Action Potentials

Question 1

All or none law Voltage Dependent Event

Answer 1

The stimulation has no real impact until a threshold is reached where a full action potential is then brought about

Question 2

What happens to the action potential with more stimulation

Answer 2

The more the stimulus, the faster the AP

Question 3

Distribution of Depolarisation effect on Neuronal Membrane

Answer 3

Very Localised

Question 4

How do K+ ions leave the cell at resting membrane potential

Answer 4

There are some K+ channels that are open at resting potential

Question 5

Discuss the flow of ions during an action potential

Answer 5

Depolarisation - Na+ Influx

Repolarisation - K+ Efflux and Na+ stops influx

Question 6

Compare the need for a greater Na+ permeability compared to K+ permeability in producing an AP

Answer 6

Na+ permeability needs to be greater to cause the depolarisation which only then is cancelled by the K+ permeability

Question 7

Why are cardiac APs so slow (200 ms)

Answer 7

Ca2+ plays a strong role in depolarisation and has a longer duration while APs involving only sodium are much faster

Question 8

How is the resting potential recovered after hyperpolarisation

Answer 8

Actions of the Sodium Potassium Pump

Question 9

Refractory Period

Answer 9

Period after an AP which influences how quickly neurons can respond to stimuli

Question 10

How to overcome a relative refractory period

Answer 10

This occurs if the consecutive stimuli are greater

Question 11

Absolute Refractory Period

Answer 11

The period during which even an increased stimulus will not allow a second action potential

Question 12

What part of impulse propagation causes a refractory period

Answer 12

Hyperpolarisation

Question 13

What are the two parts to the Na+ channel and what is their effect on the absolute refractory period

Answer 13

The absolute refractory period is caused by the notch at the bottom of the channels staying closed even with an increased stimulus

Question 14

How does an AP travel down an axon

Answer 14

The Na+ moves along the axon to continuously generate the local circuit down the axon

Question 15

Compare the Velocity of nerves relative to their diameter

Answer 15

The bigger the diameter, the faster the conduction velocity

Question 16

Compare type A nerves vs type C Nerves

Answer 16

Group A Nerves are myelinated while C are not

A nerves have a greater diameter and velocity than C nerves

Question 17

Effect of Myelin on a nerve

Answer 17

Reduces the threshold for an action potential to be propagated

Speeds up the transmission of an action potential