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Physiology > Muscle overview/skeletal muscles > Flashcards

Muscle overview/skeletal muscles Flashcards

1
Q

thin filaments of contractile apparatus

A

actin myofilaments
tropomyosin
troponin

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2
Q

troponin

A

a calcium binding protein that closely resembles calmodulin

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3
Q

thick filaments

A

myosin

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4
Q

myosin is made up of

A
  1. two heavy chains, each consisting of a tail and a globular head domain on a hinge, head contains an enzyme (myosin atpase)
  2. four light chains, two attached to each heavy chain head domain, light chains are particularly important in regulating the contraction of smooth muscle
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5
Q

layers of connective tissue

A
  1. epimesium
  2. perimesium
  3. endomesium
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6
Q

sarcomere

A

functional unit of skeletal and cardiac muscle

  • arrangement of thick and thin filaments
  • striated muscle between two z-disks (lines)
  • smallest functional unit capable of contraction as the z-lines are pulled together
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7
Q

thin filaments attach to what?

A

attached to z-disks

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8
Q

thick filaments attach to what?

A

m-lines, with tail ends of the myosin oriented toward the m-line from both sides

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9
Q

what attaches the z-lines to the m-lines

A

titin

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10
Q

largest protein known?

A

titin

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11
Q

A-band

A

entire length of thick filaments

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12
Q

H-band

A

only thick filaments, no overlap like a band

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13
Q

m-line

A

attachment of thick filaments in the middle

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14
Q

I-band

A

only thin filaments

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15
Q

z-line

A

attachment of thin filaments

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16
Q

sliding filament theory

A

myosin pulls z-lines together
I bands and H bands get smaller, may disappear
-a band remains the same size

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17
Q

myosin atpase

A

gives the power for shortening of the sarcomere

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18
Q

Things needed for sarcomere contraction

A
  1. hinge region of myosin extends if it has ADP and/or phosphate bound and flexes if not
  2. myosin has a low affinity for actin if ATP is bound and high affinity if not
  3. in the absense of ATP, the myosin remains tightly bound to the actin. this only happens after death
  4. to make the muscle relax, the myosin is prevented from binding to the actin. control of myosin’s access to actin is known as excitation contraction coupling
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19
Q

excitation contraction coupling

A

control of myosins access to actin

-through tropomyosin and troponin

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20
Q

tropomyosin

A

thin filament protein, covers actins binding site for myosin

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21
Q

toponin

A

thin filament protein that binds Ca++, causes tropomyosin to move when cytoplasmic [Ca++] increases

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22
Q

Sequence of events during EC-coupling: contraction phase

A
  1. AP is conducted to presynaptic terminal of motor neuron
  2. synapse at neuromuscular junction-exocytosis of Ach onto motor end plate
  3. Ach binds to nicotinic receptors in the motor end plate. nicotinic cation channels open
  4. a muscle EPSP occurs and triggers an action potential in the sarcolemma
  5. muscle action potential travels across the sarcolemma and down into the t-tubules
  6. Dihydropyridine (DHP) receptors in the t-tubule membrane respond to the action potential by opening Ca++ channels known as ryanodine receptors (RyR) in the sarcoplasmic reticulum (SR)
  7. Ca++ diffuses into the cytoplasm through the RyR, causing increased cytoplasmic [Ca++]
  8. Ca++ binds to troponin, which causes tropomyosin to move away from actin’s binding sites for myosin
  9. myosin begins its ATPase cycle and pulls on actin, shortening the sarcomere
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23
Q

Sequence of events during EC-coupling: relaxation phase

A
  1. Ca++ is pumped back into the SR by Ca++-atpase. inside the SR it binds to calsequestrin, a protein inside the SR that allows more Ca++ to be stored
  2. Decrease in cytoplasmic [Ca++] causes troponin to be empty and allows tropomyosin to cover myosin binding sites, stopping myosin ATPase cycle
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24
Q

Muscle twitch

A

a response of a muscle to one single action potential

-twitch of a single muscle fiber is ALL-OR-NOTHING

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25
Q

latent period

A

time between stimulus and beginning of twitch. this is when EC-coupling is occuring

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26
Q

Contraction Phase

A

beginning of the twitch, when muscle active force is increasing
-force increases as [Ca++] increases, so the contraction phase is when Ca++ is diffusing out of the Sr into the cytoplasm

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27
Q

relaxation phase

A

end of the twitch, when active force is decreasing
-force decreases as [Ca++] increases, so the relaxation phase is when Ca++ is getting pumped out of the cytoplasm into the SR

28
Q

Tetanic contraction

A

a muscle fiber responding to a high frequency of action potentials will experience temporal summation of twitches

29
Q

unfused tetanus

A

lower frequency of action potentials

-individual twitches are still evident, variable force dependent upon frequency of action potentials

30
Q

fused tetanus

A

higher frequency (above 20/sec)

  • no individual twitches. fused tetanus of a single muscle fiber is all or nothing
  • normal was of using a muscle fiber
31
Q

series elastic components of skeletal muscle

A

tendons

-are stretched by either active contraction or passive elongation of the muscle

32
Q

parallel elastic components

A

connective tissues (endomysium, perimysium, epimysium)

intracellular: titin
- are stretched by passive elongation, go slack during active contraction

33
Q

pre-load muscle

A

length-tension relationship is isometric force as a function of muscle length (preload with a weight the muscle cannot move)

  • tension on muscle before contraction
  • no preload, cant contract
  • more preload, more force produced
  • too much, cant contract. need optimal preload
34
Q

isometric contraction

A
  • muscle fibers shorten
  • tendon gets longer
  • overall length does not change
35
Q

isotonic contraction

A

force on muscle does not change

  • muscle contracts, force is on tendons, muscle, tendons, no force on mysiums
  • mysiums take force when relaxed
36
Q

mixed contraction stages

A

Isometric: increasing force to move load
Isotonic: load moves up and down
Isometric: muscle relaxes

37
Q

what stretches mysiums

A

preload

  • stretches mysiums in a relaxed muscle
  • will never feel the full weight of object lifted
38
Q

what does not stretch mysiums

A

afterload.

-causes contraction, muscles move

39
Q

what feels the tension in series

A

tendon-fiber-tendon

40
Q

what feels the tension in parallel

A

tendon-mysium-tendon

41
Q

Isotonic contraction

A
  • rare for just this type

- muscle stretches with preload, parallel muscle tension, muscle contracts=series

42
Q

mixed contraction

A
  • muscle does not feel load until after contraction
  • isometric contraction until max weight is on muscle
  • isotonic when pulling up
  • no mysium stretching
43
Q

key difference between pre-load and afterload

A

preload: stretches mysiums
afterload: give mixed contractions

44
Q

power output of a muscle

A

power=force x velocity

45
Q

corticospinal tract

A

upper motor neuron->lower motor neuron->muscle

46
Q

what happens if you cut the upper motor neuron

A

spastic paralysis

47
Q

what happens if you cut the lower motor neuron

A

complete paralysis

48
Q

crossed extensor reflex (spinal reflex)

A
  • step on tack
  • leg beings to flex while other begins to extend
  • foot on tack flexed, left leg extended
  • then pain
  • circuit causes flexion in muscles and extension in opposite
  • circuit is also used for walking
49
Q

what is pain

A

nociceptor afferent neuron

50
Q

muscle spindles

A
  • 1a fiber comes from spindle and synapses in gray matter to signal a muscle stretch
  • gamma (y) motor neurons connect to muscle from gray matter. activate, stretches sensory part of muscle spindle, sends signal to CNS (through 1a fiber)
  • muscle could be shortening, but if y activates then spindle stretches (called alpha/gamma contraction)
  • activate gamma, stretch spindle, which stretches sensory spindle, 1a motor neuron sends signal to CNS, which sends signal down alpha motor neuron to muscle, muscle contracts
51
Q

golgi tendon receptors

A

-axons arranged in between collagen fibers, axons get squished when you start pulling on tendons, send signal about force of contraction/tension

52
Q

5 sources of ATP

A
  1. atp present in cytoplasm
  2. adenylate kinase reaction
  3. creatine kinase reaction
  4. glycogen breakdown (fermentation-lactic acid)
  5. fat mobilization (aerobic catabolism)
53
Q

Adenylate kinase

A
  • transfering phosphate
  • ADP+ADPATP+AMP
  • transfers phosphate to ATP
  • does not last long (seconds)
54
Q

creatine kinase

A

-muscles have creatine phosphate stored up (for emergencies)
-keep making ATP until exhausted (seconds)
Cr-P+ADP ATP+Cr

55
Q

fermentation-lactic acid

A
  • muscles contain glycogen
  • 1 glucose-> 2 lactic acid, get 2 ATP per glucose
  • lactic acid builds up, lowers acidic [] of blood
56
Q

aerobic catabolism

A
  • glucose-> krebs cycle

- use O2 and release CO2

57
Q

reason for order of things and what do you use for sudden movement

A
  • use all of these at once for sudden movement

- affiliated numbers are more for what gets used up the quickest

58
Q

what role does epinephrine play

A

acting on B-adrenergic receptors (Gs-protein), causes increased glycogen breakdown in muscle fibers and fat mobilization by adipose tissues

59
Q

Fiber types of muscle

A
  1. glycolitic fibers

2. oxidative fibers

60
Q

glycolitic fibers

A

specialized in making fermentation ATP

-strong, high power quickly

61
Q

oxidative

A

specialize in aerobic ATP production

-less power, longer production time

62
Q

myosin types

A
  1. type 1 (slow myosin)
  2. type 2 (slow myosin)
    - Type 2A (oxidative)
    - Type 2B (glycolytic)
63
Q

Type 1

A

goes through the cycle slower

  • oxidative
  • small diameter
  • relatively small force
  • lots of mitochondria
  • myoglobin=red
64
Q

type 2A

A

fast myosin

  • oxidative
  • very small diameter
  • very small force
  • lots of mitochondria
  • myogloblin=red
65
Q

type 2B

A

fast myosin

  • glycolytic
  • large diameter
  • strong force
  • few mitochondria
  • no myoglobin-white
  • glycogen granules

Physiology (11 decks)

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