Action Potential Transmission

Question 1

What are local currents?

Answer 1

movements of ions along the neurone, caused by increase in concentration at one point causing diffusion away from region of higher concentration

Question 2

What happens to the sodium ion channels when an action potential occurs?

Answer 2

open at particular point along neurone, Na+ diffuse in down concentration gradient, ionic balance upset, where Na+ channels open = high concentration of Na+, Na+ diffuse sideways away from high concentration

Question 3

What is the voltage across the membrane at resting potential?

Answer 3

-60mV inside neurone

Question 4

What does the movement of sodium ions along the neurone do the potential difference?

Answer 4

alters the potential difference across the membrane, when it is reduces the voltage gates Na+ channels open, allows Na+ to enter neurone at point further along the membrane: action potential moves along

Question 5

What is the myelin sheath?

Answer 5

insulating layer of fatty material, sodium and potassium ions cant diffuse through this layer, ionic movement that causes action potential cant happen in much of neurone

Question 6

Where do the ionic exchanges that cause action potentials occur if not in the myelin sheath?

Answer 6

At nodes of Ranvier (gaps between Schwann cells that make up myelin sheath), in myelinated neurones the local currents elongate so Na+ diffuse along neurone from one node to next

Question 7

What is saltatory conduction?

Answer 7

the way action potential appears to jump from one node of Ranvier to the next

Question 8

What are the advantages of saltatory conduction?

Answer 8

action potential can only occur in gaps in myelin sheath, speeds up transmission (120ms-1), myelinated neurones faster than non-myelinated