Neuromuscular Junction

Question 1

what are some characteristics of a single axon terminal

Answer 1

• many mitochondria
• synaptic vesicles with acetylcholine
• dense bars
• synaptic gutter
• synaptic cleft
• sarcolemma of the skeletal muscle
• end plate potential

Question 2

what are dense bars

Answer 2

anchored to the presynaptic membrane and associated with synaptic vesicles to which they are tethered by short filaments

Question 3

what is a synaptic gutter

Answer 3

*groove or furrow in the surface of a sarcolemma in which the axon terminal makes contact with the sarcolemma

Question 4

define synaptic cleft

Answer 4

Very narrow but real gap between the axolemma of the axon terminal and the sarcolemma of the innervated muscle fiber

Question 5

what are characteristics of the sarcolemma of the skeletal muscle

Answer 5

has acetylcholine-gated ion channels

• 2 alpha proteins, 1 beta, 1 ddelta, and 1 gamma
• tubular channel remains closed until 2 acetylcholine molecules attach to its alpha subunits
• acetylcholinestase (degrades acetyl choline into acetate group and choline group)

Question 6

Where are the vesicles from acetylcholine that are transported to the axon terminal coming from

Answer 6

golgi

Question 7

where is Ach synthesized

Answer 7

cytosol of the nerve axon terminal

Question 8

what do DHP channels activate & what occurs once they are activated

Answer 8

ryanodine receptors on the SR reticulum membranes, allowing Ca++ to move quickly through the ryanodine receptors into the cytosol at the A-I boundaries

Question 9

besides DHP, what is another way that ryanodine receptors are activated

Answer 9

by the calcium release into the cytosol

Question 10

how is acetylcholine removed from the synaptic cleft

Answer 10

• degradation into choline and acetate by acetylcholinesterase
• reuptake of choline by axon end terminal
• diffusion of Ach away from site

Question 11

what drugs have the same effect on muscle fibers as acetylcholine but are not broken down by acetylcholinesterase, therefore causing spasm

Answer 11

methacholine
carbachol
nicotine

Question 12

what drugs inactivate acetylcholinesterase

Answer 12

neostigmine
physostigmine
diisopropyl

Question 13

what does curare do

Answer 13

prevents passage of impulses from nerve ending into muscle

Question 14

what are characteristics of myasthenia gravis

Answer 14

• autoimmune disease
• antibodies attack acetylcholine receptors
• end plate potentials are too weak to initiate opening of the voltage-gated sodium channels
• neostigmine can be used to inactivate acetylcholinesterase