DPT 5010 Muscle Physiology

Question 1

Muscle Contraction

Answer 1

Activation of force-generating cross-bridges between actin & myosin.

Question 2

Motor Neurons

Answer 2

nerve cells whose axon innervates skeletal muscles

Question 3

Motor Unit

Answer 3

A motor neuron plus the muscle fibers it innervates.

Question 4

All or nothing

Answer 4

AP stimulates all fibers in motor unit to contract.

It is all or nothing. NOT a graded response.

Question 5

Twitch

Answer 5

response of a single muscle fiber or motor unit to a single action potential.

Question 6

Summation

Answer 6

Increase in muscle tension from successive action potentials

Question 7

Tetanus

Answer 7

Maintained contraction in response to repetitive stimulation.

Question 8

Muscle Recruitment

Answer 8

process of increasing the # of motor units that are active @ a given time

More motor neurons = more motor units = more muscle tension

Smallest motor neurons are recruited first.

Question 9

Fiber Length

Answer 9

More sarcomeres = more shortening

Length of fibers is the result of fiber arrangement

Question 10

Parallel vs. Pennate

Answer 10

Parallel- usu longer –> can shorten more
> joint excursion

Penate- usu shorter;

Question 11

Factors Influencing Muscle Force

Answer 11

1. Muscle size
2. Muscle moment arm
3. Stretch or Length/Tension
4. Contraction Velocity
5. Fiber type
6. Level of Fiber recruitment

Question 12

Muscle Strength

Answer 12

Function of the # of cross-bridges formed

Optimal force= when full length of actin strand in contact w/ myosin (resting length of muscle)