Lecture 12

Question 1

Depolarisation vs hyperpolarisation

Answer 1

Depolarisation is -70 to -50 and hyperpolarisation is -70 to -90

Question 2

How do you change membrane potential?

Answer 2

By increasing membrane permeability to a particular ion which will cause membrane potential to move towards the equilibrium potential for that ion

Question 3

How do you get hyperpolarisation and depolarisation?

Answer 3

Increase permeability to calcium and sodium for depolarisation and increase permeability to chloride and potassium for hyperpolarisation

Question 4

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

Answer 4

Equation that calculates contribution of each ion type to membrane potential by looking at membrane permeabilties of each ion.

Question 5

What are excitatory synapses?

Answer 5

Synapses where neurotransmitter releases causes ligand gated ion channels to open. Sodium and calcium flow in and set up an EPSP (excitatory post synaptic potential)

Question 6

How does an EPSP differ from an action potential?

Answer 6

EPSP is more sustained that an AP but doesn’t cause an AP but rather brings membrane very close to an AP.

Eg acetylcholine

Question 7

What are IPSP

Answer 7

Open channels for K+ and Cl- that cause hyperpolarisation

Eg glycine

Question 8

Difference with fast and slow synaptic transmission?

Answer 8

Fast has ligand bind to ion channels directly and slow is done through G proteins.

Question 9

Other factors that influence membrane potential?

Answer 9

Potassium concentration

Normally 4.5mmol but if risen above 6 can cause problems. Can lead to depolarisation as more enters cell. Leads to arrhythmias and tachycardia of the heart. Condition known as hyperkalemia and occurs if you eat too many bananas.

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Na/K ATPase contributes a few mV to membrane potential. Indirectly sets up ion gradients that maintain it