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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
As nerve regenerates chronaxie?
Chronaxie decreased
26
Site of generation of action potential in spinal motor neurons
Initial segment > axon hillock
27
Why is this site of the action potential initial segment in spinal motor neurons
initial segment has high concentration of sodium channels per unit area
28
Which is the site of highest concentration of sodium channels
Nodes of Ranvier | 2000-12000 channels/sq micrometer
29
Axon hillock and initial segment have how many sodium channels/sq micrometer
Axon hillock -350 | Initial segment - 500 / sq micrometer
30
Dendrites and Soma how many sodium channels
50–75
31
Site of generation of action potential in sensory neuron is
Initial nodes of ranvier
32
Spinal motor neuron and sensory neuron difference | Features of just spinal motor neuron
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
33
Spinal motor neuron and sensory neuron difference | Features of just sensory neuron
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
34
Factors affecting velocity of conduction of a nerve impulse
Diameter | Myelin
35
Larger the diameter of nerve fibre Ra (axonal resistance)is ?
Lower Ra higher velocity | Know why :P
36
What produces myelin in PNS and CNS
PNS - Schwann cells | CNS- oligodendrocytes
37
Saltatory conduction
Jumping of impulse at nodes of ranvier
38
More Myelinated nerve fibres the membrane resistance is ?
More myelinated more membrane resistance
39
Large myelinated nerve fibres have ______ Ra and ______ Rm
Low Ra | High Rm
40
Maximum velocity is present in nerve fibres with _____ Rm/Ra ratio
High
41
What does myelin do to membrane resistance and membrane capacitance
Increases membrane resistance | Decreases membrane capacitance
42
Large diameter myelinated nerve fibres have ______ Ra, _______ Rm and ________ capacitance
Low Ra High Rm Low capacitance
43
Maximum velocity is present in nerve fibres with ______ resistance and ________ capacitance
``` High resistance (Rm) Low capacitance ```
44
Demyelinating disorder ______ Rm and _______ membrane capacitance
Decrease Rm | Increase membrane capacitance
45
What are the two classification of nerve fibres and their types
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
Know what each type of nerve fibres carry
Just know it (check the notes)
47
A,B,C nerve fibres diameter and velocity
Decreasing diameter and velocity (from A-C)
48
Most numerous type of nerve fibre
C
49
Aalpha carries (corresponding to type IA AND IB)
Spinal motor nerve Proprioception IA- sensory fibre from muscle spindle IB-golgi tendon organ
50
Abeta carries (corresponding to type II)
Fine touch,vibration,deep pressure(poking),proprioception(muscle spindle)
51
Agamma carries
Motor nerve to muscle spindle
52
Adelta carries (corresponding to type III)
Fast pain,temperature (cold),some mechanoreceptor
53
B fibres carry
Preganglionic autonomic
54
Type c fibres carry
Postganglionic autonomic | Crude touch,itch,tickle,pressure,slow pain,temperature (cold,warmth)
55
Most unmyelinated nerve fibre
Type IV
56
Afferent/sensory from muscle spindle
IA and II
57
Motor to extrafusal muscle fibres
Aalpha
58
Motor to intrafusal muscle fibres
Agamma
59
Susceptibility to pressure | Which nerve fibre gets affected by pressure the most to least
A>B>C
60
Susceptibility to hypoxia | Which nerve fibre gets affected by hypoxia the most to least
B>A>C
61
Susceptibility to local anaesthetic | Which nerve fibre gets affected by LA the most to least
A>B>C
62
Types of intrafusal muscle fibres
Nuclear bag (1-3) and nuclear chain (4-5)
63
Types of nuclear bag fibres
Nuclear bag dynamic and nuclear bag static
64
Sensory fibres of nuclear bag dynamic / | Sensory fibres for dynamic response
IA fibres
65
Sensory fibres of nuclear bag static and nuclear chain static / Sensory fibres for static response
IA and II
66
Motor nerve fibre of nuclear bag and nuclear chain
Agamma fibres
67
Two ways a muscle spindle can be stimulated
Increase in muscle length | Increase in Agamma motor nerve discharge
68
What is axoplasmic transport
Physical transport of substances through axoplasm
69
Name some molecular motors of axoplasm
Kinesin Dynenin Myosin-V
70
Types of axoplasmic transport
Fast -anterograde and retrograde | Slow -always anterograde
71
Eg of fast anterograde transport
Vesicles,neuropeptides,mitochondria,reticulum,lysosome
72
Eg of retrograde fast transport
Neurotropic viruses (rabies) Tetanus toxin Nerve growth factor
73
Eg of small molecule rapidly acting neurotransmitter
Class I,II,III,IV | Pls see notes
74
Sympathetic pre ganglion secretes
Acetylcholine
75
Sympathetic post ganglion secreted
Norepinephrine | Except sweat glands- Ach,renal blood vessel-dopamine
76
Parasympathetic preganglion and postganglion secretes
ACh and ACh
77
``` Fast response (fast EPSP) What is secreted and what is the receptor ```
ACh Nicotine receptor (Millisecond)
78
Slow response (slow EPSP) What is secreted and what is the receptor
ACh M1 (Second)
79
Slow response (late slow EPSP)
GnRH Peptide receptor (Min)
80
Slow response (slow IPSP)
ACh M2 (Sec)
81
Types of synapses (two)
``` Chemical and electrical Excitatory Types (EPSP in post-synaptic membrane)and inhibitory (IPSP in post-synaptic membrane) ```
82
Types of Inhibition/Inhibitory synapses
``` Post synaptic (direct) inhibition Presynaptic inhibition Feed forward inhibition Feedback inhibition Lateral inhibition ``` Know what they are -.-
83
Types of GABA receptors present on presynaptic membrane
``` Ionotropic receptor (GABAa,GABAc) Metabotropic receptor (GABAb) ```
84
Why is there a spastic paralysis in tetanus toxin
Because tetanus toxin inhibits release of GABA Which Increases the release of glutamate Hence more excitation
85
Examples of feedforward inhibition
In cerebellum Granule cells excite basket cell and stellate cells Basket cells and stellate cells are inhibitory to purkinje cells
86
Lateral inhibition examples
Between photo receptors | Two point discrimination
87
Minimum separable distance in two point discrimination on fingertips and back
Fingertips – 2 mm | Back – 65 mm
88
Seddons classification of nerve injury
Neuopraxia Axontemesis Neurontemesis Know what they are -.-
89
Wallerian degeneration | Changes in cell body
24–48 hours –chromatolysis (Disappearance of Nissl’s granules) Nucleus moves to periphery
90
Wallerian degeneration | Changes in distal segment
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
Nissl’s granule composed of
Ribosomes and mRNA
92
Empty tube of neurilemma also called
Ghost tube
93
Wallerian Degeneration | Changes in proximal segment
Similar to distal segment of nearest node of Ranvier
94
Prerequisite for regeneration of nerve
Neurilemma is intact | Distance between cut ends is less than 3 mm
95
What is the rate of regeneration of nerves
1 mm/dead or 1 inch per month | Regeneration is usually complete by one year

Physiology (7 decks)

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