Anatomy of Muscle

Question 1

Structure of skeletal muscle

Answer 1

Epimysium separates into fascicles

Each fascicle is surrounded by a perimysium

Each muscle fiber within a fascicle is surrounded by endomysium

Question 2

Where is alpha-actinin located?

Answer 2

Z line

Question 3

During contraction, which zones remain the same size?

Answer 3

A band

Question 4

What is a T tubule?

Answer 4

In skeletal muscles, it penetrates all levels of muscle fibers and are located on adjacent terminal cisternae at A-I junctions

Question 5

What is a triad?

Answer 5

The complex of T tubule and two adjacent terminal cisternae.

Important for extracellular events (nerve stimulation) with intracellular response (Ca2+ release) that lead to muscle contraction

Question 6

Types of skeletal muscle fibers?

Answer 6

Type I - slow oxidative
Type iia - fast oxidative glycolytic
Type iib - fast glycolytic

Question 7

Contraction characteristics about the different skeletal muscle fibers?

Answer 7

Type I - slow, not easily fatigues
Type iia - fast, not easily fatigued
Type iib - fast, easily fatigued

Question 8

What are intercalated discs composed of?

Answer 8

Fascia adherens
Maculae adherentes (desmosomes)
Gap junctions

Question 9

Structure of smooth muscle

Answer 9

No T system - instead have caveolae
No Z lines - instead have dense bodies/plaques containing alpha-actinin which anchor both thin and intermediate filaments
No sarcomeres
No myofibirls
Abundant Gap Junctions

Question 10

What are the regenerations of the different muscles like?

Answer 10

Skeletal - restrictive
Smooth muscle - extensive
Cardiac muscle - perhaps some limited