1. 35.2 The Nervous System

2. Neuron Cell that carries messages throughout the nervous system.

3. Cell Body Largest part of a typical neuron; contains the nucleus and much of the cytoplasm.

4. Dendrite Extension of the cell body of a neuron that carries impulses from the environment or from other neurons toward the cell body.

5. Axon Long fiber that carries impulses away from the cell body of a neuron.

6. Myelin Sheath Insulating membrane surrounding the axon in some neurons.

7. Resting Potential Electrical charge across the cell membrane of a resting neuron.

8. Action Potential Reversal of charges across the cell membrane of a neuron; also called a nerve impulse.

9. Threshold Minimum level of a stimulus required to activate a neuron

10. Synapse Location at which a neuron can transfer an impulse to another cell.

11. Neurotransmitter Chemical used by a neuron to transmit an impulse across a synapse to another cell.

12. Key Concept The nervous system controls and coordinates functions throughout the body and responds to internal and external stimuli.

13. Key Concept An impulse begins when a neuron is stimulated by another neuron or by the environment.