Communication with the Neuron

Question 1

Which ions are higher in concentration outside the axon compared to inside the axon during polarisation?

Answer 1

Sodium Na+

Question 2

Which ions are higher in concentration inside the axon compared to outside the axon during polarisation?

Answer 2

Potassium, K+ ions.

Question 3

What occurs during polarisation?

Answer 3

The sodium-potassium pump causes the diffusion of sodium ions from the outside to the inside of the axon and of potassium ions in the opposite direction, against their concentration gradient. This occurs to establish resting potential.

Question 4

What is the resting potential of the neuron?

Answer 4

-70mv.

Question 5

What causes voltage gated sodium channels in the axon membrane to open?

Answer 5

Depolarisation in previous axon spaces.

Question 6

What occurs when voltage gated sodium channels in the axon open?

Answer 6

Sodium ions diffuse into the axon and potassium ions diffuse out, along their respective concentration gradients.

= Depolarisation

Question 7

How does the charge inside the axon change when depolarisation occurs?

Answer 7

It becomes more positive.

Question 8

At what charge do the sodium channels close after depolarisation?

Answer 8

Around +40mv

Question 9

After depolarisation, which channels open after sodium channels close?

Answer 9

Potassium channels.

Question 10

What is the effect on charge that occurs when potassium channels open after depolarisation and why?

Answer 10

The axon becomes more negative because potassium K+ ions diffuse out of the axon.

Question 11

What is repolarisation?

Answer 11

The way in which the axon becomes more negative again, after potassium ions diffuse out of the cell.

Question 12

What occurs after repolarisation?

Answer 12

Hyperpolarisation

Question 13

Why does hyperpolarisation occur?

Answer 13

Potassium channels open and close very slowly.

Question 14

How is resting potential restored after hyperpolarisation?

Answer 14

Sodium and potassium ions leak back through the axon by diffusion, along their concentration gradient.

Question 15

What is the refractory period?

Answer 15

The amount of time that the membrane/axon is hyperpolarised.

Question 16

Why is the refractory period important?

Answer 16

It ensures that the action potential only travels in one direction, as no action potential can occur during the refractory period.

Question 17

What percentage of a neuron’s metabolic resources does the sodium potassium pump use for exchange?

Answer 17

40%

Question 18

What is another term for depolarisation?

Answer 18

Hypopolarisation

Question 19

What are the two types of ion channel?

Answer 19

Voltage gated and ligand gated.

Question 20

What is the threshold of excitation?

Answer 20

The charge at which sodium channels open: -60mv

Question 21

What does the all or none law suggest?

Answer 21

That an action potential either occurs or does not occur - there is no in-between.

Question 22

What is rate law?

Answer 22

The rate of firing of a neuron codes for stimulus strength

Question 23

What is salutatory conduction?

Answer 23

The increased speed of conduction due to the ‘jumping’ of an action potential at each node of ranvier. Occurs in insulated axons.

Question 24

Myelin sheath/insulated axon increases conduction speed. What is the other factor that can influence conduction speed and how?

Answer 24

The diameter of an axon.

The larger the diameter, the faster the conduction.

Question 25

What are the two types of glia?

Answer 25

Oligodendrocytes and Astrocytes.

Question 26

What do Oligodendrocytes do?

Answer 26

Lay down myelin sheath in the brain.

Question 27

What do Astrocytes do?

Answer 27

Form the blood brain barrier.