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Physiology > Nerve Physiology > Flashcards

Nerve Physiology Flashcards

1
Q

RMP of nerve

A

-70 mv

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2
Q

Firing level of nerve

A

-55mv

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3
Q

How is firing level attained

A

By giving threshold stimulus

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4
Q

Features of local potential (differentiate with action potential)

A 
By sub threshold stimulus 
Graded response 
Decremental
Not self propagated 
Can be depolarising/hyperpolarising
May/may not be followed by action 
Summation present
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5
Q

Features of action potential

Differentiate with local potential

A 
By threshold/suprathreshold stimulus 
All or none response 
Travel without decrement 
Self propogated 
Always depolarising 
Followed by action 
Summation absent
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6
Q

Types of summation

A

Spatial

Temporal

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7
Q

Eg of spatial summation

A

EPSP
IPSP
Receptor potential
Motor end plate potential

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8
Q

Phases of action potential

A

Depolarisation
Repolarisation
After depolarisation
Hyperpolarisation

Pls know why and how it happens ;)

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9
Q

Why does hyperpolarisation happen

A

Due to slow closure of K+ channels

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10
Q

Features of Na and K channels

A

Na - fast to open and fast to close
K- slow to open and slow to close

Both open in voltage range from -70mv to +30 mv

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11
Q

Types of refractory period

A

Absolute refractory period

Relative refractory period

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12
Q

What is Absolute refractory period and when

A

Stimulus will not elicit another action potential

From firing level till repolarisation is 1/3rd complete

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13
Q

What is relative refractory period and when

A

Stronger stimulus will elicit another A P

From when repolarisation is 1/3rd complete till start of depolarisation phase

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14
Q

Neuron is least excitable in which phase of action potential

A

Depolarisation phase

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15
Q

Membrane Conductance of potassium at rest compare to membrane conductance of sodium at rest

A

Membrane conductance of potassium is more then membrane conductance of sodium

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16
Q

Membrane conductance graph of sodium and potassium during action potential

A

Please check the book

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17
Q

Relationship between strength of stimulus to the time taken for response (action potential)

A

The increase in strength of stimulus the decrease in the time taken for response (action potential)

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18
Q

What is rheobase

A

Minimum strength of stimulus (electric current) which when applied for prolonged duration produces response (Action potential)

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19
Q

Utilisation time

A

Time taken by Rheobase current to produce response

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20
Q

What is chronaxie

A

Time taken by current which is twice the rheobase to produce response

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21
Q

Relationship between chronaxie and excitability of tissue

A

Lesser the chronaxie more excitable the tissue

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22
Q

Different sized neurons and their chronaxie

A

Bigger neurons lesser chronaxie

Larger diameter - larger surface area- more number of sodium channels

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23
Q

Chronaxie relationship between Skeletal Muscle, cardiac muscle, smooth muscle

A

Chronaxie of Skeletal muscle

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24
Q

Chronaxie after nerve injury

A

Increased chronaxie

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25
Q

As nerve regenerates chronaxie?

A

Chronaxie decreased

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26
Q

Site of generation of action potential in spinal motor neurons

A

Initial segment > axon hillock

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27
Q

Why is this site of the action potential initial segment in spinal motor neurons

A

initial segment has high concentration of sodium channels per unit area

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28
Q

Which is the site of highest concentration of sodium channels

A

Nodes of Ranvier

2000-12000 channels/sq micrometer

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29
Q

Axon hillock and initial segment have how many sodium channels/sq micrometer

A

Axon hillock -350

Initial segment - 500 / sq micrometer

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30
Q

Dendrites and Soma how many sodium channels

A

50–75

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31
Q

Site of generation of action potential in sensory neuron is

A

Initial nodes of ranvier

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32
Q

Spinal motor neuron and sensory neuron difference

Features of just spinal motor neuron

A

Spinal motor neuron
Aalpha motor neuron/lower motor neuron/anterior horn neuron
Multipolar neuron
Cell body lies in anterior horn of spinal cord
Spinal motor neuron carries impulses from spinal cord to muscle
Site of generation of action potential is initial segment

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33
Q

Spinal motor neuron and sensory neuron difference

Features of just sensory neuron

A

Sensory neuron
Dorsal root ganglion cell
Pseudo unipolar
Cell body lies in the dorsal root ganglion
DRG cell carries impulse from skin to spinal cord
Site of generation of action potential is 1st node of ranvier

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34
Q

Factors affecting velocity of conduction of a nerve impulse

A

Diameter

Myelin

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35
Q

Larger the diameter of nerve fibre Ra (axonal resistance)is ?

A

Lower Ra higher velocity

Know why :P

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36
Q

What produces myelin in PNS and CNS

A

PNS - Schwann cells

CNS- oligodendrocytes

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37
Q

Saltatory conduction

A

Jumping of impulse at nodes of ranvier

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38
Q

More Myelinated nerve fibres the membrane resistance is ?

A

More myelinated more membrane resistance

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39
Q

Large myelinated nerve fibres have ______ Ra and ______ Rm

A

Low Ra

High Rm

40
Q

Maximum velocity is present in nerve fibres with _____ Rm/Ra ratio

A

High

41
Q

What does myelin do to membrane resistance and membrane capacitance

A

Increases membrane resistance

Decreases membrane capacitance

42
Q

Large diameter myelinated nerve fibres have ______ Ra, _______ Rm and ________ capacitance

A

Low Ra
High Rm
Low capacitance

43
Q

Maximum velocity is present in nerve fibres with ______ resistance and ________ capacitance

A 
High resistance (Rm)
Low capacitance
44
Q

Demyelinating disorder ______ Rm and _______ membrane capacitance

A

Decrease Rm

Increase membrane capacitance

45
Q

What are the two classification of nerve fibres and their types

A

Erlanger and gasser classification-A(alpha,beta,gamma,delta),B and c [sensory,motor,autonomic]
Lloyd and hunts numerical classification- I,II,III,IV [sensory]

46
Q

Know what each type of nerve fibres carry

A

Just know it (check the notes)

47
Q

A,B,C nerve fibres diameter and velocity

A

Decreasing diameter and velocity (from A-C)

48
Q

Most numerous type of nerve fibre

A

C

49
Q

Aalpha carries (corresponding to type IA AND IB)

A

Spinal motor nerve
Proprioception

IA- sensory fibre from muscle spindle
IB-golgi tendon organ

50
Q

Abeta carries (corresponding to type II)

A

Fine touch,vibration,deep pressure(poking),proprioception(muscle spindle)

51
Q

Agamma carries

A

Motor nerve to muscle spindle

52
Q

Adelta carries (corresponding to type III)

A

Fast pain,temperature (cold),some mechanoreceptor

53
Q

B fibres carry

A

Preganglionic autonomic

54
Q

Type c fibres carry

A

Postganglionic autonomic

Crude touch,itch,tickle,pressure,slow pain,temperature (cold,warmth)

55
Q

Most unmyelinated nerve fibre

A

Type IV

56
Q

Afferent/sensory from muscle spindle

A

IA and II

57
Q

Motor to extrafusal muscle fibres

A

Aalpha

58
Q

Motor to intrafusal muscle fibres

A

Agamma

59
Q

Susceptibility to pressure

Which nerve fibre gets affected by pressure the most to least

A

A>B>C

60
Q

Susceptibility to hypoxia

Which nerve fibre gets affected by hypoxia the most to least

A

B>A>C

61
Q

Susceptibility to local anaesthetic

Which nerve fibre gets affected by LA the most to least

A

A>B>C

62
Q

Types of intrafusal muscle fibres

A

Nuclear bag (1-3) and nuclear chain (4-5)

63
Q

Types of nuclear bag fibres

A

Nuclear bag dynamic and nuclear bag static

64
Q

Sensory fibres of nuclear bag dynamic /

Sensory fibres for dynamic response

A

IA fibres

65
Q

Sensory fibres of nuclear bag static and nuclear chain static /
Sensory fibres for static response

A

IA and II

66
Q

Motor nerve fibre of nuclear bag and nuclear chain

A

Agamma fibres

67
Q

Two ways a muscle spindle can be stimulated

A

Increase in muscle length

Increase in Agamma motor nerve discharge

68
Q

What is axoplasmic transport

A

Physical transport of substances through axoplasm

69
Q

Name some molecular motors of axoplasm

A

Kinesin
Dynenin
Myosin-V

70
Q

Types of axoplasmic transport

A

Fast -anterograde and retrograde

Slow -always anterograde

71
Q

Eg of fast anterograde transport

A

Vesicles,neuropeptides,mitochondria,reticulum,lysosome

72
Q

Eg of retrograde fast transport

A

Neurotropic viruses (rabies)
Tetanus toxin
Nerve growth factor

73
Q

Eg of small molecule rapidly acting neurotransmitter

A

Class I,II,III,IV

Pls see notes

74
Q

Sympathetic pre ganglion secretes

A

Acetylcholine

75
Q

Sympathetic post ganglion secreted

A

Norepinephrine

Except sweat glands- Ach,renal blood vessel-dopamine

76
Q

Parasympathetic preganglion and postganglion secretes

A

ACh and ACh

77
Q 
Fast response (fast EPSP)
What is secreted and what is the receptor
A

ACh
Nicotine receptor
(Millisecond)

78
Q

Slow response (slow EPSP)

What is secreted and what is the receptor

A

ACh
M1
(Second)

79
Q

Slow response (late slow EPSP)

A

GnRH
Peptide receptor
(Min)

80
Q

Slow response (slow IPSP)

A

ACh
M2
(Sec)

81
Q

Types of synapses (two)

A 
Chemical and electrical
Excitatory Types (EPSP in post-synaptic membrane)and inhibitory (IPSP in post-synaptic membrane)
82
Q

Types of Inhibition/Inhibitory synapses

A 
Post synaptic (direct) inhibition
Presynaptic inhibition
Feed forward inhibition 
Feedback inhibition
Lateral inhibition

Know what they are -.-

83
Q

Types of GABA receptors present on presynaptic membrane

A 
Ionotropic receptor (GABAa,GABAc)
Metabotropic receptor (GABAb)
84
Q

Why is there a spastic paralysis in tetanus toxin

A

Because tetanus toxin inhibits release of GABA Which Increases the release of glutamate
Hence more excitation

85
Q

Examples of feedforward inhibition

A

In cerebellum
Granule cells excite basket cell and stellate cells
Basket cells and stellate cells are inhibitory to purkinje cells

86
Q

Lateral inhibition examples

A

Between photo receptors

Two point discrimination

87
Q

Minimum separable distance in two point discrimination on fingertips and back

A

Fingertips – 2 mm

Back – 65 mm

88
Q

Seddons classification of nerve injury

A

Neuopraxia
Axontemesis
Neurontemesis

Know what they are -.-

89
Q

Wallerian degeneration

Changes in cell body

A

24–48 hours –chromatolysis (Disappearance of Nissl’s granules)
Nucleus moves to periphery

90
Q

Wallerian degeneration

Changes in distal segment

A

Few hours – swelling of axis cylinder
3 to 5 days – axonal degeneration is complete
8th day -myelin degeneration starts
32nd day – myelin degeneration complete

91
Q

Nissl’s granule composed of

A

Ribosomes and mRNA

92
Q

Empty tube of neurilemma also called

A

Ghost tube

93
Q

Wallerian Degeneration

Changes in proximal segment

A

Similar to distal segment of nearest node of Ranvier

94
Q

Prerequisite for regeneration of nerve

A

Neurilemma is intact

Distance between cut ends is less than 3 mm

95
Q

What is the rate of regeneration of nerves

A

1 mm/dead or 1 inch per month

Regeneration is usually complete by one year

Physiology (7 decks)

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