Neuronal/Electrical Signaling

Question 1

What are the functions of ion channels?

Answer 1

Allows ions to move across the cell membrane.

Question 2

Describe the processes that are responsible for the movement of ions across the cell membrane.

Answer 2

Diffusion:
Fick’s Law
Ions move down their concentration gradient.

Electricity:
Ions are attracted to unlike charges, this creates an ionic current.
Ohm’s Law

Question 3

Explain equilibrium potential.

Answer 3

Refers to the electrical potential difference across the membrane which occurs simultaneously with the tendency of an ion to move down its concentration gradient.
It refers to when the electrochemical gradient for the inside of the cell is balanced with the outside of the cell.

Question 4

Which equation do we use to determine the Equilibrium Potential?

Answer 4

Nernst Equation

Question 5

Describe the Na/K ATPase.

Answer 5

Active pump that exchanges 3Na+ for 2K+

Question 6

Explain why the cell is more permeable to the K+ than other ions.

Answer 6

There are more K leak channels, that are open at rest.

Question 7

What do we use to measure the voltage of an action potential?

Answer 7

Oscilloscope

Question 8

Explain how a voltage-gated ion channel works.

Answer 8

Vestibule:
Entrance
Charged and attracts ions

Voltage sensor:
Sensors a stimulus and signals the gate to open/close

Gate:
Regulates ion flow

Selectivity filter:
very narrow region
distinguishes which ions enter the pore

Question 9

Describe how the voltage-gated Na+ channel works.

Answer 9

The activation gate is more likely to open with an increase in voltage, whereas the opposite is true for the inactivation gate.

Question 10

Name a toxin that blocks voltage-gated Na+ channels, hence blocking action potentials.

Answer 10

Tetrodotoxin (TTX)

Question 11

Describe how the voltage-gated k channels would respond to an increase in k.

Answer 11

The activation gates would open

Question 12

Explain the length constant.

Answer 12

the measure of how far the voltage travels before it decays to zero usually references to 37% remaining.
Usually determined by the resistance.
thicker neurons have lower internal resistance.

Question 13

Describe how a neuron with an infinitely high length constant and infinitely low time constant would react to a change in voltage.

Answer 13

Due to the extremely low resistance, a voltage change anywhere in the neuron would instantly change the voltage everywhere else in the neuron.

Question 14

Explain active conductance.

Answer 14

The rapid influx of sodium ions causes the membrane potential to reverse, creating an action potential, or a spike in voltage. This action potential propagates along the neuron, traveling down the axon to the next neuron or effector cell.

Question 15

Explain the mechanism behind myelinating axons.

Answer 15

It speeds up propagation velocity.

Capacitance:
reduces it.
results in fewer cations being tied up on the inner surface of the membrane. (fewer anions attracting cations)
More cations to depolarize.

Membrane Resistance:
Increases
lower transmembrane current
avails more cations to depolarize other parts.

Saltatory conduction:
jumping between nodes

Question 16

What are the factors affecting conduction velocity?

Answer 16

Larger axon diameter. This would SPEED UP action potential propagation.
Increased membrane resistance. This would SPEED up action potential propagation
Increased membrane capacitance. This would SLOW DOWN action potential propagation.
Increased axial resistance. This would SLOW DOWN action potential propagation.
Increased peak voltage-gated sodium channel conductance. This would SPEED UP action potential propagation.