The Nerve Impulse Simplified

Question 1

When a neuron is not firing, it is said to be what?

Answer 1

RESTING

Question 2

When a neuron is resting, what’s going on with its cell membrane?

Answer 2

CELL MEMBRANE IS POLARIZED

with electrical gradient

Question 3

Which side of the polarized cell’s electrical gradient contains more sodium (Na+)?

Answer 3

OUTSIDE

“Na+ pump” within electrical gradient pumps Na+ out of cell

Question 4

A neuron remains resting and polarized until what level?

Answer 4

STIMULUS pushes neuron past
THRESHOLD LEVEL
(the level at which it fires)

Question 5

What happens to Na+ when neuron fires?

Answer 5

RUSHES INTO CELL

Question 6

What happens when a neuron’s threshold level is reached?

Answer 6

COMPLETE DEPOLARIZATION
+
Na+ CHANNELS OPENED ALONG CELL MEMBRANE OF AXON
+
RESULT IS NERVE IMPULSE or ACTION POTENTIAL

Question 7

What happens after an appropriate amount of Na+ is pumped back out of a neuron?

Answer 7

RETURNS TO POLARIZED STATE

Question 8

During what period does the neuron usually not respond to incoming stimuli?

Answer 8

REFRACTORY PERIOD

Question 9

When is the refractory period taking place?

Answer 9

AS NEURON RETURNS TO NORMAL POLARIZED STATE

returning to “resting”