Phys - Skeletal Muscle

Question 1

Which regions shorten during contraction?

Answer 1

H zone (disappears)
I band

Question 2

Troponin T

Answer 2

Binds troponin complex to tropomyosin

Question 3

Troponin I

Answer 3

Binds myosin to actin

Question 4

Troponin C

Answer 4

Binding site for Ca++

Question 5

Titin

Answer 5

Connects Z line to M line

Connectin

Acts as a spring, contributes to elasticity of muscle

Question 6

Dystrophin

Answer 6

Scaffolding for myofibrils

Associated with transmembrane sarcoglycans

Question 7

Skeletal muscle resting Em

Answer 7

-90mV

Question 8

Action potentials of skeletal muscles

What is released?
Receptors?

Answer 8

Acetylcholine is released

Nicotinic receptor

Question 9

Cross-bridge cycling

Answer 9

1. Actin binding
2. Power stroke
3. ATP binding and cross bridge detachment
4. ATP hydrolysis

Question 10

What happens to the cross bridges?

Answer 10

They do not detach

Rigor

Question 11

What happens if Ca++ transported into the SR is inhibited?

Answer 11

The muscle remains contracted

Question 12

What causes the myosin head to “re-cock”?

Answer 12

ATP hydrolysis to ADP and Pi

Question 13

The velocity of muscle shortening is inversely related to the ___

Answer 13

Initial load

Question 14

Isometric contraction

Answer 14

No external shortening
Velocity = 0

The load exceeds the ability to create tension

Question 15

Twitch contraction

Answer 15

Single contractile event

Question 16

Isotonic contraction

Answer 16

External shortening

The load is less than the ability to create tension

Concentric contraction

Question 17

Eccentric contraction

Answer 17

Contraction with external lengthening

Example: going down stairs

Question 18

What is a motor unit?

Answer 18

A single alpha motor neuron and all the muscle fibers it innervates

Question 19

Motor neurons and muscle fibers are recruited from ___ to ____

Answer 19

Smallest to largest

*this permits development of smooth, graded increases in muscle tension

Question 20

Are action potentials more easily elicited in small or large neuron cell bodies?

Answer 20

Small