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Physiology > Muscles And Nerves > Flashcards

Muscles And Nerves Flashcards

1
Q

How do nerves and muscles react to stimulus

A

By changing their electrical properties

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2
Q

The structural and functional units of the nervous system are

A

Nerve cells or neurons

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3
Q

Dendrites

A

branched thick extensions of the cytoplasm of the cell body which function to receive signals from other nerve cells and conduct them toward the cell body

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4
Q

What is the first part of axon called

A

Initial segment

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5
Q

The axon ends by forming

A

Synaptic knobs or terminal buttons

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6
Q

Function of myelin sheaths

A
  1. Protect and insulate nerve fibers
  2. Increases speed of transmission of nerve impulse
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7
Q

Myelin sheaths are formed by

A

Schwann cells wrapping around axon processes

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8
Q

Myelin sheaths are separated by

A

Nodes of ranvier

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9
Q

Stimulus can be

A

Mechanical
Electrical
Chemical
Thermal

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10
Q

In studying nerves, electrical stimuli are preferred because:

A

it is similar to the natural stimuli of the body
Its intensity and duration can be controlled and measured
Do not readily damage the nerve and so can be repeated.

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11
Q

Properties of nerves

A
  • excitability
  • conductivity
  • infatiguability
  • all or none rule
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12
Q

All or None law

A

: a stimulus must reach a certain threshold before being transmitted, if sub-threshold, only a local non-propagated change will result; if however the nerve cell is stimulated by a supra-threshold stimulus, the resulting effect is similar to that of a threshold stimulus irrespective of the strength of the stimulus.

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13
Q

Factors affecting effectiveness of a stimulus

A
  • strength
  • rate of rise in intensity
  • duration
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14
Q

Stimuli of short duration (outside it limit) will not excite the nerve no matter it intensity. True or false

A

True

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15
Q

The mini MSK current that excites the nerve is called

A

Rheobase

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16
Q

Time needed by rheobase to excite the nerve is called

A

Utilization time

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17
Q

Stimuli that causes local response

A

Sub threshold

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18
Q

What is Chronaxie

A

Chronaxie is a concept in neuroscience and physiology that refers to the minimum amount of time required to stimulate a nerve or muscle to contract when an electric current of double the rheobase (the minimum current needed to just elicit a response) is applied.

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19
Q

Define membrane potential

A

An electrical potential (voltage difference) between the inside and the outside of the cell membrane

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20
Q

Membrane potentials are caused by

A

Diffusion potential

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21
Q

How is diffusion potential measured

A

This is measured by 2 electrodes; 1 in the fiber and 1 on the fiber, with both electrodes connected via an amplifier to a cathode ray oscilloscope; which functions to measure very minute and very rapid electrical changes.

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22
Q

Types of membrane potential

A
  • resting membrane potential
  • action potential
  • localized electronic potential
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23
Q

What forces and of what percent produce the resting membrane potential

A

Passive force (93%) and active force (7%)

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24
Q

The embrace is about ________ times more permeable to potassium than sodium

A

100 times

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25
Q

What constitutes the 7% of active force in attaining resting membrane potential?

A

Na/K pump

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26
Q

What is action potential?

A

This is a transient rapid reversal in the membrane polarity of an excitable membrane in response to a threshold stimulus.

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27
Q

When the stimulus is applied, there is a short irregular deflection of the baseline, this is called

A

Stimulus

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28
Q

The four phases of action potential:

A
  • latent phase
  • Depolarization phase
  • depolarization phase
  • Hyperpolarization
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29
Q

What restores balance from Hyperpolarization to resting membrane potential

A

Na / K pump

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30
Q

The speed of propagation is proportional to:

A

The speed of propagation = square root of nerve diameter

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31
Q

The jump of (+ve) charges from the resting node to the activated node in myelinated nerve fibres is called

A

Saltatory conduction

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32
Q

Importance of saltatory conduction

A
  1. Increases velocity of conduction up to 50 folds
  2. It conserved energy to be used only at nodes of ranvier
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33
Q

The speed of propagation in myelinated nerve tubes is proportional to

A

Proportional to fiber diameter and internodal distance

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34
Q

Conduction of impulse in one direction from receptors along afferent path is called

A

Orthodromic conduction

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35
Q

Abnormal direction of nerve impulse propagation .i.e. from axon terminal to cell body is called

A

Antidromic conduction

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36
Q

the time following the initiation of an action potential during which no new action potential can be generated, regardless of the strength of the stimulus

A

Absolute refractory period

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37
Q

the phase after the absolute refractory period during which a new action potential can be initiated, but only by a stimulus that is stronger than usual.

A

Relative refractory period

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38
Q

Function of refractory period

A
  1. It protects the nerve from extremely rapid repetitive stimulation which could compromise it function
  2. Also to prevent backward propagation of impulse
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39
Q

Factors that affect excitability of nerve

A
  1. Anything that increases or decreases permeability to Na
  2. Anything that increases or decreases permeability to k
  3. Na / K pump
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40
Q

Conditions that increase nerve permeability to Na

A
  1. Veratrine
  2. Low Ca in ECF
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41
Q

Conditions that decrease nerve permeability to Na

A
  1. Local anesthetic like cocaine
  2. High concentration of Ca in the ECF
42
Q

What decreases nerve excitability by blockading Na

A

Tetrodotoxin

43
Q

When tetra ethyl ammonium blockade (TEA) K what happens ?

A

Action potential is prolonged due to prolonged depolarization. Hyperpolarization is absent

44
Q

Factors that decrease membrane excitability are called

A

Membrane stabilizers

45
Q

Thickness of A fibers

A

2 - 20 microns

46
Q

Thickness of B fibers

A

1 - 5 microns

47
Q

Thickness of C fibres

A

< 1 micron

48
Q

Velocity of C fibers

A

0.5 - 2 m/sec

49
Q

Velocity of B fibers

A

5 - 15 m/sec

50
Q

Velocity of B fibers

A

5 - 15 m/sec

51
Q

Velocity of A fibres

A

20-120 m/sec

52
Q

Spike duration of A, B and C fibers

A

0.5msec
1 msec
2 msec

53
Q

What are the A fibres

A

myelinated somatic fibers

54
Q

What are the B fibers

A

Myelinated Preganglionic autonomic fibres

55
Q

What are the B fibers

A

Myelinated Preganglionic autonomic fibres

56
Q

What are the C fibers

A

Unmyelinated postgamglionic autonomic fibers

57
Q

What percentage of body weight does skeletal muscle make up?
a) 30%
b) 40%
c) 50%
d) 60%

A

b) 40%

58
Q
  1. What is the diameter range of skeletal muscle fibers?
    a) 5-20 micrometers
    b) 10-80 micrometers
    c) 20-100 micrometers
    d) 50-120 micrometers
A

b) 10-80 micrometers

59
Q
  1. What is the membrane surrounding the skeletal muscle fiber called?
    a) Myofibril
    b) Sarcoplasm
    c) Sarcolemma
    d) Endomysium
A

c) Sarcolemma

60
Q
  1. What is the primary structural unit of a myofibril between two Z-discs?
    a) Sarcoplasm
    b) Sarcomere
    c) H-zone
    d) M-line
A

b) Sarcomere

61
Q
  1. Which protein makes up the thick filament in skeletal muscle?
    a) Actin
    b) Myosin
    c) Troponin
    d) Tropomyosin
A

b) Myosin

62
Q

Name the components of actin filament

A

Actin
Tropomyosin
Troponin

63
Q

Which subunit of troponin binds to calcium ions to initiate contraction?
a) Troponin I
b) Troponin T
c) Troponin C
d) Troponin M

A

C) Troponin c

64
Q

Where is the calcium stored in the skeletal muscle fiber?
a) Sarcoplasmic reticulum
b) Transverse tubules
c) Synaptic cleft
d) Motor end plate

A

a) Sarcoplasmic reticulum

65
Q

What is the functional unit of contraction in skeletal muscle?
a) Muscle fiber
b) Sarcomere
c) Myofilament
d) Motor end plate

A

b) Sarcomere

66
Q

What causes the release of calcium ions from the terminal cisterns during muscle contraction?
a) Action potential
b) ATP depletion
c) Acetylcholinesterase activity
d) Rigor mortis

A

a) Action potential

67
Q

What type of receptor is found on the transverse tubules?
a) Acetylcholine receptor
b) DHP receptor
c) Ryanodine receptor
d) Troponin receptor

A

b) DHP receptor

68
Q

Which molecule covers the actin active sites at rest?
a) Tropomyosin
b) Troponin
c) Myosin
d) Titin

A

a) Tropomyosin

69
Q

What happens during the power stroke of muscle contraction?
a) Myosin detaches from actin
b) Myosin head bends, pulling actin filaments
c) ATP binds to myosin
d) Calcium binds to tropomyosin

A

b) Myosin head bends, pulling actin filaments

70
Q

Which enzyme destroys acetylcholine in the synaptic cleft?
a) Acetylcholine transferase
b) Acetylcholinesterase
c) DHP kinase
d) ATPase

A

b) Acetylcholinesterase

71
Q

Which enzyme destroys acetylcholine in the synaptic cleft?
a) Acetylcholine transferase
b) Acetylcholinesterase
c) DHP kinase
d) ATPase

A

b) Acetylcholinesterase

72
Q

What is the local depolarization caused by sodium influx called?
a) Action potential
b) End plate potential
c) Membrane potential
d) Synaptic potential

A

b) End plate potential

73
Q

Which protein holds actin and myosin filaments in place?
a) Titin
b) Tropomyosin
c) Troponin
d) Myosin

A

a) Titin

74
Q

What happens during rigor mortis?
a) Excess ATP causes prolonged contraction
b) Lack of ATP prevents detachment of myosin heads
c) Calcium ions are actively pumped back into the SR
d) Muscle fibers are destroyed

A

b) Lack of ATP prevents

75
Q

What happens to the Z-discs during muscle contraction?
a) They move further apart
b) They are destroyed
c) They move closer together
d) They do not change position

A

c) They move closer together

76
Q

Which structure increases the surface area for acetylcholine action at the synaptic cleft?
a) Motor end plate
b) Subneural folds
c) Synaptic vesicles
d) Synaptic gutter

A

b) Subneural folds

77
Q

What is the Fenn effect?
a) The mechanism of muscle relaxation
b) The relationship between muscle work and ATP usage
c) The process of calcium reuptake
d) The breakdown of acetylcholine in the synaptic cleft

A

b) The relationship between muscle work and ATP usage

78
Q

What is the role of the Z-disk in muscle fibers?
a) Stores calcium ions
b) Anchors actin filaments
c) Produces ATP
d) Regulates muscle relaxation

A

b) Anchors actin filaments

79
Q

Which component of the myosin molecule forms the cross-bridges?
a) Heavy chains
b) Light chains
c) Globular heads
d) Helical tails

A

c) Globular heads

80
Q

Which structure transmits the action potential from the sarcolemma to the muscle interior?

A

Transverse tubules

81
Q

What connects the sarcoplasmic reticulum to the transverse tubules for calcium release?

A

Ryanodine receptors

82
Q

What is the term for the structure formed by two terminal cisterns and one transverse tubule?

A

Triad

83
Q

What occurs during the detachment of myosin heads from actin?

A

ATP binds to the myosin head

84
Q

What is the first step of the muscle contraction cycle?
a) Calcium binding to troponin-C
b) ATP binding to the myosin head
c) Power stroke
d) Actin filament detachment

A

b) ATP binding to the myosin head

85
Q

What process occurs during rigor mortis?

A

ATP depletion prevents myosin detachment

86
Q

What is the lighter region in the center of the A-band called?
a) Z-disc
b) H-zone
c) I-band
d) M-line

A

b) H-zone

87
Q

What structural protein anchors myosin to the Z-disc?
a) Tropomyosin
b) Titin
c) Troponin
d) Actin

A

b) Titin

88
Q

What molecule is attached to G-actin and forms the active site for myosin binding?

A

b) ADP

89
Q

What happens to ATP during the power stroke of muscle contraction?

A

It is hydrolyzed into ADP and Pi

90
Q

What is the primary function of acetylcholinesterase?

A

Break down acetylcholine stops ach binding to ach receptors. Therefore stops Na influx

91
Q

Which step of muscle contraction is energy-dependent?

A

Pumping calcium ions back into the sarcoplasmic reticulum

92
Q

What causes rigor mortis after death?

A

Depletion of ATP

93
Q

What is the primary component of the Z-disc?

A

Filamentous proteins distinct from actin and myosin

94
Q

What is the primary component of the Z-disc?

A

Filamentous proteins distinct from actin and myosin

95
Q

What is the functional unit of a myofibril called?

A

Sarcomere

96
Q

What happens to the A-band during muscle contraction?

A

It remains the same length

97
Q

Which part of the sarcomere shortens the most during contraction?

A

H-zone

98
Q

What structural feature of the myosin head allows it to perform a power stroke?

A

Hinged tail and neck

99
Q

Which step follows ATP hydrolysis during the cross-bridge cycle?

A

Kinking of the myosin head

100
Q

Which component of the muscle cell stores large quantities of potassium and magnesium?fri

A

Sarcoplasm

Physiology (5 decks)

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