Muscle physiology

Question 1

name the different phases of muscle contraction?

Answer 1

1) resting and energized
2) excitation and contraction coupling
3) contraction (power stroke)
4) recharge
5) relaxation

Question 2

what is the size principle?

Answer 2

Motor units are recruited in order by size

Question 3

what are the characteristics of type I muscle fibers?

Answer 3

• more mitochondria
• more aerobic enzymes
• higher capillary density (O2 delivery)
• more myoglobin
• fatigue resistant

Question 4

What are the characteristics of type II muscle fibers?

Answer 4

• all the opposite of type I

- greater acute force production

Question 5

Describe proprioception

Answer 5

Proprioception is the sense of the relative position of neighboring parts of the body.

Question 6

what 2 structures are key to proprioception?

Answer 6

Muscle Spindles and GTOs

Question 7

what are muscle spindles? what is their function?

Answer 7

Modified muscle fibers: serve to regulate muscle contraction by responding to the lengthening of the muscle body (deformation stimulates sensory neuron; motor neuron signals muscle shortening)

Question 8

where are muscle spindles located?

Answer 8

In the muscle belly itself

Question 9

what and where are GTOs?

Answer 9

proprioceptors located in tendons near the myotendinous junction.

Question 10

what is the function of GTOs?

Answer 10

protective mechanism: the sensory neuron of the GTO stimulate an inhibitory interneuron which then inhibits the motor neuron, stopping muscle from contracting

Question 11

what is the innervation ratio?

Answer 11

efferent neurons: innervated fibers

Question 12

how is force production regulated? (force gradation)

Answer 12

rate coding or motor recruitment

Question 13

describe force gradation

Answer 13

Firing rate: overlapping action potentials will result in greater force (tetanus). If a small amount of force is required, then there will be more time between the synapses.

Question 14

explain motor recruitment

Answer 14

depending on how much force is needed different numbers of motor units are recruited.

Question 15

define motor unit

Answer 15

a single efferent neuron and all the muscle fibers it innervates

Question 16

how does an efferent neuron influence the fibers

it innervates?

Answer 16

the type of fiber (fast or slow twitch; I or II) is dependent on the kind of efferent neuron that innervates it

Question 17

afferent neurons

Answer 17

transmit information from the receptors to the CNS

Question 18

transmit information from the CNS to the muscles

Answer 18

efferent

Question 19

2 primary phases of nerve stimulation

Answer 19

depolarization and repolarization

Question 20

what is the myelin sheath? what is it’s purpose?

Answer 20

fatty covering of the axon. conducts the action potential faster down toward the NMJ

Question 21

Motor unit activation is determined by a ________

Answer 21

threshold

Question 22

describe the all or nothing principle

Answer 22

it is not possible to almost reach threshold and create some force production or over achieve threshold and create more force production. Only when threshold is reached does it produce and effect, and that effect is always of the same magnitude

Question 23

Slight relaxation between action potentials

Answer 23

incomplete tetanus

Question 24

action potential at the nerve terminal causes the release of _____________.

Answer 24

acetylcholine

Question 25

3 types of connective tissue in the muscle

Answer 25

Epimysium, Perimysium, Endomysium

Question 26

what connects the myosin to the Z line?

Answer 26

titin