Introduction to Neuronal Physiology

TL;DR

Neurons are excitable cells that transmit information through electrical and chemical signals. This communication relies on changes in ion movement across their cell membranes, creating electrical impulses called action potentials. Understanding these basic principles is crucial for comprehending how the nervous system functions.

1. The Mental Model

Think of a neuron like a tiny battery that can "fire" a signal. This firing happens when the electrical charge inside and outside the cell changes quickly, allowing it to send messages to other neurons.

2. The Core Material

Your nervous system is made up of billions of neurons, which are specialized cells that process and transmit information. To understand how they do this, we need to look at their basic physiology.

Resting Membrane Potential

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Even when a neuron isn't actively sending a signal, there's an electrical difference across its cell membrane, called the resting membrane potential. This is typically around -70 millivolts (mV), meaning the inside of the neuron is more negative than the outside.

This negative charge is maintained primarily by three things:
1. Ion concentration gradients: There's a higher concentration of sodium (Na+) ions outside the cell and a higher concentration of potassium (K+) ions inside the cell.
2. Selective permeability: The neuron's membrane is much more permeable to K+ than to Na+ at rest, meaning more K+ leaks out than Na+ leaks in.
3. Sodium-potassium pump: This active transport protein uses ATP to pump 3 Na+ ions out of the cell for every 2 K+ ions it pumps in, contributing to the negative charge inside.

Action Potentials

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