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Physiology-Exam 3 > Muscle > Flashcards

Muscle Flashcards

1
Q

The plasma membrane of a skeletal muscle fiber is called the

A

sarcolemma

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2
Q

The contractile unit within a skeletal muscle fiber is the

A

myofibril

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3
Q

Within one myofibril there are multiple

A

sarcomeres

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4
Q

A sarcomere runs from one ___ to the next

A

Z disc

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5
Q

The ____ filament within the sarcomere runs from Z disc to Z disc and allows stretch and recoil

A

elastic

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6
Q

The ___ filament is made up of 2 F actin molecules, tropomyosin, and troponin

A

actin

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7
Q

The ___ filament has two heads, two heavy chains, and two light chains

A

myosin

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8
Q

F actin is made up of

A

multiple G actin molecules linked together

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9
Q

Tropomyosin covers the ____

A

active sites of G actin

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10
Q

When Ca++ binds to troponin what happens?

A

The tropomyosin is moved and the active sites are uncovered. The myosin heads can then bind to the active sites and contraction can occur

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11
Q

The light chains contain ____ to provide energy for movement

A

ATPase enzymes

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12
Q

For the NMJ, the presynaptic terminals of a somatic motor neuron axon form a ____ with the sarcolemma of a muscle fiber

A

chemical synapse (Ach)

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13
Q

In the sarcolemma, ACh binding opens ____ that allow simultaneous passage of Na+ into the ____ and K+ out of the _____; more Na+ diffuses in than K+ out–depolarization can occur

A

ion channels; muscle fiber; muscle fiber

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14
Q

The ________ occurs as more Na+ moves into the muscle cell than K+ out of the muscle cell; depolarization causes voltage-gated sodium channels to open

A

end plate potential

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15
Q

In a relaxed muscle, Ca++ is doing what and tropomyosin is doing what?

A

Calcium is not attached to troponin and tropomyosin is blocking the binding sites on actin

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16
Q

In a stimulated muscle, Ca++ is doing what and tropomyosin is doing what?

A

Calcium moves into the sarcoplasm from the SR and attaches to the troponin which moves the tropomyosin to unblock the binding sites and myosin can then attach to actin

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17
Q

What is the first step of excitation-contraction coupling?

A

AP is propagated along the sarcolemma and down the T tubules; AP causes voltage-sensitive tubule proteins to change shape, which causes Ca++ release channels in the SR to open

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18
Q

What are steps 2-6 of excitation-contraction coupling?

A

2-calcium is released into sarcoplasm
3-calcium released binds to troponin
4-troponin moves tropomyosin to expose actin active sites
5-myosin heads attach to the actin to form cross-bridge
6-a phosphate is released from the myosin head

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19
Q

What are steps 7-10 of e-c coupling?

A

7-the hinge of the myosin bends resulting in power stroke causing the actin to move toward the center of the sarcomere which decreases the length of the sarcomere and causes contraction
8-after power stroke, ADP is released from myosin head
9-an ATP molecule binds to the myosin head and the myosin head can detach from the G actin active site
10-ATP is broken down into ADP and P by ATPase in the myosin light and the head of myosin returns to its original position=recovery stroke

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20
Q

Energy is required for what movement of the muscle?

A

contraction and relaxation

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21
Q

What needs to happen to calcium in order for a muscle to relax?

A

must be actively transported from the sarcoplasm back into the sarcoplasmic reticulum, and as it decreases the calcium diffuses away from the troponin, so tropomyosin returns and covers the active sites

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22
Q

If a single muscle fiber is stimulated by a single action potential it produces a ___

A

twitch

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23
Q

If the conditions within a cell are constant, then an individual muscle fiber will produce twitches of equal tension for _____

A

every action potential

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24
Q

If a muscle fiber is stimulated by multiple action potentials far apart enough in time, then ____

A

multiple twitches occur

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25
Q

As the ____ of action potentials increases, the fiber does not have enough time to relax between twitches and there is a summation of twitch tension

A

frequency

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26
Q

___ is the level at which the muscle can maximally contract

A

tetanus

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27
Q

What is a motor unit composed of?

A

one somatic motor neuron and all of the skeletal muscle fibers it innervates

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28
Q

When a somatic motor neuron is activated, all of the muscle fibers it innervates will ___

A

contract

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29
Q

Whole muscle contractions are produced by ______

A

asynchronous activation of motor units

30
Q

Whole muscle tension increases as more _____ are recruited

A

motor units

31
Q

Muscles with fine motor control have ___ motor units innervating a _____ of muscle fibers

A

small; small number

32
Q

Muscles with gross motor control have ___ motor units innervating a ____ of muscle fibers

A

large; large number

33
Q

When a muscle at rest is stimulated by stimuli of a constant strength at a low frequency that allows the muscle to relax between stimuli it is called

A

treppe

34
Q

In treppe, the first few contractions are ___ and then the amount of tension produced by the muscle ____

A

weak; increases to maximum

35
Q

____ contraction is when the muscle contracts and tension is produced, but the muscle stays the same length

A

isometric

36
Q

___ contraction is when the muscle contracts and tension is produced, and the muscle length changes

A

isotonic

37
Q

In isometric contraction, the force of resistance is ___ to the force of the contraction

A

equal

38
Q

In concentric isotonic muscle contraction, the muscle contracts and ___

A

shortens

39
Q

In eccentric isotonic muscle contraction, the muscle contracts and ____

A

lengthens

40
Q

In concentric muscle contraction, the force of resistance is ___ the force of the contraction

A

less than

41
Q

In eccentric muscle contraction, the force of resistance is ___ the force of the contraction

A

more than

42
Q

Which type of muscle contraction is most important in muscle building?

A

eccentric

43
Q

___ is the decreased capacity to do work

A

fatigue

44
Q

_____ occurs when muscles can still function, but individual perceives that they cannot

A

psychological fatigue

45
Q

____ occurs when there is a depletion of ATP in a muscle

A

muscular fatigue

46
Q

____ occurs when there is a depletion of ACh in a neuron; reduction in the ability of UMN to stimulate LMN or reduction in the ability of LMN to stimulate a muscle fiber

A

synaptic fatigue

47
Q

Muscle fiber type is based on _____

A

contraction speed

48
Q

Different muscle fibers have different myosin ATPase enzymes that do what?

A

break down ATP to ADP and P

49
Q

Type I muscle fibers have ____ myosin ATPase

A

slower

50
Q

Type II muscle fibers have ____ myosin ATPase

A

faster

51
Q

This muscle fiber type is resistant to fatigue and has high capacity for aerobic respiration

A

type I

52
Q

What are the muscle fiber characteristics for Type I?

A

small diameter, small motor unit, small motor neuron

53
Q

This muscle fiber type contracts rapidly and is moderately resistant to fatigue. It is adapted for both aerobic and anaerobic fatigue

A

type IIa

54
Q

What are the muscle fiber characteristics for Type IIa?

A

intermediate diameter, intermediate motor unit, intermediate motor neuron

55
Q

This muscle fiber type contracts rapidly but fatigues quickly and is adapted for anaerobic respiration

A

type IIx/b

56
Q

What are the muscle fiber characteristics for Type IIb/x?

A

large diameter, large motor unit, large motor neuron

57
Q

Muscles can have different fiber types; fibers within a motor unit are ___ fiber type

A

same

58
Q

What is measured in the muscle as a means of determining fiber type?

A

carnosine (antioxidant dipeptide)

59
Q

In smooth muscle, contraction occurs in ___ direction

A

multiple

60
Q

Depending on the function of the smooth muscle, it is either ____ or contracts when stimulated by _____ or ____

A

autorhythmic; autonomic neuron or hormone

61
Q

In single-unit smooth muscle there are ___ gap junctions

A

multiple

62
Q

In multi-unit smooth muscle there are ___ gap junctions

A

single cells or small groups of cells with

63
Q

A ____ unit smooth muscle may be autorhythmic, NT, or hormone activated

A

single

64
Q

A ___ unit smooth muscle needs NT or hormone to activate

A

multiunit

65
Q

Instead of having T-tubules, smooth muscle has

A

multiple caveolae–infoldings of sarcolemma

66
Q

In smooth muscle, the sarcoplasmic reticulum is ____

A

less developed and lacks a specific pattern

67
Q

When the cell is depolarized in smooth muscle, where is calcium?

A

extracellular Ca++ enters the cell through voltage-regulated Ca++ channels and some intracellular calcium is released from the SR

68
Q

Smooth muscle lacks both ____ and ___

A

troponin and tropomyosin

69
Q

What does calmodulin do in smooth muscle?

A

binds to calcium, activates myosin kinase and allows myosin to bind to actin and activates myosin ATPase and the cross-bridge cycle is similar to what happens in skeletal muscle

70
Q

The formation of cross-bridges is ___ in smooth muscle than in skeletal muscle

A

slower

71
Q

How does smooth muscle relax?

A

1-AP stop
2-Ca channels close
3-Ca is actively transported out of cells or back into SR
4-Ca dissociates from calmodulin
5-Calmodulin dissociates from myosin kinase and enzyme becomes inactivated
6-then myosin phosphatase removes the P from the myosin head and mysoin can’t bind to actin any longer

Physiology-Exam 3 (4 decks)

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