Anatomy and Physiology of the NMJ

Question 1

What is the NMJ?

Answer 1

Location in which signals transmitted from MOTOR NEURON to a MUSCLE FIBER

Question 2

Components of the NMJ: motor neuron

Answer 2

Made up of cell body, dentrites and nucleus

Question 3

What allows for faster impulse conduction

Answer 3

MYELIN-Covered Axon

Question 4

Each axonal process has a ____________ That innervates

Answer 4

prejunctional motor nerve ending;

One muscle fiber

Question 5

What is the synaptic cleft

Answer 5

Connect prejunctional motor nerve ending to Postjunctional muscle fiber

Question 6

What neurotransmitters are release from the motor nerve ending to attach to receptors on the postjunctional muscle fiber?

Answer 6

Acetycholine

Question 7

Mainly Ach receptors on POST JUNCTIONAL membrane

Answer 7

Nicotinic

Question 8

When an action potential travels along the axon what happens?

Answer 8

Depolarizes, Ach released and diffuse across synaptic cleft -> Once Ach bind to acetylcholine receptors in causes an action potential in the MUSCLE FIBER
–> MUSCLE MOVEMENT.

Question 9

Acetylcholine involved in transmission in both

Answer 9

Parasympathetic and Sympathetic Systems

Question 10

Ach receptors classified as (2)

Answer 10

Nicotinic

Muscarinic

Question 11

At NMJ, ACh binds to

Answer 11

NICOTINIC

Question 12

Nicotinic receptors has 5 subunits

Answer 12

2 alpha
1 beta
1 Gamma
1 Delta

Question 13

What is the only binding site/place where Ach can bind?

Answer 13

ALPHA

Question 14

What must ACH occupy to cause a CONFORMATIONAL CHANGE? which lead to

Answer 14

BOTH alpha subunits.; Action potential

Question 15

ACh is broken down into_______and ______by_____enzymes via ______(process)

Answer 15

Acetate and Choline

Acetylcholinesterase; HYDROLYSIS

Question 16

Where are the enzyme acetylcholinesterase located?

Answer 16

ADJACENT TO acetylcholine receptors

Question 17

The choline undergoes________ and together with ________, Ach is synthesized an stored

Answer 17

REUPTAKE

Acetyl-CoA

Question 18

Receptors usually suppressed in burns and sepsis

Answer 18

EXTRAJUNCTIONAL receptors

Question 19

What is important to know about EXTRAJUNCTIONAL RECEPTORS?

Answer 19

when activated, they tend to stay open for a longer period of time which CAN lead to HYPERKALEMIA

Question 20

Up-regulation of Neuromuscular Receptors

Answer 20

The number of nAChRs INCREASE which develops on the postjunctional membrane
Cause by a DECREASED stimulation of the neuromuscular junction over time

Question 21

Upregulation of receptors is associated with HYPERSENSITIVITY to _________ such as ________
and DESCREASED SENSITIVITY to _____ such as

Answer 21

Agonist; Succinylcholine

Non-Depolarizing NMBAs

Question 22

Upregulation can lead to

Answer 22

lethal potassium release from cells after SCh administration

Question 23

What determines the number ACh release into the cleft?

Answer 23

The extent of calcium influx into the presynaptic neuron determines the number of ACh quanta released into the cleft and is a function of the duration of nerve depolarization.

Question 24

What percentage of the ACh is released into the cleft? What happens to the rest of the ACh? 2 fates

Answer 24

Only approximately 50% of the ACh released into the cleft reaches the postsynaptic receptors;
the rest is either hydrolyzed by acetylcholinesterases (AChEs) contained within the cleft or diffuses out of the cleft.