THE CELL

A neuron is built to pass messages

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Dendrites

Branches that receive signals from other neurons

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Cell body

Holds the nucleus and adds up the incoming signals

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Axon

A long fiber that carries the signal away

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Terminals

Endings that pass the signal to the next cell

Inputs in on one side, output at the other.

THE LAYOUT

Receive, carry, pass on

Many axons are wrapped in segments of myelin, a fatty insulating layer that speeds the signal along.

Shape follows function.

TWO LANGUAGES

Electrical inside, chemical between

Inside a neuron The signal travels as a brief electrical pulse called an action potential

Between neurons At most connections, chemicals called neurotransmitters cross a tiny gap

Why both Electricity is fast over long distances, and chemistry allows many kinds of messages and fine adjustment

The synapse is where electricity turns into chemistry.

SCALE

A very large network

Neurons A human brain has roughly 86 billion

Connections Each neuron can receive thousands of synapses

Speed Signals in the fastest myelinated axons reach about 100 meters per second

Trillions of chemical handoffs happen every second.

WHY THIS COURSE

The chemistry is where things happen

Many drugs, diseases, and sensors act at the chemical handoff. Understanding the messengers explains how medicines work and why measuring them is one of the hardest problems in neuroscience.

To study the brain's messages, you study its molecules.

UNIT 1 STUDY COMPLETE

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Ready for the Fab Challenge?

You've covered the parts of a neuron and why a signal changes from electrical to chemical between cells.