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Honors Anatomy & Physiology > Skeletal Muscle Tissue > Flashcards

Skeletal Muscle Tissue Flashcards

1
Q

What’s excitability

A

Respond to stimuli
Produce action potentials (they get muscles to contract)

(Relates to nervous system)

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2
Q

What’s contractility

A

Contracts forcefully when stimulated

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3
Q

What’s extensibility

What muscle has the greatest stretch?

A

Ability to stretch within limits

-smooth muscle greatest stretch

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4
Q

Properties of muscle tissue? (4)

A

Excitability
Contractility
Extensibility
Elasticity

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5
Q

What’s elasticity?

A

ability to return to original length & shape after contraction
(why when you pull a muscle, it takes a while to feel better bc it went past contraction)

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6
Q

What are the functions of skeletal muscle tissue?

A 
moves bones (produce movement)
help maintain body temp (generate heat)
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7
Q

What is involved in the functions of skeletal muscle?

description? how many muscles in body?

A 
700 muscles in body
elongated cells w/ many nuclei
striated (banded)
voluntary control
regeneration is limited (which is why it's hard to build back muscle)
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8
Q

Each skeletal muscle is a ____ organ

A

Separate

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9
Q

What does each skeletal muscle contain?

A

Contains 1000s of individual cells called muscle fibers

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10
Q

What are muscle fibers surrounded by? Penetrated by? description? how develop?

A 
Surrounded by connective tissue
Penetrated by blood vessels and nerves 
-long cylindrical cells w/ striations and multiple nuclei
-develop from mesoderm cells- myoblasts
-individual cells
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11
Q

Connective tissue coverings ?

A

3 layers that strengthen skeletal muscle

1) epimysium
2) perimysium
3) endomysium

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12
Q

What’s the epimysium

A

Outer most layer

Encircles each whole muscle

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13
Q

Perimysium ?

A

Surrounds groups of 10 to 100 muscle fibers

Separates fibers into bundles called fascicles

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14
Q

Endomysium

A

Separates each individual muscle fiber within the fascicles

-connective tissue that surrounds each muscle cell/fiber

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15
Q

Levels of organization within skeletal muscle? Largest to smallest

A 
Skeletal muscle (epimysium, yellow)
Fasicle (perimysium, purple) 
Muscle fiber (endomysium, green)
Myofibril (individual pencil)
Myofilaments (action & myosin, lead & wood)
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16
Q

Skeletal muscle fibers develop from what?

A

Mesoderm cells- myoblasts

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17
Q

Shape and size of skeletal muscle fibers ?

A

Long cylindrical

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18
Q

Do skeletal muscles have striations? Multiple or single nuclei?

A

Striations (bc myosin & actin over lap)

Multiple nuclei

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19
Q

Sarcolema?

A

(Anatomy of a skeletal muscle fiber)

Aka cell/plasma membrane

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20
Q

T tubules

what do they surround? what do they form? what does it contain? function?

A

Aka transverse tubules
Form a tunnel like network into the muscle fiber
-filled with extracellular fluid
-terminal cisternae
They are deep extensions of sarcolemma that surround each myofibril
carry action potentials

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21
Q

Sarcoplasm

contains?

A

aka cytoplasm
Contains: glycogen- used for ATP synthesis
myoglobin-red-colored protein, binds oxygen in muscle cells

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22
Q

Sarcoplasmic Reticulum

A

SR aka modified endoplasmic reticulum

-forms a weblike network surrounding myofibrils

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23
Q

Myofibrils

contains?

A

contractile unit of a muscle (make up muscle)
Contains 2 types of protein filaments
-thick & thin filaments

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24
Q

Thick and thin filaments? made of? what forms when together?

A

thick- made of protein myosin
thin-made of protein actin
together form light & dark bands (striations)

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25
Q

how are filaments arranged? what separates each?

A

arranged in units called sarcomeres

-Z line separate 1 sarcomere from another

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26
Q

What surrounds myofibrils? What does it do?

A

Sarcoplasmic Reticulum surrounds myofibirls, stores & releases Ca 2+ ions

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27
Q

Terminal Cisternae

A

enlarged sections of SR found beside each T tubule

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28
Q

What forms a triad?

A

2 terminal cisternae & 1 T tubule

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29
Q

What does the sarcomere structure involve?

A

I bands, A bands, H zone, M line, and it extends from 1 z line to another

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30
Q

A band description

A

region of myofibril’s striation w/ DARK appearance
made of myosin
contains overlapping thick and thin filaments, H zone, & M line

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31
Q

I band description

A

region of myofibril’s striation w/ LIGHT appearance
made of actin
contains only thin filaments
connect to Z lines

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32
Q

H zone

A

lighter stripe in center of dark A band in the region btwn thin filaments (consists of only myosin)
decreases in size when muscle contracts

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33
Q

M line

A

line in the center of H zone consisting of protein fibers special protein that binds thick filaments in place (connects thick filaments together)

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34
Q

Z disc

A

aka Z line
zig zag line bisecting I band, sarcomere stretches from 1 to the other
function: protein disc that anchors thin filaments & connects adjacent myofibrils

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35
Q

Structure of a myofibril

made of? what do they consist of?

A

each myofibrils made of thousands of myofilaments
myofilaments consist of
-contractile proteins
-regulatory proteins
-structural proteins
(contains 2, thick and thin, protein filaments)

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36
Q

what are the 2 types of myofilaments?

A

thick & thin

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37
Q

thick filaments contain and are made of?

A
  • bundles of contractile protein myosin

- Globular head- has an active site to bind w/ actin

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38
Q

thin filaments contain and are made of?

how does actin act?

A
  • composed of proteins actin, troponin, and tropomyosin

- Actin forms “bead like” strings w/ active sites to bind w/ myosin heads

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39
Q

Tropomyosin

made of? function?

A

Rope-like regulatory protein

Covers actin’s active sites

40
Q

troponin

made of? function?

A

Globular regulatory protein
Holds tropomyosin in place & assists turning contractions on & off
-molecule that has binding site for Ca ion

41
Q

Where motor neurons activates muscle fibers to contract

A

Called a neuromuscular junction NMJ

42
Q

definition of a neuromuscular junction

A

area where action potentials occur

43
Q

define synapse

A

region btwn neuron & target cell where action potential (stimulus) is transmitted

44
Q

define synaptic cell

A

aka cleft

space that separates a neuron & target cell

45
Q

define neurotransmitters

A

chemicals that carry the stimulus

46
Q

*** Steps in action potential (excitation & excitation-contraction coupling)

A

1) Action potential arrives at axon terminal
2) Calcium ions enter the axon terminal
3) Synaptic vesicles fuse to membrane of axon terminal & release ACh
4) ACh binds to receptor sites of the motor end plate
5) Motor end plate becomes depolarized w/ exchange of sodium ions across membrane (& potassium moves out of the muscle cell)
6) Action potential is initiated on the sarcolemma & propagates down into the T tubules
7) Ca ions are released from terminal cisternae
8) Muscle cell contracts

47
Q

what causes a skeletal muscle to contract?

A

motor neuron or action potential (bc of the impulses)

48
Q

What is the place called where a motor neuron stimulates a muscle cell?

A

neuromuscular junction

49
Q

Synaptic vesicles in the axon terminal of a motor neuron contain what neurotransmitter?

A

Acetylcholine (ACh)

50
Q

an action potential in the axon terminal of a motor neuron opens w/ what type of ion?

A

Calcium

51
Q

space btwn the axon terminal and motor end plate

A

synaptic cleft

52
Q

swollen distal end of the motor neuron

A

axon terminal

53
Q

muscle cell membrane

A

sarcolemma

54
Q

structures within the axon terminal that contain neurotransmitter acetylcholine

A

synaptic vesicles

55
Q

contractile unit of the muscle cell that extends from z line to the next

A

sarcomere

56
Q

structures within skeletal muscle cells that serve as reservoirs of calcium ions

A

terminal cisternae

57
Q

folded region of the sarcolemma at the neuromuscular junction

A

motor end plate

58
Q

*** What do Ca 2+ ions cause inside the axon terminal?

A

cause synaptic vesicles to release ACh into the synaptic cleft

59
Q

*** What happens to ACh after it is released into the synaptic cleft?

A

binds to receptor sites in the motor end plate (of a muscle cell, which causes ion channels to open)

60
Q

*** What happens to the ACh after it diffuses away from its receptor on the motor end plate?

A

causes depolarization or is broken down & return to axon terminal

61
Q

*** How is the neurotransmitter removed from the synaptic cleft?

A

1) diffuses away from receptor site & back up into axon terminal
2) broken down by the enzyme acetylcholinesterase

62
Q

What attaches muscle to bone?

A

tendons

63
Q

whole muscle is composed of muscle cells (fibers) grouped in bundles called _______

A

fascicles

64
Q

connective tissue that surrounds the whole muscle is the

A

epimysium

65
Q

connective tissue that surrounds each fascicle is the

A

perimysium

66
Q

connective tissue that surrounds each muscle cell is the

A

endomysium

67
Q

sites for ATP synthesis

A

mitochondria

68
Q

interconnected tubules of the ER that surround each myofibril

A

SR

69
Q

part of sarcolemma that carries action potentials

A

t tubule

70
Q

what is actin and myosin made out of ?

A

protein

71
Q

flexing the head of the thick filament provides what?

A

a power stroke

72
Q

what are the two parts of a myosin molecule?

A

head (2) and tail (1)

73
Q

cross bridge (myosin head) contains binding sites for what two molecules?

A

actin and ATP

74
Q

what 3 molecules make up a thin filament?

A

actin
tropomyosin
troponin

75
Q

what molecule in a thin filament has a binding site for myosin?

A

actin

76
Q

what molecule in a thin filament covers the binding site when not activated

A

tropomyosin

77
Q

what molecule in a thin filament has a binding site for calcium ions?

A

troponin

78
Q

function of tropomyosin?

A

covers binding sites on actin

79
Q

function of troponin?

A

attach to tropomyosin which causes tropomyosin to move off the binding sites on actin

80
Q

what causes tropomyosin to move away from myosin binding sites?

A

calcium ions binding to troponin

81
Q

what causes tropomyosin to cover back over actin binding sites?

A

when calcium releases

82
Q

2 roles of ATP in muscle contraction

A

1) attach to the myosin for power stroke

2) release energy and release myosin from actin

83
Q

what molecule is connected to the z line?

A

actin

84
Q

*** what shortens in muscle contraction

A

SARCOMERE & H ZONE

thin and thick filaments do not shorten

85
Q

sliding filament mechanism is also known as what?

A

crossbridge cycle

86
Q

*** describe the sliding filament/cross-bridge cycle

A

(starts as a relaxed muscle)

1) Release of CA 2+ from SR exposes binding sites on thin filament. Ca 2+ binds to troponin & tropomyosin is pulled aside
2) Cross-bridge binds actin to myosin
3) Cross-bridge pulls actin filament (POWER STROKE) and ADP & P release from myosin
4) New ATP binds to myosin, causing linkage to release (myosin releases from actin)

87
Q

*** What ion is most important in muscle contraction? Why?

A

Calcium
A skeletal muscle cell can only contract from the impulses from an action potential. Without calcium, the action potential in the axon terminal of a motor neuron would not be able to open, so no contraction would be possible bc ACh would not be released. (synaptic vesicles would not be able to release ACh into the synaptic cleft via exocytosis)

88
Q

*** Why are there striations in a skeletal muscle cell?

A

because the A band is made of overlapping actin & myosin. this formation of the thick and thin filaments forming light and dark bands in a myofibril causes striations.

89
Q

*** What does ACh do?

A

it is what triggers a muscle action potential

90
Q

Sarcomere

A

functional unit of contracttion in striated muscle that extends from z line to z line. considered that bc all components for contraction are contained within each sarcomere. contains I band, A band, H zone, M line, and Z line

91
Q

how is muscle tension caused?

A

contraction causes tension

92
Q

conductivity?

A

property of muscle tissue

- conducts impulse/carries stimulus through the muscle fiber (ability for nerve impulse)

93
Q

actin

A

protein that compoases the major portion of thin filaments

1 of the proteins that make up a myofibrils, has a binding site for myosin

94
Q

myosin

A

protein that composes major portion of thick filaments

1 of the proteins that make up a myofibril

95
Q

difference btwn SR and terminal cisternae?

A

SR is between the terminal cisternae and terminal cisternae is next to the T tubules

96
Q

structural and functional relationship btwn neurons and skeletal muscle fibers?

A

structural: synaptic cleft forms btwn the two
functional: neurons activate skeletal muscle to contract

Honors Anatomy & Physiology (45 decks)

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