Coconote
AI notes
AI voice & video notes
Export note
Try for free
Resting and Action Potential Lecture
Jul 13, 2024
Resting and Action Potential Lecture by Dr. Jimmy
Introduction
Dr. Jimmy explains resting and action potential for AS and A-Level Biology students.
The concept can be challenging, so he uses a slide deck animation to aid understanding.
Resting Potential
Axon Membrane:
Plays a role in the generation of an action potential.
Contains sodium-potassium pumps.
For every 3 sodium ions pumped out, 2 potassium ions are pumped in.
Result: Inside of the axon becomes more negative.
Sodium and Potassium Channels: Open all the time.
More potassium channels than sodium channels.
Potassium diffuses out more than sodium diffuses in, maintaining negativity inside the axon.
Resting Potential Value:
-60 to -70 millivolts.
Generation of an Action Potential
Voltage-Gated Channels:
Sodium-gated and potassium-gated channels are triggered by electrical impulses.
When a stimulus reaches the axon:
Sodium-gated channels open, sodium ions flow inside.
Membrane potential increases from -70 mV to -50 mV (threshold potential).
More sodium channels open, increasing potential to +30 mV (depolarization phase).
Depolarization:
Sodium influx makes the inside of the axon more positive up to +30 millivolts.
After ~1 millisecond, sodium channels close, potassium channels open. Potassium flows out, making inside negative again (repolarization phase).
Repolarization:
Inside returns to more negative values, eventually to resting potential (-70 mV).
Hyperpolarization:
Potassium channels close slowly, making inside briefly more negative than resting potential.
Cycle of Resting and Action Potential
Potassium ions outside, sodium ions inside enable the sodium-potassium pump to work again.
Sodium pumped out, potassium pumped in, restoring resting potential.
Practical Application
Students should try to fit this sequence onto a graph for exams.
Key Graph Points:
Resting Potential (-70 mV), threshold potential (-50 mV), depolarization (+30 mV), repolarization (back to -70 mV), hyperpolarization.
Key Structures:
Sodium-potassium pump, sodium channels, potassium channels, gated channels.
Conclusion
Understanding this cycle is crucial for explaining the resting and action potential graph in exams.
Next video will cover synapses.
📄
Full transcript