Neurons & Glia

Neurons

- Individual cells in the nervous system that receive, integrate, and transmit information.

- ~85 billion neurons in the human brain

- each neuron receives >1,000 synaptic inputs

Glia

cells in the nervous system that support, nourish, and protect neurons

1. Oligodendrocytes & Schwann cells

2. Astrocytes

3. Microglia

What are the major types of Glia?

Oligodendrocytes (CNS) & Schwann cells (PNS)

wrap around the axon to provide insulation in the form of myelin.

Astrocytes

provide supporting functions for neurons; they buffer potassium ions, take up glutamate released by neurons, and provide metabolic fuel

Microglia

are the resident immune cells of the brain; become activated to help fight off infection and clear cellular debris via phagocytosis

- Excitable cells

- process info

- sense environmental changes

- communicate changes to other neurons

- command body response

Neuron functions

Histology

microscopic study of tissue structure

Nissl Stain

- stains cell bodies

- facilitates the study of cytoarchitecture in the CNS

Golgi stain

- sparsely stains whole cells

- allows imaging of a whole neuron (cell body and neurites)

- Soma (cell body)

- Neurites: axons and dendrites

What did the Golgi Stain reveal?

Golgi stain (reticular theory)

described nervous system as a continuous network

Ramón y Cajal

used Golgi Stain to illustrate Neuron doctrine

Neuron Doctrine (Cajal)

- the nervous system is made up of discrete individual cells

- neurons communicate by contact, not continuity

Transmission Electron Microscope & Images

takes block of tissue and will recreate that neuron & its surrounding neuron

Pyramidal Neuron

Pyramid shaped excitatory glutamate containing neurons located in the cortex and hippocampus.

1. Soma

2. Nucleus

3. Dendrites

4. Axon Hillock

5. Axon

6. Myelin

7. Node of Ranvier

8. Axon Collateral

9. Presynaptic Terminal

10. Synaptic Vesicles

11. Synaptic Cleft

12. Postsynaptic Density

Parts of the neuron