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Honors Anatomy & Physiology > Skeletal Muscle Tissue > Flashcards

Skeletal Muscle Tissue Flashcards

(96 cards)

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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
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

Honors Anatomy & Physiology (45 decks)

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