Lecture 6 - Synaptic Transmission & Neuromuscular Junction

Question 1

Local Anesthetics (Reversible Antagonists)

Answer 1

Procaine, Lidocaine, Novocaine and Cocaine

all bind and block voltage gated Na channels. This numbs pain. Blocks action potentials from being sent to CNS.

Wears off overtime meaning eventually they unbind

Question 2

Irreversible Antagonists

Answer 2

Tetrodotoxin binds with and blocks Na gated channels but is this case is irreversible. Does not unbind

Question 3

11 steps of Anatomy of synapse

Answer 3

Intro:

1. Neurotransmitter is made and then stored in vesicle
2. Action potential invaded presynaptic terminal
3. Depolarization of presynaptic Chanels causes open of voltage gated calcium channels
4. Influx of Calcium through channels

Middle:

5. Calcium causes vesicles to fuse with presynaptic membrane
6. transmitter is related into synaptic cleft via exocytosis
7. Transmitter binds to receptor molecules in post synaptic membrane
8. Opening or closing of post synaptic channels
9. Postsynaptic current causes excitatory or inhibitory postsynaptic potential that changes excitability of cell

Clean up + recycle:

10. Removal of neurotransmitter by glial uptake or enzyme degradation
11. retrieval of vesicular membrane from plasma membrane

Question 4

Glutamate (EPSP)

Answer 4

Glutamate (glutamatergic synapse) is most common excitatory synapse is the nervous system. Gluatmate opens channels for sodium, this makes voltage inside the post synaptic neuron MORE POSITIVE

Question 5

Gaba (IPSP)

Answer 5

Gaba (gabaergic synapse) is most common inhibitory synapse in nervous system. Gaba allows chloride to enter channels making voltage inside the post synaptic more negative.

Question 6

Post Synaptic Potentials

Answer 6

1. EPSP, one fires 1 or 2, little AP
2. Both EPSP fire and big AP
3. IPSP one first, little below -60
4. EPSP + IPSP (E1 + I), little AP
5. EPSP 1&2 + I, more AP

if threshold is crossed, action optional is initiated

Question 7

Where do synapses occur between?

Answer 7

Synapes occur between motor neurons and muscle fibres, this is how the nervous system controls muscle contractions

Question 8

Alpha motor neurons

Answer 8

Alpha (primary) motor neurons, in the ventral horn, have there cell bodies in the spinal cord. There axons connect to group of muscle fibres directly

Question 9

Acetylcholine receptor

Answer 9

Both potassium and sodium can pass through, however more sodium enters then potassium. Net affect causes more sodium flowing in then potassium out

Question 10

End plate potentials

Answer 10

If you measure voltage change, it decays exponentially at portions of the muscle fibre furthest away from endplate. Muscle fibres therefor also need AP to contract along there entire length

Question 11

Neuromuscular junction

Answer 11

Refer to photo. Allows for sodium and potassium flow. Juntional folds for increase surface area at receptor sites. Sodium is dominant in polarization