Structure and Function - Week 4 Neurotransmission Flashcards

1
Q

What is neurotransmission? (2)

A

Communication within the nervous system and of the nervous system with other systems

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2
Q

Describe synaptic transmission (3)

A

AP arrives at pre synaptic terminal
Triggers entry of Ca2+ through voltage gated Ca2+ channel
Causes synaptic vesicles to release neurotransmitters across synaptic cleft
Neurotransmitter diffuse and bind to post synaptic receptors causing a post synaptic response

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3
Q

What could the post synaptic responses be? (4)

A

Depolarization
Hyperpolarization
Changes to biochemical cascade
Change to gene expression

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4
Q

What are the two types of transmission? (2)

A

Transmission can be extra-synaptic and non-synaptic too (volume transmission).

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5
Q

Describe electrical synapse (3)

A

Allow physical connection to exist between neurons through gap junctions
Gap junctions - made of connexin subunits (called connexon channels) - allow ions and other substances to transfer between 2 cells

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6
Q

Describe characteristics of chemical synapses (4)

A

Slow, has gain, diverse postsynaptic response, unidirectional release

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7
Q

Describe characteristics of electrical synapses (4)

A

Fast, lack gain, limited postsynaptic response, mostly bidirectional

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8
Q

Give examples of how could you assess electrical coupling between two neurons? (2)

A

Dual electrode recording
Cell traces

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9
Q

What are the 3 components of chemical synapses (3)

A

Presynaptic terminal
Synaptic cleft
Postsynaptic terminal

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10
Q

What is a bouton? (2)

A

Another name for axon terminals
Terminal enlargements on the axon where it forms a synapse

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11
Q

What are the different synapse locations (4)

A

Axon to soma
Axon to dendrite / spine
Axon to axon
Dendrite to dendrite

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12
Q

Describe axo-dendritic synapse (3)

A

Axon to dendritic shaft or spine
Spines are protrusions that increase surface area
Often excitatory

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13
Q

Describe Axo-Somatic synapse (3)

A

Axon to soma (cell body)
If synapse is at the axon hillock, large influence on firing
Often inhibitory

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14
Q

Describe Axo-Axonic synapse (3)

A

Modulatory - can be excitatory or inhibitory
Increased calcium current in presynaptic terminal = increase in transmitter release
Decreased calcium current in presynaptic terminal = decrease in transmitter release

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15
Q

What are the different types of vesicles? (2)

A

Small clear core vesicles
Large dense core vesicles

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16
Q

How do non-peptide neurotransmitters get inside synaptic vesicles at axon terminal? (1)

A

Use transporters - vesicle transporters

17
Q

Describe how vesicle transporters work? (3)

A

H+ gradient is established by a V-type H+-ATPase. 2H+ exchanged for the positively charged neurotransmitter.

18
Q

What are the methods of calcium clearance? (3)

A

Buffering
Removal
Active transport

19
Q

Describe buffering as a method of calcium clearance (2)

A

Buffering by cytoplasmic Ca2+ binding proteins (Ca-B)

20
Q

Describe buffering as a method of calcium clearance (2)

A

Removal from the presynaptic terminal (e.g. Na-Ca exchangers, Ca-ATPases).

21
Q

Describe active transport as a method of calcium clearance (2)

A

Active transport to endoplasmic reticulum via Ca-ATPase pump.

22
Q

Describe vesicle recycling (2)

A

Synaptic vesicles fuse to early endosomes (an organelle)
This is where new vesicles bud from after processing (e.g. clathrin coat)

Look at lecture

23
Q

Describe dense core vesicles (2)

A

Dense core vesicles often released from extra-synaptic sites and slowly diffuse to their target

24
Q

What can happen to neurotransmitters in synaptic cleft? (4)

A

Be taken back up by a neuron
Be taken up by a glial cell
Be broken down by an enzyme
Diffuse away from the cleft

25
Q

Describe Botulinum Toxin (4)

A

Primarily affects neuromuscular junction, causing paralysis

Use in cosmetics and chronic pain

Cleaves SNARE proteins so SNARE complex does not form and neurotransmitter is not released at neuromuscular junction
Lead to muscle paralysis

26
Q

Describe Tetatnus Toxin (3)

A

Primarily affects inhibitory interneurons of the spinal cord (GABA, glycine).
Loss of inhibition to motor neurons = muscle spasms (painful, constant contraction of muscles).

27
Q

Describe post synaptic density (2)

A

Proteins for anchoring and trafficking neurotransmitter receptors, just below postsynaptic membrane

28
Q

Describe the classifications of synapses (2)

A

Asymmetric (type I) synapses
Symmetric (type II) synapses

29
Q

Describe Asymmetric (type I) synapses (2)

A

Thicker postsynaptic density (PSD). Typically excitatory

30
Q

Describe Symmetric (type II) synapses (2)

A

PSD similar width to presynaptic component
Typically inhibitory

31
Q

What are the two neurotransmitter receptors (2)

A

Ionotropic
Metabotropic

32
Q

Describe metabotropic receptors (2)

A

May interact with G-protein-gated ion channels AND/OR enzymes which generate second messengers

33
Q

What are EPSPs? (2)

A

Excitatory postsynaptic potential
A transient depolarisation
Net influx of positive ions depolarise and bring closer to firing threshold

34
Q

What are IPSPs? (2)

A

Net influx of negative ions hyperpolarise and move further from firing threshold.

IPSP = inhibitory postsynaptic potential. A transient hyperpolarisation.

35
Q

Describe PSPs (3)

A

Graded
Decay over distance

36
Q

What is integration? (2)

A

Integration (decision making) occurs at the axon – to fire or not to fire.

37
Q

What is temporal summation? (2)

A

Temporal summation as a result of one input receiving multiple stimuli close in time.

A single neuron can therefore exhibit temporal and spatial summation at the same time

38
Q

What are neural circuits? (4)

A

Divergence
Convergence
Serial Processing
Parallel processing

39
Q

Describe divergence (2)

A

Look at week 4 notes for structure and function