3.6.2.2 Synaptic transmission

Question 1

defintion of synapse

simple use

Answer 1

A synapse is the junction where one neurone connects and communicates with another neurone or with an effector (eg. muscle).

Synapses transmit information from one neurone to the next.

Question 2

structure of synapse

Answer 2

presynaptic neuron:
presynaptic knob
V- gated Ca 2+ channel
vesicle containing neurotransmitter

synaptic cleft / synapse

postsynaticc neuron :
specific complementory recptor protein

Question 3

Synaptic transmission

Answer 3

AP arrives at presynaptic knob
depolarisation of membrane
open v-gated Ca 2+ channel
facilitated diffusion of Ca 2+ in
Stimulate the vesicle fuse with membrane
neurotransmitter release to synapse by exocytosis
NT diffuse across synapse
NT bind to specific complementory recceptor protein on postsynaptic membrane
Na+ channe open, Na+ diffuse in , depolarisation of postsynaptic membrane
If threshold is reached , AP regnerated and travel along axon

Question 4

Neurotransmitter Acetyle Choline use in

Answer 4

Neuromuscular junction (NMJ)
Parasympathetic NS

Question 5

How to switch off the signal of synaptic trnasmission (2 op)

include specific example of ACh

Answer 5

Breakdown the neurotransmitter using an enzyme.
Breakdown products can be taken back up into the presynaptic knob

Pump the neurotransmitter back into the presynapse using transport proteins, removing it from the synaptic cleft.

e.g. of 1
Acetyl Choline hydrolyse by ACh Esterase enzyme into acetate + choline
Through condensation in presynapse via acetyle coenzyme A back into Acetyl Choline

Question 6

Unidirectional Information Flow
(why nerves impulse only travel towards postsynaptic neuron)

Answer 6

Neurotransmitters are only made in the pre-synaptic knob

Receptors for these transmitters are only found on the post-synaptic knob

Question 7

2 type of synapse + describe

Answer 7

Excitatory
- Na+ diffuse in
- depolarization on the postsynaptic neuron
- threshold + AP

Inhibitory
- CL - diffuse in , K+ diffuse out
- decrease membrane potential (hyperpolarisation)
- MORE Na+ need to reach threshold + hard to generate AP

Question 8

cancellation

Answer 8

The balance of impulses from multiple presynaptic neurones (excitatory and inhibitory) determines whether the threshold is exceeded and whether an action potential is triggered on the postsynaptic neurone

If they balance out no AP

Question 9

spatial and temporal summation

Answer 9

Spatial summation
- multiple neuron
- so it reach threshold
e.g. rod cell

Temporal summation
- same neuron
- high frequency impulse
- accumulation of AP reach threshold

Question 10

Neuromuscular Juntion synapse transmission

Answer 10

motor to muscle
everything the same
depolarisation - contraction of muscle
(x generate AP)

Question 11

similarity and difference in transmission between cholinergic synapse and neuromuscular juction

Answer 11

Both use ACh as Neurotransmitter
generate AP vs muscle contraction
inhibition/ stimulation vs muscle always stimulated