The nerve impulse

Question 1

What is the resting potential in humans?

Answer 1

65mV

Question 2

At resting potential, is the axon polarised or depolarised?

Answer 2

Polarised.

Question 3

What factors maintain the resting potential in an axon?

Answer 3

Phospholipid bilayer prevents diffusion of Na and K ions
Gated channel proteins are present on the membrane that are only activated in specific stimuli
Sodium potassium pump actively transports ions to maintain diffusion gradient

Question 4

At resting potential, what part of the axon is negatively charged?

Answer 4

Inside is more negatively charged relative to outside

Question 5

How is the resting potential established? (Process)

Answer 5

Sodium ions are actively transported out of the axon while potassium ions are actively transported into the axon via sodium/potassium pump
Transport of sodium ions out is greater than transport of potassium ions into the axon, 3:2 ratio
Greater concentration of Na ions in tissue fluid than K ions in cytoplasm of axon, causing electrochemical gradient as inside is more negative
K ions diffuse down conc gradient to outside of cell as gated protein channels open
Na gated protein channels are closed so cannot diffuse down concentration gradient.
Resting potential established

Question 6

What is action potential?

Answer 6

When a stimulus of suffiecient size detected by a receptor causes a temporary reversal of charges on either side of the axon membrane

Question 7

How is an action potential established? (Process)

Answer 7

At resting potential, voltage gated K+ channels are open while Na+ are closed
Energy from stimuli causes some voltage gated sodium channels to open, allowing diffusion of Na+ down the electrochemical gradient into the axon which depolarises the membrane.
As more Na+ ions diffuse into the axon, more voltage gated channels open.
Once an action potential of +40mV is established in the axon, the voltage gated Na+ channels close and voltage gated K+ channels open.
More K+ ions begin to diffuse out of the axon, starting repolarisation of the axon.
AS K+ ions diffuse out, hyperpolarisation occurs so some K+ voltage gated channels close and the Na+/K+ pump actively transports Na+ out and K+ in, causing repolarisation of the axon and resting potential to be reestablished.

Question 8

When action potential occurs, what does the charge inside the axon membrane become?

Answer 8

+40mV

Question 9

Is resting potential an active or passive process?

Answer 9

Active

Question 10

Is action potential an active or passive process?

Answer 10

Passive