5.1.3 Neuronal Communication, Generation Of An Action Potential

Question 1

Resting potential?

Answer 1

When a nerve is not sending a signal / transmitting an action potential

Question 2

How many sodium ions pumped in for how many potassium?

Answer 2

3 sodium for 2 potassium

Question 3

What does sodium / potassium ion pumping do?

Answer 3

Charges the neurone to make the inside more negative compared to outside

Question 4

Resting potential difference?

Answer 4

-60mV

Question 5

Stage 1 of action potential transmission- resting potential?

Answer 5

3 Na+ move out, 2 K+ move in using ATP; charge inside cell becomes more negative compared to the outside

Question 6

Stage 2 of action potential transmission- depolarisation?

Answer 6

Na+ ions move out of the cell, lowering polarisation; K+ channels close after a stimulus, no more can get in

Question 7

Stage 3 of action potential transmission- threshold reached?

Answer 7

The activation threshold is reached, more gated Na+ channels open, allowing more sodium to enter; membrane potential increases to +40mV (never higher)

Question 8

Stage 4 of action potential transmission- +40mV peak?

Answer 8

Na+ channels close; K+ channels open and K+ ions move out of the membrane (due to the concentration gradient); potential is lowered to become negative

Question 9

Stage 5 (linked closely to 6) of action potential transmission- repolarisation?

Answer 9

Potassium ion channels stay open, more potassium leaves the neurone; Na+ ion channels stay closed

Question 10

Stage 6 (running on from 5) of action potential transmission- hyperpolarisation?

Answer 10

The cell becomes more negatively charged compared to the outside

Question 11

Stage 7 of action potential transmission- repolarisation?

Answer 11

Resting potential is restored by the sodium / potassium pump; axon is depolarised; everything but the pump closes again

Question 12

Sodium / potassium pump?

Answer 12

Intrinsic protein that allows the passage of 3 Na+ ions out of the cell for every 2 K+ ions that come in

Question 13

Threshold?

Answer 13

Determines whether an action potential is generated based on importance / size; more gates are opened if a threshold is reached

Question 14

Refractory period?

Answer 14

Cell cannot pass another signal as it is recovering from the last one; makes sure action potential is only transmitted in one direction and constantly

Question 15

Stage 1 of transmission in myelinated neurones?

Answer 15

Sodium ions accumulate in axon; is nothing changes they will transmit the message by diffusion

Question 16

Stage 2 of transmission in myelinated neurones?

Answer 16

The positive charge (Na+ ions) cause voltage-gated Na+ channels in the closest nodes of Ranvier to open; more sodium enters

Question 17

Stage 3 of transmission in myelinated neurones?

Answer 17

Increase in voltage is produced, causing the gated channels at the next node of Ranvier to open, bringing in more Na+

Question 18

Stage 4 of transmission in myelinated neurones?

Answer 18

The charge jumps outside of the myelin, speeding it up; myelinated nerves are faster than unmyelinated nerves

Question 19

Saltatory conduction?

Answer 19

How action potential is transmitted in myelinated neurones