BIOL1040 Module 3 L2: Action Potential generation and Conduction

What is membrane potenial

voltage measured across a plasma membrane

What happens during depolarisation

the inside of the cell becomes more +ve (Na+) enters

What happens during hyperpolarisation

Inside becomes more -ve (K+ leaves)

are action potentials graded or all or nothing

they are all or nothing

How long does an action potential last

1-2ms

Which channels open Rapidly during depolarisation

Voltage gated Na+ Channels - sodium rushes in and more positive

Which channels open Slower during repolarisation

voltage gated K+ channels - K+ flows out and becomes less positive

What is the role of Na+/K+ ATPase after an action potential

restores the Na+ and K+ ion gradients (3Na+ out and 2K+ in)

What prevents another AP during absolute refractory period

Na+ channels are inactivated

what is the relative refractory period

it means an action potential can occur but only if there is a stronger stimulus

How do local anaesthetics work

Block voltage-gated Na+ channels

Where does an action potential ususally start

at the axon hillock

What are three factors affecting the speed of AP conduction

Axon DIameter, Myelination, temperature

How does axon diameter affect conduction speed?

Larger diameter = faster conduction

How does temperature affect conduction speed?

Warmer = faster conduction

What is saltatory conduction?

APs jump between nodes of Ranvier in myelinated axons. -faster

Which has more impact on conduction speed: myelination or diameter?

Myelination

What happens at the end of an axon when an AP arrives?

Neurotransmitter release

Digoxin inhibits Na+/K+ ATPase. Which ion gradients disappear?

Na+ and K+ gradients