Introduction to the Nervous System
Fall 2002

The nervous system is distributed throughout your body. (Figure 1.7 in textbook by Bear, Connors, & Paradiso)

The central nervous system (CNS) is the part of the nervous system surrounded by bone. This includes the:
1. Brain (weighs approximately 3 lbs or 2% of body weight) (fig 1.8)
2. Spinal cord (surrounded by the 31 vertebra in the back)
The peripheral nervous system (PNS) relays information from the CNS to and from the body (fig 1.9)


Neurons

The brain, like the rest of the body, is made of specialized cells
All cells have same basic structure (see Figure 2.7):

Membrane--separates intracellular and extracellular spaces
Nucleus--contains DNA (Figure 2.8)
Endoplasmic reticulum--site of protein synthesis (Figs 2.9 & 2.10)
Mitochondria--produces energy (Fig 2.12) The CNS is comprised of 2 types of cells:
1. Neurons--communication
2. Glia--supports neurons
These cells are too small to see without a microscope (There are 100 billion neurons packed inside your skull).

In contrast, the Leech has approximately 10,000 neurons. Thus, it's much easier to study neural function in a leech. Much neuroscience research is done on simple animals (e.g., slugs, leeches, mice).

Each neuron is a separate unit connected to many other neurons. The typical neuron has three primary parts (Fig. 2.4):

Main parts: dendrites, soma (cell body), & axon
Other regions: axon hillock--the junction between the soma and axon
terminal button--the end of the axon Neurons come in many shapes and sizes (Figures 2.6, 2.19, 2.20)
  Messages travel from the dentrite to soma to axon (Fig. 2.14). Glia  are located throughout the central nervous system and fulfill several functions: structural support
chemical support
insulation
remove debris
form blood-brain barrier (blocks chemicals)
guide neuron migration and growth.   Return to Psych 372 Syllabus