Nerves 5

Question 1

What is a synapse?

Answer 1

the connection where one neurone modulates the activity of a target

Question 2

What does the action potential cause in the presynaptic terminal of the NMJ?

Answer 2

opens voltage gated calcium channels

Question 3

What does the release of calcium cause in the presynaptic terminal?

Answer 3

triggers fusion of neurotransmitter contain vesicles

Question 4

What neurotransmitter is released at the NMJ?

Answer 4

acetylcholine

Question 5

What happens to acetylcholine?

Answer 5

It diffuses across synaptic cleft and binds to acetylcholine receptors (nicotinic)

Question 6

What does the acetylcholine do?

Answer 6

opens ligand gated sodium/ potassium channels and evokes a graded (Local) potential called the end plate potential

Question 7

What is significant about the endplate potential?

Answer 7

it always depolarises the adjacent membrane to threshold which opens voltage gated sodium channels to generate a new AP

Question 8

What removes ACh?

Answer 8

anticholinesterase

Question 9

What does tetrodotoxin do?

Answer 9

blocks sodium channels and so blocks the action potential

Question 10

What does joro spider toxin do?

Answer 10

blocks calcium channels and so stops transmitter release

Question 11

What does botulinum toxin do?

Answer 11

prevents vesicle fusion

Question 12

What does curare do?

Answer 12

blocks ACh receptors and so prevents endplate potential

Question 13

What do anticholinesterases do?

Answer 13

prevent breakdown of ACh and so increase transmission at NMJ

Question 14

What 4 qualities of CNS synapses makes them more complex than the neuromuscular junction?

Answer 14

• complicated synaptic connectivity
• variety of anatomical arrangement of synapse
• range of postsynaptic potentials
• range of neurotransmitters

Question 15

What kind of postsynaptic potentials does the CNS have compared to the NMJ?

Answer 15

NMJ only has the big endplate potential
CNS can have:
-Fast EPSPs (ionotropic)
-Slow EPSPs (metabotropic)
-Fast IPSPs
-Slow IPSPs

Question 16

What does the range of postsynaptic potentials in the CNS allow?

Answer 16

complex synaptic integration

Question 17

What 3 anatomical arrangements can synapses in the CNS have compared to the NMJ.

Answer 17

NMJ anatomical arrangement does not change
CNS can have:
-axo-somatic
-axo-dendritic
-axo-axonal

Question 18

What is meant by ‘synaptic connectivity’ in the CNS?

Answer 18

the different numbers and functions of neurones in a pathway to elicit an effect
NMJ is very simple and generally is just motor neurone-muscle cell but the CNS can involve lots of converging and diverging neurones and interneurones