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Physiology I > Lecture 4 Contraction of Skeletal Muscle > Flashcards

Lecture 4 Contraction of Skeletal Muscle Flashcards

1
Q

Hierarchical Organization of Skeletal Muscle

A
  1. Epimysium
  2. Muscle
  3. Perimysium
  4. Fascicle
  5. Endomysium
  6. Sarcolemma (aka plasmalemma)
  7. Myofiber (aka muscle cell)
  8. Myofibril
  9. Myofilament
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2
Q

Fascicle

A

Latin for bundle of sticks
Subunit
Covered in perimysium

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3
Q

Myofiber

A

Muscle fiber

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4
Q

Myfibril

A

Are the actin/myosin fibrils

They are intracellular

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5
Q

Endo-mysium

A

Delicate, covers myofiber

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6
Q

Perimysium

A

Provides support

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7
Q

Sarcolemma

A

Cell membrane
Where action potential will occur
T-Tubules - invaginations of sarcolemma

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8
Q

Functional unit of muscle

A

Sarcomere

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9
Q

T-tubules

A

Invaginations of sarcolemma
Lie close to cisternae of sarcoplasmic reticulum
Form triads with cisternae (swelling)
Two per sarcomere

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10
Q

Sarcoplasmic reticulum

A

ER of myofiber

Has cisternae

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11
Q

ER in muscle

A

Sarcoplasmic reticulum

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12
Q

Sarcomere Banding

A

Banding pattern is determined by actin/myosin placement

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13
Q

Z lines

A

(aka Z discs)
Anchor actin filaments
Located at each end of a sarcomere

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14
Q

I bands

A

*in the sarcomere with A bands
Composed entirely of actin
Width changes during contraction

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15
Q

A bands

A

*in the sarcomere with I bands
Composed of actin and myosin
Width does not change during contraction

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16
Q

H bands

A

Composed entirely of myosin

Width changes during contraction

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17
Q

This type of band does NOT change during contraction

A

A bands

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18
Q

Muscle band composed entirely of actin

A

I bands

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19
Q

Muscle band composed entirely of myosin

A

H bands

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20
Q

This muscle band demarcates the subcomponents

A

Z line

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21
Q

Muscle band composed of both actin and mysoin

A

A bands

22
Q

Origin of muscle is the

A

Fixed end

Direction it contracts

23
Q

Muscle band that represents the length of the myosin filaments

A 
A bands
(doesn't change)
24
Q

2 bands that get smaller during contraction

A

H and I

25
Q

Line where myosin contracts in sarcomere

A

M line

26
Q

Aligned sarcomeres

A

Produce banding pattern characteristic of striated muscle

27
Q

Sliding Filament AKA

A

Walk Along

28
Q

Sliding Filament Model Events

A
  1. Arrival of action potential at terminal end of nerve fiber
  2. Opening of voltage-gated calcium channels
  3. Release of neurotransmitter (Ach) from synaptic vesicles into synaptic cleft
  4. Opening of ligand-gated sodium channels of sarcolemma
  5. Generation of action potential on sarcolemma
  6. Voltage-gated channels on t-tubules (DHP channels) interact with ryanodine receptors on SR membrane
  7. Opening of ryanodine-sensitive calcium ion release channels
  8. Increase in calcium ion conc in cytosol
  9. Activation of sliding filament mechanism
29
Q

Terminal end

A

Distal end

30
Q

Ca+ conc on which side of cell

A

Outside

31
Q

Muscle neurotransmitter

A

Ach

32
Q

Sliding Filament Mechanism

A
  1. Released calcium ions bind to troponin
  2. Tropomyosin uncovers myosin binding sites on actin
  3. ATPase heads of myosin molecules split ATP and bind to actin
  4. Stored E in myosin head causes deformation such that thick and thin filaments slide past one another
  5. A second ATP binds to myosin and causes it to release actin
  6. Process is repeated over and over until sliding is complete
  7. Contraction stops when ATP-dependent calcium pump sequesters calcium ions back into SR
33
Q

Tropomyosin prevents

A

Binding

34
Q

Stored E in myosin head causes

A

Deformation such that thick and thin filaments slide past one another

35
Q

Muscle contraction stops when

A

ATP-dependent calcium pump sequesters calcium ions back into SR

36
Q

Where ATP is required for muscle contraction

A
  1. Most used for sliding filament mechanism
  2. Pumping calcium ions from sarcoplasm back into sarcoplasmic reticulum
  3. Pumping sodium and potassium ions through the sarcolemma to reestablish resting potential
37
Q

Concentration of ATP in muscle fiber

A

About 4mmol

Enough to maintain contraction for 1-2 seconds

38
Q

3 Types of Energy for Rephosphorylation

A
  1. Phosphocreatine
  2. Glycolysis
  3. Oxidative Metabolism
39
Q

Phosphocreatine and E for Rephosphorylation

A

Releases E rapidly
Reconstitutes ATP
ATP + phosphocreatine provides enough energy for 5-8 seconds of contraction

40
Q

Glycolysis

A

Anaerobic respiration
Can generate ATP in lack of ATP
End up with pyruvate, generate net of 2 ATP

41
Q

Glycolysis and E for Rephosphorylation

A

Lactic acid build up

Can sustain contraction for 1 minute

42
Q

Oxidative metabolism and E for Rephosphorylation

A

Provides more than 95% of all E needed for long term contraction

43
Q

2 types of muscle contractions

A
  1. Isometric

2. Isotonic

44
Q

Isometric Muscle Contraction

A

Same length, contraction is not moving. Doing work, but stays the same.

45
Q

Isotonic Muscle Contraction

A

Same tone or contraction strength
Ex. Muscle changes length, NOT always shorter, can be longer.
2 Types : 1. Eccentric 2. Concentric

46
Q

Eccentric Muscle Contraction

A

Type of Isotonic

Gets longer

47
Q

Concentric Muscle Contraction

A

Type of Isotonic

Gets shorter

48
Q

2 Muscle Fiber Types

A
  1. Fast (white) - contracts quickly, fatigue fast

2. Slow (red) - slow, but last long time

49
Q

White Muscle Fiber

A

Fast
Contracts quickly, fatigues fast
Ex. Chicken breast

50
Q

Red Muscle Fiber

A

Slow
Contracts slowly, Lasts long time
Ex. Chicken legs, thighs - flight muscles - have most amount of mitochondria, need lots of O2 from ATP

51
Q

What gives red muscle fiber color?

A

Myoglobin like hemoglobin when bound to O2 is red.

Physiology I (7 decks)

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