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University - Neuroscience > Neuronal conduction and neurotransmission > Flashcards

Neuronal conduction and neurotransmission Flashcards

1
Q

What 2 factors determine speed of depolarisation

A

The space constant

Time constant

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2
Q

What is the space constant

A

How far a current can spread passively along the axon

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3
Q

What is the space constant equation

A

Space constant = sqrt(membrane resistance/internal resistance)

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4
Q

Why is the cell membrane both a resistor and a capacitor

A

Current can pass through but not well and charge can build up on one side

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5
Q

What is myelin made of

A

Oligodendroytes/Schwann cells

Increases membrane resistance
Decrease membrane capacitance

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6
Q

What is saltatory conduction

A

Short stretch of bare axon which allows AP to conduct down the axon and jump from node to node

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7
Q

What type of disease is Multiple Sclerosis

A

Auto-immune disorder, Episodic

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8
Q

What neurons are myelinated in the body

A

In CNS and PNS including motor and proprioception

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9
Q

Why is MS symptoms better at low temperatures

A

Na+ channels inactivate more slowly

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10
Q

What is Guillain-Barre syndrome

A

Auto-immune disorder affecting PNS myelin

Symptoms - numbness, tingling and weakness

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11
Q

Why do GBS patients recover

A

PNS myelin can regenerate

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12
Q

Why are vertebrates bigger than any other organism

A

They have myelination

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13
Q

What does saltatory conduction do

A

Makes signal propagation more energy efficient

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14
Q

What is a synapse

A

A junction between two neurons allowing for signals to pass from one to the other

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15
Q

What is the name for the process in which synapses signal

A

Synaptic transmission

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16
Q

What do synapses allow for

A

Flexible processing

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17
Q

How are electrical synapses formed

A

Gap junctions that allow current to pass directly between neurons

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18
Q

What are electrical synapses good for

A

Fast communication and synchronizing neurons

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19
Q

What does a ShakB2 mutation do

A

Blocks hyperpolarising and depolarising stimulus (Connexin gene)
No gap junctions

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20
Q

What are the steps in chemical synaptic transmission

A

Package neurotransmitters in vesicles and place in pre-synaptic terminal

Action potential arrives –> voltage gated Ca2+ channels open

Ca2+ influx –> vesicles fuse to membrane and neurotransmitters released

Neurotransmitters diffuse across the synaptic cleft, activate receptors on the postsynaptic cell –> further signalling

Neurotransmitters are removed from the cleft

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21
Q

Differences in synaptic vesicles and dense core secretory granules

A

Synaptic:
Small (40-50nm), Small molecule neurotransmitters, filled by transporter proteins at the presynaptic terminal, recycled by endocytosis

Dense-core secretory granules:
Large, Peptide neurotransmitters, created and filled by the ER/Golgi secretory apparatus, one and done

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22
Q

How does The action potential causes Ca2+ channels to open

A

Calcium follows the electrical force and concentration gradient to move inside the cell
Motor neuron fills up with calcium
Triggered by depolarisation

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23
Q

How do vesicles fuse onto the membrane

A

SNARE proteins

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24
Q

How do the SNAREs bind the vesicle to the plasma membrane

A

Ca2+ binds to the synaptotogmin causing a conformational change, SNAREs to zip together so the vesicle is bound to membrane

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25
What does BOTOX and tetanus target
SNARE proteins
26
How do ionotropic receptors depolarise the cell
Neurotransmitter binds --> channels open ions enter --> depolarise the cell
27
Difference between electrical and chemical synapses
``` Chemical: Pass in one direction Signals can be inverted (inhibitory), amplified (more EPSPs), modulated... Slower Electrical: Signals can pass in both directions Fast ``` Both are plastic and allow summing up inputs at the post-synaptic neuron
28
What neurotransmitter do NMJ use
ACh
29
Does a motor neuron AP always cause muscle cell APs
Yes
30
Why is neuromuscular junction have such efficient transmission
High surface area Large number of active zones Contains junctional folds which are densely filled with neurotransmitter receptors Active zones and junctional folds are precisely aligned
31
What type of packet is neurotransmitter found in
Quantal
32
Who discovered that neurotransmitter was found in vesicles
Bernard Katz
33
What does axodentric mean
When an axon synapses to dendritic neuron
34
What should a neurotransmitter do
Be present in presynaptic terminals Be released in response to stimulation Act on postsynaptic neurons
35
What are ways to determine if there is a neurotransmitter present
Immunostaining Collect fluid around neurons after stimulation Does the molecule mimic the effect of stimulating the presynaptic cell Can you block the neurotransmitter
36
What are the amino acid neurotransmitters
Glutamate, glycine and GABA
37
What are the amine neurotransmitters
``` Ach Monoamines (dopamine, epinephrine ....) ```
38
Difference between Amino acids/amines and peptides when acting as a neurotransmitter
Amino acids/amines: Small molecules Stored in synaptic vesicles Can bind to ionotropic or metabotropic receptors Peptides Large molecules Stored in secretory granules Only bind to metabotropic
39
Why can neurons diverge
One neuron sending the same signal can cause different downstream effect
40
Why can neurons converge
Different transmitters can act on the same effector
41
What is the most neurotransmitter in the body
Glutamate (excitatory) GABA (inhibitory)
42
What neurons in glutamate found in
Amino acid so found in all neurons
43
What are the 3 glutamate receptor subtypes
AMPA NMDA Kainate
44
What do AMPA receptors do
Mediate fast excitatory transmission | Glutamate binds to AMPA triggers Na+ and K+ currents result in ESPS
45
What are NMDA receptors
Co-exist with AMPA receptors Voltage gated Mg2+ block NMDA receptors only open when the neuron is already depolarised Let Ca2+ in --> downstream signalling Act as a coincidence detector which is important for learning
46
What do mGluRs do
Allow glutamate to sometimes be inhibitory
47
How many subunits in iontropic receptors
4
48
What is the most common inhibitory transmitter in the CNS
GABA
49
What type of channel is GABAa
Chloride channel
50
When are IpSp produced
When membrane potential is above chlorides Nernst potential
51
What happens when there is too much/little GABA
Too much - coma or loss of consciousness | Too little - seizures - too much glutamate
52
How does ethanol, benzodiazepines and barbitudes work (allosteric drugs)
Activates GABAa which causes inhibition of neurons
53
What is GABAa
Ionotropic receptor Cl- Inhibitory
54
What are GABAb receptors
Metabotropic GABA receptors
55
What does GABAb and mGluRs do
They can: Open K+ channels, close Ca2+ channels and trigger other secondary messengers like cAMP Cause hyperpolarisation
56
What does glycine do?
Inhibits neurons via glycine-gated chloride channel Binds to NMDA glutamate receptors (excitatory)
57
What is dendritic integration>
5 or 6 EPSPs are needed for activation not just one
58
How do EPSPs work
Signal reaches the dendrites and slowly decays, before complete decay another signal arrives, process repeats until threshold is reached. Once reached an AP is formed which sends downstream signals
59
What is shunting inhibition
Opening of chloride conductance decreases the membrane resistance so current leaks out the membrane Inhibitory blocks EPSP towards soma GABAa dont produce IPSPs if close to chlorides nernst potential
60
Where does inhibition usually occur
Presynaptic cleft
61
What is a axoaxonic synpase
Axon synapsed to another axon
62
What is a GABAergic neuron
A neuron which can block the presynaptic release from another neuron by releasing GABA
63
What do GABAergic neurons release
GABA which inactivates calcium channels so less Ca2+ enters so less neurotransmitter is released so reduced effect on postsynaptic membrane
64
Why are inhibitory neurons important
They modulate the activity of excitatory neurons

University - Neuroscience (9 decks)

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