Module 7 - The Action Potential

Question 1

Stages of an action potential

Answer 1

• Resting
• Threshold Reached (-55mV)
• Depolarisation
• Repolarisation
• Refractory period
• Resting state

Some action potentials don’t reach the threshold and fail, however

Question 2

How ion channels interact with the stages of an action potential

Answer 2

• Resting - nothing
• Threshold reached - Na⁺ begin to open
• Peak - Na⁺ start to close and K⁺ start to open
• End of refractory - K⁺ close

Question 3

Inactivating K⁺ and Na⁺ channels

Answer 3

Sodium channels inactivate after ~1ms
Potassium channels may close but won’t stay inactive in neuronal transmission

Question 4

Absolute refractory period

Answer 4

Another action potential cannot be triggered

Question 5

Duration of cardiac action potential

Answer 5

200ms, 100x more than a normal action potential

Question 6

What is the name of the mechanism allowing the flowing movement of ions through a channel?

Answer 6

Knock on effect

Question 7

The components of ion channels

Answer 7

The gap that ions move through - selectivity filter
The internal gate that is opened - activation gate
The intracellular subunit - inactivation gate
The inner part of the channel - voltage sensor

Question 8

Sodium channels: what types are there and what is the disease associated with a lack of NaV1.1 inhibition?

Answer 8

NaV1.1-1.9 - all associated with different tissue types (NaV1.1-1.3 are associated with the CNS)

Dravet syndrome

Question 9

Dravet syndrome: what is it, what are the symptoms, and what are the treatments?

Answer 9

Caused by a mutation in the SCN1A gene which mutates the NaV1.1 channel and reduces its inhibition, causing some parts of the brain to be overactive

Sufferers rarely live long due to the high frequency of seizures, elevated temperatures during fevers, and other motor/cognitive problems that worsen with age

Cannabinoids and cannabis extracts (CBD)