chapter 2,3,4

Question 1

What is the difference between active and passive conduction?

Answer 1

Passive conduction decays over distance and active conduction is constant over distance

Question 2

What is the equilibrium potential?

Answer 2

Electrical potential at electromechanical equilibrium. There is a balance between the diffusion force and the electrical force.

Question 3

What is the reversal potential?

Answer 3

In a biological membrane, the reversal potential is the membrane potential at which the direction of ionic current reverses. At the reversal potential, there is no net flow of ions from one side of the membrane to the other.

Question 4

How is the resting membrane established?

Answer 4

It is based on two membrane properties:
1. lipid bilayer is impermeable for ions
2. specialized ion channels can conduct ions selectively
and it is based on two principles in physics
1. diffusion of particles
2. electrical forces between electrical charges

Question 5

Which ions are important for the resting membrane potential?

Answer 5

-K+ , Na+, Cl-, Ca2+

Question 6

What are the requirements for electrical signalling between nerve cells?

Answer 6

• must be fast
• travel long distances
• should not loose strength over distance

Question 7

What is the resting membrane potential?

Answer 7

The resting membrane potential is the electrical potential difference measured across the membrane (inside with respect to outside).

Question 8

What is diffusion?

Answer 8

Diffusion is the net movement of anything (for example, atoms, ions, molecules, energy) generally from a region of higher concentration to a region of lower concentration.

Question 9

Name the charges of K, Na, Cl, Ca

Answer 9

K+, Na+, Ca2+, Cl-

Question 10

Name all the components in the Nernst equation Ex=(RT/ zF) * ln ([x]out/ [x] in)

Answer 10

Ex= equilibrium potential
R= Gas constant
z= valance
F= faraday constant
T= temperature in kelvin
then concentration outside and concentration inside

Question 11

Remember the logs:
log10^𝑋=
log10=
log1=
log 1/10=

Answer 11

log10^𝑋=𝑋
log10=1
log1=0
log 1/10=-1

Question 12

Describe the action potential

Answer 12

A signal opens the voltage-gated sodium channels and causes an influx of sodium channels Na+. The overshoot of positive charge opens potassium channels (K+) which causes a potassium efflux, decreasing the cells electropositivity.

Question 13

What is the difference between an ion pump and an ion channel?

Answer 13

An ion channel allows ions to diffuse down concentration gradient and are selectively permeable to certain ions (vergelijk met een sluis)
An ion pump is an active transporter that actively moves selected ions against the concentration gradient and creates ion concentration grandients (vergelijk met een pumping station that pumps water from down to up)

Question 14

What are the differences between current-clamp and voltage-clamp measurements

Answer 14

Voltage clamp: measurements of currents
Current clamp: measurements of changes in membrane potential

Question 15

Name the different types of ion channels and their role in neuronal signalling

Answer 15

Na+ channel- influx of Na in the cell makes it more positive
Ca2+ channel
K+ channel- opens after the overshoot to remove the positive charge from the cell
Cl- channel

Question 16

Name 2 experiments to proof that the membrane is selectively permeable for different ions

Answer 16

1. use selective solutions (without N or K)
2. use selective blockers (toxins)

Question 17

Name the 2 types of gating mechanisms in Na channels and whether they open or close during depolarisation

Answer 17

1. Fast activation gates, which open during depolarisation
2. slow inactivation gates, which close during depolarisation

Question 18

Name the different components of a voltage sensitive K-channel and their function (3)

Answer 18

pore- allows ions to enter the channel
selectivity filter- makes sure the channel is specific to certain ions
sensor (voltage sensor, chemical sensor)- detects the signal that will open/close the channel through conformational change of the channel

Question 19

Reproduce the 5 phases of the action potential and mention what happens with Na and K)

Answer 19

1. resting state
2. threshold (rise of Na inside of the cell)
3. depolarisation phase (rising phase) (More Na gated channels open)
4. repolarising phase (Na does not enter the cell anymore and K goes outside of the cell)
5. undershoot

Question 20

What is the refractory period?

Answer 20

The period between action potentials where the Na channels are still inactivated. This happens because we need time to recover.

Question 21

What is the role of myelin and the nodes of Ranvier in the process of conducting action potentials?

Answer 21

To speed up the action-potential by isolating the axon and thereby preventing leaks of ions through the membrane and increasing distance for passive current flow

Question 22

What is the difference between active and passive flow in action potentials?

Answer 22

Active current flow takes place over the membrane through ion channels
passive current flow takes place along the axon

Question 23

Why does the action potential only travel in one direction, away from the soma?

Answer 23

Because inactivation of Na channels prevents action potential generation in the reverse direction

Question 24

Myelination in the brain happens due to

Answer 24

Oligodendrocytes

Question 25

What happens when there is a loss of myelin

Answer 25

This happens with Multiple Sclerosis and this leads to muscle weekness, double vision or blindness in one eye, trouble with sensation, mental/psychiatric problems