Module 3: Lecture 4

Question 1

True or False
Action potentials all have the same magnitude but the frequency effects how and what is cellularly communicated

Answer 1

True

Question 2

What is the refractory period?

Answer 2

we are unable to generate a second action potential until the first one has completed

the time period in between

Question 3

What are the 2 general phases of the refractory period?

Answer 3

1. Absolute refractory period
2. Relative refractory period

Question 4

What is the Absolute refractory period

Answer 4

period where we cannot generate a second action potential

Question 5

What is the beginning to end of the Absolute refractory period

Answer 5

initial to resting membrane

Question 6

What is the Relative refractory period?

Answer 6

where another action potential can occur, because the sodium channels have reset

Question 7

How do we restore the original concentrations of sodium and potassium?

Answer 7

sodium/potassium ATPase pump

Question 8

How does the sodium-potassium pump work?

Answer 8

• the opening for the Na+/K+ pump is facing intracellularly
• it has a very high affinity for sodium, it has a active site specifically for sodium which will bind to it
• then we phosphorylate the pump, we bring in ATP and bind a phosphate group to the pump
• as the phosphate uses its energy the protein membrane changes it’s opening to be extracellularly, which allows sodium ions to diffuse out
• now the pump has a high affinity for potassium which it now binds to the specific potassium active sites
• now the phosphate group will leave the pump, reverting the pump towards the inside of the cell allowing potassium to diffuse into the cell

Question 9

Is the sodium-potassium pump always “ON”?

Answer 9

Yasss

Question 10

True of False
The sodium-potassium pump counterbalances the rate of passive leakage

Answer 10

True

Question 11

Is the sodium-potassium pump an active or passive process?

Answer 11

primary active transport, it requires energy

Question 12

What are the 4 zones of the nerve cell?

Answer 12

1. Input zone
2. Trigger zone
3. Conducting zone
4. Output zone

Question 13

What happens in the input zone?
(dendrites and cell body)

Answer 13

• where the cell receives all of its communications from other nerves
• this is where all the graded potentials occur
• it includes the cell body (has a nucleus) and dendrites (finger-like structure)
• the message goes from the dendrites to the cell body to the trigger zone or axon hillock

Question 14

What happens in the trigger zone?
(Axon Hillocks)

Answer 14

• where the action potentials are initiated
• there is a high concentration of voltage-gated sodium and potassium channels

Question 15

What happens in the conducting zone?
(axon)

Answer 15

• where an action potential is propagated
• can be a long or a short distance

Question 16

What happens in the output zone?
(axon terminals)

Answer 16

• where the axon terminals are and they send off the continued messages

Question 17

what is the point of the dendrites?

Answer 17

they greatly increase the surface area, to receive multiple-cell communications

Question 18

What are the 2 methods of action potentials that will travel down the axon?

Answer 18

1. Contiguous conduction
2. Saltatory conduction

Question 19

How does the contiguous conduction work?

Answer 19

• it uses the initial gated channels that reach the threshold to allow one action potential to occur
• then once all the sodium is in the cell is travels along the membrane triggers more action potentials all the way down the axon

Question 20

True or False
The contiguous conduction is a self-perpetuating cycle that automatic

Answer 20

True

Question 21

Why does the action potential only travel in one directon?

Answer 21

due to refractory period

Question 22

What is saltatory conduction

Answer 22

action potentials will jump down patches due to myelinated fibers

Question 23

Are myelin sheets hydrophobic or hydrophilic?

Answer 23

hydrophobic, very good insulator

Question 24

what is the peripheral nervous cells?

Answer 24

nerve cells not including the spinal cord

Question 25

What are the central nervous cells?

Answer 25

nerve cells in the spinal cord

Question 26

How does myelination occur?

Answer 26

due to Schwann cells - individuals cells wrap around the axon leaving a gap called the nodes of ranvier

Question 27

What are the nervous cells in the central nervous system called?

Answer 27

oligodendrocytes

Question 28

What are oligodendrocytes?

Answer 28

nerve cells with large bodies and foot-like projections - wrap multiple different axons in myelin sheath

Question 29

What is the point of having cells wrapped in myelinated sheath?

Answer 29

- increases insulating effects increasing cell communication

Question 30

How long are the nodes of ranvier?

Answer 30

2 microns in length

Question 31

How often do node of ranvier occur? and why?

Answer 31

- every millimeters or so - we need them because theres voltage-gated ion channels at the nodes for action potentials to occur