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Medicine Term One > Nerves > Flashcards

Nerves Flashcards

1
Q

Examples of graded potentials

A

Generator potentials at sensory receptors
Postsynaptic potentials at synapses
Endplate potentials at neuromuscular junction
Pacemaker potentials in pace maker tissues

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2
Q

How are graded potentials decremental

A

loose signal therefore can only be used over short distances

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3
Q

How are graded potentials graded

A

as the intensity of stimuli effects signals amplitude

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4
Q

How can cells be hyperpolorised

A

Opening of Cl gates, letting Cl in- fast ISPS

Opening K gates letting K out the cell - slow ISPS

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5
Q

How can cells be depolarised

A

Opening Na gate letting Na into the cell - fast ESPS

closing K gate, so K remains in the cell - slow EPSP

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6
Q

Why is potassium gates slower in producing a response

A

are G protein coupled - metabotrophic

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7
Q

How are post synaptic potentials produced

A

by a neurotransmitter opening or closing ion channels

= ligand-gated ion channels

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8
Q

What are the two different ways Graded potentials can summate

A

Temporal - same signal

spatial - different signals

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9
Q

Name two inhibitory PSP

A

GABA and Glycine

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10
Q

What must happen for an action potential to be fired

A

reach threshold potential > -55mV

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11
Q

What depolarises cells in AP quickly

A

Na channels open and move into cell rapidly then close again

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12
Q

What are the two different threshold stimulus

A

Sub threshold -sits above threshold but decreases as travels, therefore no AP fired
Suprathreshold - remains above threshold, fired AP

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13
Q

How does the refractory period occur

A

Threshold is reached and opens Na channels they only stay open for a short time though.
K+ permeability slowly rises as more K+ channels (this time the voltage dependent ones) open and leave the cell this causes repolarisation, and we eventually return to RMP

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14
Q

How do action potentials self propagate

A

When a voltage gate opens it depolarises the next gate stimulating it to open as well

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15
Q

How can signle only move forward

A

As the neighbouring gate thats just stimulated the other gate is now in refractory period therefore can not be stimulated to open again so signal can only be passed forward

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16
Q

How is the speed of AP increased

A

Larger axons - conducts quicker as resistance decreased, passive current spreads quicker
Myelination - increase the membrane resistance, preventing current leaking out, so passive current spreads quicker

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17
Q

What are properties of AP

A 
mediated by voltage-gated channels
have a threshold
are all-or-none
can only encoded stimulus intensity in their firing frequency, not amplitude
are self-propagating 
have a refractory period
travel slowly
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18
Q

Why is the frequency of the signals encoded

A

As AP fired are all the same size due to all or non phenomenon, therefore its how stimulus intensity is measured

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19
Q

What are the gaps in-between myelin sheath called

A

Nodes of ranvier

20
Q

What is the movement because the refractory period of cells called

A

saltatory conduction

21
Q

What is myelin sheath produced by in the CNS and the PNS

A

CNS- oligodendrites

PNS- schwann cells

22
Q

Where are the voltage gated Na channles located

A

In between myelinated axons = Node of raniver

23
Q

How does myelin sheath do to our AP conduction

A

The depolarisation evoked by voltage-gated Na channels at one node of Ranvier by spreads as a local circuit While this is decremental it travels further because less current is wasted leaking out of the membrane or charging up the capacitance, therefore big enough to reach the next node and trigger another AP.

24
Q

What is the effect of demyelination

A

Big local current delays quicker, therefore does not depolarise the next node e.g. multiple sclerosis

25
Q

What is the order of action potential fibres in most sensitivity to pressure and least sensitive to anaesthetics

A 
A alpha (biggest)
A beta 
A gamma 
A delta 
B
C (smallest)
26
Q

What size of fibres are most sensitive to anaesthetics

A

small fibres - C

27
Q

What type of fibres are most likely to go numb if you lie in them for to long e.g. anoxia

A

Large fibres

28
Q

What fibre signal is the fastest and what

A

A alpha because it has the largest axon

29
Q

List what happens at NMJ?

A

Action potential in motor neurone
Opens voltage-gated Ca2+ channels in presynaptic terminal
Triggers fusion of vesicles
Acetylcholine (ACh) released
Diffuses across synaptic cleft
Binds to ACh (nicotinic) receptors
Opens ligand-gated Na+/K+ channels
Evokes graded (local) potential (end plate potential)
Always depolarises adjacent membrane to threshold
Opens voltage-gated Na+ channels - evokes new AP
ACh removed by acetylcholinesterase

30
Q

How does tetoduoxin work

A

Blocks Na+ channel

31
Q

Jaro spider toxin

A

Blocks Ca2+ channels, therefore no transmitter release

32
Q

How does Botulinum toxin work

A

Blocks transmitter release

33
Q

How does curare work

A

blocks Ach receptors and so prevents the end plate potential

34
Q

How does anticholinesterases work

A

block ACh breakdown and so increase trasnmission at the NMJ

35
Q

What is the difference between CNS synapse and NMJ

A

Range of Neurotransmitters
Range of postsynaptic potentials
There is different anatomical arrangements of synapse
Different synaptic connectivity of neurons

36
Q

What NT is made on demand

A

Nitric Oxide

37
Q

How is ACH transmitter differ from other NT

A

Is inactivated by breakdown where others are inactivated by uptake

38
Q

What type of potential does NMJ have and what is its features

A

endplate potential - only excites and is specific

39
Q

What is the range of post synaptic potentials

A

Fast EPSPs (ionotropic)
Slow EPSPs (metabotropic)
Fast IPSPs
Slow IPSPs

40
Q

What are the different anatomical synapse arrangement in the CNS

A

Axo-somatic - axon on the cell body
Axo-dendritic - axon on dendrite
Axo-axonal - axon on axon

41
Q

What is the different synaptic connectivity pathways

A

convergence
divergence
feedback inhibition
monosynaptic vs polysynaptic pathways

42
Q

How does feedback inhibition work

A

AP travels down, NT causes feedback inhibition, therefore fires one AP then stops

43
Q

What synaptic connectivity pathway gives more scope for synaptic integration i.e. add in an inhibitory neurone

A

Polysynaptic

44
Q

Where is graded and AP fired from

A

graded - dendrites/cell body

AP - trigger zone, axon helix

45
Q

What potential uses both ligand and voltage

A

graded

46
Q

What is the resting membrane potential and how is maintained

A

-70mV

leaky potassium channels

Medicine Term One (59 decks)

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