Skeletal Muscle Tissue Flashcards Preview

Honors Anatomy & Physiology > Skeletal Muscle Tissue > Flashcards

Flashcards in Skeletal Muscle Tissue Deck (96):
1

What's excitability

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

(Relates to nervous system)

2

What's contractility

Contracts forcefully when stimulated

3

What's extensibility
What muscle has the greatest stretch?

Ability to stretch within limits
-smooth muscle greatest stretch

4

Properties of muscle tissue? (4)

Excitability
Contractility
Extensibility
Elasticity

5

What's elasticity?

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)

6

What are the functions of skeletal muscle tissue?

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

7

What is involved in the functions of skeletal muscle?
description? how many muscles in body?

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)

8

Each skeletal muscle is a ____ organ

Separate

9

What does each skeletal muscle contain?

Contains 1000s of individual cells called muscle fibers

10

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

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

11

Connective tissue coverings ?

3 layers that strengthen skeletal muscle
1) epimysium
2) perimysium
3) endomysium

12

What's the epimysium

Outer most layer
Encircles each whole muscle

13

Perimysium ?

Surrounds groups of 10 to 100 muscle fibers
Separates fibers into bundles called fascicles

14

Endomysium

Separates each individual muscle fiber within the fascicles
-connective tissue that surrounds each muscle cell/fiber

15

Levels of organization within skeletal muscle? Largest to smallest

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

16

Skeletal muscle fibers develop from what?

Mesoderm cells- myoblasts

17

Shape and size of skeletal muscle fibers ?

Long cylindrical

18

Do skeletal muscles have striations? Multiple or single nuclei?

Striations (bc myosin & actin over lap)
Multiple nuclei

19

Sarcolema?

(Anatomy of a skeletal muscle fiber)
Aka cell/plasma membrane

20

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

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

21

Sarcoplasm
contains?

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

22

Sarcoplasmic Reticulum

SR aka modified endoplasmic reticulum
-forms a weblike network surrounding myofibrils

23

Myofibrils
contains?

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

24

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

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

25

how are filaments arranged? what separates each?

arranged in units called sarcomeres
-Z line separate 1 sarcomere from another

26

What surrounds myofibrils? What does it do?

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

27

Terminal Cisternae

enlarged sections of SR found beside each T tubule

28

What forms a triad?

2 terminal cisternae & 1 T tubule

29

What does the sarcomere structure involve?

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

30

A band description

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

31

I band description

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

32

H zone

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

33

M line

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

34

Z disc

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

35

Structure of a myofibril
made of? what do they consist of?

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

36

what are the 2 types of myofilaments?

thick & thin

37

thick filaments contain and are made of?

-bundles of contractile protein myosin
-Globular head- has an active site to bind w/ actin

38

thin filaments contain and are made of?
how does actin act?

-composed of proteins actin, troponin, and tropomyosin
-Actin forms "bead like" strings w/ active sites to bind w/ myosin heads

39

Tropomyosin
made of? function?

Rope-like regulatory protein
Covers actin's active sites

40

troponin
made of? function?

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

41

Where motor neurons activates muscle fibers to contract

Called a neuromuscular junction NMJ

42

definition of a neuromuscular junction

area where action potentials occur

43

define synapse

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

44

define synaptic cell

aka cleft
space that separates a neuron & target cell

45

define neurotransmitters

chemicals that carry the stimulus

46

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

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

what causes a skeletal muscle to contract?

motor neuron or action potential (bc of the impulses)

48

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

neuromuscular junction

49

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

Acetylcholine (ACh)

50

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

Calcium

51

space btwn the axon terminal and motor end plate

synaptic cleft

52

swollen distal end of the motor neuron

axon terminal

53

muscle cell membrane

sarcolemma

54

structures within the axon terminal that contain neurotransmitter acetylcholine

synaptic vesicles

55

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

sarcomere

56

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

terminal cisternae

57

folded region of the sarcolemma at the neuromuscular junction

motor end plate

58

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

cause synaptic vesicles to release ACh into the synaptic cleft

59

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

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

60

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

causes depolarization or is broken down & return to axon terminal

61

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

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

62

What attaches muscle to bone?

tendons

63

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

fascicles

64

connective tissue that surrounds the whole muscle is the

epimysium

65

connective tissue that surrounds each fascicle is the

perimysium

66

connective tissue that surrounds each muscle cell is the

endomysium

67

sites for ATP synthesis

mitochondria

68

interconnected tubules of the ER that surround each myofibril

SR

69

part of sarcolemma that carries action potentials

t tubule

70

what is actin and myosin made out of ?

protein

71

flexing the head of the thick filament provides what?

a power stroke

72

what are the two parts of a myosin molecule?

head (2) and tail (1)

73

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

actin and ATP

74

what 3 molecules make up a thin filament?

actin
tropomyosin
troponin

75

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

actin

76

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

tropomyosin

77

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

troponin

78

function of tropomyosin?

covers binding sites on actin

79

function of troponin?

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

80

what causes tropomyosin to move away from myosin binding sites?

calcium ions binding to troponin

81

what causes tropomyosin to cover back over actin binding sites?

when calcium releases

82

2 roles of ATP in muscle contraction

1) attach to the myosin for power stroke
2) release energy and release myosin from actin

83

what molecule is connected to the z line?

actin

84

*** what shortens in muscle contraction

SARCOMERE & H ZONE
thin and thick filaments do not shorten

85

sliding filament mechanism is also known as what?

crossbridge cycle

86

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

(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

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

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

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

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

*** What does ACh do?

it is what triggers a muscle action potential

90

Sarcomere

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

how is muscle tension caused?

contraction causes tension

92

conductivity?

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

93

actin

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

myosin

protein that composes major portion of thick filaments
1 of the proteins that make up a myofibril

95

difference btwn SR and terminal cisternae?

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

96

structural and functional relationship btwn neurons and skeletal muscle fibers?

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