Peter's physiology 1 - neurones, nerve conduction and synaptic transmission Flashcards
(90 cards)
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
2
Q
What is another name for the soma/ cell body of a neurone?
A
Perikaryon
3
Q
Part of the neurone which is the synthetic and metabolic centre?
A
Soma
4
Q
What’s another name for the rough endoplasmic reticulum of a neurone?
A
Nissl substance
5
Q
Name of the part of the neurone connecting the soma and initial segment of the soma?
A
Axon hillock
6
Q
What is the site of initiation of the “all or none” action potential in the neurone?
A
Axon hillock and initial segment
7
Q
What part of the neurone conducts output signals as action potentials to other neurones (or other cells)?
A
Axon
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
9
Q
What is the name for the point of chemical (usually) communication between neurones (or other cells)?
A
Synapse
10
Q
What type of infection exploits retrograde transport to infect neurones?
A
Viruses
11
Q
Difference between apical and basal dendrites?
A
Apical dendrites extend upwards whilst basal dendrites extend downwards
12
Q
What makes the axon the most excitable part of the cell?
A
Highest number of voltage activated Na channels
13
Q
What is a neurite?
A
Any projection from the cell body of a neurone
14
Q
Word to describe a neurone with one neurite?
A
Unipolar
15
Q
Word to describe a neurone with one neurite that bifurcates?
A
Pseudounipolar
16
Q
Word to describe a neurone that has 2 neurites?
A
Bipolar
17
Q
Word to describe a neurone that has 3 or more neurites?
A
Multipolar
18
Q
Example of a unipolar neurone?
A
Peripheral autonomic neurone
19
Q
Example of a pseudounipolar neurone?
A
Dorsal root ganglion (DRG) neurone
20
Q
Example of a bipolar neurone?
A
Retinal bipolar neurone
21
Q
Example of a multipolar neurone?
A
Lower motor neurone (motoneurone)
22
Q
What are the 4 functional regions which most neurones have?
A
Input
Integrative
Conductile
Output
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
24
Q
Describe golgi type II neurones?
A
Local interneurones with short axons e.g. between neurones in CNS
25
Approximate resting membrane potential of most neurones?
-70 mV
26
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?
Action potential
27
What is the name of the point of depolarisation at which the neurone fires, transmitting information to the other neurone?
Threshold potential
28
What is the usual threshold potential of a neurone?
-60mV
29
What ion channel is responsible for the upstroke part of the action potential of a neurone?
Voltage-activated Na+ channel
30
What ion channel is responsible for the downstroke part of the action potential of a neurone?
Voltage-activated K+ channel
31
What is the name for the brief period when polarity of a neurone is reversed to inside positive?
Overshoot
32
What is the name for the brief period when the neurone polarity hyper polarises beyond resting potential during the action potential of a neurone?
Undershoot
33
Why does undershoot occur?
Voltage activated K+ channels do not close instantly once resting membrane potential is achieved
34
How does the amplitude of an action potential vary as it passes along the membrane?
It stays constant
35
Why do passive signals not spread far from their site of origin within a neurone?
The nerve cell membrane is leaky = current loss occurs across the membrane
36
What is generated from current leak back to extracellular space across the membrane resistance of a neurone?
A potential change (delta Vm)
37
For a given current (I), how does potential charge (delta Vm) vary with membrane resistance (Rm)?
Delta Vm increases linearly with Rm
38
What happens to the membrane potential change in a passive neuronal process with distance?
It decays exponentially
39
In the cable theory, what does the distance over which current spreads depend upon?
Membrane resistance (Rm) and the axial resistance of the axoplasm (Ri)
40
What is lambda in the cable theory?
Length constant, measure of how far the voltage travels down the axon before it decays to 37%
41
What happens to lambda as you increase the ratio of Rm/Ri?
Increases
42
Does a larger value of lambda mean the current will travel a longer or shorter distance?
Longer
43
What affect does a greater local current spread have on AP conduction velocity?
Increases it
44
Describe how action potential occurs in a non-myelinated neurone?
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
2 ways to increase passive current spread and thus action potential velocity/
```
Decrease ri (possible by increasing axon diameter)
Increase rm (possible by adding an insulating material - myelin)
```
46
What provides myelin in the CNS?
Oligodendrocytes
47
What provides myelin in the PNS?
Schwann cells
48
What does lambda =? (equation)
λ = (rm/ri)0.5
49
What condition is caused by failure of myelination in the CNS?
Multiple sclerosis
50
Which condition is caused by failure of myelination of PNS?
Guillian barre syndrome
51
What is the name for the propagation of AP's along myelinated axons from one node of ranvier to the next?
Saltatory conduction
52
Where are the voltage-activated Na+ channels clustered on myelinated neurones?
Node of Ranvier
53
What is the name for the type of synapse where pre-synaptic cell makes contact with post-synaptic cell by axon synapsing on dendrite?
Axodendritic synapse
54
What is the name for the type of synapse where pre-synaptic cell synapses on soma of post-synaptic cell?
Axosomatic synapse
55
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?
Axoaxonic synapse (way of modulating activity of a synapse)
56
How can synapses be classified functionally?
As being excitatory or inhibitory
57
What is the most frequent excitatory transmitter in the CNS?
Glutamate
58
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?
Ionotropic receptors
59
What type of receptors does glutamate activate?
Post-synaptic, cation selective, ionotropic, glutamate receptors
60
What does activation of a postsynaptic, cation selective, inotropic glutamate receptor by glutamate cause?
A local, graded, excitatory (depolarising) response called the excitatory postsynaptic potential (e.p.s.p.)
61
What are the most frequent inhibitory transmitters in the CNS?
Gamma-aminobutyric acid (GABA), or glycine
62
What type of receptors do GABA or glycine activate?
Postsynaptic, anion selective, ionotropic, GABAa or glycine receptors
63
What does activation of a postsynaptic, anion selective, inotropic GABAa or glycine receptors cause?
A local, graded, inhibitory (hyperpolarising) response called the inhibitory post-synaptic potential (i.p.s.p.)
64
What are the 3 major amino acid neurotransmitters in the CNS?
Glutamate
GABA
Glycine
65
How does GABAa and GABAb differ?
GABAa mediates fast inhibition whilst GABAb mediates slow inhibition
66
At the chemical synapse, what separates the pre- and post- synaptic membranes?
A narrow synaptic cleft
67
What holds the pre- and post-synaptic membranes together at the chemical synapse?
A matrix of fibrous extracellular protein
68
What is located within the presynaptic terminal at a synapse and what does these store?
Vesicles
| Neurotransmitter
69
What is the part of the presynaptic membrane around which vesicles cluster?
Active zones
70
What is the name of the part of the post-synaptic membrane that contains neurotransmitter receptors?
Postsynaptic density
71
Activation of the inotropic glutamate receptors causes influx of what ion on the post-synaptic membrane?
Sodium
72
Activation of inotropic GABAa or glycine receptors causes influx of what ion on the post-synaptic membrane?
Chloride
73
In terms of synaptic integration, what does spatial summation involve?
Many inputs converging upon a neurone to determine its output
74
In terms of synaptic integration, what does temporal summation involve?
A single input may modulate output by variation in action potential frequency of that input
75
Physiologically, do spatial and temporal summation occur in isolation or as complementary processes?
Complementary processes
76
What type of neurotransmitter substances are Glutamate (Glu), gamma-amino butyric acid (GABA) and glycine?
Amino acids
77
what type of neurotransmitter substances are the following:
- ACh
- Dopamine
- Histamine
- Noradrenaline
- Serotonin (5-hydroxytryptamine, 5-HT)
Amines
78
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)
Peptides
79
What type of vesicles release amino acid and amine neurotransmitters?
Synpatic vesicles
80
What type of vesicles release peptide neurotransmitters?
Secretory vesicles
81
What type of channels can glutamate, GABA, glycine, ACh and 5-HT activate?
Ionotropic ligand-gated iom channels (LGICs)
82
What type of neurotransmission does activation of inotropic ligand-gated ion channels mediate?
Fast neurotransmission
83
What type of receptors can all neurotransmitters (except glycine) activate?
G-protein-couple receptors
84
What type of neurotransmission does activation of G-protein coupled receptors mediate?
Relatively slow neurotransmission
85
What does depolarisation of a presynaptic neurone by an action potential cause?
Ca2+ influx through voltage-activated Ca2+ channels and Ca2+ induced release of transmitter (exocytosis)
86
What are the 2 options by which a neurotransmitter can be released from the synapse?
Enzyme-mediated inactivation or reuptake of transmitter
87
Where do enzymes required for synthesis of GABA and amine neurotransmitters come from within the neurone?
Synthesised within the cell body and transported to the presynaptic terminal by axoplasmic transport along microtubules
88
Where in the presynaptic terminal are GABA and amine neurotransmitters synthesised?
Within the cytoplasm
89
Where are precursors of peptide neurotransmitters synthesised in the neurone?
In ribosomes associated with the rough ER
90
Where are precursors of peptide neurotransmitters cleaved to form active neurotransmitters?
In the golgi apparatus
