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Biology 112 > Chapter 50.5 > Flashcards

Chapter 50.5 Flashcards

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1
Q

What is muscle activity

A

a response to nervous system input

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2
Q

What is required for muscle function

A

protein filaments physically interacting

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3
Q

What does muscle cell contraction rely on?

A

thin filaments and thick filaments interacting

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4
Q

thin filaments

A

actin

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5
Q

thick filaments

A

staggered arrays of myosin

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6
Q

moves bones and the body

A

vertebrate skeletal muscles

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7
Q

characterized by a hierarchy of smaller and smaller units

A

skeletal muscle

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8
Q

consists of a bundle of long fibers, each a single cell, running parallel to the length of the muscle

A

skeletal muscle

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9
Q

What is each muscle fiber itself

A

a bundle of smaller myofibrils arranged longitudinally

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10
Q

Why is skeletal muscle also called striated muscle

A

How the myofilaments are arranged creates a pattern of light and dark bands

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11
Q

the functional unit of a muscle

A

sarcomere

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12
Q

what is sarcomere bordered by

A

Z lines

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13
Q

Z lines

A

where thin filaments attach

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14
Q

thin and thick filaments slide past each other longitudinally, what are they powered by?

A

myosin molecules

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15
Q

What does the sliding of filaments rely on

A

interaction between actin and myosin

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16
Q

What does muscle contraction require

A

repeated cycles of binding and release

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17
Q

what does the “head” of a myosin molecule

A

binds to an actin filament

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18
Q

What does the binding of the actin filament and the head of a myosin molecule form

A

a cross-bridge (and pulls the thin filament toward the center of the sarcomere

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19
Q

what two things generage the ATP needed to sustain muscle c ontraction

A

glycolysis and aerobic respiration

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20
Q

regulatory protein that binds to actin strands on thin filaments when a muscle fiber is at rest

A

tropomyosin and the troponin complex

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21
Q

What does the binding of tropomyosin and actin strands prevent

A

actin and myosin from interacting

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22
Q

What must be true for a muscle fiber to contract

A

myosin-binding sites have to be uncovered

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23
Q

how do myosin-binding sites become uncovered

A

when calcium ions bind to the troponin complex and expose the myosin-binding sites

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24
Q

When does contraction occur?

A

when there’s a high concentration of Ca2+

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25
Q

When does muscle fiber contraction stop

A

when the concentration of Ca2+ is low

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26
Q

what is the stimulus leading to contraction of a muscle fiber

A

an action potential in a motor neuron that makes a synapse with the muscle fiber

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27
Q

What does the synaptic terminal of the motor neuron release

A

the neurotransmitter acetylcholine

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28
Q

what occurs when acetylcholine depolarizes the muscle

A

it produces an action potential

29
Q

How do action potentials travel to the interior of the muscle fiber?

A

along transvers (T) tubules

30
Q

what does the action potential along T tubules cause

A

sarcoplasmic reticulum (SR) to release Ca2+

31
Q

a specialized endoplasmic reticulum

A

sarcoplasmic reticulum

32
Q

binds to the troponin comlex on the thin filaments

A

Ca2+

33
Q

what does the binding of Ca2+ to the troponin complex do

A

exposes myosin-binding sites and allows the cross-bridge cycle to proceed

34
Q

What happens when motor neuron input stops

A

the muscle cell relaxes

35
Q

What do transport proteins in the SR do

A

pump Ca2+ out of the cytosol

36
Q

What do regulatory proteins bound to thin filaments do

A

shift back to the myosin-binding sites

37
Q

interferes with the excitation of skeletal muscle fibers

A

amyotrophic lateral sclerosis (ALS)

38
Q

an autoimmune disease that attacks acetylcholine receptors on muscle fibers

A

myasthenia gravis

39
Q

What does “contraction of a whole muscle is graded” mean

A

the extent and strength of its contraction can be voluntarily altered

40
Q

Two basic mechanisms by which the nervous system produces graded contractions

A
  1. varying the number of fibers that contract

2. varying the rate at which fibers are stimulated

41
Q

although each fiber is controlled by only one motor neuron, what could occur?

A

each motor neuron may synapse with multiple muscle fibers

42
Q

consists of a single motor neuron and all the muscle fibers it controls

A

a motor unit

43
Q

What does the strength of the resulting contraction depend on

A

how many muscle fibers the motor neuron controls

44
Q

how many motor units may be in the whole muscle

A

hundreds

45
Q

what does recruitment of multiple motor neurons result in

A

stronger contractions

46
Q

what does a twitch result from

A

a single action potential in a motor neuron

47
Q

what do more rapidly delivered action potentials produce

A

a graded contraction by summation

48
Q

a state of smooth and sustained contraction produced when motor neurons deliver a volley of action potentials

A

tetanus

49
Q

There are several distinct types of skeletal muscles, each of which…

A

is adapted to a particular function

50
Q

what are skeletal muscles classified by

A

either the source of ATP powering the muscle activity or the speed of muscle contraction

51
Q

what do oxidative fibers rely mostly on to generage ATP

A

aerobic respiration

52
Q

What do oxidative fibers have

A
  1. many mitochondria
  2. a rich blood supply
  3. a large amount of myoglobin
53
Q

a protein that binds oxygen more tightly than hemoglobin does

A

myoglobin

54
Q

what do glycolytic fibers use as their primary source of ATP

A

glycolysis

55
Q

What is the difference between glycolytic fibers and oxidative fibers

A

glycolytic fibers have less myoglobin and get tired more easily

56
Q

In poultry and fish, what is light meat composed of

A

glycolytic fibers

57
Q

In poultry and fish, what is dark meat composed of

A

oxidative fibers

58
Q

contract more slowly bus sustain longer contractions

A

slow-twitch fibers

59
Q

what are all slow-twitch fibers

A

oxidative

60
Q

contract more rapidly but sustain shorter contractions

A

fast-twitch fibers

61
Q

what are fast-twitch fibers

A

either glycolytic or oxidative

62
Q

What do most skeletal muscles contain in barying ratios

A

both slow-twitch and fast-twitch

63
Q

In additon to skeletal muscle, what do vertebrates also have

A

cardiac muscle and smooth muscle

64
Q

found only in the heart

A

cardiac muscle

65
Q

consists of striated cells electrically connected by intercalated disks

A

cardiac muscle

66
Q

what can cardia muscle do without neural input

A

generate action potentials

67
Q

found mainly in walls of hollow organs such as those of the digestive tract

A

smooth muscle

68
Q

contractions are relatively slow and may be initiated by the muscles themselves

A

smooth muscles

69
Q

what may smooth muscle contractions also be caused by

A

stimulation from neurons in the autonomic nervous system

Biology 112 (13 decks)

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