Unit 8: Muscular System

Tom’s Story

Tom seemed like most other young boys,

though his mother noted that he was slow

to crawl and didn’t start walking until he

was 18 months.

At the age of three, his mother was

concerned by how often he would fall. took him to a specialist who performed a

neurological assessment.

She

What do you think is involved in this

assessment?

Student Guided NotesOne of the tests the doctor asked

Tom to perform is to sit on the floor

and then move to a standing

position.

The doctor looked concerned when

Tom went through several steps to

stand up. On the chart he wrote

the term “Gowers Maneuver.”

The doctor said they would

need to do blood tests to see if

there was something wrong

with Tom’s muscles.

Gowers ManeuverMuscular System

Functions:

- movement of the body

- maintaining posture

- generates body heat

- role in other body systems

(respiration, digestion, urination)Types of Muscle

● Skeletal – striated, voluntary

● Smooth – involuntary (digestive)

● Cardiac - heart

If there is a problem with

Tom’s muscles, how could this

affect his entire body?Muscle Fiber Structure

Muscles are composed of many FIBERS that are arranged in

bundles called FASCICLES

These fibers are found

within muscle cells,

called myocytes.Individual muscles are separated by FASCIA, which

also forms tendons.Three Different Types of Connective Tissue

= outermost layer, surrounds entire muscle.

EPIMYSIUM PERIMYSIUM = separates and surrounds fascicles

(bundles of muscle fibers)

ENDOMYSIUM =

surrounds each

individual muscle fiber This model of straws to represent fibers.

the muscles uses

Green = endomysium

Yellow = perimysium

Blue = epimysiumMuscle Layers

Muscle Fiber

Endomysium

Perimysium

EpimysiumPerimysium

Epimysium

Endomysium

What tissue surrounds the fascicles?Muscles Cells (Myocytes)

Sarcolemma = muscle fiber

membrane

Sarcoplasm = inner material

surrounding fibers (like

cytoplasm)

Sarcoplasmic Reticulum - transport

Myofibrils = individual parallel muscle fibers within sarcoplasmNucleus

Sarcolemma

Mitochondrion

Sarcoplasm

MyofibrilMyofibrils are made of

ACTIN = thin MYOSIN = thick filaments

filamentsMyofilaments ACTIN (thin) and MYOSIN (thick)

-- form dark and light bands

■A band = dArk • thick (myosin)

■I band = lIght • thIn (actin)E F

A= Sarcolemma

B = Sarcoplasm

C = Myofibrils

D = Myofilaments (Actin / Myosin)

F = Light (I) Band

E = Dark (A) Band

A

B

C

D

Click for

AnswersAssignment:

Sarcomere

ColoringIt is important to remember the hierarchy

fascicles

myofibrils

myofilaments

actin myosinTom’s Tests

Elevated Creatine Kinase (CK) levels

- if these levels are high, it means

that the muscles have deteriorated by

some abnormal process.

Based on his high levels of CK, a

is ordered.

muscle biopsy Blood is also sent for genetic testing.Healthy muscle tissue Tom’s muscle tissue.

What do you notice about Tom’s muscles?The sample of muscle is also stained to look

protein.

at the levels of DYSTROPHIN Dystrophin is a protein

located between the

sarcolemma and the

myofilaments.

It is a cohesive protein, that

maintains the structure of the

muscle fibers.Without the stabilizing

effects of dystrophin,

the muscle becomes

damaged, scar tissue

replaces muscle tissue

and muscles become

weaker over time.

Tom’s cells

have a defect

in these fibers.

sarcolemmaGenetic Tests show that Tom has a mutation in the gene that codes for dystrophin.

Tom’s Diagnosis: Duchenne Muscular Dystrophy (DMD)

Tom’s Story: ~5 min

Why is this disease

described as

“progressive?”

What will happen to

Tom over time?How did Tom get this disease?

*What are the chances that his

sister could have the disease?

This mutation is carried on the X

chromosome.

XD Xd

XD

YTom’s Prognosis - DMD is a fatal disease, as eventually muscle

weakness affects the heart and diaphragm.Treatment Options for DMD -

1. Corticosteroids to slow progression

2. Physical therapy to strengthen muscles

3. Surgery (tracheostomy, pacemakers)

EXONDYS 51

4. Gene Therapy - -newly approved for those with a specific mutation (exon51)

-repairs the gene that makes dystrophinHow Does Exon Skipping Work? (EXONDYS 51)

The dystrophin gene is made up of exons that are linked together to provide instructions for

making dystrophin. The dystrophin gene contains 79 exons, it is one of the largest genes in the

body. The 51st exon is missing, and the 50-52 exons cannot link together. If you skip over this

region, you creator a shorter, but functional protein.

Does not link

See Video on this pageMuscles and the Nervous System

Some disorders of the muscles relate to the signals between the

muscle and nerves - NEUROMUSCULAR JUNCTIONNEUROMUSCULAR JUNCTION - where a nerve and muscle

fiber come together

MOTOR END PLATE - folded area where muscle communicate

and neuron

SYNAPSE - gap between the neuron and motor end (synaptic cleft)

SYNAPTIC VESICLES - where neurotransmitters plate

are stored

*these are released into the cleft and tell

the muscle to contractNeuromuscular Junction

1. Neuron 2. Sarcolemma (or motor end plate)

3. Vesicle 4. Synapse 5. Mitochondria

6. Receptors 7. Acetylcholinevesicles

The neurotransmitter that cross the gap is ACETYLCHOLINE ,

which is stored in vesicles

ACH is broken down by CHOLINESTERASESLIDING FILAMENT THEORY (MODEL)

The theory of how muscle contracts is the sliding filament theory. The contraction

of a muscle occurs as the thin filament slide past the thick filaments.

What is needed:

ATP

Calcium

Myosin and Actin

Acetylcholine

CholinesteraseWellcome

Animation

5 min

Hank explains muscles and the sliding filament model.Sliding Filament (TabletopWhale)

Check out the animation at

http://tabletopwhale.com/2014/08/12/a-users-guide-to-muscles.html -Energy Source

-ATP is produced by CELLULAR RESPIRATION

which occurs in the mitochondria

Why do you

breathe more

when exercising?-Creatine phosphate increases

regeneration of ATP

* Only 25% of energy produced during

cellular respiration is used in metabolic

processes - the rest is in the form of HEAT.

- maintains body temperature.

Do you think these

supplements work

to increase muscle

growth? Why or

why not?Creatine kinase is elevated in

people who have suffered heart

attacks and people with DMD. It

leaks out of muscles that have

been damaged.

Biomarkers are substances that

can indicate damage to muscles.

They can be used to diagnose

diseases like DMD or to determine

if a patient is having a heart attack

(infarction)Muscles and Exercise

Muscle Fatigue - muscle

loses ability to contract after

prolonged use

Muscle Cramp - a sustained

involuntary contraction

Oxygen Debt - not have

enough oxygen causes

to accumulate in

the muscles → Soreness

lactic acid Magic School Bus:

Works Out

Season 3, Ep 9~4 minChanges in Muscles

Hypertrophy - muscles enlarge

Atrophy - muscles become small and

weak due to disuse

In patients with muscular dystrophy,

the muscles can become larger even

as they become weaker. This is due

to scar tissue and fat replacing

working muscle cells.Muscles and Death - What is rigor mortis?

A few hours after a person or animal dies, the joints of the body stiffen and

become locked in place. This stiffening is called rigor mortis. Depending on

temperature and other conditions, rigor mortis lasts approximately 72 hours.

Crime Scene InvestigationDisorders of the Muscular System

Tetanus causes cholinesterase to not break down the acetylcholine

in the synapse. This results in a person's muscles contracting and

not relaxing.

A tetanus shot must be

administered shortly after

exposure to the bacteria.

Once you develop

tetanus, there is no cure.Myasthenia Gravis?

- Means "grave muscular weakness."

- Autoimmune disease

- Acetylcholine receptors are damaged

Symptoms

● A drooping eyelid

● Blurred vision

● Slurred speech

● Difficulty swallowing

● Weakness / FatigueALS

ALS, or amyotrophic lateral

sclerosis, is a progressive

neurodegenerative disease.

The motor nerves degenerate

and stop sending messages to

the muscles, causing atrophy.

Symptoms get worse over time. A-myo-trophic comes from the Greek language.

"A" means no. "Myo" refers to muscle, and

"Trophic" means nourishment – "No muscle

nourishment." When a muscle has no

nourishment, it "atrophies" or wastes away.Muscular Dystrophy

Many forms which all cause a

weakening of the muscles

Myotonic

Duchenne

Becker

Oculopharyngeal

Distal

Limb-Girdle

What type does

Tom have?Poisons that Affect the Neuromuscular Junction

BOTULISMBotox?Strychnine

Lowers the threshold level

for an action potential,

making it more likely the

muscles will contract

Death occurs from

convulsions and asphyxiaCurare

flaccidity neuromuscular blocking agent - causes

in skeletal muscle by competing

with the neurotransmitter acetylcholine

Also used as an early form of anesthetic