Week 2 Lectures (Neuron form and function)

Question 1

What part of neurons conduct electrical signals?

Answer 1

The cell membrane

Question 2

What is the resting membrane potential difference?

Answer 2

Around 70Mv

Question 3

What is the direction of flow in a neuron?

Answer 3

Dendrites - Cell body - Axon - Axon terminal

Question 4

Why is there a negative resting potential in a neuron?

Answer 4

Because sodium (Na+) is being pumped out faster than K+ is being pumped in

This means there is a build up of more positive Na+ ions outside the cell than there is K+ ions inside the cell

Question 5

How much of the brains energy is consumed by maintaining the resting potential?

Answer 5

Around 60%

Question 6

What happens in the dendrites in response to a stimulus?

Answer 6

1. There is a stimulus
2. This causes a graded potential change in the dendrites as more positive ions are pumped into the cell, driving the potential back towards 0
3. This causes a ripple of depolarisation across the dendrites
4. These can add up to a larger ripple when they converge on the cell body

Question 7

Over how many mm does the neural signal in the dentrites decay?

Answer 7

1-2mm

Question 8

What kind of channel is there in the axon initial segment?

Answer 8

A voltage-gated sodium channel

Question 9

What happens when a certain potential is reached at the voltage gated sodium channel?

Answer 9

Sodium ions flood in

Question 10

What happens when the voltage gated sodium channels are opened?

Answer 10

1. There is a big depolarising spike of potential change which goes up into positive level
2. Homeostatic mechanisms kick in and the resting potential is bought back down
3. It overshoots (hyperpolarisation) before settling back to -70Mv

Question 11

What are two characteristics of the action potential?

Answer 11

It is an all or nothing stimulus

It only passes in one direction

Question 12

Where are passive potentials located and where are action potentials located?

Answer 12

Passive potentials are located in the dendrites

Action potentials are located in the axon

Question 13

What is an axodendritic synapse?

Answer 13

Between axon and dendrite

Question 14

What is an axoaxonic synapse

Answer 14

axon to axon

Question 15

What is an axosomatic synapse?

Answer 15

Axon to soma