are thought to contribute:

• Poor mitochondrial functioning — damaged by

free radicals.

• Altered stress response (i.e. excess cortisol,

adrenal fatigue).

• Post-viral and chronic toxic load e.g. heavy

metals, chemicals.

• Poor gut health — dysbiosis, leaky gut syndrome.

• Serotonin and noradrenaline deficiencies —

play a role in pain tolerance.

• Sleep dysregulation (fatigue, ↑pain, ↓activity).

Fibromyalgia

SIGNS AND SYMPTOMS:

• Widespread (diffuse) musculoskeletal pain.

• Pain that results from gentle pressure.

• Feeling of swollen joints, often with no

actual swelling.

• Debilitating fatigue and severely-disturbed

sleep.

• Headaches (muscular or migraine type).

• IBS symptoms, numbness, tingling, and

weakness.

• Anxiety and depression.

Fibromyalgia: Diagnosis

Criteria for diagnosis: Excess pain on palpation

in at least 11 of 18 predefined anatomical points.

• The patient experiences pain at

tender points at a decreased

threshold. However:

• Normal biopsy.

• Normal electrical muscle tests.

• Drug studies show no benefit

of NSAIDs but benefits of

antidepressants.

• It is also an ‘exclusion diagnosis’.

Fibromyalgia

ALLOPATHIC TREATMENT:

• Medications, e.g. pain relief. Pain clinics.

NATURAL TREATMENT:

• Gut — checking for dysbiosis, parasites etc. Digestive support. • Detox — supporting the liver, removing heavy metals and chemical exposures, limiting EMF exposure, castor oil (liver). • Mitochondrial support — CoQ10, antioxidants,

magnesium malate, B vitamins, essential fats.

• Reducing stress — nervine herbs (e.g.

passionflower and valerian); breathing exercises.

• Acupuncture, homeopathy.

Muscular Dystrophies

Muscular dystrophies are a group of

inherited muscular diseases that cause

muscle degeneration and weakness.

• Many types of muscular dystrophies exist.

• Muscular dystrophies are characterised by:

⮚ Progressive skeletal muscle atrophy.

⮚ Death of muscle cells and tissue

(final stages).

⮚ Defects in muscle proteins.

myo- = muscle

Myasthenia Gravis

Myasthenia gravis is an autoimmune disease of the neuromuscular junction, characterised by fluctuating muscle fatigue and weakness.

• Antibodies block acetylcholine

receptors on the motor end plate

preventing a nerve impulse being

sent to muscle fibres. The muscle

becomes progressively weaker.

• Most common in women, age 20‒50. • Muscles of face and neck are commonly affected.

-asthenia = weakness gravis = serious; heavy

Myasthenia Gravis

SIGNS AND SYMPTOMS:

• Weakness of ocular muscles; double vision and ptosis.

ptosis = from Greek ‘fall’ It is drooping of the upper eyelid

• Weakness in facial muscles (expressions)

which spreads to the proximal limbs.

• Difficulty with speech, chewing, swallowing.

• Death may result from failure of the

respiratory muscles.

• Symptoms worsen throughout the day.

Myasthenia Gravis

ALLOPATHIC TREATMENT:

• Acetylcholinesterase inhibitors, corticosteroids

to reduce effects of the antibodies. Adverse

effects include osteoporosis, indigestion,

nausea, insomnia, mood changes, diabetes).

• Plasma exchange in severe cases; injections

of normal immunoglobulins from healthy donors.

NATURAL TREATMENT:

• Herbal medicine (immune modulation),

acupuncture, homeopathy, nutritional (nerve

and muscular function) — calcium, magnesium.

Duchenne Muscular Dystrophy

^{Caused by a single gene defect on the X}chromosome, affecting males, whilst females

can be carriers. Affects 1 in 3500 males.

• Usually diagnosed three‒five years of age.

• Associated with a lack of a protein called

dystrophin in muscle cells. Dystrophin anchors the

cytoskeleton to the extracellular matrix.

• If this protein is missing, when the cell contracts

there is no support and the cell membrane

becomes leaky, allowing materials to flood in.

• This results in muscle degeneration and necrosis.

Duchenne Muscular Dystrophy

SIGNS AND SYMPTOMS:

• Delayed walking.

• Difficulty getting up from sitting or lying position.

• Clumsiness, frequent falls. • Waddling gait.

• Speech delay.

• Gowers’ sign.

DIAGNOSIS:

• Serum creatine kinase (10‒100 x normal). This is also often

raised in carriers.

• Genetic analysis and muscle biopsy.

Duchenne Muscular Dystrophy

• All muscle types affected: Skeletal, smooth and cardiac.

• Small amounts of dystrophin also

present in nerve cells (IQ is affected).

• Prognosis poor: Usually wheelchair

support needed by 10 years and

ventilation by 20 years.

• Most die in their late twenties, often

from pneumonia and cardio-respiratory failure.

• Therapeutic strategies aimed at prolonging independent walking, managing scoliosis, Nutrition and weight management.

Summary Quiz:

1. Name the FOUR properties of muscle.

2. Indicate TWO locations where smooth muscle is found. 3. What is the function of the following muscles:

Hamstrings, tibialis anterior, biceps brachii, masseter.

4. List ONE unique feature of cardiac muscle.

5. Where is: a) oxygen and b) calcium stored in a muscle fibre? 6. Define the condition fibromyalgia.

7. Describe the movements that typically aggravate shoulder impingement symptoms.

8. Who is commonly affected by Duchenne muscular dystrophy? List TWO symptoms of the disease.

Lecture 3: Muscular System

Biomedicine: Human Sciences

Lecture 3:

Muscular System

Learning Outcomes

In today’s topic you will learn:

⮚ The types of muscles in the human body;

how they differ in terms of structure and

function.

⮚ Be able to identify major skeletal muscles

of the body and recognise their functions.

⮚ The signs, symptoms, investigation

procedures and some orthodox treatments

of muscular system pathologies.

Functions

1. Movement — a result of muscular contraction. This relies on the integrated functioning of the muscles, bones and joints.

2. Maintaining posture — stabilising joints, posture and balance through continued partial muscle contraction.

3. Heat production — also known as thermogenesis. Helps maintain normal body temperature (36.5‒37.5°C). Shivering describes involuntary contractions of skeletal muscles.

thermo- = heat

genesis = creation 3

Functions ^sphincter^{= a}

circular muscle

4. Storage of substances — glycogen and oxygen.

5. Movement of substances:

- The heart muscle pumps blood around the body.

- Sphincters prevent out-flow from hollow organs.

- Smooth muscle in blood vessel walls helps

control blood flow.

- Smooth muscle moves food through the

digestive tract and urine through the urinary system.

- The diaphragm draws air into airways / lungs.

Muscle Properties

1. Contractility 🡪 ability to contract (shorten).

2. Excitability 🡪 ability to conduct an

electrical current. Nerve impulses

cause muscles to contract.

3. Extensibility 🡪 ability to stretch

without being damaged.

4. Elasticity 🡪 ability to return to

original length and shape after

contraction or extension (spring).

Striated and Non-Striated Muscle

Muscles in the body contain cells that are either striated or non-striated.

• Striated muscles contain cells that are aligned in parallel bundles, so that their different regions form stripes visible with a microscope.

• Non-striated muscles contain cells that are randomly arranged (no stripes visible).

• Skeletal and cardiac muscle is striated, whilst

Striated muscle: Non-striated:

smooth muscle is non-striated._striated_{= striped} 6

Muscle Types

There are three types of muscle in the body:

Muscle type:	Key features:
Skeletal muscle:	• Striated — attaches between bones and creates movement at joints. • Voluntary muscle.
Cardiac muscle:	• Striated — forms the heart muscle. • Involuntary muscle that generates its own rhythmic contraction (‘autorhythmic’).
Smooth muscle:	• Non-striated — found in the walls of blood vessels, walls of the gut and in the iris (coloured part of eye). • Involuntary muscle.

Striated Non-Striated Striated

Skeletal Muscle

There are 640 skeletal muscles in the body,

accounting for about 40% of body weight.

• All of these muscles are voluntary.

• Functions include: Motion and posture, speech

(larynx, lips, tongue) and breathing.

• Skeletal muscle is covered by fascia

— a dense sheet of connective tissue

that organises muscle, secures it to

skin, and provides stability. Collagen

is a major component.

Skeletal Muscle Cells

• The cell membrane of a skeletal muscle fibre is called the sarcolemma.

• The muscle cell cytoplasm is the sarcoplasm.

• Tubes called transverse tubules extend from the cell membrane into the muscle cells.

• Contain a sarcoplasmic reticulum, which stores calcium needed for

muscle contraction.

^{• Contain red coloured, iron and oxygen}binding protein called myoglobin.

• Contain many mitochondria for aerobic respiration — located close to myoglobin.

sarco- = flesh

plasm- = meaning fluid myo = muscle

globin = a sphere / protein fibril = relating to fibre

Skeletal Muscle Cells

Skeletal muscle is made up of long cells called

myocytes (also known as muscle fibres).

• Muscle fibres are formed from the fusion of cells

called myoblasts in the embryo. This is why

skeletal muscle cells contain many nuclei.

• Once mature muscle cells are formed (becoming

‘myocytes’), they can no longer undergo mitosis.

• However, there is limited regenerative capacity —

by satellite cells.

• This means that the number of skeletal muscle fibres each person has is set at birth.

myo- = muscle

cyt- = cell

blast = immature cell 11

Skeletal Muscle Cells

Myofibrils are cylindrical structures formed of bundles of protein filaments within the muscle fibre. They are contractile threads arranged in a striated pattern:

• Each myofibril is surrounded by a

network of sarcoplasmic reticulum.

• Myofibrils are made up of smaller filaments called myofilaments. There are two types: - Actin (thin filaments).

- Myosin (thick filaments) — shaped like golf clubs; the ‘myosin heads’ can bind to actin.

• The myofilaments overlap to form sarcomeres. © CNM: Human Sciences – Muscular System. BQ/MC

myo- = muscle

fibril = fibre/filament 12

Sarcomeres

A sarcomere is the basic unit of

striated muscle and contains the

following areas:

- H zone = myosin only.

- A band = dark area where actin

and myosin overlap.

- I band = light area of only actin

filaments.

- Z disc = filaments of actin that

are arranged at 90° angles,

where they separate sarcomeres.

sarco = flesh, muscle mere = ‘part’

epi = ‘upon’ or ‘over

Connective Tissue

Skeletal muscles consist of muscle fibres bound by connective tissue.

• Collagen fibres in connective tissue assist to tightly intermingle with other structures. — connections transfer force better.

• Individual muscle fibres are surrounded by a thin sheath called the endomysium.

• Bundles of between 10‒100 muscle fibres are bound together to form fascicles, which are surrounded by the perimysium.

• The entire muscle is surrounded by the epimysium that attaches it to fascia and tendons.

peri = ‘around’

endo = ‘within’

Skeletal Muscle Hierarchy

• Myocytes contain myofibrils that are

made up of smaller myofilaments

called actin and myosin.

• Myocytes are bundled together

and surrounded by the

perimysium to form fascicles.

• Fascicles accumulate together to

form the entire muscle, which is

surrounded by the epimysium.

• The epimysium provides an

attachment for the muscle to the

periosteum of bone. ₁₅ © CNM: Human Sciences – Muscular System. BQ/MC

Neuromuscular Junction (NMJ)

The neuromuscular junction is the meeting point (synapse) where motor neurons meet a muscle fibre.

• The neuron ending is the synaptic end bulb, which contains vesicles that store the neurotransmitter acetylcholine.

• Acetylcholine diffuses across the gap and causes the nerve impulse to continue along the sarcolemma.

neuro- = nerves

muscular = muscle

Synaptic end bulb

Muscle fibres

Neuromuscular Junction (NMJ)

• The motor end plate describes the

location where motor neurons terminate

in tiny pads on the muscle fibre.

• The strength of muscle contraction

depends on the number of motor

neurons that are conducting an

electrical impulse at one time, as

well as the frequency of impulses.

Sliding Filament: Contraction

1. Nerve impulse arrives at the neuromuscular junction.

2. The action potential spreads along the

sarcolemma and transverse tubules into the

muscle cell releasing calcium (Ca²⁺) from

storage in the sarcoplasmic reticulum.

3. Calcium and ATP cause the myosin head to

bind to the actin filament next to it. As

the actin and myosin bind, this movement causes the filaments to slide over each other, thereby shortening the fibre.

In a contracted state, the actin and myosin are bound together.

Sliding Filament: Relaxation

1. Nerve stimulation stops (no nerve impulse).

2. Using magnesium and ATP, calcium is actively

transported (pumped back) into storage,

breaking the actin and myosin bond.

3. Actin and myosin slide back into starting

positions, lengthening the fibre again

(relaxation).

• Magnesium makes muscle fibres less

excitable and prevents myosin binding with actin.

Sliding Filament Model

• As the image below highlights, muscle contraction is associated with the binding of actin and myosin. This causes the sarcomere (and muscle overall) to shorten.

• Muscle relaxation is associated with lengthening of the sarcomere and muscle overall.

a- = absence

Muscle Growth

Muscle growth is called muscle hypertrophy.

hyper- = increase

-trophy = growth in size

• Calcium, magnesium, sodium, potassium and iron are essential ingredients for effective muscle activity and athletic performance.

• The following hormones promote muscle hypertrophy:

⮚ Growth hormone ⮚ Testosterone ⮚ Thyroid hormones

Hence considerable muscle development occurs from puberty.

• During strength training, individuals experience

high levels of muscle tissue breakdown and

hence protein is required to support hypertrophy.

Muscle Metabolism

Muscles are highly energy-demanding and

require large quantities of ATP.

• The ability to produce ATP depends upon the

availability of nutrients such as glucose, fatty acids

and amino acids. More ATP is also generated in the presence of oxygen.

• To obtain these substances, muscles must receive a rich blood supply.

• There are two main pathways for ATP synthesis: • Aerobic respiration — with oxygen present.

This is how we transform the food we eat into energy.

• Anaerobic respiration — in the absence of oxygen.

Aerobic Respiration

Aerobic respiration requires oxygen to generate ATP.

• Requires a continual blood supply. The oxygen needed comes from breathing.

• Aerobic respiration occurs in the mitochondria.

• Each reaction produces 38 ATP molecules. However, as two ATP molecules are used up in the reaction, a net of 36 ATP molecules is produced.

• Aerobic respiration is used most of the time, as long as oxygen delivery is maintained.

ATP = adenosine triphosphate aerobic = with oxygen

Mitochondria perform aerobic respiration in cells. These are often located next to myoglobin.

Oxygen + (glucose) 🡪 carbon dioxide + water + energy 23

Anaerobic Respiration

Anaerobic respiration allows cells to produce ATP in the absence of oxygen.

• Utilised for intensive short-term activity.

• Anaerobic respiration takes place in the cytoplasm and occurs via glycolysis (breaking down of glucose). The reaction produces a net of two ATP molecules.

• Also produces lactic acid which lowers the muscle pH and can cause muscle fatigue.

Glucose 🡪 lactic acid + energy

an- = without

aerobic = with oxygen -lysis = breakdown

Creatine Phosphate

Creatine phosphate is a protein unique

to muscles and is an energy storage form.

• This is important because muscle cells have

very little energy within them that they can use up immediately.

• Creatine phosphate provides a small, but ready source of energy during the first 15 seconds of contraction.

• There is three to six times more creatine

phosphate in a muscle cell than ATP.

• Creatinine is a by-product from the

breakdown of creatine phosphate.

Types of Skeletal Muscle

Based on colour, skeletal muscle fibres can be categorised into two types: red and white.

myo- = muscle

globin = spherical protein

• The colour of the muscle reflects its content and functions.

White muscle fibres	Red muscle fibres
• White due to the low quantity of myoglobin.	• Red due to the large quantity of myoglobin.
• Large diameter fibres.	• Small diameter fibres.
• Anaerobic respiration.	• Aerobic respiration (hence lots of mitochondria).

• Fast and strenuous work, hence fatigue quickly.

• Designed for sustained activity with no fatigue.

Types of Skeletal Muscle

Skeletal muscle fibres can be categorised as one of three types:

Fibre type:	Slow oxidative (SO):	Fast oxidative glycolytic (FOG):	Fast glycolytic (FG):
Colour:	Dark red	White-pink	White
Respiration:	Aerobic	Aerobic / anaerobic	Anaerobic
Myoglobin and mitochondria:	Highest	Less	Least
Duration:	Longest	Resistant to fatigue	Fatigue quickly
Good for:	Endurance	Walking / sprinting	Weights
Diameter:	Small	Intermediate	Large

Types of Skeletal Muscle

Human muscles contain a genetically-determined mixture of fibres. About 50% of all fibres are SO.

• Most skeletal muscles are a mixture of muscle fibres: • Shoulders / arms: High amount of FG fibres.

• Legs and back (postural): FOG and SO fibres.

• Proportions also vary depending on individual training.

• Exercise can cause muscle fibres to change: • Endurance athletes often have more SO fibres. • Strength training increases the size

hyper = beyond normal trophy = development glyco - = sugar

-lytic = ‘to release’

(hypertrophy) and strength of fast glycolytic fibres.

Summary Quiz:

1. List THREE functions of the muscular system.

2. Name TWO types of muscle that are striated.

3. What does the endomysium surround?

4. Name the neurotransmitter at the neuromuscular junction. 5. Complete the sentence: ______ and ______ are needed for muscle contraction.

6. Name the TWO myofilaments.

7. Explain what is meant by muscle hypertrophy and atrophy. 8. Compare aerobic and anaerobic respiration.

9. Explain why some muscles appear red.

10. Indicate the type of cell respiration that slow oxidative muscle fibres use.

Skeletal Muscles: Face

The names of many skeletal muscles also describe some of their key features, e.g. size, shape, action, location, sites of attachment:

Name:	Function / Action:
Occipitofrontalis: occiput = back of head frontalis = front	Raises eyebrows.
Orbicularis oculi: orbi = circular, oculi = eyes	Closes eyes.
Orbicularis oris: orbi = circular, os- = mouth	Closes / pouts lips.
Masseter:	Mastication.
Temporalis:	Mastication.

Skeletal Muscles: Face

Orbicularis

oculi

Masseter

Skeletal Muscles: Neck

Name:

Function /

Action:

Sternocleidomastoid: sterno = sternum

cleido = clavicle

mastoid = mastoid process of the temporal bone

Turns and tilts head.

Trapezius:

trapeza = table

Pulls head

backwards.

Elevates (shrugs) and retracts

shoulders.

Skeletal Muscles: Back

Name:

Function / Action:

Supraspinatus:

(one of the rotator cuff muscles).

Initial abduction of shoulder.

Psoas:

(anterior to the lumbar spine).

Hip flexor (pulls thigh

towards trunk).

Latissimus dorsi:

latissimus = widest

dorsi = of the back.

Extends, adducts and

internally rotates arms.

Quadratus lumborum:

quad = four, lumbo = lumbar region attached to four of the five lumbar vertebrae.

Bending backwards or sideways (vertebral

extension or lateral flexion).

Erector spinae: (muscle group) erector = erect, spinae = spine.

Extension of the vertebral column. Keeps spine upright.

Skeletal Muscles: Back

Quadratus

_{lumborum Erector spinae}Latissimus dorsi

Psoas

Skeletal Muscles: Chest and Abdomen

Name:	Function / Action:
Pectoralis major: pector = chest, major = largest attaches from clavicle and sternum to humerus.	Draws arms forward: Shoulder flexion and medial rotation.
Rectus abdominis: rectus = fascicles parallel to midline abdominis = of the abdomen attaches from pubis to lower sternum and ribs.	Vertebral flexion: Bending forward (crunches).
Internal and external obliques: internal = inner, external = outside.	Rotation, bending sideways.

Skeletal Muscles: Chest and Abdomen _{Pectoralis major}Rectus

_abdominisAbdominal obliques

Respiratory Diaphragm

Name:

Function / Action:

Attaches to the lower six ribs,

sternum and

upper lumbar

spine.

When contracts, it descends into the abdominal cavity, increasing the

space for air to

enter the lungs.

Vital structures pass through the diaphragm, which further emphasises its importance in the body. These structures include the aorta, inferior vena cava, vagus nerve and oesophagus.

Skeletal Muscles: Arm

Name:	Function / Action:
Deltoid: Attaches from the scapula, acromion and clavicle to the humerus.	Flexion, abduction and extension of shoulder joint.
Biceps brachii: biceps = two heads, brachii = arm Attaches from the scapula to the radius.	Stabilises shoulder joint; flexion and supination of forearm.
Triceps brachii: triceps = three heads of origin brachii = arm.	Arm adduction; extends elbow.
Flexor carpi muscle: flexor = decrease angle, carpi = wrist.	Flexes the hand at the wrist joint.
Extensor carpi muscle: extensor = increase angle, carpi = wrist.	Extends the hand at the wrist joint.

Skeletal Muscles: Arm

^DeltoidBiceps brachii

Triceps brachii

Skeletal Muscles: Legs

Name:	Function / Action:
Gluteus maximus: glute = buttock, maximus = largest Attaches from the ilium (pelvis) to the femur.	External rotation, abduction and extension of the hip joint.
Piriformis: Attaches from the sacrum to the femur.	Externally rotates hips.
Hamstring: Three separate muscles in the posterior thigh.	Bends knee (flexes knee).
Rectus femoris: (One of four quadricep muscles) Attaches from the pelvis to the tibia.	Flexes hip and extends knee (e.g. kicking a football).

Skeletal Muscles: Legs

^{Gluteus maximus and piriformis: The Hamstrings:}Rectus femoris:

The sciatic nerve often runs

through the belly of the muscle

‘piriformis’. This makes the sciatic

nerve particularly vulnerable to

compression in this location.

Skeletal Muscles: Legs

Name:	Function / Action:
Thigh adductors: Attach from the pubis to the femur.	Squeeze the thighs together.
Tibialis anterior: ‘front of tibia’ Attaches from the tibia to the metatarsals.	Dorsiflexion and inversion of the foot (and supports medial arch of foot).
Soleus Attaches from the posterior tibia and fibula to the calcaneum (heel bone).	Plantar flexion of the foot at the ankle.
Gastrocnemius gastro = belly, knēmē = leg Attaches from the femur to the calcaneum (heel).	Flexes leg at the knee. Plantar flexion of foot.

Skeletal Muscles: Legs

Thigh

adductors:

Gastrocnemius:

Soleus (deep to the gastrocnemius):

Tibialis anterior:

Skeletal Muscle Mechanics

Tendons attach the skeletal muscles to the

periosteum of bone.

• The fleshy part of a muscle is called the muscle belly.

• When tendons span across a joint they can produce

movement (i.e. flex or extend the joint).

• When fibres contract, the muscle becomes thicker and shorter. This exerts a force on the tendons which pull on bones, producing movement at a joint.

• The location of muscle attachment points to bone are simply called muscle attachments.

Skeletal Muscle Mechanics

Muscles can be prime movers, antagonists,

synergists and fixators, depending on the movement.

• Most skeletal muscles are arranged in antagonistic

pairs over a joint, e.g. biceps brachii / triceps brachii.

• Depending on the movement, one muscle is the

prime mover, whilst the other is the antagonist.

• A synergist assists the prime mover in its action,

e.g. when flexing the elbow, brachialis helps the biceps

by pulling the ulna towards the humerus.

• A fixator is a muscle that keeps the origin bone stable

while a prime mover contracts, e.g. in the shoulder.

Cardiac Muscle

Cardiac muscle is a specialised muscle that is only found in the heart. It forms the myocardium.

• Cardiac muscle fibres are striated and involuntary.

• Cardiac muscle cells are joined end-to-end by specialised structures known as intercalated discs. These are unique to cardiac muscle and allow contraction to spread from cell to cell like a wave.

• Cardiac muscle cells are branching cells, so each cell is in contact with three to four other cells. This enables the wave of contraction to spread to more cells.

myo- = muscle

cardia- = heart

Cardiac Muscle

• Cardiac muscle is autorhythmic — it generates its own rhythm of contraction, which is approx. 75 times per minute at rest.

• Cardiac muscle stays contracted 10-15 times longer than skeletal muscle.

• Can also use lactic acid to produce ATP.

auto = automatic

rhythmic = rhythm

Mitochondria

Smooth Muscle

Smooth muscle is found in the walls of blood vessels, airways, hollow organs (i.e. stomach, bladder), as well as the iris and arrector pili in the skin.

• Used to change diameter, shape

arrector = Latin for ‘to raise’

pili = Latin for hair

The iris:

or orientation of the tissue.

• Under autonomic nervous system control (involuntary).

• Also contracts in response to hormones, cell-to-cell signalling, and local chemical agents.

Stomach:

Smooth Muscle

• Smooth muscle cells are the smallest

type of muscle cell and contain a single

elongated, central nucleus.

• Smooth muscle fibres are non-striated:

giving it a smooth appearance.

• Filaments are attached to structures called

dense bodies (similar function to Z-discs in

skeletal muscle) that are not arranged in lines.

• During contraction the dense bodies are

pulled closer together by the filaments causing

the muscle to shorten and twist like a

Smooth Muscle Properties

• Smooth muscle contraction is slower and

longer. It also shortens and stretches more

than skeletal muscle.

• Produces stress-relaxation response —

allows organs such as stomach and

bladder to expand when filled, causing

a contraction in order to carry contents.

• Smooth muscle maintains partial contraction

(important for blood pressure regulation).

• Smooth muscle contracts in response to

the autonomic nervous system,

hormones, stretch and blood gases.

Smooth Muscle Microscopy

Intestine cross-section:

Artery cross-section:

Arrector pili:

Muscle Regeneration

All muscle types can hypertrophy

(increase in size).

Muscle fibre

Skeletal muscle:

• Skeletal muscle cells can’t divide.

• Limited regeneration by satellite cells — when damage occurs, they divide slowly and fuse with existing fibres.

Smooth muscle:

• Can increase in number (hyperplasia) — often seen in the uterus and blood vessels. • Regeneration can occur from stem cells in blood vessels.

hyper = beyond normal trophy = development plasia = formation or development

Muscle Regeneration

Cardiac muscle:

• Post-heart attack, tissue remodeling

by fibroblasts (scarring).

• More recent evidence has identified

that stem cells in the endothelium

can undergo division.

• Hypertrophy can be physiological

(i.e. athletes) or pathological

(i.e. heart disease).

Homeostasis

Within all body systems, muscle tissue:

• Produces movement.

• Stabilises body position.

• Moves substances within the body.

• Produces heat to help maintain body temperature.

Integumentary system (skin):

– Facial expression.

– Muscle action increases blood flow to skin.

Skeletal system:

– Movement and joint stability.

Homeostasis

Nervous system

• Shivering — generates heat and raises body temperature.

Endocrine (glands and their secretions — hormones).

• Exercise can improve action of some hormones, e.g. insulin. • Muscle protects some endocrine glands.

Cardiovascular

• Cardiac muscle pumps blood.

• Smooth muscle in blood vessel walls controls blood flow. • Muscle contraction in legs helps return blood to the heart. • Exercise leads to hypertrophy of cardiac muscle.

• Lactic acid produced in skeletal muscle can be used to make ATP in the heart.

Homeostasis

Lymphatic (the interconnected system of spaces and vessels between body tissues and organs by which lymph circulates throughout the body).

• Muscle protects lymph nodes and vessels.

• Promotes lymph flow.

• Exercise can increase or decrease immune response.

Respiratory (concerned with breathing / respiration)

• Respiratory muscle facilitates airflow in and out of lungs. • Smooth muscle adjusts airway size.

• Skeletal muscle in larynx controls airflow

past vocal cords — changes voice.

• Coughing and sneezing — clears airways.

• Exercise improves breathing efficiency.

Homeostasis

^Digestive• Skeletal muscle protects and supports digestive

organs.

^{• Chewing and swallowing.}• Smooth muscle sphincters control flow. _{• Smooth muscle in intestinal wall helps mix}

contents (‘peristalsis’).

^Urinary• The bladder controls the release of urine.

^Reproductive• Skeletal and smooth muscle contractions eject

semen.

• Smooth muscle contractions propel egg along

uterine tubes, control menstrual flow and expel

baby from uterus in childbirth.

Activity

Identify the locations of the following muscles on the body surface:

1) Sternocleidomastoid.

2) Trapezius.

3) Pectoralis major.

4) Rectus abdominis.

5) Gluteus maximus.

6) Deltoid.

7) Triceps brachii.

8) Rectus femoris.

Muscular Pathologies:

Muscle Fatigue

Muscle fibres can fatigue if overused.

• Common in sports, occupational overuse and poor posture. This is now commonly seen in those who sit at desks with poor posture.

• Associated with a depletion of metabolic reserve. Cell respiration becomes anaerobic and by-products that can cause pain, such as lactic acid, are produced.

Ideal ergonomic setup:

• It is essential to prevent poor posture and provide

muscles with the time needed to rest. Meditation,

relaxation exercises, yoga, Pilates, essential oils,

manual therapy, acupuncture, nutrition (e.g.

magnesium), herbs and homeopathy can support this.

Muscle Shortening

If a muscle is continuously contracted, the

actin-myosin filaments remain attached.

• Chronic muscle contracture causes muscle

fatigue but also places a strain on the

skeletal muscle attachments.

• For example, a stressed individual

commonly sustains prolonged contraction of the upper trapezius muscle fibres. As this muscle attaches to the cervical

vertebrae, this may cause a strain of

these joints and possibly produce headaches.

• Recall that muscles require magnesium to break the actin-myosin bond.

Epsom salts

(magnesium)

Muscle Strain and Tear

Muscle strain:

• Over-stretching of muscle fibrils or the tendon, occurring when a joint is forced beyond its normal range (‘pulled muscle’).

• The muscle remains whole and blood supply intact to permit healing.

• Leg and back strains are common. Muscle tear:

Why do muscle tears often

cause bruising?

• More significant, where the muscle tears and is no longer whole. More likely to cause bruising.

• Prevents natural complete healing. Can lead to fibrosis. • A tear is suggested if movement is not possible.

Muscle Strain and Tear

TREATMENTS:

• Would you always RICE (rest, ice,

compression, elevation)?

• Herbal medicine (inflammation,

pain, connective tissue repair),

acupuncture, homeopathy (arnica),

Nutritional support (anti

inflammatory and tissue repair).

• If torn: Avoid heat, exercise,

massage, rest initially.

Impingement Syndrome

Impingement syndrome describes a shoulder condition in which movements of the shoulder can be painful and limited.

syndrome = a condition associated with a collection of signs or symptoms.

• The sub-acromial space is the area

between the humeral head and acromion.

• The rotator cuff tendons connect the

humerus and scapula. Normally,

when moving the shoulder, the rotator

cuff has to manoeuvre intricately in order

to prevent impingement.

Impingement Syndrome

CAUSES:

• Overuse and working with the arms raised

overhead.

• More common with increasing age as blood

supply is poor and the tendons degenerate.

• Positional fault — when the head of the

humerus does not sit well in the socket.

• Bone spurs — can reduce the space

available for the bursa and tendons

to move under the acromion.

• Oddly-sized acromion resulting in reduced space.

Impingement Syndrome

SIGNS AND SYMPTOMS:

• Shoulder ache in early stages.

• Pain when abducting the shoulder or

rotating (i.e. reaching into back pocket).

• Painful arc of movement.

• A catching sensation is felt on

lowering the arm.

• Weakness and inability to raise the

arm may indicate rotator cuff tear.

Impingement Syndrome

ALLOPATHIC TREATMENT:

• Cortisone injection, NSAIDs, surgery.

NATURAL TREATMENT:

• Herbal medicine, acupuncture,

homeopathy (arnica), nutritional

support (anti-inflammatory).

• Osteopathy, chiropractic, exercise.

• Essential oils, i.e. peppermint, frankincense.

Fibromyalgia

fibro = fibrous tissue myalgia = muscle pain

Fibromyalgia is a chronic pain disorder, heavily associated with widespread musculoskeletal pain and fatigue.

• Often accompanied by multiple, unexplained

symptoms, anxiety, depression and functional

impairment of daily activities.

• Women are 10 times more commonly affected

than men; mostly occurring age 30‒50.

• Has a neurophysiologic basis, characterised by abnormalities in pain processing by the central nervous system (CNS).

• A form of central sensitisation: Pain perception to sensory stimuli that would not normally be painful.

Fibromyalgia: Pain Processing

Fibromyalgia is associated with central

sensitisation — a central disturbance in pain

processing.

• Normally, sensory input such as light touch and

temperature is sent as nerve signals to the brain /

spinal cord where it synapses with nerves.

• In fibromyalgia, alterations occur in pain processing

in the spinal cord and brain (centrally).

• High levels of substance P are found in synapses; this makes nerves more sensitised to pain.

• Excess post-synaptic nitric oxide production also causes the synapses to amplify pain signals.

We must try to understand why pain processing is faulty.

Fibromyalgia: Causes and Triggers

Biological, environmental and possibly genetic

factors are thought to contribute:

• Poor mitochondrial functioning — damaged by

free radicals.

• Altered stress response (i.e. excess cortisol,

adrenal fatigue).

• Post-viral and chronic toxic load e.g. heavy

metals, chemicals.

• Poor gut health — dysbiosis, leaky gut syndrome.

• Serotonin and noradrenaline deficiencies —

play a role in pain tolerance.

• Sleep dysregulation (fatigue, ↑pain, ↓activity).

Fibromyalgia

SIGNS AND SYMPTOMS:

• Widespread (diffuse) musculoskeletal pain.

• Pain that results from gentle pressure.

• Feeling of swollen joints, often with no

actual swelling.

• Debilitating fatigue and severely-disturbed

sleep.

• Headaches (muscular or migraine type).

• IBS symptoms, numbness, tingling, and

weakness.

• Anxiety and depression.

Fibromyalgia: Diagnosis

Criteria for diagnosis: Excess pain on palpation

in at least 11 of 18 predefined anatomical points.

• The patient experiences pain at

tender points at a decreased

threshold. However:

• Normal biopsy.

• Normal electrical muscle tests.

• Drug studies show no benefit

of NSAIDs but benefits of

antidepressants.

• It is also an ‘exclusion diagnosis’.

Fibromyalgia

ALLOPATHIC TREATMENT:

• Medications, e.g. pain relief. Pain clinics.

NATURAL TREATMENT:

magnesium malate, B vitamins, essential fats.

• Reducing stress — nervine herbs (e.g.

passionflower and valerian); breathing exercises.

• Acupuncture, homeopathy.

Muscular Dystrophies

Muscular dystrophies are a group of

inherited muscular diseases that cause

muscle degeneration and weakness.

• Many types of muscular dystrophies exist.

• Muscular dystrophies are characterised by:

⮚ Progressive skeletal muscle atrophy.

⮚ Death of muscle cells and tissue

(final stages).

⮚ Defects in muscle proteins.

myo- = muscle

Myasthenia Gravis

Myasthenia gravis is an autoimmune disease of the neuromuscular junction, characterised by fluctuating muscle fatigue and weakness.

• Antibodies block acetylcholine

receptors on the motor end plate

preventing a nerve impulse being

sent to muscle fibres. The muscle

becomes progressively weaker.

• Most common in women, age 20‒50. • Muscles of face and neck are commonly affected.

-asthenia = weakness gravis = serious; heavy

Myasthenia Gravis

SIGNS AND SYMPTOMS:

• Weakness of ocular muscles; double vision and ptosis.

ptosis = from Greek ‘fall’ It is drooping of the upper eyelid

• Weakness in facial muscles (expressions)

which spreads to the proximal limbs.

• Difficulty with speech, chewing, swallowing.

• Death may result from failure of the

respiratory muscles.

• Symptoms worsen throughout the day.

Myasthenia Gravis

ALLOPATHIC TREATMENT:

• Acetylcholinesterase inhibitors, corticosteroids

to reduce effects of the antibodies. Adverse

effects include osteoporosis, indigestion,

nausea, insomnia, mood changes, diabetes).

• Plasma exchange in severe cases; injections

of normal immunoglobulins from healthy donors.

NATURAL TREATMENT:

• Herbal medicine (immune modulation),

acupuncture, homeopathy, nutritional (nerve

and muscular function) — calcium, magnesium.

Duchenne Muscular Dystrophy

^{Caused by a single gene defect on the X}chromosome, affecting males, whilst females

can be carriers. Affects 1 in 3500 males.

• Usually diagnosed three‒five years of age.

• Associated with a lack of a protein called

dystrophin in muscle cells. Dystrophin anchors the

cytoskeleton to the extracellular matrix.

• If this protein is missing, when the cell contracts

there is no support and the cell membrane

becomes leaky, allowing materials to flood in.

• This results in muscle degeneration and necrosis.

Duchenne Muscular Dystrophy

SIGNS AND SYMPTOMS:

• Delayed walking.

• Difficulty getting up from sitting or lying position.

• Clumsiness, frequent falls. • Waddling gait.

• Speech delay.

• Gowers’ sign.

DIAGNOSIS:

• Serum creatine kinase (10‒100 x normal). This is also often

raised in carriers.

• Genetic analysis and muscle biopsy.

Duchenne Muscular Dystrophy

• All muscle types affected: Skeletal, smooth and cardiac.

• Small amounts of dystrophin also

present in nerve cells (IQ is affected).

• Prognosis poor: Usually wheelchair

support needed by 10 years and

ventilation by 20 years.

• Most die in their late twenties, often

from pneumonia and cardio-respiratory failure.

• Therapeutic strategies aimed at prolonging independent walking, managing scoliosis, Nutrition and weight management.

Summary Quiz:

1. Name the FOUR properties of muscle.

2. Indicate TWO locations where smooth muscle is found. 3. What is the function of the following muscles:

Hamstrings, tibialis anterior, biceps brachii, masseter.

4. List ONE unique feature of cardiac muscle.

5. Where is: a) oxygen and b) calcium stored in a muscle fibre? 6. Define the condition fibromyalgia.

7. Describe the movements that typically aggravate shoulder impingement symptoms.

8. Who is commonly affected by Duchenne muscular dystrophy? List TWO symptoms of the disease.