Neurones and action potentials

Question 1

Describe depolarisation

Answer 1

VD Na channels start to open due to stimulus crossing the threshold causing Na+ to move into the axon due to conc gradient opening more channels (positive feedback)

Question 2

Describe re polarisation

Answer 2

VD Na+ channels close, VD K+ open allowing K+ to diffuse out of the axon down an electrochemical gradient

Question 3

Describe refractory period

Answer 3

Hyperpolarised
VD K+ channels close
K+ channels are always open so K+ ions move back into the axon to recreate resting potential

Question 4

Describe salutatory conduction

Answer 4

Myelin sheath acts as an electrical insulator
Allows nerve impulses to jump from nodes of ranvier to node of ranvier which quickens the process
Axon membrane is only permeable to ions at the nodes of ranvier
Depolarisation only at N of R
made of schwann cells

Question 5

Describe the route of the impulse?

Answer 5

Stimulus - receptor- sensory - relay - motor - effector

Question 6

Describe resting potential

Answer 6

Na+/K+ pump creates conc gradient - K+ inside and Na+ outside
K+ diffuses out of cell down conc gradient making the outside more positive and inside negative = potential difference
Potential difference pulls K+ back into cell
Two gradients counteract each other and no net movement of K+