1. Nervous System Notes Part 3

2. EVEN MORE INTERESTING NERVOUS SYSTEM FACTS The human brain alone consists of about 100 billion neurons. If all these neurons were to be lined up, it would form a 600 mile long line. At any given point in time, only four percent of the cells in the brain are active, the rest are kept in reserve.

3. NOTES – CELLS OF THE NERVOUS SYSTEM • NEURONS • 3 basic parts 1. Cell Body • 1 nucleus 2. Dendrites • carry information TOWARD the cell body

4. 3. Axon • carries information AWAY from the cell body • many neurons are surrounded by a MYELIN SHEATH • fatty tissue that speeds up the nerve impulse

5. Structural Classification of Neurons • 3 Types • based on number of processes extending from cell body 1. Multipolar Neuron • many processes extending from cell body – most common

6. 2. Bipolar Neuron • neuron with two process coming from cell body – more rare – found in sense organs (compare multipolar and bipolar neurons)

7. Unipolar Neuron • single process coming from cell body – found in peripheral nervous system

8. NEUROGLIA (or just GLIA) • supporting nerve cells of different types • function is to support, insulate, protect neurons • 6 Types 1. oligodendrocytes • Function: produce myelin sheaths

9. 2. microglia • Function: disposal of debris, dead brain cells, bacteria, etc. 3. ependymal cells • Function: line cavities of brain & spinal cord – cilia helps circulate CSF

10. 4. Schwann Cells • Function: form myelin sheaths in Peripheral Nervous System (PNS) 5. satellite cells • Function: protects, cushions cells

11. 6. astrocytes • Function: form barrier between capillaries & neurons – protects neuron • Gray Matter & White Matter • white matter • axons with myelin • gray matter • cell bodies, axons without myelin, dendrites, neuroglia