Neuromuscular Junction Flashcards Preview

physiology (Woods) > Neuromuscular Junction > Flashcards

Flashcards in Neuromuscular Junction Deck (14):
1

what are some characteristics of a single axon terminal

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

2

what are dense bars

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

3

what is a synaptic gutter

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

4

define synaptic cleft

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

5

what are characteristics of the sarcolemma of the skeletal muscle

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

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

golgi

7

where is Ach synthesized

cytosol of the nerve axon terminal

8

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

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

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

by the calcium release into the cytosol

10

how is acetylcholine removed from the synaptic cleft

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

11

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

methacholine
carbachol
nicotine

12

what drugs inactivate acetylcholinesterase

neostigmine
physostigmine
diisopropyl

13

what does curare do

prevents passage of impulses from nerve ending into muscle

14

what are characteristics of myasthenia gravis

*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