Chapter 2 - Resting Membrane Potential

Question 1

In regards to signals, what can neurons do?

Answer 1

Can : receive signals (dendrites)
Generate signals (axon hillock )
Conduct signals (axon)

Question 2

Na+ is a …

Answer 2

Cation

Question 3

Cl- is a…

Answer 3

Anion

Question 4

What are the two types of ion channels?

PS : don’t forget the cation specificity

Answer 4

Cation channels : -non specific (any +)

-specific (only Na+, only Ca++,…)

Question 5

The ion channels also differ in how they are gated. Explain

Answer 5

Leak channels : passive channels open all the time

Gated channels : active channels thy can be opened by certain changes (light, mechanical, …)

Question 6

What and how gives rise to a resting potential?

Answer 6

• Leak channels are always open so give rise to the resting potential.
• The movement of charged particles across a membrane is what gives rise to a resting potential.

Question 7

What are neural signals, or action potentials?

Answer 7

Neural signals consist of transient changes in this resting potential, which travel from the soma down the axon to the nerve terminal.

Question 8

What are the two forces that govern the movement of particles across a permeable membrane?

Answer 8

1) diffusion : when there is a difference on concentration of a certain uncharged particle, the diffusion also force is going to push for equilibrium on both sides of the membrane.
2) the electric force : here we’re talking about charged particles —> opposite charges attract and like charges repel

Question 9

Explain potential energy.

Answer 9

• opposite charges attract and require energy to be separated
• therefore spectated charges have potential energy as a result of the separation
• measure of potential energy = voltage
• voltage is always measured btw two points and is called the potential difference btw 2 points

Question 10

What is the electrical current?

Answer 10

Movement of positively charged particles.

Question 11

What is conductance?

Answer 11

Movement of ions through ion channels.

Question 12

What is voltage?

Answer 12

Voltage is the electrical force exerted on a charged particle. It reflects the difference in charge between the anode and the cathode.

Question 13

What is the current? And what is its unit?

Answer 13

Current is the motion of charged particles. Measured in Amperes (I)

Question 14

What I the relation of voltage and current also known as Ohm’s law?

Answer 14

V=IR

Question 15

What is the other formula for Ohm’s law?

Answer 15

I=gV

Where g is the conductance measured in Siemens and equal to 1/R.

Question 16

In slide 23 how is equilibrium reached?

Answer 16

When electrical force pulling K+ back into the cell is equal to the chemical force driving K+ out of the cell, equilibrium is reached.

Question 17

What is equilibrium potential?

Answer 17

The electrical potential difference that exactly balances an ionic concentration gradient.

Question 18

What is the ionic driving force? What is the formula?

Answer 18

Ions are driven across the membrane at a rate proportional to the difference between the membrane potential (Vm) and the equilibrium potential

Question 19

What does the Nernst equation calculate?

Answer 19

It calculates the equilibrium potential for an ion if the concentration difference across a membrane is known

Question 20

What is the equilibrium potential for potassium?

Answer 20

E__K = -80mV

Question 21

How does the driving force work (Vm>Ek, …)?

Answer 21

K flows out of cell when Vm>Ek

No net flow when Ek=Vm

K flows in when Vm

Question 22

What happens when the membrane is permeable to more than one ion?

Answer 22

• Each ion will try to pull the membrane potential to its respective equilibrium potential.
• …so what’s going to determine the membrane’s potential is the permeability (or conductance) of the membrane to an ion.

Question 23

At rest, to what is the membrane most permeable?

And to what is the resting membrane potential closest to??

Answer 23

1) most permeable to K+

2) is closer to Ek than E Na

Question 24

What is the formula for the net ion flux across a membrane?

Answer 24

I (ion) = g (ion) . (Vm-E(ion))

Also known as permeability x driving force

Question 25

Why is a neuron at rest constantly leaking out?

Answer 25

The permeability for K+ is high so potassium is leaking out ((( whereas the in force is weak.

Question 26

What does the potassium/sodium pump do?

What does this pump require to function?

Answer 26

It pumps out 3Na+ and in 2K+

It requires ATP

Question 27

How is extra cellular K+ removed?

Answer 27

Astrocytes use spatial buffering to remove the ions.