Synapses

Question 1

What is resting membrane potential?

Answer 1

• When a neurone is not sending a signal it is at rest
• The inside of a a neurone has a negative charge relative to the outside (-70mV)
• It involves a sodium-potassium pump where 3 Na+ are actively moved out of the membrane, whilst 2 K+ are actively transported into the axon
• so more ions are pumped out than are coming in giving it an overall negative charge

Question 2

Describe the transmission across a synapse

Answer 2

1. an action potential arrives
2. the membrane depolarises, calcium channels open, calcium ions enter the neurone
3. calcium ions cause synaptic vesicles containing neurotransmitters to fuse with the presynaptic membrane
4. neurotransmitter is released into the synaptic cleft
5. neurotransmitter binds with receptors on the postsynaptic membrane. Cation channels open. Sodium channels flow through the channels
6. The membrane depolarises and initiates an action potential
7. When released the neurotransmitter will be taken up across the presynaptic membrane, or it can diffuse away and be broken down