Lecture 3

Question 0

What is the conduction velocity of an AP determined by?

Answer 0

Membrane resistance

Cytoplasm resistance

Question 1

Can an action potential be elicited in a refractory period?

Answer 1

No

Question 2

What ratio gives the fastest conduction velocity of AP?

Answer 2

High Rm:Rin ratio

Question 3

How is cytoplasm resistance related to diameter of the cell?

Answer 3

Rin is proportional to 1/diameter of the cell

Question 4

How have vertebrates adapted to have high AP conduction velocities?

Answer 4

They have developed myelinated axons

Question 5

What is myelination?

Answer 5

Layers of insulation due to wrapping layers of membrane

Question 6

What is a node of ranvier?

Answer 6

Where there is a gap in the myelin sheath and the signal is boosted

Question 7

Describe an electrical synapse

Answer 7

A channel made up of 2 connexons which electrically couples cells cytoplasm

Question 8

Describe a chemical synapse

Answer 8

Uni directional with a dendrite with a sprit on the post synaptic saide and an axon with synaptic terminals on the pre synaptic side

Question 9

What is the process of transmission of an action potential across a chemical synapse? (There are 7 steps)

Answer 9

1) Action potential arrives at the synaptic terminal
2) Action potential causes the opening of voltage gated Ca channels
3) Ca influx
4) triggers exocytosis which causes vesicular release of acetyl choline
5) acetyl choline diffuses across the synaptic cleft
6) binds to acetyl choline receptors in the post synaptic membrane
7) acetyl choline receptor ligand gated ion channels, opens na/K current which causes depolarisation

Question 10

What enzyme hydrolyses acetyl choline?

Answer 10

Acetyl cholinesterase

Question 11

What are miniature end plate potentials?

Answer 11

A quanta is spontaneously released from the motor neuron is not stimulated. This causes a small depolarisation of the skeletal muscle fibre

Question 12

What do excitatory synapses cause in the post synaptic membrane?

Answer 12

Depolarisation

Question 13

What do inhibitory synapses cause in the post synaptic membrane?

Answer 13

Hyperpolarisation

Question 14

What is synaptic integration?

Answer 14

Sumated EPs mount up to reach the threshold

Question 15

What action of chemical transmitters is indirect/slow?

Answer 15

Receptor + g-protein + effector

Question 16

Direct/fast transmission is operated by:

Answer 16

Ligand gated ion channel