week 2- resting membrane potential

Question 1

nature of communication within a neuron?

Answer 1

electrical signalling

because…
-neurons can extend over long distances.
-signals move from one part of neuron to another.
-diffusion of chemicals would be too slow.

Question 2

what is action potential?

Answer 2

‘electrical excitability’

a sudden change in membrane voltage of a neuron in response to stimulus.

depends on resting membrane potential.

Question 3

what is membrane potential?

Answer 3

the difference between the electrical potential inside the cell and the electrical potential outside the cell.

for a neuron= -70Mv

altered by movement of ions in and out of cell.

Question 4

how do neurons send info to other neurons?

Answer 4

by temporarily altering their overall polarity (electrical charge)

Question 5

what two forces prevent ions from moving in and out of the cell?

Answer 5

-diffusion

-electrostatic pressure (opposites attract)

Question 6

what are the two types of ions (charged molecules)

Answer 6

• cation (+vley charged ions)
• anion (-vley charged ions)

Question 7

what is intercellular fluid?

Answer 7

the fluid inside the cell.
It contains potassium (K+) ions

Question 8

what is extracellular fluid?

Answer 8

the fluid outside the cell.
It contains sodium (Na+) and chloride (Cl-) ions.

Question 9

what charge is the inside of the cell?

Answer 9

negative

Question 10

what charge is outside the cell?

Answer 10

positive

Question 11

where do the ions want to go?

Answer 11

potassium (K+) = wants to leave the cell (diffusion) but can’t (electrostatic pressure).

chloride (Cl-) = wants to go into the cell (diffusion) but can’t (electrostatic pressure)

sodium (Na+) = wants to go into the cell (diffusion) CAN go in (electrostatic pressure)

Question 12

what is the sodium potassium pump?

Answer 12

a lot of Na+ ions travel into the cell.
quite a few lucky K+ ions manage to sneak out as the concentration inside the cell increases.

the sodium potassium pump pumps all the Na+ ions out of the cell and pump the escaped K+ back into the cell.

Question 13

what is the threshold of excitation?

Answer 13

a certain amount of action potential to be able to send a signal.

all or nothing process.

Question 14

what happens during a neuron firing?

Answer 14

voltage-dependent ion channels open or close depending on the current membrane potential of a neuron.

these ion channels are what allow ions to enter/leave the neuron.

Question 15

at various parts of the firing process the neuron is depolarised and hyperpolarized.

what are these?

Answer 15

depolarization = decrease from normal resting potential. charge moves closer to zero (more positive)

hyperpolarization = increase in action potential. overall charge becomes more negative.

Question 16

process of a neuron firing after threshold of excitation is reached?

Answer 16

1. = Na+ channels open and Na+ enters the cell.
2. = K+ channels open and K+ leaves the cell
3. = meanwhile the cell becomes more positive.
   at 40Mv Na+ channels close
4. = K+ carries on leaving cell
   membrane potential returns to resting (more negative)

membrane potential overshoots and drops below resting potential

5.= K+ channels close
sodium potassium pump resets the Na+ levels

6.= escaped K+ from the overshoot diffuses away