Neurons [RMP + AP1]

Question 1

What is the RMP value usually?

Answer 1

-50 to -70mV (typically -65)

Question 2

What factors affect RMP?

Answer 2

Concentrations inside or outside the cell causing gradients and movement of ions.
Permeability - different depending on ion.
Electrogenic Na/K pump (small)

Question 3

What are the two types of ion channels affecting permeability?

Answer 3

Leak channels - open at rest.

Gated channels - closed at rest. Maintain RMP.

Question 4

Channels in glia? RMP value?

Answer 4

Leak K+ channels

RMP = Ek (-80mV)

Question 5

Rule #1: the higher the permeability of the cell membrane to a particular ion, _______.

Answer 5

The greater the ability of this ion to shift the RMP towards its equilibrium potential.

Question 6

Equilibrium potential definition

Answer 6

Intracellular potential where net flow of ions = 0 in spite of a gradient + perm.

Question 7

What does the Nerst eqn. calculate?

Answer 7

The equilibrium potential for each individual ion which contributes to RMP.

Question 8

What is ENa in a mammal cell?

Answer 8

+60mV

Question 9

Nerdy eqn only applies when ____

Answer 9

Cell membrane is only permeable to one ion (only has leak channels for one ion.)

Question 10

What does the Goldman eqn calculate?

Answer 10

RMP

Question 11

Fast depolarisation

Answer 11

To about 30mV after the membrane potential reaches the threshold. Overshoot. PNA»>Pk. Voltage-gated Na+ channels open very fast.

Question 12

Repolarisation

Answer 12

Na+ channels inactivate and voltage-gated K+ channels open. Transient. Pk»>PNa.

Question 13

After-hyperpolarisation

Answer 13

Voltage gated K+ channels remain open for a while and then close. PNa»>PNa then Pk»PNa.
Goes down a bit then back to RMP.

Question 14

What happens before stage 1?

Answer 14

Depolarisation to threshold. Slow and graded. Stimulus, physical or chemical. Voltage gated Na+ channels start to open near threshold. Pk>PNa.

Question 15

What is refractory period? Two different types?

Answer 15

Not excitable.
1+2 = Absolute refractory period (2nd stimulus does not evoke AP)
3 = relative refractory period (recovers excitably but strong stimulus needed to depolarise into threshold.)

Question 16

What is amplitude usually? What does it depend on?

Answer 16

100mV. Constant, doesn’t depend on stimulus. Provided stimulus is suprathreshold.

Question 17

What does graded mean?

Answer 17

Amplitude of AP is determined by stimulus strength.

Question 18

What stuff is graded?

Answer 18

Subthreshold depolarisations or hyperpolarisations which are graded

Question 19

Rule #2: When current generates by an outside source flows_____

Answer 19

Through the membrane from outside to inside, hyperpolarisation (more negative). Inside to outside, (more positive), depolarisation.

Question 20

Where do the two currents flow in an action potential?

Answer 20

1. Outside from + to -

2. Across membrane and inside axon.