Valley Physiology of the Neuron

Question 1

Stimulation of presynaptic and postsynaptic nicotinic receptors at the neuromuscular junction leads to which of these responses?
(increased/decreased) release of acetylcholine
(increased/decreased) motor endplate potential

Answer 1

increased release of acetylcholine

decreased (depolarized) motor end plate potential

Question 2

How many molecules of acetylcholine are required to open a channel of the motor end-plate?

Answer 2

2

Question 3

Sodium, calcium, and potassium ions diffuse in which directions when the channels of the motor end-plate of skeletal muscle are stimulated to open?

Answer 3

sodium moves inward
calcium moves inward
potassium moves outward

Question 4

The release of acetylcholine from the neuromuscular junction will be increased in which of the following conditions?

• Hyponatremia
• Hypocalcemia
• Hypomagnesemia
• Hypokalemia

Answer 4

Hypomagnesemia

Question 5

The presynaptic action of succinylcholine does what to the postsynaptic action?

• Enhances
• Antagonizes
• No change

Answer 5

Succinylcholine antagonizes it’s postsynaptic action.

Question 6

What NDMR is associated with dose-dependent histamine release?

Answer 6

atracurium

Question 7

Which agent has antimuscarinic actions?

• Succinylcholine
• Pancuronium
• Mivacurium
• D-Tubocurarine

Answer 7

Pancuronium

Question 8

What electrolyte abnormality is a potential adverse effect of succinylcholine administration?

Answer 8

Hyperkalemia

Question 9

What is the earliest sign of malignant hyperthermia?

Answer 9

Increase in end-tidal CO2

Question 10

When you use a nerve-muscle stimulator on the right wrist of a patient paralyzed on the right side, what will you see during a train-of-four?

Answer 10

Greater amplitude of twitches on the right compared with the left d/t exntrajunctional receptors.

Question 11

What will happen to a non-depolarizing neuromuscular blockade if the patient receives neomycin during the case? A depolarizing blockade?

Answer 11

They will both increase.

Question 12

What will you see with the nerve-muscle stimulator if the patient has been given a non depolarizing neuromuscular relaxant?

Answer 12

Fade on train-of-four and post-titanic potentiation

Question 13

It is best to reverse non depolarizing neuromuscular blockade when there are how many twitches in the train-of-four?

Answer 13

Four (controversial)

I believe in class we were told 2-3, leaning towards 3

Question 14

Non depolarizing neuromuscular blockade is increased by each of the following EXCEPT:

• isoflurane
• penicillin
• lidocaine
• lithium

Answer 14

penicillin

Question 15

What happens to the number of nicotinic receptors in skeletal muscle in a patient with a spinal cord injury?

Answer 15

The number increases in denervated skeletal muscle.

Question 16

A patient with biliary disease is given vecuronium. How will the vecuronium be eliminated?

Answer 16

through both metabolism (biliary metabolism) and renal elimination

Question 17

Cisatracurium is eliminated how?

Answer 17

Hofmann elimination

Question 18

With a non depolarizing block, DBS3,3 produces what type of twitches?

Answer 18

2 unequal (fading) twitches

Question 19

A vital capacity of at least 20 ml/kg occurs when what percentage of neuromuscular receptors are blocked?

Answer 19

75%

Question 20

At the neuromuscular junction, does the pre-synaptic action of succinylcholine enhance or antagonize its post-synaptic action?

Answer 20

Succinylcholine, by stimulating the pre-synaptic nicotinic receptor, AUGMENTS the release of ACh. Since the released ACh opens channels and depolarizes the motor end-plate like succinylcholine, the pre-synaptic action of succinylcholine ENHANCES its post-synaptic action.

Question 21

If you use a nerve-muscle stimulator on the right wrist of the patient with right-sided hemiplegia, will the twitch be less than, the same as, or greater than the twitch on the left?

Answer 21

The twitch on the right will be greater than the left! Nicotinic receptors are up-regulated on the right, hemiplegic side.

Question 22

Why isn’t cardiac muscle directly involved in malignant hyperthermia?

Answer 22

Because cardiac myocytes (muscle fibers) express the RyR2 isoform of the ryanodine receptor INSTEAD of the RyR1 receptor found embedded in the sarcoplasmic reticulum of skeletal muscle.