Physiology 3120 Lecture Notes - Lecture 9: Botulism, Ion, Clostridium
9 May 2018
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Physiology 3120
Lecture 9
Clinical Scenario – MS
A patient complains about numbness in their face and extremities. They are frequently tired with little
energy. Their vision has become blurry with some eye pain and they are having difficulty with bowel
and bladder control. After a series of neurological scans and test it is confirmed that the person has
multiple sclerosis (MS).
MS is an autoimmune disease where the body’s immune system attacks, damages and can eventually
destroy the myelin sheath surrounding the neurons of the CNS.
Questions:
1. If the myelin sheath around a motor neuron was partially damaged, how would that affect the AP
propagation? What symptoms might you see?
- you will start leaking out ions, so your AP may or may not reach the next node of ranvier
- so your AP may slow down or stop completely some APs reach the node and some don’t
- you would see muscle weakness
2. If the myelin was completely damaged, how would that affect the action potential
propagation?
- AP wont be able to reach the node of ranvier, so you cant propagate the AP
- muscles can not work
Action Potential Propagation
- so with a damaged myelin, before the +ive charge can reach the next node,
the +ive charges leak out of the axon and the AP wont reach the node
- In MS, the +ive charge (current) leaks out before it can reach nodes of
ranvier to open VG channels
Neuromuscular Junction (NMJ) (EC 75)
- one motor neuron has several branches that go to a muscle cell
- alpha motor nerves innervate the muscle cells
- it’s a peripheral nerve, so its myelin is being created by schwann cells
- the synaptic vesicles contain our neurotransmitter ACh
- the special set of VG Ca2+ channels
o they respond to the AP coming down the axon terminal
- the alpha neuron will them come into contact with our muscle cell
- the region directly underneath the axon terminal is called synaptic folds – to increase SA of NMJ
o the region thrown into folds is called the muscle cell end plate
- the gap bw the axon terminal and the muscle cell endplate is called the synaptic trough
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Document Summary
A patient complains about numbness in their face and extremities. Their vision has become blurry with some eye pain and they are having difficulty with bowel and bladder control. After a series of neurological scans and test it is confirmed that the person has multiple sclerosis (ms). Ms is an autoimmune disease where the body"s immune system attacks, damages and can eventually. So your ap may slow down or stop completely (cid:523)some aps reach the node and some don"t(cid:524) destroy the myelin sheath surrounding the neurons of the cns. Ap wont be able to reach the node of ranvier, so you cant propagate the ap. You will start leaking out ions, so your ap may or may not reach the next node of ranvier. You would see muscle weakness so with a damaged myelin, before the +ive charge can reach the next node, the +ive charges leak out of the axon and the ap wont reach the node.
