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BMS1052 > 5 - Synaptic Transmission & Integration > Flashcards

5 - Synaptic Transmission & Integration Flashcards

1
Q

What’s saltatory conduction?

A

AP leaping from one node of ranvier to the next

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2
Q

T/F - it’s faster for AP to occur at every point in axon than passive diffusion

A

False - faster for passive diffusion to occur between Nodes than for AP to occur at every pt in axon

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3
Q

Is the Na/K-ATPase pump involved in changing mempot during an AP?

A

NO

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4
Q

What does the Na/K-ATPase pump help with then?

A

Helps reset Na and K+ concentrations after AP

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5
Q

What are the 2 classes of synapses?

A
  1. Electrical

2. Chemical

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6
Q

Electrical synapses

A

Direct electrical coupling between cytosol of 2 neurons

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7
Q

Chemical synapses

A

Electrical signals converted into chemical signal

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8
Q

Gap junctions used in which synapses?

A

Electrical - connect cytosol of 2 neurons so changes in Vm of one immediately affect the other

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9
Q

How many subunits form cone on in each cell membrane with a gap junction?

A

6

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10
Q

Are gap junctions selective?

A

No - allow ions and small molecules through

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11
Q

Gap junctions electrically….

A

Couple neurons

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12
Q

Cytosol connections are limited by what?

A

Number of ions that can pass through gap junctions

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13
Q

Are gap junctions unidirectional?

A

No - bidirectional; change in Vm in post-synaptic neuron reflected in pre-synaptic and vice versa

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14
Q

T/F - chemical synapses are fast but weak

A

False - slow but powerful

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15
Q

Pre-synaptic active zones

A

Location of specialised proteins that bind vesicles, releasing neurotransmitter

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16
Q

What are the different types of chemical synapses based on axon location?

A

Axo-dendritic
Axo-somatic
Axo-axonic

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17
Q

Axo-dendritic

A

Most common; axon-dendrite connection on dendrite spines or shaft

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18
Q

Axo-somatic

A

Axon-soma connection; commonly inhibitory

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19
Q

Axo-axonic

A

Axon-axon connection; can module signal before transmission

20
Q

Different types of chemical synapses based on microscopic structure

A

Gray’s type I and Gray’s type II

21
Q

Gray’s type I

A
  • asymmetrical
  • round vesicles
  • e- dense
  • usually excitatory
  • contact dendritic spines
22
Q

Gray’s type II

A
  • symmetrical
  • oval vesicles
  • less e- dense
  • usually inhibitory
  • contact dendritic shaft/soma
23
Q

What does number & size of synapses connecting 2 neurons indicate?

A

Strength and importance of the signalling

24
Q

4 criteria of a neurotransmitter

A
  1. Synthesised in pre-synaptic neuron
  2. Defined action on post-synaptic neuron/effect after release
  3. Exogenous administration mimics actions of endogenous transmitter
  4. Specific mechanism exists for removing substance from synaptic cleft
25
Q

What are the 3 types of neurotransmitters?

A

Amino acids
Amines
Peptides

26
Q

Amino acids

A

Small organic molecules

Eg: glutamate (excitatory - opens cation channels), GABA (usually opens Cl- channels)

27
Q

Amines

A

Small organic molecules

Eg: dopamine, acetylcholine

28
Q

Peptides

A

Short amino acid chains stored in and released from secretory granules

29
Q

Neuromuscular junction

A

Special synapse in periphery connecting moto neurons to muscle fibres

30
Q

What are the steps for communication via a chemical synapse?

A
  1. Neurotransmitter synthesis
  2. Neurotransmitter loading into synaptic vesicles
  3. Vesicles fuse w/ pre-synaptic terminal
  4. Neurotransmitter binds post-synaptic receptors
  5. Post-synaptic response
  6. Removal of neurotransmitter from synaptic cleft
31
Q
  1. Neurotransmitter synthesis
A

Must be synthesised in neuron from which it will be released
Most neurons only release one type
A) simple amino acids available in all cells
B) GABA & amines need special enzymes for synthesis
C) peptides packaged into secretory granules in nucleus then transported to terminal

32
Q
  1. Neurotransmitter loading into vesicles
A

Vesicles from phospholipid bilayer, approximately all same size and contain similar amounts of neurotransmitter

33
Q

Are secretory granules smaller than vesicles?

A

Nope - larger

34
Q
  1. Vesicles binding & neurotransmitter release
A

Exocytosis to release vesicle contents & endocytosis to recover vesicle membrane & reuse
When AP reaches axon terminal, Cav channels in active zone open.
Intracellular Ca2+ triggers fusion of synaptic vesicle w/ membrane, releasing neurotransmitter into cleft

35
Q
  1. Neurotransmitter binding to post-synaptic receptors

What are the 2 mechanisms of neurotransmitter action at post-synaptic membrane?

A
  1. Ionotropic

2. Metabotropic

36
Q

Ionotropic

A

Ion channel gated by ligand (neurotransmitter), fast & brief

37
Q

Metabotropic

A

Receptor indirectly linked w/ ion channel, need signalling cascade, slower and longer action, broader effects

38
Q
  1. Response to neurotransmitter
A

Post-synaptic potential

39
Q

Post-synaptic potential (PSP)

A

Transient change in mempot due to neurotransmitter-mediated channel opening

40
Q

Excitatory PSP

A

Transient depolarisation (eg: Na+ channels opened)

41
Q

Inhibitory PSP

A

Transient hyperpolarisation (eg: Cl- channels opened)

42
Q

Size of PSP depends on what?

A

Amount of neurotransmitter released, no. Binding sites that can receive it, no. Neurotransmitter molecules that successfully bind

43
Q
  1. Recycling the neurotransmitter
A

Signal turned off by diffusion, reuptake or enzymatic destruction

44
Q

How do we get Ca+2 out of axon terminal?

A

Na/Ca exchanger (NCX) moves 3 Na+ into cell & 1 Ca+2 out) uses [Na+] gradient

45
Q

Dendrites ___________ inputs from each synapse

A

Integrate

46
Q

Spatial summation

A

Summation across input from many axons

47
Q

Temporal summation

A

Summation across time from single axon

BMS1052 (10 decks)

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