Neuromuscular Junction

Question 1

Which ion moves into the presynaptic terminal to trigger the release of ACh?
A.  Ca2+
B.  Cl-
C.  K+
D.  Mg2+
E.  Na+

Answer 1

A. Ca2+

Question 2

Which ion moves into the cell post-synaptically to create a mini endplate potential (mEPP)?
A.  Ca2+
B.  Cl-
C.  K+
D.  Mg2+
E.  Na+

Answer 2

E. Na+

Question 3

What type of receptor does ACh join to in the post-junctional membrane?

A. Muscarinic
B. Nicotinic

Answer 3

B. Nicotinic

Question 4

What enzyme is responsible for the degradation of ACh at the level of the neuromuscular junction?

A. Adenyl cyclase
B. Phospholipase C
C. Acetylcholinesterase
D. Protein kinase A

Answer 4

C. Acetylcholinesterase

Question 5

What does Botulinum toxin do at the neuromuscular junction?

Answer 5

It prevents ACh release because the toxin cleaves one of the SNARE proteins presynaptically to prevent vesicles fusion.

Question 6

What do organophosphate do at the neuromuscular junction?

Answer 6

They prevent the break down of ACh by inhibiting the enzyme acetylcholinesterase. This creates a build up of ACh in the neuromuscular cleft and in the parasympathetic nervous system causing an inability of the muscle to relax and excessive activity of the PNS respectively.

Question 7

What is myasthenia gravies and how does it effect the neuromuscular junction?

Answer 7

It is an autoimmune disease resulting from antibodies (IgG) against the nAChR. nAChR depletion prevents sustained action potentials and therefore muscle contractions.

Question 8

What do neuromuscular blockers do at the neuromuscular junction?

Answer 8

These muscle relaxants are nAChR competitive antagonists, which mean they prevent ACh from binding to nAChRs.