Electricity and neural function: resting membrane potential, action potential, synaptic transmission

Question 1

What is membrane potential?

Answer 1

Difference in charge between extracellular and intracellular fluid of the cell

Question 2

What are the three main ionic contributors to membrane potential?

Answer 2

Na+, K+, A-

Question 3

What is A-?

Answer 3

Organic anions

Question 4

Can A- cross cell membranes?

Answer 4

No

Question 5

Sodium concentration outside cell

Answer 5

150

Question 6

Sodium concentration inside cell

Answer 6

15

Question 7

Potassium concentration outside cell

Answer 7

5

Question 8

Potassium concentration inside cell

Answer 8

150

Question 9

A- concentration outside cell

Answer 9

0

Question 10

A- concentration inside cell

Answer 10

65

Question 11

Equation for equilibrium potentials

Answer 11

E = 61log (c0/ci)
61 = RT/zF

Question 12

What is C0?

Answer 12

Outside concentration

Question 13

What is Ci?

Answer 13

Inside cell concentration

Question 14

What is R?

Answer 14

Gas constant

Question 15

What is z?

Answer 15

Valence of ion

Question 16

What is F?

Answer 16

Electrical constant

Question 17

If the membrane was impermeable to Na+ and K+, what would the potential be?

Answer 17

-90mV

Question 18

What is the resting potential?

Answer 18

-70mV

Question 19

What is depolarisation?

Answer 19

Membrane becomes positively charged - caused by influx of sodium

Question 20

What is repolarisation?

Answer 20

Voltage changes from +40mV to negative again - caused by efflux of potassium

Question 21

What is the threshold potential?

Answer 21

-55mV

Question 22

What happens to activation gates when the threshold potential is reached?

Answer 22

They open, allowing extracellular particles to enter
Very quickly reverses intracellular concentration of sodium so potential is now positive
When threshold potential reached, inactivation gate activated
Sodium leaks into cell

Question 23

At what potential will voltage gated potassium channels open?

Answer 23

+30mV

Question 24

In which direction does the sodium concentration gradient point?

Answer 24

Outside cell

Question 25

When is inactivation of voltage-gated sodium channels activated?

Answer 25

-55mV

Question 26

When do potassium channels open?

Answer 26

Activated at -55mV but open at +30mV

Question 27

How does GABA work?

Answer 27

By triggering a hyper-polarization of the post-synaptic membrane when it binds to receptors. It does this by stimulating an efflux of K+

Question 28

What is an ionotropic receptor?

Answer 28

Membrane bound receptor that contains an ion channel

Question 29

What is temporal summation?

Answer 29

A single action potential in the presynaptic neuron releases low levels of neurotransmitter that are not high enough to trigger an action potential in the postsynaptic neuron. However, two or more action potentials in neuron 1 in quick succession release enough neurotransmitter to trigger an action potential in neuron 2

Question 30

What is spatial summation?

Answer 30

Release of neurotransmitter from each of the presynaptic neurons does not trigger an action potential in the postsynaptic neuron. However, when neurons simultaneously release neurotransmitter, an action potential is triggered

Question 31

In what direction does the electrical gradient for potassium go?

Answer 31

Into the cell

Question 32

In what direction does the concentration gradient for potassium go?

Answer 32

Out of cell

Question 33

In what direction does the electrical gradient for sodium go?

Answer 33

Out of the cell

Question 34

In what direction does the concentration gradient for sodium go?

Answer 34

Into cell