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CNS CLERKSHIP > Excitatory and inhibitory neurotransmission in the CNS > Flashcards

Excitatory and inhibitory neurotransmission in the CNS Flashcards

1
Q

Na+ channels.

A

Flow inwards.

  • Depolarisation.
  • Excitatory.
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2
Q

Ca2+ channels.

A

Flow inwards.

  • Depolarisation.
  • Excitatory.
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3
Q

Cl- channels.

A

Flow inwards.

  • Hyperpolarisation.
  • Inhibitory.
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4
Q

K+ channels.

A

Flow outwards.

  • Hyperpolarisation.
  • Inhibitory.
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5
Q

Na+ channel agonists act to cause?

A

Excitation.

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6
Q

Na+ channel antagonists act to cause?

A

Inhibition.

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7
Q

Give an example of a Na+ channel antagonist.

A

Local anaesthetics e.g. Lidocaine.

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8
Q

K+ channel agonists act to cause?

A

Inhibition.

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9
Q

K+ channel antagonists act to cause?

A

Excitation.

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10
Q

Neuron structure can be divided into four morphological regions, which are?

A
  • soma
  • dendrites
  • axon
  • synapse
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11
Q

What part of the neuron receives incoming signals?

A

Dendrites.

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12
Q

What part of the neuron carries outgoing information?

A

Axons.

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13
Q

What are the two major families of ligand-gated channels?

A
  • Nicotinic, GABAa, Glycine receptors.

- Glutamate receptors.

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14
Q

Glutamate is the major excitatory neurotransmitter but may also have inhibitory effects via its response at which receptors?

A

Metabotropic Glutamate receptors.

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15
Q

How may Ionotropic glutamate receptors be classified?

A

Via their response to non-endogenous agonists mimicing glutamate.

  • non-NMDA.
  • NMDA
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16
Q

Non-NMDA receptors bind what to control what?

A

Agonists Kainate or AMPA to control a channel permeable to Na+ and K+.

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17
Q

NMDA receptors control what?

A

A channel permeable to Na+, Ca2+ and K+.

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18
Q

Non-NMDA ionotropic receptors mediate what?

A

Fast excitatory synaptic transmission in the CNS.

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19
Q

NMDA receptors contribute what to the excitatory synaptic potential?

A

The slow component.

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20
Q

NMDA have a high permeability to what?

A

Ca2+.

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21
Q

NMDA’s high Ca2+ permeability is thought to promote what?

A

Neurotoxicity.

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22
Q

Ketamine and psychomimetric agents e.g. phencyclidine are selective blockers of what channels?

A

NMDA-operated channels.

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23
Q

How do metabotropic glutamate receptors exert their effect as they do not have an integral ion channel?

A

Activation of a second messenger cascade.

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24
Q

What is the role of metabotropic glutamate receptors?

A

Modulation of neurotransmission.

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25
Q

Give an example of how metabotropic glutamate receptors modulate neurotransmission?

A

Presynaptic inhibtion e.g. inhibition of Ca2+ channels.

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26
Q

What is the main inhibitory neurotransmitter in the CNS?

A

GABA.

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27
Q

Which 2 types of receptors does GABA act on?

A
  • Ionotropic GABAa receptor.

- Metabotropic GABAb receptor.

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28
Q

An Ionotropic GABAa receptor operates what type of channel?

A

Cl- channel

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29
Q

A Metabotropic GABAb receptor often activates what type of channel?

A

K+ channel.

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30
Q

Benzodiazepines are what to GABAa receptors?

A

Positive allosteric modulators.

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31
Q

Benzodiazepines act on GABAa receptors to do what?

A
  • Enhance Cl- entry.
  • Decrease rmp.
  • Enhance inhibition in the presence of GABA.
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32
Q

Barbituates have what effect at the GABAa receptor?

A

Potentiate the effect of GABA.

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33
Q

Baclofen acts on the GABAb receptor as what?

A

An agonist to enhance the K+ current and thus increase inhibition.

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34
Q

Glycine is an inhibitory neurotransmitter that acts on what receptor?

A

Glycine ionotropic receptor that gates a Cl- channel.

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35
Q

What releases glycine?

A

Interneurones in the spinal cord to inhibit antagonist muscle motoneurones.

36
Q

Describe the speed of ionotropic receptor gating of ion channels?

A

Rapid

37
Q

Describe the speed of metabotropic receptor gating of ion channels?

A

Slow (-er than ionotropic).

38
Q

What action do metabotropic receptors typically have?

A

Modulatory synaptic actions.

39
Q

Metabotropic and ionotropic receptors act on channels in the presynaptic terminal to modulate what?

A

Transmitter release.

40
Q

Metabotropic and ionotropic receptors modulate transmitter-gated channels to regulate what?

A

The size of the post-synaptic potential.

41
Q

Metabotropic and ionotropic receptors modulate the resting and voltage-gated ion channels in the neuronal soma to alter what?

A

Resting Em and AP firing pattern.

42
Q

Cholinergic synaptic transmission in the autonomic ganglia display both what actions?

A

Direct and indirect.

43
Q

Fast EPSP is due to activation of what?

A

Nicotinic (ionotropic) ACh receptors - channels that conduct Na+ and K+.

44
Q

Slow EPSP follows activation of what?

A

Muscarinic receptros.

45
Q

What does EPSP stand for?

A

excitatory post synaptic potential

46
Q

What is EPSP?

A

Depolarising change in rmp due to excitatory neurotransmission.

47
Q

Multiple/very large EPSP may cause what?

A

RMP to cross threshold and result in an action potential.

48
Q

What is an inhibitory post synaptic potential (IPSP)?

A

Negative change in rmp due to inhibitory neurotransmitter release.

49
Q

What does IPSP inhibit?

A

rmp crossing threshold thus inhibiting an action potential.

50
Q

what is graded potential?

A

Change in rmp due to EPSP or IPSP.

51
Q

Changes in rmp due to EPSP/IPSP are caused by what?

A

Release of excitatory/inhibitory neurotransmitters.

52
Q

What receives the stimulus in a graded potential?

A

Cell body.

53
Q

The strength of a graded potential is determined by what?

A

How much charge enters the cell.

54
Q

Why does the strength of a graded potential diminish over distance?

A

Due to current leak and cytoplasmic resistance.

55
Q

What causes increase in amplitude of a graded potential?

A

Sodium entering.

56
Q

As amplitude of a graded potential increases, what happens to the spread of signal?

A

It goes further.

57
Q

What is the result of a graded potential that does not go beyond threshold at the trigger zone?

A

No action potential will be generated.

58
Q

What is glutamate?

A

The major excitatory neurotransmitter.

59
Q

What does glutamate act on?

A

Ionotropic receptrs to allow Na+ and Ca2+ in, and K+ out of the cell.

60
Q

What is the net result of Glutamate’s action?

A
  • EPSP.
  • Depolarisation.
    Excitation.
61
Q

What is GABA?

A

The major inhibitory neurotransmitter.

62
Q

What does GABA act on?

A

Ionotropic receptors to allow Cl- into the cell.

63
Q

What is the net result of GABA’s action?

A
  • IPSP.
  • Hyperpolarisation.
  • Inhibition.
64
Q

What is an interneurone?

A

A locally acting neurone that typically releases GABA.

65
Q

What is the function of an interneurone?

A
  • GABA release brings about an IPSP and inhibition.

- Function is local processing of information.

66
Q

What is a projection neuron?

A

A neuron responsible for conveying signals to other parts of the brain.

67
Q

A projection neurone typically release what?

A

Glutamate to bring about an EPSP.

68
Q

Excitatory neurones release what?

A

A depolarising neurotransmitter e.g. glutamate.

69
Q

Glutamate is an example of what kind of neurotransmitter?

A

Depolarising/excitatory.

70
Q

GABA is an example of what kind of neurotransmitter?

A

Hyperpolarising/inhibitory.

71
Q

The influence of a synapse depends on what?

A

The distance the current has to travel to the neurones trigger zone.

72
Q

Neurotransmitter is released in discrete packages called what?

A

Quanta.

73
Q

A quanta refers to what/

A

The release of a neurotransmitter from a single vesicle.

74
Q

The number of quanta released varies with what?

A

The stimulus.

75
Q

Name a strategy to increase quantal release.

A
  • Extensive innervation.

- Megahumongous presynapse.

76
Q

Give an example of extensive innervation to increase quantal release.

A
  • Purkinje cell - Inferior Olivary Neuron Synapse.

- The inhibitory basket cell (common in cerebellum, hippocampus and cortex).

77
Q

Give an example of a megahumungous presynapse.

A
  • Calyx of Held synapse.
78
Q

Describe the relationship between purkinje cells and parallel fibres.

A

A single Purkinje cell is contacted by approx. 400 parallel fibres. These fibres contact multiple Purkinje cells.

79
Q

Purkinje cells are innervated by parallel fibres and what else?

A

Climbing fibre.

80
Q

Activation of an excitatory input produces what?

A

A large EPSP at the trigger zone- initial segment.

Cation selective channels Na+ and K+.

81
Q

Activation of an inhibitory input produces what?

A

A large IPSP at the initial segment (opens Cl- channels).

82
Q

Simultaneous activation of excitatory and inhibitory input results in what?

A

Reduced EPSP as the inhibitory input shunts the excitatory current.

83
Q

In the absence of inhibitory input, what happens to a spontaneously active neurone?

A

It discharges rhythmically.

84
Q

In the presence of inhibitory input, what happens to a spontaneously active neurone?

A

A distinct pattern of discharge.

85
Q

Summation of postsynaptic membrane potentials allows what?

A

Multiple synaptic inputs to be integrated.

86
Q

Describe spatial summation.

A

EPSPs and IPSPs are spatially distributed but timed together.

87
Q

Describe temporal summation.

A

EPSPs occur in temporal sequence to trigger threshold.

CNS CLERKSHIP (43 decks)

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