The nervous system is composed of neurons that transmit signals in the form of electrochemical impulses. There are three main types of neurons - sensory neurons that receive stimuli, motor neurons that activate muscles and glands, and interneurons that connect neurons within the central nervous system. The nervous system is divided into the central nervous system, composed of the brain and spinal cord, and the peripheral nervous system composed of nerves that connect to the rest of the body. The central nervous system processes sensory information and coordinates motor responses through complex neural pathways and circuits in the brain and spinal cord.

1. THE NERVOUS SYTEM

4. Estructure of a Neuron Cell Body Dendrites Axon from other neurons Axon Myelin Dendrites from other neurons Audesirk Audesirk Byers Sixth Ed. Biology Life on earth, Instructions Resource CD-ROM, 2002 Prentice Hall Synaptic Terminals

12. RESTING POTENTIAL ( Extracellular fluid ) (Negatively charge d neuron cytoplasm) ( Neuronal Membrane ) Org - Na + Org - Org - Org - Org - K + K + K + K + K + Cl - Cl - Cl - Cl - Na + Na + Na + Potassium Chanel Sodium chanel (c losed ) Audesirk Audesirk Byers Sixth Ed. Biology Life on earth, Instructions Resource CD-ROM, 2002 Prentice Hall

13. BEGINING OF ACTION POTENTIAL Org - K + K + K + Cl - Na + Na + K + Na + Na + Na + ( Extracellular fluid) ( Positive charge ) ( Negative charge ) Audesirk Audesirk Byers Sixth Ed. Biology Life on earth, Instructions Resource CD-ROM, 2002 Prentice Hall Org - Na + Org - Org - K + K + Cl - Na + K + K + K + K + Na + Na + Cl -

14. BEGINING OF ACTION POTENTIAL Audesirk Audesirk Byers Sixth Ed. Biology Life on earth, Instructions Resource CD-ROM, 2002 Prentice Hall

15. PROPAGATION OF ACTION POTENTIAL Audesirk Audesirk Byers Sixth Ed. Biology Life on earth, Instructions Resource CD-ROM, 2002 Prentice Hall

31. http://www.nda.ox.ac.uk/wfsa/html/u05/u05_011.htm