Synaptic Transmission Lab

Question 1

Why do individual MEPP’s vary substantially in amplitude?

Answer 1

The reason that there’s variation in the amplitude of EPSPs is biological variation. Not all vesicles are the same size or contain the same number of neurotransmitter molecules.

Question 2

What does a notch or inflection of the AP rising phase reflect?

Answer 2

This is depolarization of the cell via opening of ACh sodium channels.

Question 3

Did the electrode come out of the cell? If so, why?

Answer 3

…

Question 4

signs/symptoms of botulism

Answer 4

FLACCID paralysis.

Question 5

MOA of botulism

Answer 5

inhibits vesicle fusion with presynaptic membrane by cleaving synaptobrevin (SNARE protein).

Question 6

Causes of botulism

Answer 6

1) in infants often caused by honey 2) most commonly canned foods 3) wounds

Question 7

Treatment for botulism

Answer 7

antitoxin and supportive care. may need to be on a ventilator.

Question 8

Why is botulism relatively more common in Colorado, compared to other places?

Answer 8

more home canning

Question 9

Can you observe discreet “steps” in the amplitudes of successive EPP’s?

Answer 9

…

Question 10

Are the “steps” about the size of a MEPP?

Answer 10

…

Question 11

signs/symptoms of myasthenic syndrome

Answer 11

weakness of legs and arms. leg involvement usually more severe than in MG. proximal muscle weakness. respiratory muscle weakness. similar to MG presentation but eye signs are much more PROMINENT in MG. Distinct characteristic is that with muscle use, REFLEX STRENGTH INCREASES.

Question 12

MOA of myasthenic syndrome

Answer 12

auto-antibodies block presynaptic voltage-gated calcium channels.

Question 13

causes of myasthenic syndrome

Answer 13

1) usually paraneoplastic syndrome associated with lung cancer. 2) may also be associated with autoimmune diseases (eg. hypothyroidism/DM type 1)

Question 14

Treatment for myasthenic syndrome

Answer 14

1) if paraneoplastic treatment with chemo or radiation usually leads to resolution of symptoms. 2) you can also improve symptoms with pyridostigmine. 3) if autoimmune IVIG and plasma exchange

Question 15

Mg/Low Ca solution – why is evoked but not spontaneous release affected by this solution?

Answer 15

spontaneous release isn’t dependent on calcium.

Question 16

Why does high frequency stimulation in the Mg/Low Ca solution allow muscle contraction?

Answer 16

facilitation due to increase in intracellular calcium ion concentration.

Question 17

How does Mg/Low Ca solution work?

Answer 17

produces a presynaptic block, similar to myasthenic syndrome, by reducing transmitter release.

Question 18

Why does the muscle begin to twitch when the curare solution is first added?

Answer 18

Curare just hasn’t had time to act yet.

Question 19

EPP

Answer 19

nerve-evoked end plate potential.

Question 20

MEPP

Answer 20

miniature end plate potentials.

Question 21

What would be the effect of a therapeutic dose of neostigmine on a normal person?

Answer 21

Probably wouldn’t have much of an effect because you normally have an excess of ACh.

Question 22

effect of neostigmine overdose? MOA of effect?

Answer 22

DUMBBELS

Question 23

signs/symptoms of botulism?

Answer 23

usually starts with cranial muscle weakness, ANS signs including dry mouth/constipation/postural hypotension, difficulty talking and nausea, vomiting. classic triad of bulbar palsy + descending paralysis + clear senses and mental status. NO fever.

Question 24

differentiate between spontaneous end plate potentials (MEPPs) and nerve-evokd end plate potentials EPPs)

Answer 24

MEPPs are spontaneous depolarizations of the postsynaptic membrane from a single vesicle. EPPs result from an AP in the presynaptic cell releasing neurotransmitters that bind to ACh receptors and depolarize the membrane.

Question 25

what is the mechanism at play in repetitive stimulation in curare?

Answer 25

depression

Question 26

what is the mechanism at play in elevated Mg/low Ca solutions?

Answer 26

facilitation