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Medicine > Neurophysiology revision > Flashcards

Neurophysiology revision Flashcards

1
Q

what happens to info in a neuron

A

info arrives at cello body (where it is processed) via dendrites
processed info digitised into APs transmitted along axon
info passed to target at bouton

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2
Q

where to action potentials start

A

axon hillocks

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3
Q

how are action potentials graded

A

all or none response
but increasing frequency increases intensity

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4
Q

why does the inside of a neuron have a negative potential and what is it

A

-70mV (resting membrane potential)
3Na out
2k in for each atp consumed

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5
Q

describe to action potential

A

stimulus causes the potential to push to the threshold (-55mV)
membrane depolarises, Na channels open and flows in
peaks
na channels become refractory
k channels open and k flows out therefore becomes more negative
hit absolute refractory period (all na channels closed) and relative refractory period (some na channels open but more k open-need large stimulus)- so only 1 direction and stimulates the next one
vectoial transmission

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6
Q

what happens when voltage gated sodium channels close

A

resting potential na channels and activation gate is closed
depolarisation opens activation gate and causes a conformational change
blocking of channel by inactivation gate
repolarisation of cell resets gates to their equilibrium

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7
Q

what increases efficiency of conduction

A

myelin sheath
increased diameter

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8
Q

where are oligodendrocytes found

A

cns

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9
Q

what is saltatory conduction

A

describes the way an electrical impulse skips from node to node down the full length of an axon
flows rapidly inside axon to node
ap takes place (only a few ions are needed- energy saving)

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10
Q

normal conduction velocity

A

50-60 metres/second
fastest alpha motor neurons 120m/s

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11
Q

are neurons hard wired

A

no they are separate entities

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12
Q

are neurons elongated secretory cells

A

yes and they are polaried
secretion at bouton
exocytosis occurs

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13
Q

explain vesicle docking

A

v-snare on vesicle complexes and t-snare at pre-synaptic membrane
allow vesicle to dock by drawing them close to membrane
exocytosis clamped by complexin
ap triggers calcium influx at end bulb, induces synaptotagmin (displaces complexin and causes exocytosis

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14
Q

what does botulinum toxin do

A

inactivates snare and therefore ach process

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15
Q

what is clostridium botulinum

A

bacteria that releases the toxin botulinum

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16
Q

what are the two receptors

A

ionotropic
metabotropic

can be excitatory or inhibitory

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17
Q

how to visualise opening of pores

A

cryo-electron microscopy

18
Q

what are post synaptic responses

A

excitatory or inhibitory post synaptic responses
EPSP AND IPSP
Single ones rarely result in ap
therefore add multiple

19
Q

how do epsp and ipsp work together

A

spatial and temporal summation
spatial- add together
temporal-ap separate

20
Q

what does summation lead to

A

integration of information

21
Q

sensory receptors need to reach threshold

A
22
Q

how to sensory receptors respond

A

slowly adapting from constant input then constant output
rapidly adapting respond when it is changing then falls off (only respond on up phase)

one to change and one to extent of change

23
Q

what is a stretch reflex there for

A

stabalising effect
prevent damage to muscle by activating reflexes via spindle fibre mechanisms
feedback info on stretch
contraction therefore controlled by output of stretch recpetors

24
Q

what does gamma motor neuron efferent from spinal cord do

A

regulate degree of contraction

25
Q

what does sensory afferent to spinal cord do

A

gives info on stretch

26
Q

what do grp 1a and grp 2 outputs do

A

give cns different info
1a rapdily adapting
2 respond to length

give info on rate and extent of shortening

27
Q

how is reflex protective

A

feedback to same muscle group
and feedbacks inhib way to antagonist muscle
therefore control extent of movement around joint

28
Q

how to measure nerve conduction

A

we measure the sum not individual action potentials in a nerve
or
resulting stimulus detected in target cell eg. skeletal muscle
compare latency (gap between stimulation and what happens in muscle)
difference in latency gives speed of conduction

29
Q

what does reduced amplitude in a nerve conduction exam mean

A

less axons

30
Q

what does slowed conduction velocity mean in nerve conduction study
or increase latency

A

less myelin

31
Q

what is CMAP

A

Compound muscle action potential
stimulate into a muscle and measure potential changes in target muscle cells

32
Q

what is snap

A

sensory nerve action potential
record from superficial radial nerve
ring electrodes placed around the thumb and recorded using surface electrodes at the wirst

33
Q

what are neuropathies

A

damage or dysfunction of one or more nerves that typically results in numbness, tingling, muscle weakness and pain in the affected area

34
Q

what are neuropathies

A
35
Q

what happens in carpal tunnel syndrome

A

median nerve is compressed
amplitude is reduced
latency not changed

36
Q

what are channelopathies

A

defect in channels

37
Q

what are the different types of channelopathies

A

inherited
autoimmune

38
Q

name inherited channelopathies

A

calcium, chloride potassium, sodium, glycine, gaba, ach
neurological
cardiac

39
Q

what are autoimmune channelopathies

A

myasthenia gracis
lambert-eaton myasthenic syndrome
limbic encephalitits

40
Q

What is myasthenia gravis

A

autoimmune condition related to nmj mechanism
pplus also mutation/genetic assocations
antibodies to enzyme which degrade ach
itll downregulate the ability of ach to stiumlate its target
tired by end of day
eyelid droop
treat with supplements of NT

Medicine (54 decks)

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