| A | B |
|---|
| alcholism | a disease in which a person is both physically addicted to and emotionally dependent on alchol |
| anabolic steroid | synthetic chemicals that are similar to hormones produced in the body and that may increase muscle size and cause mood swings |
| autonomic nervous system | the group of nerves that controls involuntary actions |
| axon | a thread like extension of a neuron that carries nerve impulses away from the cell body |
| brain | the part of the central nervous system that is located in the skull and controls most functions in the body |
| brainstem | the part of the body that controls many body functions that occur automatically |
| central nervous system | the brain and spinal cord; the control center of the body |
| cerebellum | the part of the brain that coordinates the actions of the muscles and helps maintain balance |
| cerebrum | the part of the body that interprets input from the senses, controls the movement of skeletal muscles, and carries out complex mental processes |
| cochlea | a snail-shaped tube in the inner ear lined with sound receptors;nerve impulses are sent from the cochlea to the brain |
| cornea | the clear tissue that covers the front of the eye |
| dendrite | a threadlike extension of a neuron that carries nerve impulses toward the cell body |
| depressant | a drug that slows down the activity of the central nervous system |
| drug | any chemical that causes changesin a person's body or behavoir |
| drug abuse | the deliberate misuse of drugs for purposes other than appropriate medical ones |
| eardrum | the small,tightly stretched,drumlike membrane that seperates the outer ear from the middle ear, and that vibrates when sound waves strike it |
| farsightedness | the condition in which distant objects can be seen clearly but nearby objects look blurry |
| interneuron | a neuron that carries nerve impulses from one neuron to another |
| iris | the ring of colored muscle that surrounds the pupil and regulates the amount of light entering the eye |
| lens | the flexible structure that focuses light that has entered the eye |
| motor neuron | a neuron that sends an impulse to a muscle,causing the muscle to contract |
| nearsightedness | the condition in which nearby objects can be seen but distant objects can be blurry |
| nerve | a bundle of nerve fibers |
| nerve impulse | the message carried by a neuron |
| neuron | a cell that carries messages through the nervous system |
| peripheral nervous system | all the nerves located outside the central nervous system; connects the central nervous system to all parts of the body |
| pupil | the opening through which light enters the eye |
| reflex | an automatic response that occurs very rapidly and without conscious control |
| retina | the layer of receptor cells at the back of the eye on which an image is focused; nerve impulses are sent from the retina to the brain |
| semicircular canals | structures in the inner ear that are responsible for the sense of balance |
| sensory neuron | a neuron that picks up stimuli from the internal or external environment and converts each stimulus into a nerve impulse |
| somatic nervous system | the group of nerves that controls voluntary actions |
| spinal cord | the thick column of nerve tisse that is enclosed by the vertebrae and that links the brain to most of the nerves in the peripheral nervous system |
| stimulant | a drug that speeds up body processes |
| synapse | the tiny space between the tip of an axon and the next structure |
| tolerance | a state in which a drug user, after repeatedly taking a drug, needs larger and larger doses of the drug to produce the same effect |
| withdrawal | a period of adjustment that occurs when a drug-dependent person stops taking the drug |
