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Physiology > Week 6 Ch. 6 Skeletal muscle contraction > Flashcards

Week 6 Ch. 6 Skeletal muscle contraction Flashcards

1
Q

Sarcolemma is

A

the thin membrane enclosing fiber - muscle cell membrane

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2
Q

Sarcolemma is made of

A

polysacccharide chains and collagen fibrils

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3
Q

Myfibrils are made up of

A

Actin and Myosin

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4
Q

Sarcomere

A

point between Z-disks that shorten during muscle contraction

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5
Q

Z-disk - function and action

A

provides anchorage for actin

passes from microfibril to microfibril all around muscle fiber

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6
Q

Titin: function and location

A

large protein that maintains interaction between actin and Myosin
(tethers myosin to Z-disk0

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7
Q

Sarcoplasm

A

instead of cytoplasm in muscles, fills spaces between myofibrils

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8
Q

What is in the sarcoplasm

A

K+, magnesium phosphate, protein enzymes, mitochondria

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9
Q

Sarcoplasmic reticulum role

A

instead of smooth ER

regulates calcium storage, release and reuptake

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10
Q

Action potential for contraction moves from ____ to _____

A

motor nerve to muscle fibers (sarcolemma)

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11
Q

Neurotransmitter that is secreted for muscle contraction

A

Acetylcholine (Ach)

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12
Q

Acetylcholine binds______ to _____

A

on Ach gated cation channels on sarcolema

open sodium channels

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13
Q

Voltage gated sodium channels (role in muscle contraction)

A

open and action potential is initiated (becomes more positive with influx of Na)

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14
Q

Action potential begins, muscle membrane is depolarized, and then:

A

SR releases calcium ions

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15
Q

Calcium allows

A

actin and myosin to attract and slide, which causes contraction

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16
Q

At end of action potential, calcium:

A

goes back in SR

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17
Q

Contraction of muscle causes

A

cross-bridges from myosin and actin filaments

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18
Q

Myosin is the (heavy or light chain?)

A

heavy

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19
Q

Actin is the (heavy or light chain?)

A

light

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20
Q

Head of myosin functions as

A

ATPase

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21
Q

Tropomyosin (location and function)

A

wraps around actin, lies on top of active sites to block interaction with myosin

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22
Q

Troponin (location and function)

A

bound to tropomyosin, attatches to actin and tropomyosin

“staples” tropomyosin to actin

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23
Q

Troponin has what binding sites (4)

A
  1. to actin
    2.to tropomyosin
  2. to another troponin
  3. to calcium
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24
Q

In the presence of troponin, tropomyosin

A

blocks actin and myosin binding

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25
Q

In the presence of calcium, what happens?

A

troponin-tropomyosin become inhibited

Calcium causes a conformation change and tropomyosin is pulled away from active sites

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26
Q

G actin subunit role

A

bears active sites for myosin head attachment

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27
Q

What is the sliding filament model of contraction?

A

Shortening occurs when tension generated by cross bridges on thin filaments exceeds forces opposing shortening

thin filaments slide past thick filaments, causing actin and myosin to overlap

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28
Q

Contraction ends when crossbridges become

A

inactive

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29
Q

What causes Ca2+ to release into cytosol?

A

Voltage- sensitive proteins in T tubules change shape (Na+ causes voltage change)

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30
Q

Cross bridge cycling steps (once Ca+ is released)

A
  1. Ca+ binds to troponin
  2. Troponin changes shape and moves tropomyosin away from myson-binding sites
    3.Myosin heads mind to actin, forming crossbridge
  3. Cycling initiates, causing sarcormere to shorten and contract
  4. Ca+ pumped back into SR and contraction ends
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31
Q

What causes a muscle contraction to caese

A

Nervous stimulation ceases, Ca+ goes pumps back into SR

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32
Q

Cross bridge cycling steps

A
  1. Crossbridge forms
  2. Working (power stroke)
  3. Cross bridge detatchment
  4. COcking of myosin head
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33
Q

Crossbridge forms:

A

hi energy myosin head attatches to actin thin filament active site

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34
Q

Working (power) stroke:

A

ADP and Pi are released from myosin head, causing head to pivot and bend, pulling actin filament towards M line

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35
Q

Cross bridge detachment:

A

ATP attatches to myosin head causing cross bridge to detatch

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36
Q

Cocking of myosin head:

A

ATP is hydrolyzed to ADP and Pi, which attatch to myosin head and return it to cocked position

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37
Q

Myosin “cocked” position:

A

Pre-stroke, high energy state

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38
Q

Muscle tension definition and cause

A

cause: contraction

Definition: force exerted on load or object to be moved

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39
Q

Isometric contraction

A

muscle tension increases but does not exceed load

40
Q

Isometric contraction example

A

You are trying to push down wall but cant (load is greater than max tension can generate)

Muscle cannot change length

41
Q

Isotonic contraction

A

muscle changes in length and moves load

42
Q

Isotonic contraction example

A

Lifting weights

43
Q

Two types of isotonic contraction:

A
  1. Concentric
  2. Eccentric
44
Q

Concentric contractions: What happens and example

A

Muscle shortens and does work

ex. picking up weight in bicep curl

45
Q

Eccentric contraction: what happens and example

A

Muscle lengthens and generates force

ex setting down or lower weight

46
Q

Motor unit definition (s)

A

nerve-muscle functional unit

motor neuron and all muscle fibers it supplies

47
Q

Muscle twitch is a _______ resulting from______

A

Muscle fiber’s response

a single action potential from motor neuron

48
Q

Myogram

A

observes and records muscle twitch

49
Q

Latent period of muscle twitch: What is happening and what will you see

A

Exciting-contraction coupling occuring, no muscle tension seen

(Ach crossing, Ca+ release, myosin binding)

50
Q

Period of contraction muscle twitch: what is happening what will you see?

A

Cross bridge formation

you will see tension increase

51
Q

Period of relaxation muscle twitch: What is happening and what will you see?

A

Ca+ reentry into SR

you will see tension decline to zero

52
Q

Different strength and duration of twitches are due to

A

variations in metabolic properties and enzymes

53
Q

contraction speed and hold

A

vary between muscles
ex) eye muscles contract rapid and brief, calf muscles contract more slowly and are held longer

54
Q

Graded muscle repsones

A

varied strength of contraction for different demands

55
Q

Responses of contraction are graded by (2):

A
  1. Changing frequency of stimulation
  2. changing strength of stimulation
56
Q

Wave (temporal) summation results if

A

2 stimuli are received by a muscle in rapid succession

57
Q

In wave (temporal) summation, there is a

A

summative increase in muscle tension d/t frequency of stimuli

58
Q

Unfused (incomplete) tetanus occurs when

A

summation reaches near max tension to sustain (quivering)

59
Q

Fused (complete tetanus) occurs when

A

if stimuli frequency further increases and muscle tension reaches maximum

can lead to muscle fatigue

60
Q

Recruitment is also called

A

multiple motor unit summation

61
Q

Multiple motor unit summation:

A

stimulus is sent to more muscle fibers

62
Q

Multiple motor unit summation leads to

A

more precise control

63
Q

Subthreshold stimulus

A

no contraction seen

64
Q

threshold stimulus

A

first observable contraction

65
Q

Maximal stimulus

A

strongest stimullus that increases max contractile force

66
Q

Stimulus involved in recruitment:

A
  1. sub-threshold
  2. threshold
  3. maximal
67
Q

Muscle response to changes in stimulus strength method:

A

recruitment of motor unit works on size principle

68
Q

Recruitment size principle

A

Motor units are recruited smallest muscle fibers—>largest muscle fibers

69
Q

Motor units in muscles contract asynchronously to

A

avoid quick fatigue/use of materials

70
Q

ATP is made available for contractions by (3):

A
  1. Direct phosphorylation of ADP by creatine phosphate
  2. Anaerobic pathway: glycolysis and lactic acid formation
  3. Aerobic respiration - Kreb’s cycle
71
Q

Direct phosphorylation of ADP by creatinine phosphate creates ATP by

A

donates P to ADP, turning it into ATP

72
Q

Anaerobic glycolysis ATP formation

A
  1. glucose is broken down to pyruvic acid (2 ATP)
  2. Pyruvic acid is converted into lactic acid for re use
73
Q

Aerobic respiration

A
  1. Glucose is broken down into pyruvic acid
  2. pyruvic acid goes through the Kreb’s cycle in the mitochondira (32 ATP)
74
Q

Aerobic respiration is used during

A

aerobic endurance (running)

75
Q

anaerobic threshold

A

Muscle metabolism converts to anaerobic pathways (HIIT)

76
Q

Force of muscle contraction is dependent on (4):

A
  1. Number of muscle fibers stimulated (recruitment)
  2. Relative size of fibers
  3. Frequency of stimulation
  4. Degree of muscle stretch
77
Q

Number of muscle fibers and force of contraction

A

More motor units recruited = greater force

78
Q

Relative size of fibers and force of contraction

A

bulkier muscle, more tension can develop

79
Q

Frequency of stimulation and force of contraction

A

higher frequency = greater force

80
Q

Degree of muscle stretch and force of contraction: when do sarcomeres generate more force during contraction?

A

sarcomeres that are 80-%-120% their normal resting length at contraction generate more force

81
Q

How fast a muscle contracts and how long it can stay contracted depends on (3):

A
  1. muscle fiber type
    2 load
  2. recruitment
82
Q

Speed of contraction is determined by

A

the speed at which myosin and ATPases split ATP

83
Q

Oxidative fiber use

A

aerobic pathways

84
Q

Glycolytic fibers use

A

anaerobic pathways

85
Q

Muscle fiber type is classified according to (2):

A
  1. Speed of contraction
  2. Metabolic pathways used for ATP synthesis
86
Q

Skeletal muscles fibers can be classified into 3 types:

A
  1. slow oxidative
  2. fast oxidative
  3. fast glycolytic
87
Q

Slow oxidative fibers are used in

A

low intensity endurance activities
i.e. maintaining posture, soleus

88
Q

Fast oxidative fibers are used in

A

Medium intensity activities

i.e. sprinting or walking

89
Q

Fast glycolytic fibers are used in

A

short term intense or powerful movements

i.e. HITT exercise

90
Q

Load and recruitment:

A

muscles contract fastest with no load. increase load = increase contraction time

more motor units contracting = faster and longer

91
Q

Aerobic exercise leads to (3)

A
  1. increased msucle cappilaires
  2. increased #mitochonria
  3. Increasead myoglobin synthesis
92
Q

Resistance exercise leads to (3)

A
  1. muscle hypertrophy
  2. increased mitochondira, myofilaments, glycogen stores, connective tissue
  3. increase muscle strength and size
93
Q

Hypertrophy

A

Increased actin and myosin

94
Q

Hyperplasia

A

Formation of new muscle cells

95
Q

Lengthening causes
-force generation
-shortening capacity
-imax concentration velocity?

A

-No change in force generation
-increased shortening capacity
-increased maximum concentration velocity

96
Q

Hypertrophy and hyperplasia cause
-force generation?
-shortening capacity?
-max contraction velocity?

A

-increased FORCE
-no change in shortening capacity
-no change in max velocity of contraction

Physiology (13 decks)

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