Neuromuscular Junction

Question 1

Motor end plate

Answer 1

Region of the sarcolemma where NMJ occurs

Question 2

Synaptic cleft

Answer 2

Space btwn the axon terminal and the motor end plate (contains extracellular fluid- electrolytes Ca, Na, Cl, K, nutrients, enzymes

Question 3

Synaptic vesicles

Answer 3

Small envelope- like structures that contain the neurotransmitter acetylcholine (Ach)

Question 4

Calcium channels (gates)

Answer 4

Protein gated channels located on the membrane of the axon terminal. Open and close in response to changes in the membrane potential

Question 5

Acetylcholine receptors

Answer 5

Receptors on the motor end plate that have an affinity for Ach. Associated with sodium channels

Question 6

Sodium channels (gates)

Answer 6

Protein gated channels located on the motor end plate. Open and close in response to changes in the membrane potential

Question 7

Acetylcholinesterase (AChase)

Answer 7

Enzyme located in the synaptic cleft. Function is to destroy free Ach

Question 8

Action potential

Answer 8

Electrical current which has the capacity (potential to cause a response. In the case of the NMJ the response will be muscle contraction.

Question 9

What’s the name of the autoimmune disease that affects your NMJ?

Answer 9

Myasthenia Gravis

Question 10

Step 1

Answer 10

Action potential is generated and then propagated down the axon to the axon terminal

Question 11

Step 2

Answer 11

The change in the electrical status of the axon terminal stimulates voltage gated Ca++ channels to open

Question 12

Step 3

Answer 12

Ca++ diffuses through the Ca++ channels into the axon terminal

Question 13

Step 4

Answer 13

The presence of Ca++ in the axon terminal stimulates the movement synaptic vesicles to migrate to the axon terminal membrane

Question 14

Step 5

Answer 14

Synaptic vesicles fuse with the axon terminal membrane and release their neurotransmitter (ACh) into the synaptic cleft via exocytosis

Question 15

Step 6

Answer 15

ACh diffuses across the synaptic cleft and some will bind with ACh-receptors on the motor end plate (sarcolemma)

Question 16

Step 7

Answer 16

The presence of ACh on the ACh-receptors stimulates the opening of ligand gates Na+ channels stimulating them to open.

Question 17

Step 8

Answer 17

Na+ moves from the synaptic cleft, through the Na channels and into the motor end plate

Question 18

Step 9

Answer 18

The change in the electrical charge of the motor end plate results in depolarization of the sarcolemma

Question 19

Step 10

Answer 19

Free ACh, in the synaptic cleft, is degraded by Chase. As the free ACh concentration falls, the ACh on the ACh-receptors will detach resulting in immediate closure of the Na+ gates.

Question 20

Step 11

Answer 20

Closure of the ligand gated Na+ channels results in the cessation of the AP transfer across the
NMJ.

Question 21

Step 12

Answer 21

Free ACh is immediately destroyed by AChase