4.9 - Neural Signals

Question 1

What are action potentials?

Answer 1

This occurs when nerual signals are sent through the nervous system as waves of fluctuating charges

Question 2

What does polarization mean in terms of the sending of a neural signal?

Answer 2

It’s the seperation and charge switch of the polarity of the axon membrane when sending a neural signal

Question 3

What is membrane potential?

Neural signals

Answer 3

Due to the axon’s membrane being negatively charged on the inside and positively charged on the outside, an action potential causes this to become temporarily reversed.

Question 4

What charge is an axon’s membrane on the outside compared to the inside?

Answer 4

Outside: positive charge
Inside: negative charge

Question 5

How is an electrical potential difference (voltage) created along the axon?

Answer 5

It’s created by difference in charge along the membrane

Question 6

How is membrane potential maintained?

Neural signals

Answer 6

Na-K pumps are used

Question 7

What are Na-K pumps?

Neural Signals

Answer 7

• are proteins imbedded in the mebrane that use ATP to pump Na+ ions out and K+ ions in
• 3 Na+ ions are pumped out of the axon
• 2 K+ ions are pumped into the axon
• the charges of the membrane switch.

Question 8

What needs to occurs for an action potetial to start?

Answer 8

• the stimulus needs to strong enough to open the first few Na+ channels on the axon
• if the stimulus is NOT strong enough, the signal will not be created
• more than one stimulus can be combined to start an action potential which is called summation
• a strong stimulus DOES NOT affect the AP strength, its the frequency that determines the strength of the response

Question 9

What are the 5 stages of an action potential?
Briefly describe them.

Answer 9

• Resting state: Na+ and K+ channels are closed
• Depolarizing state: the channels are disurbed so Na+ channels open letting in Na+ ions in the axon
• Rising phase of the action potential: nearby channels of Na+ open as well, causing more ions to flow in. This also causes the inner potential to become positive
• Repolarizing phase: the voltage change causes K+ channels to open and the Na+ channels to close. The K+ ions diffuse in quicker than Na+ ions & the inside becomes negative again. Starts to go back to it’s og potential state
• Undershoot: the membrane is back at its resting state as K+ channels close. Though some K+ ions may slip through the membrane making it become hyperpolarized (falling below the resting potential state)

Question 10

What is the refractory period?

Answer 10

• the time needed for an axon to return back to it’s og resting state
• no new action potential can begin untill resting potential is fully restored
• this ensures that action potentials only move in one direction