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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

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

25
Line where myosin contracts in sarcomere
M line
26
Aligned sarcomeres
Produce banding pattern characteristic of striated muscle
27
Sliding Filament AKA
Walk Along
28
Sliding Filament Model Events
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
Terminal end
Distal end
30
Ca+ conc on which side of cell
Outside
31
Muscle neurotransmitter
Ach
32
Sliding Filament Mechanism
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
Tropomyosin prevents
Binding
34
Stored E in myosin head causes
Deformation such that thick and thin filaments slide past one another
35
Muscle contraction stops when
ATP-dependent calcium pump sequesters calcium ions back into SR
36
Where ATP is required for muscle contraction
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
Concentration of ATP in muscle fiber
About 4mmol | Enough to maintain contraction for 1-2 seconds
38
3 Types of Energy for Rephosphorylation
1. Phosphocreatine 2. Glycolysis 3. Oxidative Metabolism
39
Phosphocreatine and E for Rephosphorylation
Releases E rapidly Reconstitutes ATP ATP + phosphocreatine provides enough energy for 5-8 seconds of contraction
40
Glycolysis
Anaerobic respiration Can generate ATP in lack of ATP End up with pyruvate, generate net of 2 ATP
41
Glycolysis and E for Rephosphorylation
Lactic acid build up | Can sustain contraction for 1 minute
42
Oxidative metabolism and E for Rephosphorylation
Provides more than 95% of all E needed for long term contraction
43
2 types of muscle contractions
1. Isometric | 2. Isotonic
44
Isometric Muscle Contraction
Same length, contraction is not moving. Doing work, but stays the same.
45
Isotonic Muscle Contraction
Same tone or contraction strength Ex. Muscle changes length, NOT always shorter, can be longer. 2 Types : 1. Eccentric 2. Concentric
46
Eccentric Muscle Contraction
Type of Isotonic | Gets longer
47
Concentric Muscle Contraction
Type of Isotonic | Gets shorter
48
2 Muscle Fiber Types
1. Fast (white) - contracts quickly, fatigue fast | 2. Slow (red) - slow, but last long time
49
White Muscle Fiber
Fast Contracts quickly, fatigues fast Ex. Chicken breast
50
Red Muscle Fiber
Slow Contracts slowly, Lasts long time Ex. Chicken legs, thighs - flight muscles - have most amount of mitochondria, need lots of O2 from ATP
51
What gives red muscle fiber color?
Myoglobin like hemoglobin when bound to O2 is red.

Physiology I (7 decks)

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