Resting Potential And Action Potentials

Question 1

When an axon is not conducting an impulse

Answer 1

• the inside of the axon is negative.
• the voltage is about 70 mv
• this charge is due to unequal distribution of ions:

Question 2

More sodium (N+) outside the axonthen inside.
More potassium (k+) inside the axon than out.
Maintained by somium-potassium pumps

Answer 2

Kin

Question 3

Action potentials

Answer 3

Is rapid change in electrical charge during a nerve impulse.

Question 4

It has

Answer 4

• an all or none phenomenon
• occurs if a stimulus reaches the threshold
• a strong stimulus does not change strength of an action potentials, it charges the frequency of firing
• requires two types of gated protein channels:
Gated sodium channels.
Gated potassium channels.

Question 5

There is two steps for action potentials

Answer 5

1- sodium (N+) gates open
Moves into the axon
The charge changes from 70 mv to 35 mv
This is called depolarization because the inside of the axon charges from negative to positive.

Question 6

2- potassium (k+) gates open

Answer 6

Moves out of the axon.
The charge return to 70 mv
This is called repolarization because the inside of the axon returns to its original negative charge.

Question 7

Conduction of an action potentials

Answer 7

1- in nonmyelinated axons
Traveling down an axon one small segment at time
When action potentials has moved on the previous section undergoes a refractory period:
The N+ gates caused reope
K+ continues to leave diffuse out causing hyperpolarization thus action cannot move backward.
When the referctory period ends the N+ ,k+ pumps restore the previous ion distribution

Question 8

In myelinated

Answer 8

• The gated ion channels for Na+ K+ are concentrated in nodes of ranvier. Thus ion exchange occurs only at the nodes
• results in faster action the in nonmyelinated axons.
The jumping of action from node to node in myelinated axons is known as saltatory conduction.

Question 9

Axon terminal

Answer 9

Is every axon branches into many fine endings, each tipped by a small swelling and each terminal lies very close to either the dendrite or the cell body of another neuron or muscle cell. This called synapse or chemical synapse