| A | B |
|---|
| central nervous system (CNS) | the body's primary information processing system; includes the brain and the spinal cord |
| peripheral nervous system (PNS) | network of nerves carrying signals into and out of the central nervous system |
| nerve | bundle of neuron fibers surrounded by connective tissue |
| stimulus | environmental change that triggers a response |
| sensory neuron | nerve cell that carries information from the environment to the central nervous system |
| sensory receptor | specialized cell that transmits signals to sensory neurons |
| interneuron | nerve cell located entirely in the central nervous system that integrates sensory information and sends motor commands |
| motor neuron | nerve cell that carries signals from the central nervous system to muscle or gland cells |
| reflex | rapid, automatic response to a stimulus |
| dendrite | neuron fiber that receives signals and carries them toward the cell body |
| axon | neuron fiber that carries electric impulses away from the cell body and toward other cells |
| myelin sheath | thick coat of material that surrounds and insulates the axon of some neurons |
| node | uninsulated spaces between the "beads" of myeline sheath where an action potential can be transmitted |
| resting potential | voltage across the plasma membrane of a resting neuron |
| depolarization | voltage change that occurs when the difference in charge across a membrane decreases |
| threshold | minimum change in a membrane's voltage that must occur to generate an action potential |
| action potential | change in voltage across the plasma membrane of a neuron resulting in a nerve signal |
| synapse | junction between two neurons or a neuron and another cell where electrical or chemical signals are relayed |
| synaptic cleft | tiny space separating a knob of a transmitting neuron from a receiving neuron or other cell |
| neurotransmitter | chemical messenger that carries information from one neuron to another or to another cell |
| somatic nervous system | subdivision of the motor division of the peripheral nervous system that controls the voluntary movement of skeletal muscles |
| autonomic nervous system | subdivision of the motor division of the peripheral nervous system that regulates the internal environment |
| sympathetic division | division of the autonomic nervous system that generally prepares the body for energy consuming activities |
| parasympathetic division | division of the autonomic nervous system that conserves energy |
| cerebrum | largest and most complex part of the brain, made up of left and right hemispheres |
| corpus callosum | band of nerve fibers that support communication between the two cerebral hemispheres |
| cerebral cortex | the outer region of the cerebrum containing integration centers for higher brain functions |
| cerebellum | part of the brain located below the cerebrum and above the spinal cord; planning center that coordinates body movement |
| brainstem | lower section of the brain including the medulla oblongata, pons, and midbrain that filters information going to and from the brain |
| thalamus | brain region that sorts and exerts some control over information going to and from the cerebral cortex |
| hypothalamus | region of the brain that is the "master control center" of the endocrine system; functions in maintaining homeostasis by regulating temperature, blood pressure, and other conditions |
| limbic system | system of regions of the brain that interact with the cerebral cortex in emotion and memory |
| sensation | awareness of sensory stimuli |
| perception | meaningful interpretation of sensory data by the central nervous system |
| cornea | transparent area at the front of the eye through which light enters |
| iris | colored part of the eye; controls the amount of light the enters the eye by regulating the size of the pupil |
| pupil | opening in the iris that admits light into the eye |
| retina | inner surface of the eye that is lined with millions of photoreceptor cells |
| cone | photoreceptor cell in the retina that is stimulated in bright light, enabling color vision |
| rod | photoreceptor in the retina that enables vision in dim light |
| auditory canal | part of the outer ear that channels sounds from the outside to the eardrum |
| eardrum | sheet of tissue separating the outer ear from the middle ear that vibrates when stimulated by sound waves |
| auditory tube | air passage between the middle ear and throat that equalizes air pressure on either side of the eardrum |
| cochlea | coiled tube in the inner ear containing hairlike projections that function in hearing |
| tolerance | resistance to a drug's effects such that more of the drug is needed to produce the same effect |
| addiction | uncontrollable dependence on a drug |
| withdrawal | psychological and/or physical symptoms experienced when a person stops taking a drug to which he or she is addicted |
| stimulant | drug, such as caffeine, nicotine, and cocaine, that generally increases activity in the central nervous system |
| depressant | drug such as alcohol or tranquilizers that, in general, slows central nervous system activity |
| opiate | narcotic, such as morphine or heroin, that is derived from opium poppies |
| marijuana | drug made from dried pieces of the hemp plant |
| hallucinogen | drug that causes a person to see, hear, and perceive things that do not exist |
| Ecstasy | synthetic drug that causes stimulant-like and hallucinogenic-like effects in the user |
| inhalant | substance, such as certain aerosols, whose vapors produce mind-altering effects |
