Nervous System: Resting Membrane Potential

Question 1

What part of a nerve cell communicates through electrical signals

Answer 1

Dendrites, cell body, axon

Question 2

What part of a nerve cell communicates through chemical signals

Answer 2

synapses

Question 3

Another name for the axon terminal

Answer 3

synaptic boutons

Question 4

The function of the axon

Answer 4

to carry signals

Question 5

The function of dendrites

Answer 5

Receive information input

Question 6

The function of the cell body

Answer 6

To compute information (decision making, respond or not to respond to a stimulus)

Question 7

How does an action potential occur?

Answer 7

a stimulus is applied causes the membrane potential to depolarise (become less negative) and then it recovers back to its negative resting potential

Question 8

Which types of cells respond to stimuli with a transient change of membrane potential (i.e. an action potential )

Answer 8

Neurons and muscle fibres

Question 9

the two methods for measuring intracellular potential

Answer 9

microelectrode recording technique and patch-clamp technique

Question 10

What is resting membrane potential

Answer 10

the electrical potential difference across the cell membrane which results from separation of charge (unequal distribution of ions)

Question 11

Membrane potential outside the cell

Answer 11

0mV

Question 12

Membrane potential inside the cell

Answer 12

-70mV

Question 13

Three reasons why the membrane potential inside the cell is negative

Answer 13

1. Unequal concentration of [Na+] and [K+] inside and outside the cell
2. Unequal permeability of the cell membrane to these ions (more permeable to K+ than Na+)
3. [Electrogenic action of the Na-K pump - only a small contribution!]

Question 14

[K+] outside the cell

Answer 14

5mM

Question 15

[K+] inside the cell

Answer 15

100mM

Question 16

[Na+] outside the cell

Answer 16

150mM

Question 17

[Na+] inside the cell

Answer 17

15mM

Question 18

What maintains the concentration gradient across the cell membrane

Answer 18

the Na+/K+ pump (NA/K ATPase)

Question 19

Na+/K+ pump (NA/K ATPase) ratio of ions brought in and out

Answer 19

3/2 ratio: 3Na+ out and 2K+ in

Question 20

How does the Na+/K+ pump (NA/K ATPase) maintain a negative membrane potential within the cell

Answer 20

it removes more Na+ than K+ it brings in = total negative charge

Question 21

What are the two main type of ion channels in nerve cells

Answer 21

1. Non-gated leak channels

2. Gated channels (volatge-gated, ligand-gated, chemically gated channels, mechanically gated) - closed at rest

Question 22

Leak channel composition of nerve cells

Answer 22

many leak K+ channels but very few Na+ channels, ~40:1 (K+: Na+)

Question 23

Equilibrium potential

Answer 23

an intracellular potential at which the net flow of ions is 0, in spite of a conc gradient and permeability

Question 24

Nernst equation

Answer 24

Eion = 61.5mV x log [ion] outside (o) / [ions] inside (i)

Question 25

What does the Nernst equation tell us?

Answer 25

the permeability of the cell membrane to one ion

Question 26

What is ENa = ?

Answer 26

+60mV

Question 27

Rule 1 of neurons

Answer 27

the higher the permeability of the cell membrane to a particular ion, the greater the ability of this ion to shift the RMP towards its equilibrium potential

Question 28

What ion is the RMP closer to in neurons

Answer 28

its closer to K+ because of the leak channels

Question 29

Goldman Equation

Answer 29

Vm = 61.5mV x log (Pk[K+]o + PNa[Na+])/(Pk[K+]i + PNa[Na+])

Question 30

What does the Goldman Equation tell you

Answer 30

a way of calculating the value of the RMP taking into account both the concentration gradients and the relative permeability of the resting cell membrane to K+ and Na+ ions