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anatomy final exam prep > muscle tissue > Flashcards

muscle tissue Flashcards

1
Q

what are the functions of muscle tissue

A
  • produce movements of skeleton
  • maintain posture and body position
  • stabilize joints
  • generate heat
  • store and move things through body
  • serve as nutrient reserve
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2
Q

what are the characteristics and properties of muscular tissue

A
  • excitable
  • contractible
  • extensibility
  • elasticity
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3
Q

what does excitable mean

A

has the ability to respond to a stimuli by producing action potentials

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4
Q

what is contractility

A

ability to contract when stimulated by an action potential

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5
Q

what is extensibility

A

ability to stretch without being damaged

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6
Q

what is elasticity

A

ability to return to its original shape

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7
Q

what are the characteristics of muscle

A
  • organs made up of muscles, connective tissues and nerve tissue
  • all have one artery and veins
  • has a nerve ending
  • they span a joint and attach to 2 bones
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8
Q

what is the basis of the organization of a muscle

A
  • each skeletal muscle is a separate organ composed of 100s of muscle fibers –> cells
  • a skeletal muscle contains CT wrapped around muscle fibers, blood vessels and nerves
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9
Q

what are the 3 layers of connective tissue involved in the organization of a muscle

A

epimysium
perimysium
endomysium

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10
Q

what is epimysium (also known as a fascia)

A
  • the outer layer of CT
  • the membrane that surrounds the whole muscle + acts as a covering
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11
Q

what is perimysium

A
  • the membrane that surrounds and wraps around 100s of muscle fibers into bundles (fascicles)
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12
Q

what is a fascicle

A
  • bundle of muscle fibers
  • a muscle is define as a group of fascicles working together
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13
Q

what is endomysium

A
  • is inside each fascicle
  • wraps around each individual muscle fiber
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14
Q

what is the basis of the organization of a muscle fiber

A

each muscles fiber is made from the fusion of 100s of myoblasts

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15
Q

what are the parts included in the organization of the muscle fiber

A

myofibrils
myofilaments
t tubues
sarcoplasmic reticulum
cisternae
sarcolemma
sarcoplasm
sarcomere

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16
Q

what is the sarcolemma

A

the cell membrane of muscle fibers

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17
Q

what are transverse tubules

A
  • enfolding’s in the sarcolemma that encircle the muscle fibers
  • ensures the act pot excites all parts of the muscle fiber
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18
Q

what is the sarcoplasm

A
  • cytoplasms of the muscle cell
  • contains glycogen and myoglobin
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19
Q

what is the role of glycogen

A

synthesizes atp

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20
Q

what role of myoglobin

A

release oxygen when needed by the mitochondria

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21
Q

what is the role of the mitochondria

A

site of oxidative respiration

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22
Q

what is sarcoplasmic reticulum

A

membrane system that wraps around myofibrils
- net pattern

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23
Q

what are myofibrils

A
  • bundles of myofilaments wrapped in sarcoplasmic reticulum
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24
Q

what are terminal cisternae

A
  • sac-like area of the sarcoplasmic reticulum
  • stores calcium
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25
Q

what are triads

A
  • junction site between T tubules and 2 cisternae
  • it’s the site where electrical impulses can enter inside a muscle cell
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26
Q

what is a sarcomere

A
  • the contractile unit of a muscle fiber
  • contains myofilaments
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27
Q

what are myofilaments

A
  • the contractile elements
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28
Q

what are the 2 kinds of myofilament

A
  • actin
  • myosin
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29
Q

what’s actin

A
  • the thin filaments
  • light bands
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30
Q

what is myosin

A
  • the thick filaments
  • dark bands
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31
Q

in the overlap region of the actin and myosin, what is the ratio

A

1 myosin for every 2 actin

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32
Q

what are the components that are found/make up the sarcomere

A

myosin
actin
z line
A bands
I bands
H zone
M line

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33
Q

what is the A band

A
  • dark band
  • the entire length of dark band/thick filament
  • contains myosin with overlapping actin
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34
Q

what is the I band

A
  • the light band
  • contains only thin filaments and no thick filaments
35
Q

what is the Z line

A
  • found in the middle of the I band
  • holds actin in place
36
Q

what is the H zone

A
  • area in the center of each A band
  • thick but no thin (no overlap)
37
Q

what is the m line

A
  • in the middle of the A band
  • holds myosin in place
38
Q

what are the 3 types of muscle proteins

A

contractile
regulatory
structural

39
Q

what is the role of the contractile proteins

A

generates force during the muscle contraction

40
Q

what is the role of regulatory proteins

A

help switch the contraction process off and on

41
Q

what is the role of structural proteins

A
  • keeps thick and thin filaments in their proper alignment
  • give elasticity to myofibril
  • link myofibrils and sarcolemmas
42
Q

describe the molecular structure of myosin (thick)

A
  • 1 myosin is shaped like 2 golf clubs twisted together
  • rod like tails with globular heads
43
Q

what is the importance of the myosin heads

A
  • each head contains 2 binding sites: actin binding and atp binding
  • act as the cross bridges
44
Q

describe the molecular structure of actin

A

form a helix shape

45
Q

what important elements does actin contain

A
  • myosin binding sites for myosin heads
  • regulatory proteins
46
Q

what are the 2 regulatory proteins that actin contains

A

tropomyosin
troponin

47
Q

what is the role of tropomyosin

A
  • covers the actin binding sites when at rest
48
Q

what is the role of troponin

A
  • binds calcium and changes shape
  • attached to tropomyosin
49
Q

what is the role of atp during contraction

A

activates myosin
detached flexed myosin head from actin

50
Q

what is the role of calcium in contraction

A
  • trigger for muscle contraction
  • binds to troponin that pulls on tropomyosin, which exposes the active sites of actin
51
Q

where is calcium stored

A

in terminal cisternae

52
Q

what are the changes in the sarcomere when contraction occurs

A
  • sarcomeres shorten
  • z lines move closer together
  • A bands move closer together but stay the same width
  • I bands get smaller
  • H zone gets smaller
53
Q

what is the sliding filament mechanism

A
  • thin filaments are pulled towards each other, sliding over thick filaments
  • this increases overlap of actin and myosin
  • occurs in all sarcomeres at the same time
54
Q

why does the sliding occur in the sliding filament mechanism

A
  • cross bridges attach and detach
  • myosin heads attach and walk along thin filaments at both ends of the sarcomere
55
Q

what are the steps of a contraction

A

step 0: muscle at rest
step 1: trigger and atp hydrolysis
step 2: attachment of myosin to actin
step 3: power stroke
step 4: cross bridge detachment

56
Q

what is the step 0 of the contraction

A

muscle is at rest
1. myosin heads are activated
2. atp is hydrolyzed to to adp + P and is attached to the myosin head
3. actin sites are covered by troponin
4. actin and myosin overlap slightly
5. calcium is in cisternae

57
Q

what is the step 1 of contraction

A
  1. electrical signal travel along the sarcolemma and down the t tubules
  2. when the signal reaches the cisternae, it causes the release of calcium into the sarcoplasm
  3. the calcium binds to troponin, which pulls at the tropomyosin to expose the actin binding sites
58
Q

what is step 2 of contraction

A
  1. the myosin heads are energized (when atp initially binded to the atp binding site of the myosin head, it works as an enzyme to break down the atp and store the energy from the hydrolysis) and is standing at high alert
  2. the heads bind to the myosin binding site and released the bound phosphate group that it was holding onto
  3. binding forms a cross bridge
59
Q

what is step 3 of contraction

A
  1. myosin head flexes and goes from 90 deg to 45 deg
  2. the change in angle pulls the thin actin towards the center of the sarcomere
  3. this causes tension
  4. the energy for the power stroke comes from the stored energy from the hydrolyzed atp
  5. adp + p falls off the head
60
Q

what is the step 4 of contraction

A
  1. myosin head only detaches when another atp binds to it
  2. atp reactivates the head and it returns to upright position (90 deg)
  3. cycle repeats as long as atp and calcium are present
61
Q

what is rigor mortis

A

whe the cross bridges dont disconnect due to lack of atp

62
Q

what is a neuromuscular junction

A

when the electrical signal travels down the axon of a neuron to the axon terminal, where the axon terminal forms a junction with the muscle

63
Q

how is an electrical signal transferred from neuron to muscle

A

by the release of a NT

64
Q

what is a motor end plate

A

specialized area of the muscle that binds NT

65
Q

what is a motor neuron

A

neuron that connects to a muscle rather than another neuron

66
Q

describe the steps that trigger the release of calcium from the neuron to the muscle

A
  1. motor neuron sends the electrical signal to the muscle, where it travels down the axon of the motor neuron and arrives at the axon terminal
  2. calcium gates open due to the arrival of the act pot and calcium moves into the synapse.
  3. the presence of calcium triggers the vesicles containing ACH
  4. ACH is released into the synaptic cleft and diffuses across the cleft
  5. ACH binds to receptors on the motor end plate
  6. the binding opens channels which causes ions to move in or out. when Na moves in, it triggers an electrical impulse that travels along the sarcolemma
  7. ach esterase in synaptic cleft removes NT
67
Q

what’s an isotonic contraction

A

muscle contraction results in change of muscle length

68
Q

whats an isometric contraction

A

tension forms but no change in length
- cross bridge forms but no sliding happens

69
Q

what is muscle tone

A

partial contraction of muscle

70
Q

how is tension/forced produced by a muscle

A
  • it pulls on the tendon that overcomes a resistance
71
Q

what causes the force produced by a muscle to vary

A
  • degree of overlap of filaments (30% change in sarcomere = optimal tensions)
  • frequency of stimulation (inc internal cytoplasmic calcium)
  • recruitment
72
Q

what is recruitment

A

increase in muscle tension is due to inc in number of stimulated motor units

73
Q

what is a muscle twitch

A

single stimulus contraction relaxation cucle in a muscle fiber

74
Q

how long does a muscle twitch last

A

7-100 msec

75
Q

what are the periods in a muscle twitch

A
  • latent period
  • contraction phase
  • relaxation phase
76
Q

what is the latent period

A

time for molecular events that release calcium

77
Q

what is the contraction phase

A

increased tension due to cross bridge formation

78
Q

what is the relaxation phase

A
  • calcium levels are falling
  • tension returns to resting state
79
Q

what is a wave summation

A

when many successive stimuli arrive before relaxation phase can go to completion

80
Q

why are the following contractions after the initial contraction in a wave summation have a high contraction

A
  • due to higher amounts of calcium in sarcoplasm
  • pumps has too little time to restore sarcoplasm conditions
81
Q

what is a treppe

A
  • when a second stimulus occurs after rexation
  • causes step wise increase in muscle response
82
Q

does a treppe or wave summation have more muscle tension

A

wave summation

83
Q

what is complete tetanus

A
  • sustained maximum smooth contraction
  • result of rapid delivery of stimuli overtime with no relaxation
84
Q

what is incomplete tetany

A

quivery contraction

anatomy final exam prep (8 decks)

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