Chapter 7 and 8 - Electrical excitability and action potentials & Synaptic transmission and NMJ (2019) - Evals #5 by Keim

Question 1

In myelinated peripheral nerves, the myelin sheath is interrupted at regular intervals forming short uncovered areas. What are these areas called?

Answer 1

Nodes of Ranvier

Question 2

What is TRUE regarding “use dependent” action of local anesthetics ?

Answer 2

Inhibition of Na+ current progresses in a time-dependent manner with increasing repetitive stimulation or firing of action potentials.

Question 3

Which NMJ structure is targeted by tetanus toxin?

Answer 3

Synatobrevin

Question 4

Which channel is activated to produce excitatory end plate current or called end plate potential (EPP) in the muscle membrane.

Answer 4

ACh receptor channel

Question 5

Which part of Nav and Cav subunits are homologous to a single subunit of a voltage gated potassium channel?

Answer 5

Domains 1-4 of alpha subunit

Question 6

What channel often give rise to a more sustained depolarizing current which is the basis for the long-lived action potentials in cardiac cells and smooth muscle cells?

Answer 6

Ca2+ channel

Question 7

S stimulates A, what events will take place in the presynaptic terminal of the cell

Answer 7

Axonal membrane will be depolarized and action potential is generated

Question 8

A patient was given a tubocurarine inhibitor. Which channel in the NMJ is the target of the drug?

Answer 8

Acetylcholine receptor channel

Question 9

Sequence of simple action potential?

Answer 9

1. stimulation of action potential
2. depolarizing stimulus makes it more positive than the threshold
3. slower repolarization (negative going) phase
4. negative resting membrane potential

Question 10

Replacing or destruction of acetylcholine which has the most important effect?

Answer 10

Destruction of Ach by AChE

Question 11

An organic cation applied to an axon that Prevents the outward current of K+ and reveals Na+ inward?

Answer 11

Tetraethylammonium

Question 12

True about graded response potential?

Answer 12

Hyperpolarization is always ineffective

Question 13

Also known as Anomalous Rectifier which conducts more K in inward direction?

Answer 13

Kir K+ channels

Question 14

Mr. Balboa is a famous boxer. After his bout he cannot raise his arms and his speech is slurred. What probability increases that it is not LEMS?

Answer 14

Mr. Balboa is not exposed to cold

Question 15

As the graded response spreads, its magnitude decays exponentially with distance from the site of stimulation because of passive loss of electrical current to the medium. This decay is called?

Answer 15

Electrotonic conduction

Question 16

The part of action potential that lies above 0 mv

Answer 16

Overshoot

Question 17

True or False:

As the graded response spreads, its magnitude decays exponentially with distance from the site of stimulation.
TRUE

Answer 17

True

Question 18

What is the nature of relationship between strength and duration of stimulus to evoke action potential?

Answer 18

Inversely proportional

Question 19

10 y.o px had a punctured wound at right sole. Px had muscle spasms at right leg. Px was diagnosed with tetanus. The toxin blocks the fusion of synaptic vesicle (or cleaves) at what SNARE protein?

Answer 19

Vesicular SNARE Synaptobrevin (v-SNARE)

Question 20

Increase Ca and Mg in presynaptic terminals have effect on quantal release of Acetylcholine and EPP?
A. Increase Ca2+, Increase Mg2+  
B. Increase Ca2, Normal Mg2+ 
C. Decrease Ca2+, Decrease Mg2+ 
D. Decrease Ca2+, Normal Mg2+

Answer 20

B. Increase Ca2, Normal Mg2+

Question 21

Which of the ff is responsible for the continuous depolarizing of nerve and skeletal cells?

a. Conotoxin
b. Tetrodotoxin
c. Tubocurarine
d. Nicotine

Answer 21

d. Nicotine

Question 22

Which of the following locations has the least number of Na+ channels?
A. Nodes of ranvier
B. Unmyelinated portion
C. Myelinated portion
D. None of the choices

Answer 22

C. Myelinated portion

Question 23

Which vesicular protein acts as calcium sensor thus favors fusion of the vesicles with the presynaptic membrane? 
A. Synaptotagmin
B. Synaptobrevin
C. SNAP-25
D. Syntaxin A

Answer 23

A. Synaptotagmin

Question 24

Steps in metabotropic receptor?

Answer 24

1. Muscarinic ACh receptor activation
2. Release of alpha-GTP + Beta-gamma from the heterotrimeric G protein
3. Activation of inward rectifier K+ channel by Beta-gamma
4. Membrane Hyperpolarization
5. Decrease in heart rate

p 208 Fig 8-3