ActionPotentials - Week 16 PBL

Question 1

How is a resting membrane potential maintained?

Answer 1

Sodium-potassium ATPase pump
2K+ into cell
3NA+ out of cell

Question 2

What is the concentration of ions in and out of a cell?

Answer 2

More Na out of cell
More K inside cell
More Ca2+ out of cell
More Cl- out of cell

Question 3

Describe an action potential?

Answer 3

resting potential at -70mv
Stimulus opens some voltage gated Na+ channels
All or nothing threshold reached at -55mv
Depolarisation
More VG Na+ channels open, Na flows into cell
VG Na+ channels close, VG K+ channels open and K flows out of cell
Repolarisation
Hyperpolarisation - refractory period occurs here
Back to resting membrane potential

Question 4

Why does an action potential propagate unidirectionally?

Answer 4

Due to the refractory period

Question 5

What is Saltatory conduction?

Answer 5

Myelin sheath insulates axon and allows faster conduction.
The nodes of ranvier = unmyelinated regions along tree axon