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3rd Year - Neurology > Peter's physiology 1 - neurones, nerve conduction and synaptic transmission > Flashcards

Peter's physiology 1 - neurones, nerve conduction and synaptic transmission Flashcards

1
Q

What is the part of the neurone which receives inputs from other neurones and conveys graded electrical signals passively to the soma?

A

Dendrites

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2
Q

What is another name for the soma/ cell body of a neurone?

A

Perikaryon

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3
Q

Part of the neurone which is the synthetic and metabolic centre?

A

Soma

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4
Q

What’s another name for the rough endoplasmic reticulum of a neurone?

A

Nissl substance

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5
Q

Name of the part of the neurone connecting the soma and initial segment of the soma?

A

Axon hillock

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6
Q

What is the site of initiation of the “all or none” action potential in the neurone?

A

Axon hillock and initial segment

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7
Q

What part of the neurone conducts output signals as action potentials to other neurones (or other cells)?

A

Axon

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8
Q

Describe the direction when the axon mediated transport of materials between the soma and presynaptic terminal?
Vice versa?

A

Anterograde direction

Retrograde direction

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9
Q

What is the name for the point of chemical (usually) communication between neurones (or other cells)?

A

Synapse

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10
Q

What type of infection exploits retrograde transport to infect neurones?

A

Viruses

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11
Q

Difference between apical and basal dendrites?

A

Apical dendrites extend upwards whilst basal dendrites extend downwards

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12
Q

What makes the axon the most excitable part of the cell?

A

Highest number of voltage activated Na channels

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13
Q

What is a neurite?

A

Any projection from the cell body of a neurone

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14
Q

Word to describe a neurone with one neurite?

A

Unipolar

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15
Q

Word to describe a neurone with one neurite that bifurcates?

A

Pseudounipolar

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16
Q

Word to describe a neurone that has 2 neurites?

A

Bipolar

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17
Q

Word to describe a neurone that has 3 or more neurites?

A

Multipolar

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18
Q

Example of a unipolar neurone?

A

Peripheral autonomic neurone

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19
Q

Example of a pseudounipolar neurone?

A

Dorsal root ganglion (DRG) neurone

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20
Q

Example of a bipolar neurone?

A

Retinal bipolar neurone

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21
Q

Example of a multipolar neurone?

A

Lower motor neurone (motoneurone)

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22
Q

What are the 4 functional regions which most neurones have?

A

Input
Integrative
Conductile
Output

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23
Q

Describe golgi type I neurones?

A

Projection neurones with long axons which connect CNS to periphery e.g. from dorsal horn of spinal cord to brain structures

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24
Q

Describe golgi type II neurones?

A

Local interneurones with short axons e.g. between neurones in CNS

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25
Q

Approximate resting membrane potential of most neurones?

A

-70 mV

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26
Q

What is the name given to the change in electrical potential associated with the passage of an impulse along the membrane of a muscle or nerve cell?

A

Action potential

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27
Q

What is the name of the point of depolarisation at which the neurone fires, transmitting information to the other neurone?

A

Threshold potential

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28
Q

What is the usual threshold potential of a neurone?

A

-60mV

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29
Q

What ion channel is responsible for the upstroke part of the action potential of a neurone?

A

Voltage-activated Na+ channel

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30
Q

What ion channel is responsible for the downstroke part of the action potential of a neurone?

A

Voltage-activated K+ channel

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31
Q

What is the name for the brief period when polarity of a neurone is reversed to inside positive?

A

Overshoot

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32
Q

What is the name for the brief period when the neurone polarity hyper polarises beyond resting potential during the action potential of a neurone?

A

Undershoot

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33
Q

Why does undershoot occur?

A

Voltage activated K+ channels do not close instantly once resting membrane potential is achieved

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34
Q

How does the amplitude of an action potential vary as it passes along the membrane?

A

It stays constant

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35
Q

Why do passive signals not spread far from their site of origin within a neurone?

A

The nerve cell membrane is leaky = current loss occurs across the membrane

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36
Q

What is generated from current leak back to extracellular space across the membrane resistance of a neurone?

A

A potential change (delta Vm)

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37
Q

For a given current (I), how does potential charge (delta Vm) vary with membrane resistance (Rm)?

A

Delta Vm increases linearly with Rm

38
Q

What happens to the membrane potential change in a passive neuronal process with distance?

A

It decays exponentially

39
Q

In the cable theory, what does the distance over which current spreads depend upon?

A

Membrane resistance (Rm) and the axial resistance of the axoplasm (Ri)

40
Q

What is lambda in the cable theory?

A

Length constant, measure of how far the voltage travels down the axon before it decays to 37%

41
Q

What happens to lambda as you increase the ratio of Rm/Ri?

42
Q

Does a larger value of lambda mean the current will travel a longer or shorter distance?

43
Q

What affect does a greater local current spread have on AP conduction velocity?

A

Increases it

44
Q

Describe how action potential occurs in a non-myelinated neurone?

A

Stimulus e.g. mechanoreceptor activation, neurotransmitter, etc. promotes action potential
Charge segregation develops
Local current is therefore set up whereby positive charge spreads passively to region over which the action potential is still to reach
Positive charge moves ahead of AP, depolarises the membrane and, if it reach threshold, opens voltage activated Na+ channels

45
Q

2 ways to increase passive current spread and thus action potential velocity/

A 
Decrease ri (possible by increasing axon diameter)
Increase rm (possible by adding an insulating material - myelin)
46
Q

What provides myelin in the CNS?

A

Oligodendrocytes

47
Q

What provides myelin in the PNS?

A

Schwann cells

48
Q

What does lambda =? (equation)

A

λ = (rm/ri)0.5

49
Q

What condition is caused by failure of myelination in the CNS?

A

Multiple sclerosis

50
Q

Which condition is caused by failure of myelination of PNS?

A

Guillian barre syndrome

51
Q

What is the name for the propagation of AP’s along myelinated axons from one node of ranvier to the next?

A

Saltatory conduction

52
Q

Where are the voltage-activated Na+ channels clustered on myelinated neurones?

A

Node of Ranvier

53
Q

What is the name for the type of synapse where pre-synaptic cell makes contact with post-synaptic cell by axon synapsing on dendrite?

A

Axodendritic synapse

54
Q

What is the name for the type of synapse where pre-synaptic cell synapses on soma of post-synaptic cell?

A

Axosomatic synapse

55
Q

what is the name for the type of synapse where pre-synaptic cell makes axon-dendritic contact with another pre-synaptic cell making contact with the axon of the first pre-synaptic cell?

A

Axoaxonic synapse (way of modulating activity of a synapse)

56
Q

How can synapses be classified functionally?

A

As being excitatory or inhibitory

57
Q

What is the most frequent excitatory transmitter in the CNS?

58
Q

What type of receptor involves a receptor protein that forms part of a ligand-gated ion channel, so that binding of the ligand to the receptor causes opening of the channel, permitting ions to flow through it?

A

Ionotropic receptors

59
Q

What type of receptors does glutamate activate?

A

Post-synaptic, cation selective, ionotropic, glutamate receptors

60
Q

What does activation of a postsynaptic, cation selective, inotropic glutamate receptor by glutamate cause?

A

A local, graded, excitatory (depolarising) response called the excitatory postsynaptic potential (e.p.s.p.)

61
Q

What are the most frequent inhibitory transmitters in the CNS?

A

Gamma-aminobutyric acid (GABA), or glycine

62
Q

What type of receptors do GABA or glycine activate?

A

Postsynaptic, anion selective, ionotropic, GABAa or glycine receptors

63
Q

What does activation of a postsynaptic, anion selective, inotropic GABAa or glycine receptors cause?

A

A local, graded, inhibitory (hyperpolarising) response called the inhibitory post-synaptic potential (i.p.s.p.)

64
Q

What are the 3 major amino acid neurotransmitters in the CNS?

A

Glutamate
GABA
Glycine

65
Q

How does GABAa and GABAb differ?

A

GABAa mediates fast inhibition whilst GABAb mediates slow inhibition

66
Q

At the chemical synapse, what separates the pre- and post- synaptic membranes?

A

A narrow synaptic cleft

67
Q

What holds the pre- and post-synaptic membranes together at the chemical synapse?

A

A matrix of fibrous extracellular protein

68
Q

What is located within the presynaptic terminal at a synapse and what does these store?

A

Vesicles

Neurotransmitter

69
Q

What is the part of the presynaptic membrane around which vesicles cluster?

A

Active zones

70
Q

What is the name of the part of the post-synaptic membrane that contains neurotransmitter receptors?

A

Postsynaptic density

71
Q

Activation of the inotropic glutamate receptors causes influx of what ion on the post-synaptic membrane?

72
Q

Activation of inotropic GABAa or glycine receptors causes influx of what ion on the post-synaptic membrane?

73
Q

In terms of synaptic integration, what does spatial summation involve?

A

Many inputs converging upon a neurone to determine its output

74
Q

In terms of synaptic integration, what does temporal summation involve?

A

A single input may modulate output by variation in action potential frequency of that input

75
Q

Physiologically, do spatial and temporal summation occur in isolation or as complementary processes?

A

Complementary processes

76
Q

What type of neurotransmitter substances are Glutamate (Glu), gamma-amino butyric acid (GABA) and glycine?

A

Amino acids

77
Q

what type of neurotransmitter substances are the following:

  • ACh
  • Dopamine
  • Histamine
  • Noradrenaline
  • Serotonin (5-hydroxytryptamine, 5-HT)
78
Q

What type of neurotransmitter substances are the following:

  • Cholecystokinin (CCK)
  • Dynorphin
  • Enkephalins (Enk)
  • Neuropeptide Y
  • Somatostatin
  • Substance P
  • Thyrotropin-releasing hormone (TRH)
  • Vasoactive intestinal polypeptide (VIP)
79
Q

What type of vesicles release amino acid and amine neurotransmitters?

A

Synpatic vesicles

80
Q

What type of vesicles release peptide neurotransmitters?

A

Secretory vesicles

81
Q

What type of channels can glutamate, GABA, glycine, ACh and 5-HT activate?

A

Ionotropic ligand-gated iom channels (LGICs)

82
Q

What type of neurotransmission does activation of inotropic ligand-gated ion channels mediate?

A

Fast neurotransmission

83
Q

What type of receptors can all neurotransmitters (except glycine) activate?

A

G-protein-couple receptors

84
Q

What type of neurotransmission does activation of G-protein coupled receptors mediate?

A

Relatively slow neurotransmission

85
Q

What does depolarisation of a presynaptic neurone by an action potential cause?

A

Ca2+ influx through voltage-activated Ca2+ channels and Ca2+ induced release of transmitter (exocytosis)

86
Q

What are the 2 options by which a neurotransmitter can be released from the synapse?

A

Enzyme-mediated inactivation or reuptake of transmitter

87
Q

Where do enzymes required for synthesis of GABA and amine neurotransmitters come from within the neurone?

A

Synthesised within the cell body and transported to the presynaptic terminal by axoplasmic transport along microtubules

88
Q

Where in the presynaptic terminal are GABA and amine neurotransmitters synthesised?

A

Within the cytoplasm

89
Q

Where are precursors of peptide neurotransmitters synthesised in the neurone?

A

In ribosomes associated with the rough ER

90
Q

Where are precursors of peptide neurotransmitters cleaved to form active neurotransmitters?

A

In the golgi apparatus

3rd Year - Neurology (17 decks)

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