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Lecture 4

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

Human Biology
Course Code
Franco Taverna

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HMB200 Lecture 4:
Imagine a neuron:
Inward. The conc gradient and the voltage gradient are pulling the Na inwards.
For K the Nernsy equation value is 10/1 = 55mV.
What if both:
The voltage will be -30mV.
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.
The action potential takes 2-5ms.
Easiest way:
Na is quicker and it opens first.
Check your:
Narrower action potential.
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.
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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