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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
Q

What does BOTOX and tetanus target

A

SNARE proteins

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26
Q

How do ionotropic receptors depolarise the cell

A

Neurotransmitter binds –> channels open ions enter –> depolarise the cell

27
Q

Difference between electrical and chemical synapses

A 
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
Q

What neurotransmitter do NMJ use

A

ACh

29
Q

Does a motor neuron AP always cause muscle cell APs

A

Yes

30
Q

Why is neuromuscular junction have such efficient transmission

A

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
Q

What type of packet is neurotransmitter found in

A

Quantal

32
Q

Who discovered that neurotransmitter was found in vesicles

A

Bernard Katz

33
Q

What does axodentric mean

A

When an axon synapses to dendritic neuron

34
Q

What should a neurotransmitter do

A

Be present in presynaptic terminals
Be released in response to stimulation
Act on postsynaptic neurons

35
Q

What are ways to determine if there is a neurotransmitter present

A

Immunostaining

Collect fluid around neurons after stimulation

Does the molecule mimic the effect of stimulating the presynaptic cell

Can you block the neurotransmitter

36
Q

What are the amino acid neurotransmitters

A

Glutamate, glycine and GABA

37
Q

What are the amine neurotransmitters

A 
Ach
Monoamines  (dopamine, epinephrine ....)
38
Q

Difference between Amino acids/amines and peptides when acting as a neurotransmitter

A

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
Q

Why can neurons diverge

A

One neuron sending the same signal can cause different downstream effect

40
Q

Why can neurons converge

A

Different transmitters can act on the same effector

41
Q

What is the most neurotransmitter in the body

A

Glutamate (excitatory)

GABA (inhibitory)

42
Q

What neurons in glutamate found in

A

Amino acid so found in all neurons

43
Q

What are the 3 glutamate receptor subtypes

A

AMPA
NMDA
Kainate

44
Q

What do AMPA receptors do

A

Mediate fast excitatory transmission

Glutamate binds to AMPA triggers Na+ and K+ currents result in ESPS

45
Q

What are NMDA receptors

A

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
Q

What do mGluRs do

A

Allow glutamate to sometimes be inhibitory

47
Q

How many subunits in iontropic receptors

A

4

48
Q

What is the most common inhibitory transmitter in the CNS

A

GABA

49
Q

What type of channel is GABAa

A

Chloride channel

50
Q

When are IpSp produced

A

When membrane potential is above chlorides Nernst potential

51
Q

What happens when there is too much/little GABA

A

Too much - coma or loss of consciousness

Too little - seizures - too much glutamate

52
Q

How does ethanol, benzodiazepines and barbitudes work (allosteric drugs)

A

Activates GABAa which causes inhibition of neurons

53
Q

What is GABAa

A

Ionotropic receptor
Cl-
Inhibitory

54
Q

What are GABAb receptors

A

Metabotropic GABA receptors

55
Q

What does GABAb and mGluRs do

A

They can:
Open K+ channels, close Ca2+ channels and trigger other secondary messengers like cAMP
Cause hyperpolarisation

56
Q

What does glycine do?

A

Inhibits neurons via glycine-gated chloride channel

Binds to NMDA glutamate receptors (excitatory)

57
Q

What is dendritic integration>

A

5 or 6 EPSPs are needed for activation not just one

58
Q

How do EPSPs work

A

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
Q

What is shunting inhibition

A

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
Q

Where does inhibition usually occur

A

Presynaptic cleft

61
Q

What is a axoaxonic synpase

A

Axon synapsed to another axon

62
Q

What is a GABAergic neuron

A

A neuron which can block the presynaptic release from another neuron by releasing GABA

63
Q

What do GABAergic neurons release

A

GABA which inactivates calcium channels so less Ca2+ enters so less neurotransmitter is released so reduced effect on postsynaptic membrane

64
Q

Why are inhibitory neurons important

A

They modulate the activity of excitatory neurons

University - Neuroscience (9 decks)

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