FoM:L8 - cell-cell communication

Question 1

Describe the structure of a typical neuron and what each part is responsible for?

Answer 1

dendrites: input
soma: integration of EPSP and IPSP
axon hillock: origin of AP
axon: output (AP)

Question 2

What is the axon hillock?

Answer 2

• start of axon, where AP generated
• lots of V-G Na+ channels (open at -55mV)

Question 3

What are the main stages in an action potential?

Answer 3

• depolarisation: Na+ influx
• peak: V-G Na+ channels close
• repolarisation: K+ efflux, V-G K+ open
• hyperpolarisation: V-G K+ channels close

Question 4

What is the absolute refractory period?

Answer 4

V-G Na+ channels are inactivated and another AP cannot be generated

Question 5

What is the relative refractory period?

Answer 5

• Hyperpolarisation
• V-G Na+ are returned to og state
• greater stimulus needed

Question 6

What impacts the speed of conduction?

Answer 6

• size of neuron (large = faster)
• myelination

Question 7

How does an AP propagate along a neuron?

Answer 7

• local depolarising currents (positive charge moving down)
• Na+ ions leak further down the axon
• V-G Na+ channels further down will open

Question 8

Why cant APs travel backwards?

Answer 8

refractory period