📑 Lecture Notes

1 What is neuroscience?

• Neuroscience = the study of the nervous system and the cells in it.
• The nervous system has two divisions:
• CNS (Central Nervous System) = the brain + spinal cord.
• PNS (Peripheral Nervous System) = all other neurons outside the CNS.

2 The CNS is made of neurons & glial cells

• The brain has diverse cell types in huge numbers — the single working unit is the neuron.
• It's often called the most complex "machine" known.

Source: Allen Institute "Brain Atlas"; counts from von Bartheld, Bahney & Herculano-Houzel (2016).

3 Neurons have distinct structures

• Dendrites — receive information.
• Cell body (soma) — contains the cellular machinery and integrates signals.
• Axon — sends the signal in one (unidirectional) direction.
• Axon terminal — bulbs at the end of the axon; forms the synapse.

4 The brain has about as many glial cells as neurons

• ~70–80 billion glial cells — roughly the same order as neurons (not "mostly glia").
• Two highlighted on this slide: microglia and astrocytes.

5 What glial cells do

• Glia support neurons and maintain homeostasis in the nervous system:
• Astrocytes — support the blood–brain barrier and synapses; supply neurons with nutrients and other essential molecules.
• Microglia — the immune cells of the brain.
• Oligodendrocytes — provide myelin to CNS neurons.
• Schwann cells — provide myelin to PNS neurons.