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Other names for Action Potential
- Spike
- Nerve Impulse
- Discharge
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Membrane potential moves from ____mV to ____ mV for a very brief time
-65mV to +40mV
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Rising Phase:
Rapid depolarization of membrane to +40mV
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Problems with Na+ channels:
Channelopathy
- Generalized epilepsy with febrile seizures
- •Increase temp.=seizures
- •Due to slowing of Na+ channel inactivation = prolonging of APs
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Problems with Na+ channels:
Tetrodotoxin (TTX)
- In puffer fish
- Clogs Na+ pore = blocks AP
- Result = FATAL (paralysis of diaphragm and heart muscle due to nerve and muscle block)
- If served correctly: numb around mouth
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Problems with Na+ channels:
Saxitoxin
- Clams, muscles, shellfish that feed on certain dinoflaggelates
- Blocks Na+ channel
- Result = FATAL (paralysis of diaphragm due to nerve and muscle block)
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Problems with Na+ channels:
Batrachotoxin
- Skin on Columbian frog
- Causes Na+ channels to open at more negative Vm and stay open longer = scrambles AP code/info being sent
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Voltage-gated K+ channels are involved in what _______ phase as it helps with repolarization
Falling phase
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Multiple Sclerosis
- Demyelinating Disease
- Symptoms: Weakness, impaired coordination, vision, and speech
- Cause of disease is not well understood
- Cause of sensory and motor problems: MS attacks myelin sheath of axons
- Multiple: many areas of nervous system at once
- Sclerosis: "hardening" lesions around axons
- Diagnose:
- •MRI
- •Conduction velocity: slowed by destruction of myelin
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Guillain-Barre Syndrome
- Attacks myelin of PNS
- •slows conduction velocities
- Saltatory conduction is disrupted
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