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Sensory and Motor Neuroscience > NNN I > Flashcards

NNN I Flashcards

1
Q

what is the resting membrane potential of a neuron and why

A

-70mV
it is like this because the transporters and ion channels create a distribution of ions/ charges

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2
Q

what is depolarisation or excitation

A

Any entry or +ions (Ca, K, Na) or exit of - ions (Cl)

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3
Q

what is hyperpolarization of inhibition

A

any exit of +ions or entry of -ions.
This causes the membrane potential to be lower than the rmp

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4
Q

what is repolarisation

A

when the membrane potential returns to its resting state after depolarisation.

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5
Q

opening of channels for a neurone at rest typically

A

Na channels: flows inwards (depolarization, excitatory)
Ca channels: flows inwards (depolarization, excitatory)
Cl channels: flows inwards (hyperpolarization, inhibitory)
K channels: flows outwards (hyperpolarization, inhibitory)

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6
Q

what does an agonist of a Na channel do

A

opens channel, causes Na flow in cell, causes excitation

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7
Q

what does a Na channel antagonist do

A

closes channel, stops Na ion flow, favours inhibition…. e.g. local anaesthetics like lidocaine

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8
Q

what does an agonist of of K channel do

A

opens K channel, causes K flow out of the cell, makes more negative and is therefore inhibitory

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9
Q

what does a K channel antagonist do

A

closes K channel, retains K in the cell, favours positive rmp and is therefore excitatory

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10
Q

neurotransmitter: events at the synapse

A

1) action potential depolarises axon terminal
2) depolarization opens voltage gated Ca2+ channels and Ca2+ enters
3) Calcium entry triggers exocytosis of synaptic vesicles
4) Neurotransmitters travel across synaptic cleft and bind to receptors on the postsynaptic cell
5) Neurotransmitter binding initiates a response in the postsynaptic cell

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10
Q

neurotransmission: Inactivation of neurotransmitters

A

1) neurotransmitters can be returned to axon terminals for reuse or transported into glial cells
2) Enzymes inactivate neurotransmitters
3) Neurotransmitters can diffuse out of the synaptic cleft

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11
Q

what is an astrocyte

A

a type of glial cell that provides support and protection to neurons in the central nervous system

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12
Q

function of an astrocyte in the reuptake of neurotransmitters

A

help regulate the concentration of neurotransmitters in the synaptic cleft by taking up neurotransmitters such as glutamate.

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13
Q

how do the astrocytes take up the glutamate

A

there are glutamate transporters on the astrocyte and this is important for the termination of glutamates synaptic action.

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14
Q

Post-synaptic action of a NT, there are 2 modes of action, what are they

A

neurotransmitters act directly or indirectly on ion channels.

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15
Q

how does direct gating happen

A

Ionotropic receptors. The receptor is an integral component of the molecule that forms the channel it controls.

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16
Q

how does indirect gating happen

A

Mediated by activation of Metabotropic receptors. Receptor and the channel it controls are distinct.

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17
Q

what are the two major families of ligand gated channels.

A

Ionotropic glutamate receptors
Nicotinic acetylcholine receptors

18
Q

why could glutamate have a inhibitory response despite being a major excitatory neurotransmitter

A

its response at metabotropic glutamate receptors

19
Q

which receptor controls a channel permeable to Na+, Ca2+ and K+

A

NMDA

20
Q

what are the non- NMDA ionotropic receptors and how quickly do they elicit a response

A

AMPA and Kainate
mediate fast excitatory synaptic transmission in the CNS

21
Q

how quickly does NMDA elicit a response

A

NMDA contributes a slow component to the excitatory synaptic potential.

22
Q

what does NMDA have a high permeability to

A

Ca2+ hence thought to promote neurotoxicity

23
Q

metabotropic glutamate receptors dont have an integral ion channel, how do they exert their effect

A

by activation of a second messenger cascade

24
Q

what is the main inhibitory neurotransmitter

A

GABA

25
Q

what are the two receptors GABA acts on

A

Ionotropic GABAa receptor that operates a Cl- channel

GABAb a metabotropic receptors, often activates a potassium channel

26
Q

how do benzodiazepines work

A

positive allosteric modulator of GABAa receptor so enhance Cl entry, decreasing the rmp, enhancing inhibition in presence of GABA

27
Q

how do barbiturates work

A

positive allosteric modulator of GABAa, enhances Cl- entry, lowering rmp, enhancing inhibition in presence of GABA

28
Q

how does Baclofen work

A

agonist of GABAb receptor, enhances K current increasing inhibition

29
Q

what type of neurotransmitter is glycine and how does it act

A

inhibitory
acts on glycine ionotropic receptor that gates Cl- channel. released by interneurones in spinal cord to inhibit antagonist muscles motoneurones.

30
Q

ionotropic gating of ions is what

A

rapid

31
Q

metabotropic gating is what

A

slower

32
Q

slow actions of metabotrobic receptors are not sufficient to trigger an action potential rather they what

A

they have a modulatory synaptic action

33
Q

how do metabotropic modulate synaptic action

A

acting on channels in the presynaptic terminal to modulate transmitter release

modulating transmitter-gated channels to regulate the size of the post synaptic potential

modulate the resting and voltage-gated ion channels in the neuronal soma to alter e.g. resting Em and AP firing pattern

34
Q

cholinergic synaptic transmission in autonomic ganglia display both what

A

direct and indirect transmitter actions

35
Q

what is fast excitatory post synaptic potential (EPSP) due to

A

the activation of nicotinic (ionotropic) Ach receptors. Channels conduct Na+ and K+

36
Q

what does slow EPSP follow

A

it follows the activation of muscarinic (G protein coupled) Ach receptors. Ach closes a K+ channel (M-type)

37
Q

EPSP meaning

A

(Excitatory postsynaptic potential)
Depolarizing change in rmp caused by the actions of excitatory neurotransmission. Multiple ESPSs or very large ESPSs can cause rmp to cross threshold and result in an action potential

38
Q

IPSP meaning

A

(Inhibitory postsynaptic potential)
negative change in rmp caused by release of an inhibitory neurotransmitter. Inhibits crossing of the threshold and inhibits AP.

39
Q

Graded potential meaning

A

a change in the rmp caused by an EPSP or IPSP, such a change is caused by (inhibitory or excitatory) neurotransmitter release and is not of a magnitude large enough to cross threshold in an AP

40
Q

If a graded potential does not go beyond the threshold at the trigger zone, what happens

A

an action potential will not be generated

41
Q

what is an interneurone

A

a locally-acting neurone, typically releases GABA ad so brings about an IPSP and inhibition, function is locally processing of information

42
Q
A

Sensory and Motor Neuroscience (3 decks)

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