Uploaded September 2018 | Updated September 2026, 3 weeks ago

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This video is about the general physiology of a nerve
(Potentials, Polarizations, Permeability, and Excitability)

Content:
0:00 Introduction
1:25 Basic Physiological Rules of a Cell
3:25 Rules of Transport Across the Membrane
3:36 Passive Transport
6:24 Active Transport
8:40 Membrane Potentials
13:54 Action Potentials
17:55 Impulse Conduction
19:40 Saltatory Conduction
20:25 All-or-None Law

Basic physiological rules of the cell:
- More negative inside the cell than on the outside.
- Difference in extracellular and intracellular fluid
- Nernst Equation calculates the charged ions across a membrane

Transport through the cell membrane:
Passive Transport:
- Simple diffusion (has to be small, lipophilic and no charge)
- Facilitated diffusion (Ion channel and Gated channels)
- Filtration
- Electrokinetic transport
- Osmosis
Active Transport:
Primary Active Transport: Na/K Pump, Ca Pump
Secondary Active Transport: Na/Glucose, Na/Amino Acids, Na/H

Nerve:
Functionally divided into three parts:
Receptive Part: Dendrites
Integrating part: Cell body and Axon Hillock
Transmitting part: Axon

Resting Potential:
Typically -70 mV
- Chemical gradient outside, Electrical Gradient inside = Electrochemical gradient outside
- Sodium and Potassium goes in and out of cell throguh Ion Channels
- Sodium potassium pump pumps 3 sodium out, 2 potassium in

Action potential:
- Voltage-Gated Channels
- Excitability
- Two gates on VG-Channel - Activation gate and inactivation gate
- Changes of excitability during an action potential
- Permeability of cell membrane during different stages of action potential:
1. resting state: Sodium and Potassium are unable to pass through the gated channels. Inside the cell: Negative
2. Depolarization: Sodium starts flowing in, inside the cell: positive
3. After depolarization comes repolarization, where the sodium channel close, and the potassium channel opens. Outflux of potassium brings cells back to more negative than the initial state (Hypoerloarization). This is the refractory period

Conduction of action potential through a nerve axon.
- Continous Conduction (Unmyelinated)
- Saltatory Conduction (Myelinated)

All-Or-None Law
- Either we get a action potential, or not.
- Chemical Synapse with Ligand gated channels, or chemically gated channels
- Excitatory or Inhibitory

#nervephysiology #physiology #nerve #neuron #actionpotential