Neuronal signalling 4 (2nd lecture)

Question 1

Which ligand gated ion channel causes an EPSP?

Answer 1

Na+

Question 2

Which ligand gated ion channels cause an IPSP?

Answer 2

K+ and Cl-

Question 3

How is does the membrane potential reach the threshold?

Answer 3

Via many EPSPs

Question 4

What is the threshold?

Answer 4

The membrane potential which causes the VG channels to open

Question 5

What is the resting potential of the neuron dependent on?

Answer 5

The balance of the ions on either side of the membrane

Question 6

At rest, what makes up the bulk of the -ve charge in a neuron?

Answer 6

Anions (proteins)

Question 7

Resting concs of Na+ and K+ (inside compared to outside)?

Answer 7

Na–> Low in cell, high outside of cell
K+–> High inside cell, low outside of cell

Question 8

What is resting potential?

Answer 8

membrane potential of a neurone that is not being stimulated (determined by the Goldman Equation)

Question 9

What is equilibrium potential?

Answer 9

the potential of the membrane, for a single ion, that that stops further movement of that ion across the membrane (Nernst Equation)

Question 10

What is reversal potential?

Answer 10

potential at which no further charge movement across the membrane occurs

Question 11

What is the same for the movement of one ion?

Answer 11

Reversal potential and equilibrium potential

Question 12

What is summation?

Answer 12

Integration of many diff EPSPs and IPSPs

Question 13

Two mechanisms of summaiton?

Answer 13

Spatial and temporal

Question 14

Spatial summation?

Answer 14

simultaneous stimulation from two or more nearby synapses; each synapse is excitatory or inhibitory

Question 15

Temporal summation?

Answer 15

multiple stimulation at one synapse in a short period of time-> additive

Question 16

Does spatial summation have to have the same type of input

Answer 16

No–> can be one EPSP then an IPSP which cancels out the EPSP

Question 17

First event following threshold being reached?

Answer 17

VG Na+ channels open

Question 18

When does Na+ stop moving into the cell through VG channels?

Answer 18

Opposing force of the charge inside the cell prevents further movement
reversal potential

Question 19

What happens when no more Na+ can enter the cell?

Answer 19

K+ channels open which allow K+ to leave the cell

Question 20

What is the result of K+ moving out of the cell?

Answer 20

Repolariation

Question 21

Hyperpolarisation?

Answer 21

Dip below the resting potential following an AP

Question 22

How many phases does an AP have?

Answer 22

4

Question 23

Phases of an AP?

Answer 23

Depolarization–> VG Na+ open
Repolarization–> VG K+ open
Hyperpolarization–> refractory period
Fourth phase–> return to resting pot

Question 24

State of Na+ channels during hyperpolarisation?

Answer 24

Inactivated–> not really closed
cant respond to a change in membrane potential

Question 25

Role of refractory period?

Answer 25

Governs how the AP propagates along the axon

Question 26

Two parts of refractory period?

Answer 26

Absolute and relative

Question 27

Which ion channels produce an AP?

Answer 27

Na+ and K+

Question 28

How is an AP carried from one region of an axon to the next?

Answer 28

Passive spread of current

Question 29

What is used to restore the Na+ gradient?

Answer 29

Na,K antiporter (pump)

Question 30

What does the Na,K antiporter do?

Answer 30

exchanges two K ions from outside the cell with 3 Na ions from inside the cell and uses ATP.