Synapses Flashcards

1
Q

The synapse

A

Junction that allows 2 neurones to communicate with each other using neurotransmitters

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2
Q

Pre synaptic neurone

A

The one receiving the action potential that will send it to the next one

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3
Q

Post synaptic neurone

A

The neurone that receives neurotransmitter from pre synaptic neurone to stimulate the generation of a new action potential

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4
Q

Where in the neurones are impulses transmitted over the synapse?

A

From the synaptic knob of pre synaptic neurone (at axon terminal end) to the dendrites of the cell body on the post synaptic neurone

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5
Q

Types of synapses

A

Excitatory
Inhibitory

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6
Q

Excitatory synapse

A

Stimulates the development of new action potentials at post synaptic neurone

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7
Q

Neurotransmitters

A

Allows for communication of neurones over the synapse by diffusion of the neurotransmitter from one neurone to the next

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8
Q

What neurotransmitter is on the specification ?

A

Acetyl choline

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9
Q

Cholinergenic synapse

A

Type of synapse that communicates to next neurone using acetyl choline

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10
Q

What happens when action potentials arrive at the synaptic knob of presynaptic neurone?

A

Depolarises the pre synaptic membrane

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11
Q

What happens when the synaptic knob is depolarised?

A

Voltage gated Ca2+ channel proteins are triggered to open so
Ca2+ ions diffuse into synaptic knob down electrochemical gradient using channel proteins

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12
Q

What happens when Ca2+ ions enter the synaptic knob?

A

Causes synaptic vesicles in synaptic knob to fuse with the presynaptic neurone membrane

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13
Q

Fusion of synaptic vesicles with synaptic knob

A

The synaptic vesicles containing acetyl choline will release acetyl choline into synaptic cleft

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14
Q

Once acetyl choline is in the synaptic cleft…

A

It will diffuse to the post synaptic membrane and bind to receptors on the membrane

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15
Q

When acetylcholine binds to receptors on post synaptic membrane in an excitatory synapse

A

Na+ channel proteins are triggered to open (on post synaptic membrane) so Na+ ions are triggered to diffuse into the post synaptic neurone

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16
Q

In an excitatory synapse, what happens when Na+ diffuses into post synaptic neurone?

A

Causes depolarisation of neurone membrane
If threshold is reached, this generates new action potentials to be sent along post synaptic neurone

17
Q

Inhibitory synapse

A

Stops the generation of new action potentials at the post synaptic membrane

18
Q

What happens in an inhibitory synapse when acetyl choline binds to receptors on post synaptic neurone?

A

Triggers opening of K+ channel proteins so K+ diffuses out of the post synaptic neurone by facilitated diffusion
Also causes Cl- channels to open, causing Cl- to diffuse into the postsynaptic neurone
Membrane potential more negative than resting potential
Causes hyper polarisation of post synaptic neurone
So less likely to reach threshold and won’t generate an action potential because more Na+ needs to enter to reach threshold

19
Q

Summation

A

Determining whether threshold potential will be reached in post synaptic neurone thus an action potential generated in post synaptic neurone

20
Q

2 types of summation

A

Temporal
Spatial

21
Q

Temporal summation

A

A higher frequency of impulses is sent along presynaptic neurone in a given time so more neurotransmitter is released so more likely for post synaptic membrane to reach threshold and generate a new impulse

22
Q

Spatial summation

A

If a post synaptic neurone membrane is connected at the synapse to 2 or more pre synaptic neurones so will receive neurotransmitter from more than 1 neurone
More likely to trigger enough depolarisation and reach threshold to generate new impulse

23
Q

Neurone to myofibril synapse

A

Same mechanism but the post synaptic neurone is the myofibril, it’s membrane is the sarcolemma and an impulse is sent along the muscle fibre not neurone

24
Q

When returning to the rest state, what happens at the pre synaptic neurone?

A

Can2+ ions are actively transported OUT of the synaptic knob to stop synaptic vesicles fusing with the membrane thus stops release of acetyl choline

25
Excess acetyl choline in the synaptic cleft is…
Hydrolysed by the enzyme acetyl cholinesterase into ACETATE + CHOLINE
26
What enzyme hydrolyses acetyl choline?
Acetyl cholinesterase
27
What is acetyl choline hydrolysed into?
Acetate + choline
28
Choline from hydrolysis of acetyl choline will…
Diffuse back into pre synaptic knob by facilitated diffusion Then reforms acetyl choline by reacting with acetate (catalysed by an enzyme)
29
How is acetyl choline repackaged into synaptic vesicles
By active transport
30
Why do synaptic knobs have a lot of mitochondria?
For a lot of aerobic respiration to produce a lot of ATP: Active transport of acetyl choline into synaptic knob For Na+K+ carrier protein pump for resting potential
31
Why can an impulse only be transmitted from presynaptic to post synaptic?
Acetyl choline can only be released from pre synaptic neurone Receptors to acetyl choline only present on post synaptic neurone
32
3 aspects of synaptic communication on the spec
Inhibition or excitation Unidirectionality Spatial or temporal summation
33
How to describe affect of drug
Blocks channel protein SO ions cant enter pre synaptic neurone Describe synaptic transmission No generation of another action potential in post synaptic neurone