Physiology of Muscles

Epimysium

Is a connective tissue that covers the muscle belly.

Fascicles

Are bundles of muscle fibers found inside the muscle belly.

Perimysium

tissue covering the fascicles.

Muscle fiber (cell)

individual muscles found inside the fascicles.

Endomysium

Connective tissue covering the muscle fibers. It is an areolar connective tissue

Sarcoplasmic Reticulum

calcium storage factory (filamentous endoplasmic reticulum structure)

Sarcomere

Structural and functional unit. From Z disc to Z disc.

Sarcolemma

plasma membrane structure.

Myofibril

Many different connections of thick and thin filaments and accessory proteins.

Z-Disc

Main protein that makes up the Z-Disc is called Alpha-actinin.

Thick Filament

is a protein structure composed of myosin, which consists of a tail and two globular heads, each with an ATP binding site and an actin binding site.

Titin

Links/Anchors the thick filament to the Z disc. Also Anchors to the M-line to stabilize the structure of the thick filaments.

M-Line

Made up of Myomesin, C-proteins, and Creatine Kinase (functional enzyme).

M-Line

Connects to the Titin, and the Titin is connecting the thick filament to the Z-disc. Acts as an accessory protein that can help to stabilize the thick filament. Runs right down the middle of the sarcomere.

A-Band

Is the entire length of the thick filament. From one end of the thick filament to the other ON THE SAME SARCOMERE

from Z-disc to Z-disc.

What determines a Sarcomere?

I-Band

Distance between the ends of two thick filaments from different sarcomeres.

Myosin

Protein coming off of a thick filament. It is made up of the regions: a tail, neck, and two heads.

-Head

-Myosin ATPase

-ADP

-Inorganic Phosphate

The ______ is what binds into the Actin active sites, allowing for moving/sliding of myofilaments. It has an enzyme component called _____________ which cleaves ATP into ____ and ________ ________.

Regulatory light chain

can undergo Phosphorelation and help to change the activity of the Myosin. (Binds the phosphate and change the overall shape to play a role in contraction.

Essential light chain

Structurally stabilizes the myosin head and neck.

Thin Filament

Is anchored to the z-disc by the black protein called Nebulin.

Nebulin

Black protein running from the Z-disc all the way the length of the thin filament. Acts as a supportive structural protein

H-zone

Distance between thin filament to thin filament on the same sarcomere.

Actin

Is a supermolecular helix consisting of G-Actin and F-Actin

Globular Actin (G-Actin)

Is a monomer.Polymerizes into F-Actin

Filamented Actin (F-Actin)

Polymerized G-Actins.

Active Sites

Where Myosin binds to cause contractions.

Tropomyosin

Is a chord-like protein. When the muscle is at rest, blocks the active sites on Actin preventing the myosin heads from binding. Covers the active sites of the Actin during rest.

Troponin

Has three different sites. Are good markers for certain types of heart damage. Indicator for heart attack.

Troponin C

Site that binds to Calcium.

Troponin T

Site that binds to Tropomyosin.

Troponin I

Site that binds to Actin.

-Troponin

-Tropomyosin

-Myofilaments

Excitation-Contraction Coupling Example:

When Ca binds into the __________, it changes the shape of the Troponin T component. And when it changes the shape of the Troponin T component, it pulls on the ____________, and when it pulls on the Tropomyosin, it opens up the active sites (of the Actin) for the myosin heads to plug in and cause the movement of the ____________.

Dystrophin

Links the Actin to the Extracellular membrane/sarcolemma

Sarcolemma

Is the outer cell/extracellular membrane of a muscle cell.

Muscular Dystrophy

Caused by a mutation in the Dystrophin gene, when they don't produce any dystrophin.

x-linked recessive disorder (more common in males)

Muscular Dystrophy is usually an?

-Duchenne

-Becker

2 Most Common Muscular Dystrophies:

Duchenne

more severe Muscular Dystrophies, develops at age 5-6 years old. No Dystrophin produced. Nonsense mutation.

Becker

less severe Muscular Dystrophies, develops my age 10-20 years old. Due to a misfolded protein. Missense mutation.

Dilated Cardiomyopathy

Caused by dystrophin. The cardiac muscles become very dilated and floppy.

-Physical Treatment

-Glucocorticoid Therapy

Treatment for Dystrophy: