Membrane and Action Potentials

Question 1

ion concentrations in cells: for K+/ Na+/ Cl-

Answer 1

[K+] is high inside the cell relative to outside
[Na+] is low inside the cell relative to inside
Lots of Cl- ions outside the cell

Question 2

sodium potassium pump is fuelled by?

Answer 2

breakdown of ATP

Question 3

Sodium/Potassium Pump:

Answer 3

Actively transports 3 Na+ ions outside the cell & then intakes 2 K+ ions inside the cell
Active transport process

Question 4

Resting potential

Answer 4

membrane potential of the cell that isn’t sending signals
e.g epithelial cells are always in a resting state

Question 5

Equilibrium potential

Answer 5

the membrane potential at which the electrical & chemical gradients of a specific ion are balanced

Question 6

Ek

Answer 6

potassium equilibrium potential

Question 7

ENa

Answer 7

sodium equilibrium potential

Question 8

Goldman equation:

Answer 8

Used to calculate the resting membrane potential of a cell taking into account multiple ion permeabilities

Question 9

Depolarisation

Answer 9

membrane potential is more positive than resting potential

Question 10

Repolarisation

Answer 10

membrane potential returns to resting potential after depolarisation

Question 11

Hyperpolarisation

Answer 11

membrane potential is more negative than the resting potential

Question 12

If depolarisation shifts the membrane potential sufficiently, it results in?

Answer 12

action potential

Question 13

Neuronal action potential

Answer 13

Neurons receive signals &transmit them down the axon
At the end of the nerve terminal something will happen e.g. release a neurotransmitter, stimulate another nerve (electrically/chemically)
The stimulus needs to cause sufficient depolarisation to raise the voltage above the threshold

Question 14

threshold

Answer 14

-55mV

Question 15

mechanism of action of drugs such as local anaesthetics relieve pain how?

Answer 15

Work by blocking these channels (Na+ e.g) which means that neurons can’t fire action potentials–> can’t feel pain in that region because the action potentials transmit information electrically
If signal isn’t sent–> don’t feel pain

Question 16

How nerves send electrical signals:

Answer 16

Action potential spreads along the axon
Depolarisation of the first part of the axon will spread to the next part of the axon etc.
At the synapse, an action potential will result in the release of neurotransmitters
Receptors on the post-synaptic membrane receive the signal

Question 17

Cardiac action potential has how many phases

Answer 17

longer process than in neuronal cells: 4 phases
Phase 0- phase 4

Question 18

cardiac action potential phase 0

Answer 18

depolarisation
Na+ channels open

Question 19

cardiac action potential phase 1

Answer 19

repolarisation begins
Na+ inactivate and K+ channels open

Question 20

cardiac action potential phase 2

Answer 20

Plateau
K+ channels still open, but some channels are activated too which results in plateau
Intake of Ca+ is important

Question 21

cardiac action potential phase 3

Answer 21

repolarisation
Ca2+ channels close
K+ channels open

Question 22

cardiac action potential phase 4

Answer 22

most Na+ and K+ channels closed