Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

BRS Term 1 > Membrane potentials and action potentials (2) > Flashcards

Membrane potentials and action potentials (2) Flashcards

1
Q

What is equilibrium potential?

A
  • the potential at which electrochemical equilibrium has been reached
  • electrical force prevents diffusion of the ion down its concentration gradient
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What does the Nernst equation calculate?

A

equilibrium potential, E, for each ion if you know the conc. of ions on either side of membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the extracellular concentration of Na+?

A

150mM

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the extracellular concentration of K+?

A

5

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the intracellular concentration of Na+?

A

10

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the intracellular concentration of K+?

A

150

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Why do membrane potentials not rest at Ek or Ena?

A

because membranes have mixed K+ and Na+ permeability but at rest K>Na

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the Goldman-Hodgkin-Katz (GHK) equation?

A
  • takes into account relative permeabilities of all ions at one time
  • describes the resting membrane potential (Em)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is depolarisation?

A

membrane potential increases from negative (-70mV) towards 0

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is repolarisation?

A

membrane potential decreases towards resting potential (becomes more -ve)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the overshoot?

A

membrane potential becomes more positive than 0

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is hyperpolarisation?

A

membrane potential decreases (becomes more -ve) beyond resting potential

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are graded potentials?

A
  • decay down the length of axon
  • changes in membrane potential in response to stimulation
  • occur at synapses/ sensory receptors
  • contribute to initiating or preventing APs
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How do ion channels change their permeability depending on their conformational state?

A
  • opened by depolarisation
  • inactivated by sustained depolarisation
  • closed by membrane hyperpolarisation/repolarisation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How does resting membrane potential occur? (Phase 1 of action potential)

A
  • set up by K+ flowing out of cell, leaving -ve charge in cell
  • Pk>Pna (permeability)
  • membrane potential nearer to equilibrium potential for K+ than Na+
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How is an action potential initiated? (phase 2: depolarising stimulus)

A
  • activation of a receptor to produce a graded potential

- stimulus depolarises membrane potential to threshold value–> more +ve

17
Q

What happens after the threshold potential is reached? (phase 3: upstroke)

A
  • voltage-gated sodium channels open, so inc. Pna–> Na+ enters cell down electrochemical gradient
  • membrane potential moves towards the Na+ equilibrium potential
18
Q

How does repolarisation occur (Phase 4)?

A
  • voltage-gated sodium channels close–> dec. Pna–> Na+ entry stops
  • more voltage-gated K+ channels open–> inc. Pk–> K+ leaves cell down its electrochemical gradient, REPOLARISING cell…membrane potential moves towards K+ equilibrium potential
19
Q

What is the refractory period?

A
  • inactivation plug stops functioning of Na+ channel for a small period of time
  • cannot restimulate nerve even w/ v. strong stimulus
20
Q

What occurs during phase 5, after-hyperpolarisation?

A
  • K+ continues to leave cell down electrochemical gradient
  • sodium channels still inactivated
  • membrane potential moves closer to K+ equilibrium
  • returns to resting potential
21
Q

How do voltage-gated sodium channels inactivate?

A
  • part of protein plugs membrane rapidly, stopping sodium moving through
  • cannot reactivate channel until you get rid of the plug
22
Q

How does active propagation of action potentials occur?

A
  • adjacent area to peak of action potential becomes more depolarised until it reaches threshold
  • then sodium influx activated and moves down axon a bit further etc…
23
Q

What is the purpose of myelination?

A
  • insulation–> conducts more effectively bc sheath is interrupted by nodes of Ranvier, so AP jumps
  • ^ SALTATORY CONDUCTION
  • speeds up transmission
24
Q

What factors affect conduction velocity?

A
  • diameter of axon bc larger= less resistance to ions moving along (bc more space)
  • myelination
  • small diameter, non-myelinated axons 1m/s, whereas large diameter, myelinated axons 120m/s
25
Q

What diseases reduce myelination?

A

multiple sclerosis and diphtheria

BRS Term 1 (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions