MVC - Synaptic Integration II

Question 1

How does myelin influence capacitance and resistance?

Answer 1

Decreases the capacitance

Increases resistance

Question 2

Does axon diameter alter resistance?

Answer 2

Yes a bigger diameter fibre will have a lower resistance to current (faster conduction)

Question 3

What do exponential equations model in membrane properties?

Answer 3

Exponential equations model passive and active membrane properties, including ion channels

Question 4

How are passive and active properties of neurons distinguished?

Answer 4

Passive properties are observed at rest

Active properties change with time and voltage during cellular activity

Question 5

How does the addition of an ion channel (Kv3.4) affect action potential firing?

Answer 5

It increases the frequency of action potential firing

Question 6

What are voltage clamps?

Answer 6

Used to separate the contribution of currents by different ion channels

Question 7

What are patch clamps?

Answer 7

A technique to make a high resistance seal between glass and bilipid membrane to record very small currents.

Question 8

Voltage Clamps vs Current Clamps

Answer 8

Voltage Clamps → Clamps the voltage (MEASURES CURRENT)

Current Clamps → Clamps the current (MEASURES VOLTAGE)

Question 8

What provides the current input to neurons in vivo?

Answer 8

Stimulation of free nerve endings

Synapses

• Electrical
• Chemical

Question 9

Explain the ion current plotting convention

Answer 9

INWARD
Entry of positive current into the cell → depolarises the cell (Vm more positive)

• Exit of negative current from the cell

OUTWARD
Entry of negative current into the cell → hyperpolarises the cell (Vm more negative)

• Exit of positive current from the cell

Question 10

How to calculate the equilibrium potential for an ion?

Answer 10

Nernst Equation

Question 11

What are the typical ion concentrations?

Answer 11

Na+
INSIDE: 15mM
OUTSIDE: 145mM

K+
INSIDE: 140mM
OUTSIDE: 5mM

Cl-
INSIDE: 4-30mM
OUTSIDE: 110mM

Question 12

What are properties of Glutamate-activated ion channels (iGLuRs)?

Answer 12

• Selective cation channels
• When they open, the cell depolarises. By bringing the cell close to threshold they have an excitatory effect on neurons

Question 13

What are GABAa receptors selective for ?

Answer 13

Cl- ions

Question 14

How does chloride concentration change during neuronal development?

Answer 14

Early in development, chloride concentrations are higher inside neurons; as neurons mature, KCC2 symporter is expressed, leading to lower intracellular [Cl]

Question 15

How is the current carried by an ion determined?

Answer 15

The current is determined by its conductance multiplied by the driving force for that ion

Question 16

What is the process of integrating excitatory and inhibitory inputs in neurons? (3)

Answer 16

• Neurons received multiple synaptic inputs
• The resulting currents are summed by the cell, integrating the input information
• The net effect of these inputs modifies the output of the neuron