Lecture 24: Transmission at the synapse

Question 1

What do electrical synapses do?

Answer 1

transmits signals btw cells that are physically connected via gap junctions
- RAPID

Question 2

What do chemical synapses do?

Answer 2

transmit signals btw cell that are not physically connected

• releases neurotransmitters –> trigger AP in postsynaptic cell
• SLOWER than electrical

Question 3

What structures are found in the presynaptic cells?

Answer 3

• Axon terminal/bouton/knob
• vesicles which contain neurotransmitters
• cytoskeleton allows movement of vesicles when triggered by Ca+ channels
• Voltage gated Ca+ channels

Question 4

What structures are found in postsynaptic cells?

Answer 4

• neuron transmitter receptors
• Na+ channels which are triggered by neurotransmitters binding to receptors —-> Na+ channels open and depolarise postsynaptic cells

Question 5

What are the steps needed for synaptic transmission?

Answer 5

1. Depolarisation of presynaptic knob
2. voltage-gated Ca+ channels open - trigged by depolarisation
3. influx of Ca+ triggers vesicles to release their neuron transmitters into the synaptic cleft
4. Neuron transmitters bind to specific receptor on the post-synaptic membrane
5. binding triggers Na+ channels to open and depolarise the membrane - EPSP
   - AP then propagates down axon

Question 6

To stop the chemical transmission what happens to the neuron transmitters?

Answer 6

• removed from synaptic cleft
• degraded by enzymes
• undergo re-uptake not the presynaptic cells or nearby glia