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Lecture 4

HMB200H1 Lecture Notes - Lecture 4: Opioid, Sodium-Potassium Alloy, Myelin


Department
Human Biology
Course Code
HMB200H1
Professor
Franco Taverna
Lecture
4

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HMB200 Lecture 4:
Imagine a neuron:
Inward. The conc gradient and the voltage gradient are pulling the Na inwards.
Nerst:
For K the Nernsy equation value is 10/1 = 55mV.
What if both:
The voltage will be -30mV.
Both:
It will be somewhere near 55mV.
At rest:
For the small leak channel, V = IR.
The action:
they guessed correctly that this is due to a very small change in sodium permeability causing the spike.
Electrical activity:
If the voltage reaches a certain threshold in the integration zone, they all start opening. If the voltage
does’t get high eough, they do’t ope ad the sigal stops.
Proposed scheme:
One of the transmembrane domains has lots of charged amino acids on it and it seems to be respobible
for the change in voltage allowing the chanel to open/close.
Channe; dynamics:
The more they open, the moore often they open or they could open for longer periods of time.
Threshold:
The action potential takes 2-5ms.
Easiest way:
Na is quicker and it opens first.
Check your:
Narrower action potential.
Different:
Mechnical stress or heat can open in channels at sensory endings like n the skin.
Action potentials:
Myelin insulates the axon so the action potential can go further and faster. This diffusin happens very
quickly. The action potential regenerates at the nodes of ranvier.
Electrical:
The refractory period lasts longer than it takes for the action potential to reach the next node of ranvier
preventing the AP from going in reverse.
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