Action Potentials

Question 1

What is ‘Hyperpolarisation?’

Answer 1

-Membrane Potential becomes more negative
(inside)
-Returns cell to Resting Membrane Potential

Question 2

What is ‘Depolarisation?’

Answer 2

• Membrane Potential becomes more positive

- (less negative inside)

Question 3

How does Depolarisation occur?

Answer 3

• Entry of Sodium ions (influx) into cell

- Positive ions

Question 4

What type of Channels are Sodium Channels?

Answer 4

-Ligand Gated Channels

Question 5

What does it mean by ‘Sodium Channels’ require a Driving Force?

Answer 5

• net electromotive force that acts on the ion
• (Vm-ENa)
• Membrane Potential-Sodium Equilibrium Potential

Question 6

Name X3 ways an ion channel is stimulated

Answer 6

• Physical Stimuli
• Membrane Voltage
• Chemicals

Question 7

What type of channel is responsible for downstream depolarisation of a neuron?

Answer 7

• Voltage Gated Sodium Channels

- Voltage Gated Potassium Channels

Question 8

Which channels are responsible for Hyperpolarisation/Reploraisation?

Answer 8

-Voltage Gated Potassium Channels

Question 9

What is a Threshold Value?

Answer 9

-Minimum value membrane potential must be for an Action Potential to be fired triggering depolarisation

Question 10

Is Resting Membrane Potential below Threshold value?

Answer 10

YES

Question 11

Explain the five stages of Action Potential Firing

Answer 11

1) Threshold Value is met
2) -Action Potential is Fired
3) -Depolarisation Occurs (Upstroke)
4) Repolarisation (Downstream) – Return to Resting Potential
5) Return to Resting Membrane Potential (Hyperpolarisation-more negative)

Question 12

What is Upstroke more commonly known as?

Answer 12

Depolarisation

Question 13

What is Upstroke more commonly known as?

Answer 13

Repolarisation

Question 14

What is Upstroke more commonly known as?

Answer 14

Depolarisation

Question 15

What is the difference between Hyperpolarisation and Reploraisation?

Answer 15

-Repolarisation comes before Hyperpolarisation

Repolarisation-Entry Potassium Ions and inactivation of sodium channels
Hyperpolarisation- CLOSURE of potassium channels

Question 16

When do Sodium Channels become inactivated?

Answer 16

• During repolarisation become inactivated

- Voltage Gated Potassium Channels open

Question 17

What is the Refractory Period?

Answer 17

• Amount of time cell not producing an Action Potential before ready for next one to be fired
• Ensures Action Potential is successful when occurs

Question 18

What is Absolute Refractory Period?

Answer 18

• NO Stimulus

- ALL Channels are inactivated

Question 19

What is Relative Refractory period?

Answer 19

• Very STRONG stimulus

- Can cause Second Action Potential as mixed-some activated and some inactivated channels-still partially capable

Question 20

What is order of movement through a neuron?

Answer 20

1) Dendrites
2) Axon Hillock (trigger period)
3) Axon (Conducting part)
4) Axon Terminal (Output)

Question 21

What is Contagious Conduction?

Answer 21

-Process-Spreading Action Potentials from one area to the next

Question 22

What is Salatory Conduction?

Answer 22

-Action potential jumps from one node to another

Question 23

What is Myelin Sheath?

Answer 23

• iInsulating Layer

- Speeds up transmission of electrical impulses