Skeletal Muscle Tissue

Question 1

What are the myofiber types in skeletal muscle?

Answer 1

Type IA- slow red: high mitochondria, intense staining for oxidative enzymes, rich in NADH transferase, myoglobin and ATPase, oxidative phosphorylation used most.

Type II A- intermediate: resistance to fatigue, contracts faster than type I, uses both aerobic and anaerobic respiration. Intermediate staining for oxidative enzymes.

Type IIB- fast white: fatigues quickly, low staining for oxidative enzymes, anaerobic respiration, contracts more rapidly.

Question 2

Compare skeletal muscle to cardiac and smooth muscle.

Answer 2

Skeletal Cardiac Smooth

N- Multi Mono Mono

P- Periphery Central Central

S- Yes Yes No

I- Motor neuron Gap junctions ANS/Gaps

Question 3

What are the three types of tissue and what are the 3 types of muscle tissue?

Answer 3

Muscle, epithelial, connective, and nervous.

The three types of muscle are:

Cardiac
Skeletal
Smooth

Question 4

What is the hierarchy of skeletal muscle?

Answer 4

Epimysium-covers the muscle made up of fascicles

Perimysium- made up of fibroblasts and type I collagen, covers the fascicles or myofibers.

Endomysium- consists of a basal lamina and reticular fibers and covers the myofibril.

Question 5

What are the H,I,A, M, bands and Z lines?

Answer 5

H bands- myosin filaments, shorten during contraction.

I bands- actin filaments p, shorten during contraction.

A band - consists of only myosin, doesn’t move

M line- middle of myosin tails

Z line- end of sarcomere where actin attaches

Question 6

What is the purpose of creating phosphate?

Answer 6

Replenishes ATP levels during muscle contraction as a back up energy source.

Question 7

What is the structure of myosin?

Answer 7

It’s a dimeric protein with 2 heads at one end with binding sites for actin, ATP, and light chains.

Question 8

What is the structure of actin?

Answer 8

Polymer of G-actin

2 polymers wound in an alpha helix.

Question 9

What are actin associated molecules?

Answer 9

Troponin and tropomyosin

Question 10

What are the three types of troponin?

Answer 10

I-inhibits binding between actin and myosin

C- binds calcium ions

T- binds to tropomyosin

Question 11

What is A beta crystallin

Answer 11

A beta crystallin-heat shock protein that protects desmin from mechanical stress

Question 12

What is dystrophin?

Answer 12

Links alpha actinin/desmin complex to cytoplasmic side of the sarcolemma.

Reinforces sarcolemma during muscle contraction.

Question 13

What is dystroglycan complex?

Answer 13

Links dystrophin (intracellular) to laminin-2 (extracellular)

Question 14

What is alpha actinin?

Answer 14

Attaches actin to Z line

Question 15

What is Titin?

Answer 15

Extends from Z line to middle of H band and connects thick filaments to Z line.
Gives myosin elasticity-centers them

Question 16

What are Desmin intermediate filaments?

Answer 16

Surrounds the z line and Links myofibrils laterally to the sarcolemma.

Question 17

What is plectin?

Answer 17

Binds desmin filaments

Question 18

What is nebulin?

Answer 18

Regulates actin’s length.

Question 19

What is dystrophin?

Answer 19

Gives stability during muscle contraction.

Question 20

What is muscular dystrophy?

Answer 20

Degeneration of skeletal muscle due to lack of dystrophin- Duchenne’s

Or abnormal dystrophin- Becker’s

Question 21

What are satellite cells?

Answer 21

Stem cells that repair and maintain skeletal muscle that already exists, doesn’t make new muscle.

Question 22

What is a neuromuscular spindle? And what are its parts?

Answer 22

Sensory portion of the muscle.

Extrafusal-skeletal muscle fibers
Intrafusal- sensory region in the nuclear bag.

Question 23

What type of neurons innervate the neuromuscular spindle?

Answer 23

Alpha- innervates extrafusal
Gamma- innervates intrafusal fibers
Primary and secondary afferent- send signals back to the nervous system.