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Week 7 - 12 > Synapse 1 > Flashcards

Synapse 1 Flashcards

1
Q

Functions of neurons:

A

Cell processes

Interconnect cells

Transmit information

Use electrical signals

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2
Q

What’s important to know about neurons?

A

Separate entities - separate cells that communicate with each other

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3
Q

What’s the only way that neurons can communicate with each other?

A

Through axons

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4
Q

Direction of signal in dendrites?

A

Propagates towards cell body

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5
Q

Direction of signal in axons?

A

Propagates away from cell body

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6
Q

Potential difference in axon before electrical activity generated?

A

-70 mV

Resting membrane potential

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7
Q

Characteristics of action potentials:

A

Self propagates

Travels in one direction - vectorial down axon

No ‘volume control’ - always same size of AP

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8
Q

What happens if there is a higher frequency of action potentials?

A

Faster signal

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9
Q

How are action potentials graded?

A

In frequency not amplitude

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10
Q

Where do action potentials start?

A

At cell body (axon hillock)

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11
Q

Where are action potentials transmitted in axons?

A

Towards end of axon - to end bulb/synapse

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12
Q

What do action potentials cause at the end of the axon?

A

Secretion of chemicals (neurotransmitters)

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13
Q

What essentially are neurons?

A

Elongated secretory cells that are polarised

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14
Q

How are neurons similar to secretory cells?

A

Axon is equivalent to apex of secretory cell

Dendrites are equivalent to basal aspect of secretory cell

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15
Q

What’s the axon end bulb the site of?

A

Chemical neurotransmitter release

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16
Q

What is the gap between two neurons called?

A

Synaptic cleft

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17
Q

WHat’s the cell before the gap called?

A

Presynaptic cell

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18
Q

What’s the cell called after the gap?

A

Postsynaptic cell

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19
Q

What does the swelling in terminal of presynaptic cell form?

A

Bouton

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20
Q

What is reception of signals by?

A

Via highly branched processes - dendrite tree and dendritic spines

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21
Q

How does vesicle and presynaptic membrane recognise each other?

A

v-SNARE on vesicle complexes with t-SNARE at presynaptic membrane

22
Q

What do v-SNARE and t-SNARE do?

A

They form a complex that folds strongly to draw vesicle and presynaptic membranes close

23
Q

What happens when vesicle and presynaptic membranes are drawn close?

A

Vesicle is docked on membrane - clamped by synaptotagmin

24
Q

What removes vesicle from synaptotagmin clamp?

A

Action potential triggers calcium influx at end-bulb

This reorient membrane and helps align SNARE complex for fusion

25
Q

Where are peptide neurotransmitters made?

A

RER

Packaged into vesicles in Golgi

26
Q

What happens after peptide neurotransmitters leave Golgi?

A

Transported along microtubules to axon terminal

Vesicles are then charged in axon terminal

27
Q

What are the two classes of receptors for neurotransmitters on post synaptic membrane?

A

Ionotropic receptors - fast signals

Metabotropic - slow signals

28
Q

How do ionotropic receptors work?

A

Neurotransmitter binds to receptor - induces conformational change

Pore opens + ions flow in/out

Voltage of cell then changes

29
Q

What can ionotropic receptors do to voltage of cell?

A

Decrease potential = negative ions out or positive ions in

Increase potential = negative ions in or positive ions out

30
Q

Give an example of ionotropic receptor:

A

Acetylcholine receptor

31
Q

Give an example of metabotropic receptor:

A

G protein-linked receptor

32
Q

What happens in metabotropic receptors?

A

Receptor binds G-protein (GTP replaces GDP)

Active G-protein then leaves + binds target enzyme

Enzyme generates messenger

Messenger binds channel + channel opens

33
Q

What happens after metabotropic receptor causes ion channel to open?

A

GDP-ase removes P from GTP which then inactivated G protein

G protein then leaves enzyme - inactivated enzyme

G protein is then free + ready to bind to receptor

34
Q

Summary of how an ionotropic receptor works:

A

Neurotransmitter binds

Channel opens

Ions flow across membrane

35
Q

Summary of how metabotropic receptors work:

A

Neurotransmitter binds

G-protein is activated

G-protein subunits or intracellular messengers modulate ion channels

Ions flow across membrane

Ion channel opens

36
Q

What have electrophysiological experiments shown?

A

That the release of neurotransmitters is quantal - in packets

37
Q

What does quanta relate to?

A

The release of contents of single vesicles at the presynaptic membrane

38
Q

What results in a stronger signal at the post synaptic membrane?

A

More vesicles released

39
Q

What are PSPs caused by?

A

The passage of ions through ion channels which have opened following receptor/neurotransmitter interactions

40
Q

What does PSP stand for?

A

Post synaptic potential

41
Q

What is an excitatory PSP (EPSP)?

A

A net flow of positive ions into the cell

Causes depolarisation of membrane - brings closer to threshold

42
Q

Single ESPs:

A

Rarely result in action potential

43
Q

Amplitude in inhibitory and excitatory PSPs:

A

Amplitude of signal decreases with distance and time

44
Q

What’s the typical amplitude of an EPSP?

A

Positive deflection (depolarisation) of between 1-5mV

45
Q

What’s the typical amplitude of an IPSP?

A

Negative deflection (hyperpolarisation) of between 1-5 mV

46
Q

What’s spatial summation?

A

Multiple end-bulbs on same dendrite

Make large change in potential

47
Q

What’s temporal summation?

A

One axon firing very quickly

Recovery is slow

48
Q

Difference between single EPSP and summed SPSPs:

A

Single = potential difference may not reach threshold

Summed = threshold reached and AP generated

49
Q

What’s hyperpolarisation caused by?

A

Inhibitory PSP

IPSP

50
Q

What can APSPs be caused by?

A

Direct (ionotropic) or indirect (metabotropic) gating

Week 7 - 12 (38 decks)

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