Nervous System
Nervous System
Terms
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- 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
- threshold
- minimum level of a stimulus required to activate a neuron
- resting potential
- electrical charge across the cell membrane of a resting neuron
- addiction
- uncontrollable dependence on a drug
- semicircular canal
- one of three structures within the inner ear that help monitor the position of the body
- epithelial tissue
- tissue that covers the surface of the body and lines internal organs
- drug
- any substance, other than food, that causes a change in the structure or function of the body
- hypothalamus
- brain structure that acts as a control center for recognition and analysis of hunger, thirst, fatigue, anger, and body temperature
- lens
- transparent object behind the iris that changes shape to help adjust the eye's focus to see near or distant objects
- cone
- in gymnosperms, a seed-bearing structure; in the retina of the eye, a photoreceptor that responds to light of different colors, producing color vision
- rod
- photoreceptor in eye that is sensitive to light but not to colors
- specialized cell
- cell that is uniquely suited to performing a particular function
- drug abuse
- intentional misuse of any drug for nonmedical purposes
- retina
- innermost layer of the eye; contains photoreceptors
- muscle tissue
- tissue that controls the internal movement of materials in the body, as well as external movement
- action potential
- reversal of charges across the cell membrane of a neuron; also called a nerve impulse
- myelin sheath
- insulating membrane surrounding the axon in some neurons
- feedback inhibition
- process in which the product or result stops or limits the process
- synapse
- location at which a neuron can transfer an impulse to another cell
- sensory receptor
- neuron that reacts to a specific stimulus, such as light or sound, by sending impulses to other neurons and eventually to the central nervous system
- stimulant
- drug that speeds up the actions regulated by the nervous system
- neurotransmitter
- chemical used by a neuron to transmit an impulse across a synapse to another cell
- neuron
- cell that carries messages throughout the nervous system
- thalamus
- brain structure that receives messages from the sense organs and relays the information to the proper region of the cerebrum for further processing
- depressant
- drug that decreases the rate of functions regulated by the brain
- brain stem
- structure that connects the brain and spinal cord; includes the medulla oblongata and the pons
- reflex arc
- sensory receptor, sensory neuron, motor neuron, and effector that are involved in a quick response to a stimulus
- fetal alcohol syndrome
- group of birth defects caused by the effects of alcohol on a fetus
- reflex
- quick automatic response to a stimulus
- axon
- long fiber that carries impulses away from the cell body of a neuron
- homeostasis
- process by which organisms maintain a relatively stable internal environment
- cerebrospinal fluid
- fluid in the space between the meninges that acts as a shock absorber that protects the central nervous system
- connective tissue
- tissue that holds organs in place and binds different parts of the body together
- taste bud
- sense organ that detects the flavor of a substance
- cerebrum
- area of the brain responsible for all voluntary activities of the body
- cochlea
- fluid-filled part of the inner ear; sends nerve impulses to the brain through the cochlear nerve
- nervous tissue
- tissue that receives messages from the body's external and internal environment, analyzes the data, and directs the response
- pupil
- small opening in the middle of the iris through which light enters the eye
- cerebellum
- region of the brain that coordinates body movements
- meninges
- three layers of connective tissue in which the brain and spinal cord are wrapped