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Neuromuscular transmission


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what two types of neurons are in the efferent peripheral nervous system?
-autonomic neurons
-somatic neurons
what do they innervate?
-autonomic neurons
-somatic neurons
auto = cardiac/smooth muscle and glands.

somatic = skeletal muscle
what is a motor unit?
an alpha motor neuron and the muscle cells it innervates.
how many cells do motor units innervate?
from 3 to 1700
what do smaller motor units control?
fine movement.
where do alpha motor neurons originate?
in the ventral horn of the spinal cord.
what is different between a post-synaptic potential and a motor-end-plate potential?
-PSPs can be excitatory OR inhibitory; are generally small.

-EPPs are generally LARGE and are ONLY excitatory.
How many EPPs are necessary to generate an action potential?
only one
if EPPs are always excitatory, how can they be inhibited?
-By inhibiting the alpha motor neuron within the spinal cord.
what in general are 5 effects of chemical agents and diseases on somatic movement?
1. Botulism
2. Black Widow Spiders
3. Organophosphates and other
4. Curare
5. Myasthenia gravis
What is Botulism?
disease caused by clostridium toxin; it blocks release of AcH and since the excitatory neuron can't reach EPPs, causes paralysis.

-not usually cause of death, but maybe respiratory failure
what is caused by a black widow spider?
too MUCH acetylcholine release.
what do organophosphates, nerve gas, herbicides/pesticides do to the nervous system?
-block acetylchololinesterase so you get tremendous excition!
what does Curare do?
blocks the nictotinic AcH receptor and works as an anasthetic.

binds the receptor, without activatating.
what does is myasthenia gravis?
automimune disease where Ab form to the Nicotinic receptors; causes muscle weakening and is treated by blocking AcHesterase.
how does blocking AcHesterase treat myasthenia gravis?
it allows AcH to stay in the synaptic space longer, so the chances of it binding a receptor are better.
what 5 chemical agents cause tremendeous excitation of all cholineric receptors? how?
-nerve gas
Blocks AcHesterase.

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