Neuromuscular transmission
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- what two types of neurons are in the efferent peripheral nervous system?
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-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?
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-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?
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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?
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-organophosphates
-nerve gas
-sarin
-herbicides/pesticides
Blocks AcHesterase.