| A | B |
|---|
| Neuron | Cell that carries messages throughout the nervous system |
| Cell Body | Largest part of a typical neuron, contains the nucleus and much of the cytoplasm |
| Dendrite | extension of the cell body of a neuron that carries impulses from the environment or from other neurons toward the cell body |
| Axon | Long fiber that carries impulses away from the cell body of a neuron |
| Myelin Sheath | Insulating membrane surrounding the axon on some neurons |
| Resting Potential | Difference in electrical charge across the cell membrane of a resting neuron |
| Action Potential | Reversal of charges across the cell membrane of a neuron |
| Threshold | minimum level of a stimulus that is required to activate a neuron |
| Synapse | location at which a neuron can transfer an impulse to another cell |
| Neurotransmitter | Chemical used by a neuron to transmit an impulse across a synapse to another cell |
| Central Nervous System | The brain and spinal cord |
| Meninges | Three layers of connective tissuse in which the brain and spinal column are wrapped |
| Cerebrospinal Fluid | fluid in the space between the meninges that acts as a shock absorber that protects the central nervous system |
| Cerebrum | Area of the brain responsible for all voluntary activities of the body |
| Cerebellum | Region of the brain that coordinates body movements |
| Brain Stem | Connects brain to spinal cord; contains medulla oblongata |
| Thalamus | brain structure that receives messages from the sense organs and relays the information to the proper region of the cerebrum for further processing |
| Hypothalamus | Brain structure that acts as a control center for recognition and analysis of hunger, thirst, fatigue, anger, and body temperature |
| Reflex | quick automatic response to a stimulus |
| Sensory Receptor | Neuron that reacts directly to light, sound or other stimuli by sending impulses to other neurons and eventually to the central nervous system |
| Pupil | small opening in the middle of the iris through which light enters the eye |
| Lens | Transparent object behind the iris that changes shape to help adjust the eye's focus to see near or far |
| Retina | innermost layer of the eye |
| Rod | Photoreceptor in eye that is extremely sensitive to light |
| Cone | Photoreceptor that is less sensitive to light, but shows color |
| Cochlea | Fluid-filled part of inner ear that brings in messages to the brain concerning sound |
| Semicircular Canal | One of the three structures within the inner ear that help an organism maintain balance |
| Taste Bud | sense organ that detects the flavor of a substance |
| Drug | any substance, other than food, that causes a change in the structure or function of the body |
| Stimulant | Drug that speeds up the actions regulated by the nervous system |
| Depressent | Drug that decreases the rate of functions related by the brain |
| Addiction | Uncontrollable craving for more of a drug |
| Fetal Alcohol Syndrome | Group of birth defects caused by the effects of alcohol on a fetus |
| Drug Abuse | use of any drug in a way that most doctors would not approve |
