Muscle and Nerve Histology

Question 1

Anatomy of myosin (thick filaments)

Answer 1

Contains 2 heavy chains w/ globular heads and 2 light chains.
The heavy chains have Actin binding sites with ATPase domains.
Chains held together via Titin proteins connected to Z disk.

Question 2

Actin (thin filaments)

Answer 2

Made of F-actin monomers.
Tropomyosin strands wrap between actin strands. Troponin sits on tropomyosin stabds and covers myosin binding sites on actin.

Question 3

Nebulin

Answer 3

Actin binding protein that regulates its length. Considered “ruler” of actin.

Question 4

Sarcomere components (5)

Answer 4

M line: attachment site for myosin.
Z disk: separates sarcomeres. Attachment site for actin and titin.
H band: space on ether side of of M line where there is no actin.
A band: distance from the end of one myosin head to the head of the opposite mysoin head.
I band: space on either side of the Z disk where there is no myosin.

Question 5

Muscle contraction overview

Answer 5

Myosin binds actin once Ca2+ binds troponin and reveals the binding site.

Question 6

Sliding filament model

Answer 6

Thin filaments slide past thick filaments.

Z disks shorten.

Question 7

Type I muscle fibers

Answer 7

Slow, less powerful.
Many mitochondrion.
Abundant myoglbin.
Nt easily fatigued.
For aerobic respiration.

Question 8

Type IIA muscle fibers

Answer 8

Fast, intermediate contraction.
Many mitochondrion.
Many myoglobin.
Intermediate fatigability.
Intermediate aerobic respiration.

Question 9

Type IIB muscle fibers

Answer 9

Fast, powerful contraction.
Few mitochondrion.
Few myoglobin.
Rapid fatigability.
Anaerobic respiration.

Question 10

Neuromuscular spindle apparatus function

Answer 10

Reflective response to prevent overstretching of a muscle.

Question 11

Extrafusal muscle fibers

Answer 11

Contract the muscle.

Question 12

Intrafusal muscle fibers

Answer 12

Sense length and rate of change of muscle.

Question 13

Type Ia sensory nerve fibers

Answer 13

Affarent innervation of intrafusal fibers.

Question 14

a-motor nerve fibers

Answer 14

Efferent innervation of extrafusal muscle fibers. Receive signal from type Ia.

Question 15

g-motor nerve fibers

Answer 15

efferent innervation of intrafusal muscle fibers. Receive signal from type Ia.