Resting and Action Potentials

Question 0

The lipid bilayer of cells performs what function

Answer 0

A barrier preventing ion movement, creating different concentrations

Question 1

The internal negative charge of a cell is mainly due to…?

Answer 1

The presence of negatively charged proteins

Question 2

At rest, a neurone permits what?

Answer 2

The diffusion of K+

Question 3

In a resting neurone, the Na+ channels are…?

Answer 3

Closed

Question 4

Two forces act upon K+ to allow it’s movement. What are they and what’s their direction?

Answer 4

Diffusion force - K+ diffuse out and electrical force - K+ move in

Question 5

The resting membrane potential is around what value?

Answer 5

-60mV

Question 6

Ion pumps provide what function?

Answer 6

Move ions against their concentration gradient

Question 7

An ion pump is involved in maintaining the resting potential. What is it’s function?

Answer 7

It pumps 3 Na+ out of the cell for every 2 K+ it pumps in, maintaining the internal cell negativity

Question 8

The equation for membrane K current is…?

Answer 8

Ik = gk (Vm - Ek)

Vm must not = Ek

Question 9

The equilibrium potential is defined as what?

Answer 9

The electrical potential difference that exactly balances an ionic concentration gradient

Question 10

The voltage produced by a difference in concentration on a single ion across a membrane can be calculated by…?

Answer 10

The Nernst equation

Question 11

At body temperature, the Nernst equation is…?

Answer 11

61.54mV log(X+)o/(X+)i

Question 12

Goldman-Hodgkin-Katz equation is better than Nernst equation, why?

Answer 12

Because it considers the concentration gradients and permeabilities of all ions involved

Question 13

The electrical activity created by a depolarising current is defined as what?

Answer 13

An action potential

Question 14

Where are action potentials generated?

Answer 14

The axon hillock

Question 15

How is a depolarisation wave created?

Answer 15

Positive ions flow towards negative areas and vice versa, creating local currents that depolarise adjacent membranes areas

Question 16

The overshoot phase of depolarisation is characterised by what?

Answer 16

A membrane potential of above 0mV

Question 17

The membrane potential decreasing is known as what, and how is it caused?

Answer 17

Repolarisation, due to closure of Na+ channels and opening of K+ channels

Question 18

What affect does tetrodotoxin have on the body?

Answer 18

Blocks voltage gated Na+ channels, so action potentials cannot form

Question 19

Voltage gated ion channels are in what state, for which ions?

Answer 19

Na+ and K+ both closed

Question 20

The arrival of a stimulus has what affect at a membrane?

Answer 20

Causes voltage gated Na+ channels to open and depolarisation

Question 21

Repolatisation it brought about by what changes?

Answer 21

Closure of Na+ VGIC and the opening of K+ VGIC

Question 22

What is the value if Ena?

Answer 22

61.54mV

Question 23

How are different sized stimuli represented in action potentials?

Answer 23

Action potentials are more frequent, with the same amplitude as the stimulus increases

Question 24

The absolute refractory period allows for…?

Answer 24

No further action potential to take place, allowing unidirectional propagation

Question 25

The relative refractory period allows for…?

Answer 25

Only larger stimuli to elicit an action potential

Question 26

Nodes of ranvier occur on what type of axon?

Answer 26

Myelinated

Question 27

What is in high concentration at the node of ranvier?

Answer 27

Voltage gated ion channels

Question 28

Myelinated axons transmit action potentials via what method?

Answer 28

Saltatory conduction; enhancing transmission