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Physiology > Muscle Physiology > Flashcards

Muscle Physiology Flashcards

1
Q

What are the muscle characteristics

A

Excitability which is the ability to generate atp
contractility which shortens the muscle
extensibility which allows the muscle to stretch without tearing
elasticity which is the ability to recoil or return to original length

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2
Q

What are some muscle functions

A

They produce movements
Maintain posture and body position
Stabilize joints
Generate heat and electricity

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3
Q

What are characteristics of cardiac muscles

A

Involuntary control
Uninucleated and highly branched
Contains intercalated disks
Striated

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4
Q

What are characteristics of skeletal muscle

A

Voluntary
Multi-nucleated
Banded and striated
Surrounds bone

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5
Q

Characteristics of smooth muscle

A

Surround hollow organs or glands and tubes in body
Involuntary control
Uninucleated and not striated
Cigar or spindle shaped

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6
Q

Characteristics of red muscle

A

High mitochondria
High blood supply
High oxygen content
Uses oxidative phosphorylation
Sustained atp content
Low power, low fatigue
No large amount of force

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7
Q

Characteristics of white muscle

A

Low mitochondria content
Low blood supply and low oxygen content
Uses glycolysis
Fatigues quickly and uses high power

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8
Q

From outside to inside name the layers of a muscle

A

Epimysium, fascicle, perimysium, endomysium

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9
Q

What is the cell membrane of a myofiber

A

Sarcolemma

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10
Q

What are the major myofibrils in this unit

A

Actin and myosin

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11
Q

What does thick filaments contain

A

Myosin

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12
Q

What do thin filaments contain

A

Actin, troponin and tropomyosin

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13
Q

What do elastic filaments contain

A

Titin

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14
Q

What is myosin

A

Two globular heads with a long braided tail
Contains atp and actin binding sites
Binds to actin during muscle contraction

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15
Q

What is actin

A

Filamentous protein made of globular subunits knows as g actin
Two filament strands which form the thin filament
Binds to myosin during muscle contraction

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16
Q

What is tropomyosin

A

Filamentous protein that spirals around actin
Inhibits myosin by blocking the myosin binding site on actin

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17
Q

What is troponin

A

Interacts with tropomyosin
Made up of TnI, TnT, and TnC
TnI is the inhibitory subunit that covers the myosin binding site on actin
TnT is what binds to tropomyosin
TnC is the calcium binding subunit

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18
Q

What is dystrophin

A

Stabilizing protein that anchors the thin filament to the sarcolemma and aids in membrane stability

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19
Q

What is titin

A

Binds thick filament to Z disc of sarcomere and allows for extensibility

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20
Q

What is the sarcoplasmic reticulum characteristics

A

Tubules run along the axis of the myofibrils
Terminal cisterns run perpendicular to the A and I band junction
Regulates intracellular Ca levels

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21
Q

What is the region between a discs

A

The sarcomere

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22
Q

What is the m line

A

Where myosin fuses with myomesin
Myosin abuts

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23
Q

What is the Z disc

A

When actin aligns

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24
Q

What is the I band

A

Made up of only thin filaments

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25
Q

What is the A band

A

Overlapping thick and thin filaments

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26
Q

What is the H zone

A

Only thick filaments

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27
Q

What gives muscles the banded appearance

A

Alternating thick and thin filaments of actin and myosin

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28
Q

What are t tubules

A

Deep invaginations in the sarcolemma
They increase surface area
Place the sarcolemma in close association with sarcoplasmic reticulum
Carries action potentials deep within the muscle fiber

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29
Q

What is the triad

A

Terminal cistern, t tubule, terminal cistern

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30
Q

What do integral proteins on the t tubule act as

A

Voltage sensors
Example is the DHP receptor
DHP receptor connected to the SR receptor

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31
Q

What do integral proteins of the sarcoplasmic reticulum act as

A

Calcium channels such as the rhyandine receptor

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32
Q

What does myosin do to actin during contraction

A

Myosin grabs the actin filament and the actin filament slides over the top of myosin which increases the degree of overlap

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33
Q

What is the motor end plate

A

Allows chemical signaling between the muscle and motor neuron
Portion of the myofiber that receives the synaptic bulb

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34
Q

What is a motor unit

A

One neuron and all the muscle fibers it communicates with

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35
Q

What is a motor neuron

A

Signal sent from brain to tell skeletal muscle fiber to contract
This signal is sent as an action potential

36
Q

What is the neuromuscular junction

A

Synapse between a somatic motor neuron and a muscle fiber

37
Q

What is the portion of a motor neuron at the neuromuscular junction called

A

The synaptic bulb

38
Q

What is the synoptic cleft

A

Space between the motor end plate and synaptic bulb

39
Q

What forms the doyeres eminence

A

The lateral edges of a motor end plate meeting the Schwann cell of a motor neuron

40
Q

What important receptor is on the motor end plate

A

Achetocoline receptor

41
Q

Explain the nerve stimulus at a neuromuscular junction

A

Synaptic vesicles with acetylcholine are found in the synaptic bulb
An action potential reaches the synaptic bulb
Voltage gates calcium channels open and Ca2+ influxes
Calcium binds to acetylcholine containing vesicles and these vesicles fuse to SNAPs on the neurolemma
Acetylcholine is exocytosed into synaptic cleft and binds to ligand gated Na channel on the motor end plate

42
Q

What does a highly folded sarcolemma at the motor end plate allow for

A

More acetylcholine receptors

43
Q

Explain how an action potential is generated in a myofiber

A

Acetylcholine in the synaptic cleft binds to its receptor on ligand gated Na channels which causes influx of Na
Then depolarization which causes threshold to be reached at the motor end plate and voltage gated Na and K channels activated
Influx of Na caused M.P to go up which causes generation of action potential

44
Q

How do you generate an action potential in a motor neuron

A

Ligand binds to ligand gated channel and it opens which causes Na influx
Na diffuses across cell and threshold is reached which opens the Na V.G activation gate
Na influxes again and m.p reverses polarities which generates the action potential
Action potential is propagated down the motor neuron and reaches the axon terminal

45
Q

How is Ca released from the sarcoplasmic reticulum

A

Action potential propagates down sarcolemma and reaches DHP receptor in t tubule
There is a confirmation change in the DHP receptor which causes confirmation change in ryanodine receptor (DHP is connected to ryanodine on SR)
Ryanodine receptor acts as gated channel and opens which allows Ca to efflux from SR to sarcoplasm

46
Q

Explain how you make a cross bridge and what is is

A

Ca is released from SR and binds to TnC receptor on troponin and troponin undergoes confirmation change which causes confirmation change in tropomyosin
Tropomyosin then slides around actin, exposing myosin binding site allows myosin to bind
The actin myosin interaction is the cross bridge

47
Q

Explain cross bridge cycling

A

Myosin has an ADP and inorganic phosphate attached to it but then myosin binds to actin which causes the phosphate to be released
Myosin undergoes confirmation change and bends at the elbow which pulls on the actin filament
This causes ADP to be released and opens ATP binding site on myosin
ATP binds to myosin which causes myosin to detach from actin
ATP is then hydrolyzed into ADP and Pi which returns myosin to cocked position

48
Q

What does myosin do when it rebinds to actin

A

It binds at a location further up on the actin filament

49
Q

How do you stop a cross bridge cycle

A

There is no longer a signal so acetylcholine is cleared from the synaptic cleft and an AP in the myofiber is stopped
Ca stops being released in the SR and is pumped back into SR using Ca ATPase
Ca is also no longer bound to troponin and tropomyosin can return to normal confirmation of blocking myosin binding site

50
Q

As you move away from a blood vessel what happens

A

The overall concentration of O2 lessens

51
Q

What is anoxia

A

Concentration of oxygen dies off

52
Q

What is muscle tension

A

Force exerted by a muscle
The opposing force this is called the load

53
Q

What is isometric contraction

A

Muscle contracts but doesn’t shorten

54
Q

What is isotonic contraction

A

Muscle contracts and shortens

55
Q

What is concentric contraction

A

Muscle contracts and shortens but the force exceeds the load

56
Q

Eccentric contraction is what

A

When a muscle contracts but lengthens and the load exceeds the force

57
Q

How many neurons innervate muscle fibers

A

Multiple
Each muscle has one nerve but each nerve has multiple neurons

58
Q

What increases force of contraction

A

An increase in the number of myofiber activated

59
Q

A neuron plus an associated fiber is what

A

Motor unit

60
Q

What is motor unit recruitment

A

Generates more force by activating more motor units

61
Q

When and why do motor units oscillate

A

They oscillate during sustained contraction to reduce fatigue
This is why you shake during strong forcible contraction

62
Q

When you activate a motor unit what happens to the force of the muscle

A

It increases

63
Q

What is subthreshold stimulus

A

A stimulus sent to the muscle but no observable contraction

64
Q

What is threshold stimulus

A

Stimulus sent to muscle and results in observable contraction

65
Q

What is maximal stimulus

A

All motor units recruited which results in maximal tension

66
Q

What are the three phases of a muscle twitch

A

Latent period
Period of contraction
Relaxation

67
Q

What is a muscle twitch

A

A motor units response to a single action potential

68
Q

What is wave summation

A

An increase in frequency of action potentials which results in an increase in twitches
Muscle tension increases due to increased stimulus frequency

69
Q

What is unfused tetanus

A

Sustained but quivering contraction which results in partial relaxation in between stimuli

70
Q

What is fused tetanus

A

Maximal tension sustained which is the result of no relaxation between stimulus

71
Q

What causes muscle tone

A

Caused by feedback mechanism involving stretch receptors

72
Q

What phosphorylated ADP directly to make ATP

A

Creatine phosphate

73
Q

What is lactic acid fermentation

A

ATP from glucose via glycolysis produces pyruvic acid and in absence of oxygen pyruvic acid is converted to lactic acid

74
Q

How many ATP per creatine phosphate? What about per glucose?

A

1 per creatine phosphate
2 atp per glucose

75
Q

What is aerobic respiration

A

ATP from glucose from glycolysis and aerobic respiration which usually provides hours of energy

76
Q

How many ATP per glucose molecule are made in aerobic respiration

A

28

77
Q

What is muscle fatigue

A

Physiological inability to contract in the presence of a stimulus most likely causes with a lack of atp

78
Q

What is physiological contracture

A

State of fatigue where neither contraction or relaxation can occur due to lack of atp

79
Q

What is rigor

A

Muscle state where the muscles are locked in the contracted state which is caused by a lack of atp that operates the calcium atpase so calcium can’t be cleared from the sarcoplasm

80
Q

What is rigor mortis

A

Calcium atpase breaks down and calcium leaks out of the SR

81
Q

What is EPOC

A

Excessive post exercise oxygen consumption where oxygen reserves in myoglobin are depleted and need to be replenished
Lactic acid needs to be converted to pyruvic acid and glycogen stores need replenished
ATP and creatine phosphate stores also need to be replenished

82
Q

What determines speed of contraction

A

How fast the myosin atpase splits atp

83
Q

What are characteristics of slow fibers

A

Slow muscle twitch but more fatigue resistant

84
Q

What are characteristics of fast fibers

A

Fast twitch but fatigue more readily

85
Q

What are oxidative fibers

A

Use aerobic respiration

86
Q

What do glycolysis fibers use

A

Anaerobic pathway

Physiology (13 decks)

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