MUSCULAR SYSTEM - TEST 3 REVIEW

Myology

Study of muscle tissue

Muscles compose ___ of total body weight.

40 - 50%

Functions of muscle:

- Movement: internal and external movement accomplished by contraction of muscle.
- Thermogenesis: When muscles contract, work is done. A by product is heat. Muscle contractions will generate 85%
of body heat for the human.
- Maintaining posture
- Involved with all systems (cardiovascular, respiration, reproduction, etc.)
- Communication
- Heart beat
- Constriction of organs and vessels

VOCAB: muscle cell

= muscle fiber

VOCAB: cytoplasm

= sarcoplasm

VOCAB: muscle cell membrane

= Sarcolemma

VOCAB: endoplasmic reticulum

= sarcoplasmic reticulum

VOCAB: muscle

= myo

VOCAB: flesh

= sarco

VOCAB: Contractility

to shorten forcefully (resulting in movement)

VOCAB: Excitability

to respond to a stimulus

VOCAB: Extensibility

to stretch beyond normal resting length, yet still contract

VOCAB: Elasticity

to recoil to original length

3 types of muscle tissue:

skeletal, smooth and cardiac

Skeletal muscle:

- voluntary muscle
- fibers run parallel to each other
- multinucleated
- alternations of dark and light areas
which are striations
- Sarcomeres exist in this type of muscle
- They develop from myoblast and
their number remains constant.
- They are responsible for locomotion, facial expressions, posture, respiratory movements
and other types of body movement

Smooth muscle:

- Involuntary muscle
- fibers are tapered at ends
- spindle shaped
- uninucleated
- smooth cytoplasm
- found in walls of internal organs hollow vessels, eye, glands, skin
- contract longer than skeletal muscle
- functions are to propel urine, mix food in digestive tract, dilating/constricting pupils and
regulating blood flow
- In some locations they are autorhythmic
- controlled involuntarily by endocrine and
autonomic nervous systems

Cardiac muscle:

- involuntary muscle only found in heart
- major source of movement of blood in the body
- uninucleated, branching formation, intercalated discs
- Contain large number of mitochondria.
- Contracts rhythmically and constantly.
-Sarcomeres exist in this type of muscle.

3 layers of connective tissue:

Epimysium, Perimysium, Endomysium

Epimysium:

The muscle itself is surrounded by epimysium

Perimysium:

Each muscle is composed of bundles ( fasciculus) of muscle fibers and
each fasciulus is surrounded by

Endomysium:

Each fiber within the fascicles is surrounded by another layer of connective
tissue called the

TENDONS

The 3 layers of connective tissue will extend out farther than the muscle tissue and form ____

VOCAB: Tendon

Connective tissue that attaches muscle to the periosteum of the bone

VOCAB: Fascia

- connective tissue sheet that forms a layer under the skin
- Holds muscles together and separates them into
functional groups
- Allows free movements of muscles and carries nerves (motor neurons, sensory neurons), blood
vessels, and lymphatics
-It is continuous with connective tissue of tendons and periosteum

VOCAB: Myofibrils

- Within each muscle fiber which is a single cell, there are smaller subunits called _____
- composed of many MYOFILAMENTS

2 types of myofilaments:

Actin Myofilaments and Myosin Filaments

VOCAB: MYOSIN MYOFILAMENTS

- composed of a type of protein called MYOSIN
- made of two heavy myosin molecules which are wound together to form the rod portion
- parallel to the actin myofilament
- head regions extend towards the actin myofilaments and can bind to sites in the actin, forming CROSS BRIDGES.
- The heads can bend and straighten during contraction releasing energy.
- Part of the energy is used to bend the hinged region of the myosin molecule during contraction

VOCAB: ACTIN MYOFIL

- composed of 3 different protein subunits. The strands of actin form adouble helix and attached at either end of the sarcomere
- Actin, Tropomyosin, and Troponin

ACTIN:

- The protein that is most abundant These are globule proteins, each having a MYOSIN BINDING SITE on it

TROPOMYOSIN and TROPONIN:

- these are 2 more pr that compose the actin myofilament and are closely associated with each other, making up the T-T COMPLEX.
- Tropomyosin is the elongated protein where as
- Troponin has three subunits one that binds with actin, second that binds with tropomyosin and the third unit that binds to the calcium ions.

VOCAB: SARCOMERES

- Units of organization found in skeletal and cardiac muscle, making these types of muscle appear striated.
- Each _____ lies between 2 Z DISKS and are ordered repeating units of myofilaments.The Z disc serves as attachment for actin myofilaments.

The striated appearance of the muscle is due to:

I & A Bands, H zone, and M line

VOCAB: I bands

light and extends from Z disks to the ends of the thick filaments

VOCAB: A bands

dark and thick andextends the length of thick filaments

VOCAB: H zone

- a region in A band where actin and myosin do not overlap

VOCAB: M line

- is in the middle of H zone.
- is made of protein that holds the myosin filaments which thus holds myosin in place to avoid its sliding during contraction.

RELAXATION (Sliding filament mechanism of skeletal muscle contraction)

- During ______, sarcomeres lengthen.
- happens because of contraction of antagonistic muscles.
- Antagonistic muscles
act opposite to the contracting muscles

CONTRACTION (Sliding filament mechanism of skeletal muscle contraction)

- During _____ actin slides past myosin myofilament and the Z disks come closer to each other.
- This results in shortening of the sarcomeres and the muscle contracts

TENSION (Sliding filament mechanism of skeletal muscle contraction)

- Overlapping of actin filaments over myosin filaments is defined as tension in the muscle.

VOCAB: MOTOR UNIT

neuron + muscle fibers that it controls

Motor Unit Facts:

- These motor units vary in size according to location.
- Usually, 1 neuron will control 150 muscle fibers.
- However, in the large muscles, such as in the leg, 1 neuron may control as many as 2000 fibers.
- In other locations where more delicate and precise movement is needed, such as in the eyes and fingers, 1 neuron may control only
2 to 3 muscle fibers.

VOCAB: T-Tubules

- Tunnel-like folds of sarcolemma that goes deep into the muscle fiber and lies near the SARCOPLASMIC RETICULUM.
- These tubules run perpendicularly to the Sarcoplasmic Reticulum.

VOCAB: SARCOPLASMIC RETICULUM

- fluid-filled structures that, when the muscle fiber is relaxed, will contain CALCIUM IONS.
- After the impulse is established on the sarcolemma, it will travel along the sarcolemma, down into the fiber along the T-Tubule, and cause the S.R. to release its Ca++

Sacroplasmic Reticulum releases Ca++

- This Ca++ goes into the sarcoplasmic reticulum to the troponin, changing the shape of the T-T complex.
- The T-T comples then moves exposing the myosin binding sites on the actin
- engagement occurs, the power stoke follows and muscles contraction is accomplished

During RELAXATION, there is:

- A low concentration of Ca++ in the sarcoplasm, high concentration in sarcoplasmic reticulum
- The myosin binding sites on actin are covered by T-T complex
- Therefore no contact exists between the actin and myosin and the muscle relaxes.

During CONTRACTION:

- Actin and myosin myofilaments stay the SAME LENGTH
- Actin moves past myosin myofilament, But myosin remains in the same position.
- Z disks come closer to each other
- sarcomeres get shorter

Muscle Relaxtion:

- A muscle fiber must relax.
- In order to do this, the A.P (Action Potential) must stop. This occurs at the synapse.
- After ACh is released from the neuron and binds to the receptors, it will quickly be destroyed by
ACETYLCHOLINESTERASE (AChE).
- This is an enzyme that is released by the motor end plate.
- Ca concentration isnow low in the Sarcoplasmic Reticulum (SR) Ca++ then returns to the S.R. from the sarcoplasm
- The T-T Complex returns to cover the actin, causing the myosin to detach.
- The muscle returns to a relaxed position.

ATP (energy) is needed for muscle contraction and relaxation

VOCAB: MYASTHENIA GRAVIS

Disease characterized by DROOPING eyelids, difficulty swallowing and talking, muscle weakness. This is an autoimmune disease in which the body has produced antibodies that DESTROY ACh receptors

VOCAB: MUSCULAR DYSTROPHY

A group of inherited skeletal MUSCLE-DESTROYING diseases. They are characterized by DEGENERATION of individual muscle fibers leading to atrophy of the skeletal muscle. DUCHENNE’S MUSCULAR
DYSTROPHY is a type of MD that usually is seen in males who have inherited it from their mother.

VOCAB: CURARE

- An arrowhead poison used by natives of South America, binds to the ACh receptors and blocks the attachment of the Ach, prohibiting an A.P. from being established. Muscles CANNOT contract and breathing STOPS.
- Curare is also used clinically in small amounts to allow for intubation and prevention of muscular movements during surgery

VOCAB: RIGOR MORTIS

- Calcium is important in contraction and relaxation of a muscle.
- When death occurs, there is deterioration within the muscle fibers that allows for the calcium to leak out of the sarcoplasmic reticulum.
- This Ca++ will bind to the troponin and sustained muscle contraction, due to the lack of ATP to disengage the filaments, will occur.
- This RIGOR MORTIS will last for a few hours after death. Finally, the muscle filaments deteriorate and it no longer can hold the contraction
- Another type of connective tissue that muscle is associated with is blood.
- Muscle is well vasculated ( very active tissue, needs a lot of O2 and nutrients and removal of CO2) so there will be many blood vessels (capillaries) within this tissue.

VOCAB: Contraction

Contractions are responses to stimulus ( nervous impulse). However not all stimuli are strong enough to get a response.

VOCAB: TWITCH

It is a jerky response to a single stimulus

Nervous system controls...

muscle contractions through action potentials(AP)

Resting membrane potentials there is

- a voltage difference across membranes (polarized)

VOCAB: Depolarization (contraction)

Inside of plasma membrane becomes less negative. If change reaches threshold, depolarization occurs. This is due to Na+ influx through fast acting Na channels.

VOCAB: Repolarization (Relaxation)

It is the return of resting membrane potential. This is due to K+ outflux through the slow acting K+ channels

VOCAB: Hyper polarization

During repolarization, the membrane potential drops lower and becomes more negative than its original resting potential, then rebounds. This is because Na plus K together are higher on the outside now, but then Na/K pump restores the resting potential back to its value

VOCAB: Propagation of Action Potential

Action potential does not move along the membrane but new action potential is formed at each successive location

VOCAB: Frequency of AP

number of action potential produced per unit of time

The ATP needed for muscle contractions comes from three sources:

1. CREATINE PHOSPHATE
2. ANAEROBIC RESPIRATION
3.AEROBIC RESPIRATION

VOCAB: CREATINE PHOSPHATE

During rest, creatine phosphate is produced in the muscle cells. As the muscles begin to contract, the stored creatine phosphate combines with available ADP and produces ATP + creatine

Formula for CREATINE PHOSPHATE

ADP + Creatine Phosphate --> Creatine + ATP

VOCAB: ANAEROBIC RESPIRATION

- At the beginning of muscle contraction, there may not be much oxygen going to the muscles.
- In the environment, the muscle can still contract, due to production of ATPs in the absence of O2 - anaerobic respiration.
- Here the substrate is Glucose.
- For each molecule of glucose metabolized, 2 ATP molecules will be produced in addition to lactic acid.

VOCAB: AEROBIC RESPIRATION

- As the muscles continue to contract, more blood carrying oxygen will go to them
- requires oxygen to break down glucose into ATP, CO2 and WATER.
- This type of respiration is much more efficient than anaerobic respiration, producing 38 ATP molecules.
- Also, A.R. uses a greater variety of molecules, such as fatty acids, Glucose or amino acids to produce the ATPs.
- Although aerobic metabolism produces more ATPs, the process is more complex and takes longer.
- This method of ATP production will be used in long-distance running or in other endurance exercise

VOCAB: OXYGEN DEBT

- After intense exercise, the rate of metabolism remains elevated for a while and heavy breathing
continues after activity ends.
- The oxygen that is taken in at this time is above the amount needed for aerobic respiration and is referred to as OXYGEN DEBT.
- This increased oxygen will reestablish normal ATP levels in the muscle and blood.

VOCAB: MUSCLE FATIGUE

- results from ATP depletion.
- Without adequate ATP levels in muscle fibers, cross bridges cannot function normally
- PHYSIOLOGIC CONTRACTURE occurs when there is not enough ATP available to disconnect the cross bridges

VOCAB: PHYSIOLOGIC CONTRACTURE (CRAMPS)

This is extreme muscular fatigue due to lack of ATP. Here actin and myosin filaments cannot disengage

VOCAB: SYNAPTIC FATIGUE

- This type of fatigue occurs in the neuromuscular junction. If the number of action potentials is great enough on the neuron, the release of the Ach is greater than the amount that is available.
- The synaptic vesicles become depleted and there is not enough to stimulate the muscles fibers.
- This is rare and occurs only as a result of extreme exertion.

Two types of Fibers in Skeletal Muscle:

TYPE I fibers (Red meat) & TYPE II fibers (white meat)

TYPE I fibers (Red meat)

- Slow twitch fibers: In these fibers there are a large number of mitochondria, many blood capillaries and myoglobin.
- They contract slowly, but can sustain a contraction for a long time. ex. neck and postural muscles or Red meat of the chicken leg

TYPE II fibers (white meat)

- Fast twitch There is a low concentration of myoglobin in these fibers as well as few mitochondria, blood vessels and myoglobin.
- These fibers contract quickly but fatigue quickly. Ex. eye muscles or white meat of the chicken breast

VOCAB: hypertrophy

A muscle size increases in size

VOCAB: atrophy

A muscle may also get smaller when movement is limited. This can be seen if a persons arm or leg is in a cast or if a person becomes bedridden.

HYPERTROPHY

The increase in size of a muscle is due to

ANABOLIC STEROIDS can be used to

increase hypertrophy of muscles

Possible problems (when abusing ANABOLIC STEROIDS) include:

bloating face, shriveled testes, infertility, liver damage leading to liver cancer, aggressive behavior

When ANABOLIC STERIODS are used by females there will be

an increase in definition of muscle, increase body hair and decrease in pitch of voice.

VOCAB: Fibromyalgia

a condition that causes pain all over the body (also referred to as widespread pain), sleep problems, fatigue, and often emotional and mental distress

VOCAB: Tetanus Disease

A serious bacterial infection that causes painful muscle spasms and can lead to death.

VOCAB: Subthreshold stimulus

a stimulus that is too small in magnitude to produce an action potential in excitable cells

VOCAB: Threshold Stimulus

the minimum intensity required from a stimulus to produce a response from a human or an animal

VOCAB: Submaximal Stimulus

When the strength of a stimulus presented to a nerve was less than a MTS

VOCAB: Maximal Stimulus

the voltage or current at which the isometric twitch force produced is maximal

VOCAB: Supramaximal Stimulus

stimulation having intensity (voltage or current) significantly above that required to activate all the muscle fibers

VOCAB: Incomplete tetanus

-Successive muscle contractions begin to blend, almost appearing as a single large contraction

VOCAB: Complete tetanus

individual muscle contractions completely fuse to produce one large muscle contraction

VOCAB: Multiple wave summation

occurs when stimulations are delivered to a muscle fiber faster than it is able to completely relax

VOCAB: Treppe

a condition where muscle contractions become more efficient

The major functions of the nervous system include

1. Sensory
2. Integration
3. Maintains Homeostasis
4. Controls Muscles and Glands

VOCAB: SENSORY input

sensory receptors found internally and externally monitor stimuli, like heat, cold, pain,
smell, sound, pressure etc. detects stimuli in internal and external environment

VOCAB: INTEGRATION

The nervous system analyses sensory information, stores it and makes decisions and
many times establishes a motor response.

The CNS consists of

the brain and the spinal cord

The PNS consists of

cranial nerves, spinal nerves and other nerves

PNS includes:

- Sensory Receptors
- Nerves
- Cranial Nerves
- Ganglions
- Plexus

VOCAB: Plexus

- a network of axons and sometime includes their neuron cell bodies as well.
- is located outside of the CNS

Division of PNS, Its two main divisions:

Sensory & Motor

Sensory (afferent) Functions:

transmits action potentials from receptors to CNS

Motor (efferent) Functions

Transmits action potentials from CNS to effectors

Effectors can be....

muscles or glands