Neuromuscular Junction Flashcards Preview

physiology (Woods) > Neuromuscular Junction > Flashcards

Flashcards in Neuromuscular Junction Deck (14)
Loading flashcards...
1
Q

what are some characteristics of a single axon terminal

A
  • many mitochondria
  • synaptic vesicles with acetylcholine
  • dense bars
  • synaptic gutter
  • synaptic cleft
  • sarcolemma of the skeletal muscle
  • end plate potential
2
Q

what are dense bars

A

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

3
Q

what is a synaptic gutter

A

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

4
Q

define synaptic cleft

A

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

5
Q

what are characteristics of the sarcolemma of the skeletal muscle

A

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)
6
Q

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

A

golgi

7
Q

where is Ach synthesized

A

cytosol of the nerve axon terminal

8
Q

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

A

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

9
Q

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

A

by the calcium release into the cytosol

10
Q

how is acetylcholine removed from the synaptic cleft

A
  • degradation into choline and acetate by acetylcholinesterase
  • reuptake of choline by axon end terminal
  • diffusion of Ach away from site
11
Q

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

A

methacholine
carbachol
nicotine

12
Q

what drugs inactivate acetylcholinesterase

A

neostigmine
physostigmine
diisopropyl

13
Q

what does curare do

A

prevents passage of impulses from nerve ending into muscle

14
Q

what are characteristics of myasthenia gravis

A
  • 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