Lecture 6 - Neuromuscular Junction

Question 1

What is anchored to presynaptic membrane and assoc with synaptic vesicles to which they are tethered by short filaments?

Answer 1

Dense bars

Question 2

What organelle is located in high quantities at the axon terminal?

Answer 2

Mitochondria

Question 3

how many neuro transmitters in a vesicle?

Answer 3

300k

Question 4

what is neurotransmitter in synaptic vesicle at axon terminal?

Answer 4

ach

Question 5

in order for ach ion gated channel to open, how many ach are needed?

Answer 5

2

Question 6

What are the inlets under the axon terminal at the bottom of the synaptic trough?

Answer 6

subneural cleft

Question 7

What happens in the subneural cleft?

Answer 7

the Ach receptors are located and the local potential is created in the sarcolemma. Na will move in and if it is strong enough, it will be enough to activate the voltage gated Na channels and activate the Action potential.

Question 8

order of action potential

Answer 8

1. end plate potential on muscle fiber
2. action potential created on the sarcolemma
3. dihydropyridine channels allow open Ryanodine channels for Ca entry into sarcomere

Question 9

What is the synaptic gutter?

Answer 9

also called the trough, is a groove or furrow in the surface of the sarcolemma in which the axon terminal makes contact with the sarcolemma

Question 10

vesicles for ach are transported to the axon terminal from where?

Answer 10

Golgi

Question 11

The end plate potential is what kind of potential?

Answer 11

a local potential and not an action potential.

Question 12

what is a local potential and an Action potential? list all their differences.

Answer 12

• Local Potentials: Ligand regulated, may be depolarizing or hyperpolarizing, reversible, local, decremental
• Action Potentials: Voltage regulated, begins with depolarization, irreversible, self-propagating, nondecremental.

Question 13

Where is Ach synthesized and actually is happening?

Answer 13

In the cytoplasm of the axon terminal, an acetyl group is combined with a choline and stored in the vesicles.

Question 14

What other than the DHP, secondarily activates the ryanodine channels to release even more Ca?

Answer 14

The Ca being released. Think cooperative effect.

Question 15

What promotes Ryanodine channel closure?

Answer 15

a high level of cytosolic Ca, So yes, the Ryanodine channels are undergo a quasi + feedback and - feed back signal from the same ion Ca.

Question 16

What is meant by excitation -contraction (electro-mechanical) coupling?

Answer 16

Action potential is excitation, and the contraction from Ca channel.

Question 17

What things can inactivate AChesterase

Answer 17

Neostigmine, physostigmine, and diisoproply fluorophosphates.

Question 18

3 drugs like AcH are?

Answer 18

nicotine, carbachol, and methacholine

Question 19

drugs that act like Ach or inactivate acetylcholinesterase do what?

Answer 19

they both have the effect of causing spasms

Question 20

What does the drug Curare do?

Answer 20

prevents passage of impulses from nerve into muscle

Question 21

Explain the pathophysiology of Myastenia Gravis?

Answer 21

it’s an Autoimmune disease where the body attacks the ACH receptors on the motor endplate and it becomes very difficult for the local end plate potentials to initiate opening of the voltage gated potentials.