Chapter 9 Nervous System
Terms
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- Any change or signal in the environment that can make an organism react in some way.
- stimulus
- What the body does in reaction to a stimulus
- response
- A cell that carries messages through the nervous system.
- neuron
- The message carried by a neuron.
- nerve impulse
- A threadlike extension of a neuron that carries nerve impulses toward the cell body.
- dendrite
- A threadlike extension of a neuron that carries nerve impulses away from the cell body.
- axon
- A bundle of nerve fibers.
- nerve
- A neuron that picks up stimuli from the internal or external environment and converts each stimulus into a nerve impulse.
- sensory neuron
- A neuron that carries nerve impulses from one neuron to another.
- interneuron
- A neuron that sends an impulse to a muscle, causing the muscle to contract.
- motor neuron
- The tiny space between the tip of an axon and the next structure.
- synapse
- The brain and spinal cord; the control center of the body.
- central nervous system
- All the nerves located outside the central nervous system; connects the central nervous system to all parts of the body.
- peripheral nervous system
- The part of the central nervous system that is located in the skull and controls most functions in the body.
- brain
- The thick column of nerve tissue that is enclosed by the vertebrae and that links the brain to most of the nerves in the peripheral nervous system.
- spinal cord
- The part of the brain that interprets input from the senses, controls the movement of skeletal muscles, and carries out complex mental processes.
- cerebrum
- The part of the brain that coordinates the actions of the muscles and helps maintain balance.
- cerebellum
- The part of the brain that controls many body functions that occur automatically.
- brainstem
- The group of nerves that controls voluntary actions.
- somatic nervous system
- The group of nerves that controls involuntary actions.
- autonomic nervous system
- An automatic response that occurs very rapidly and without conscious control.
- reflex
- A bruiselike injury of the brain that occurs when the soft tissue of the cerebrum bumps against the skull.
- concussion
- The opening through which light enters the eye.
- pupil
- The circular structure that surrounds the pupil and regulates the amount of light entering the eye.
- iris
- The flexible structure that focuses light that has entered the eye.
- lens
- 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.
- retina
- The condition in which nearby objects can be seen clearly but distant objects look blurry.
- nearsightedness
- The condition in which distant objects are seen clearly but nearby objects look blurry.
- farsightedness
- The membrane that separates the outer ear from the middle ear, and that vibrates when sound waves strike it.
- eardrum
- A snail-shaped tube in the inner ear lined with sound receptors; nerve impulses are sent from the cochlea to the brain.
- cochlea
- Structures in the inner ear that are responsible for the sense of balance.
- semicircular canal
- Any chemical that causes changes in a person's body or behavior.
- drug
- The deliberate misuse of drugs for purposes other than appropriate medical ones.
- drug abuse
- 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.
- tolerance
- A period of adjustment that occurs when a drug-dependent person stops taking the drug.
- withdrawal
- A drug that slows down the activity of the central nervous system.
- depressant
- A drug that speeds up body processes.
- stimulant
- Synthetic chemicals that are similar to hormones produced in the body and that may increase muscle size and cause mood swings.
- anabolic steroids
- A disease in which a person is both physically addicted to and emotionally dependent on alcohol.
- alcoholism