Chemical Synaptic Transmission

Question 1

Where does action potential arrive in a neuron?

Answer 1

The presynaptic membrane

Question 2

Which channel opens when an action potential arrives at the presynaptic membrane?

Answer 2

Ca+ (Calcium channel)

Question 3

What happens to the Ca+ channel when it is opened by the action potential?

Answer 3

• There is an influx of Ca+ ions
• localised depolarisation of the neuron

Question 4

What is synaptotagmin & what does it do?

Answer 4

A protein in the vesicle membrane that sense local rise in Ca2+

Question 5

What protein senses a local rise in Ca2+ ions when the channel opens?

Answer 5

synaptotagmin

Question 6

Where is synaptotagmin found?

Answer 6

In the vesicle membrane

Question 7

What causes the synaptic vesicles to fuse with the presynaptic membrane in the active zone?

Answer 7

rise in Ca2+ ions

Question 8

Where does the synaptic vesicle fuse with the presynaptic membrane?

Answer 8

active zone

Question 9

What proteins drive the fusion of the synaptic vesicle and presynaptic membrane?

Answer 9

SNAREs

Question 10

What are v-SNAREs associated with

Answer 10

the vesicle

Question 11

What are T-SNAREs associated with

Answer 11

the presynaptic target membrane

Question 12

Where is the neurotransmitter released to?

Answer 12

the synaptic cleft / gap

Question 13

What happens to neurotransmitter molecules in the synaptic gap?

Answer 13

They DIFFUSE across the gap and BIND to specific receptors on the post-synaptic membrane

Question 14

Which neurons open the Na+ channels?

Answer 14

Excitatory neurons

Question 15

What happens once the excitatory neurons open the Na+ channels

Answer 15

This causes and influx of Na+ into the dendrite

Question 16

What happens when sufficient Na+ enters the dendrite?

Answer 16

depolarisation occurs resulting in action potential (this carries the chemical signals to the next neuron)

Question 17

What are the 5 steps of action potential?

Answer 17

1) a stimulus (from sensory/ other neuron) causes target cell to depolarize toward the threshold potential

2) If threshold is reaches, all Na+ channels open and membrane depolarizes

3) At the peak of action potential, K+ channels open. K+ begins to leave cell. Na+ channels also close

4) membrane hyperpolarizes as K+ ions leave. Membrane enters a refractory period and cannot fire.

5) K+ channels close. Na+ and K+ transporter restores resting potential

Question 18

What are the 3 major structural components of the chemical synapse?

Answer 18

• Presynaptic swelling of the axon
• postsynaptic element of recipient cell (dendrites)
• Synaptic gap

Question 19

What are the 4 main steps of chemical synapse transmission?

Answer 19

1. Arrival of an action potential at the presynaptic swelling (axon terminal)
2. Depolarisation of the presynaptic membrane
3. Release of neurotransmitters
4. Neurotransmitters diffuse across the synaptic gap and bind rapidly to the post synaptic receptors on the dendrite

Question 20

What is the function of a V-SNARE

Answer 20

mediate the process of exocytosis

Question 21

What is the function of a T-SNARE

Answer 21

To form stable subcomplexes and guide V-snares

(Associated with the presynaptic target membrane)