Science Vocab Ch 20

Front 1

stimulus

Back 1

a change in an organism's surroundings that cause the organism to react

Front 2

response

Back 2

an action or change in behavior that occurs as a result of a stimulus

Front 3

neuron

Back 3

a cell that carries messages through the nervous system

Front 4

nerve impulse

Back 4

the message carried by a neuron

Front 5

dendrite

Back 5

a threadlike extension of a neuron that carries nerve impulses toward the cell body

Front 6

axon

Back 6

a threadlike extension of a neuron that carries nerve impulses away from the cell body

Front 7

nerve

Back 7

a bundle of nerve fibers

Front 8

sensory neurons

Back 8

a neuron that picks up stimuli from the internal or external environment & converts each stimulus into a nerve impulse

Front 9

interneuron

Back 9

a neuron that carries nerve impulses from 1 neuron to another

Front 10

motor neuron

Back 10

a neuron that sends an impulse to a muscle, causing the muscle to contract

Front 11

synapse

Back 11

the tiny space between the tip of an axon and the next structure

Front 12

central nervous system

Back 12

the brain and spinal cord- major organs
the control center of the body

Front 13

peripheral nervous system

Back 13

all the nerves located outside the central nervous system; connects the central nervous system to all parts of the body

Front 14

brain

Back 14

the part of the central nervous system that is located in the skull and controls most functions in the body

Front 15

spinal cord

Back 15

the thick column of nerve tissue that is enclosed by the vertebrae and that links the brain to most nerves in the peripheral nervous system

Front 16

cerebrum

Back 16

the part of the brain that interprets input from the senses, controls the movement of skeletal muscles, and carrries out complex mental processes

Front 17

brainstem

Back 17

the part of the brain that controls many body functions that occur automatically

Front 18

somatic nervous system

Back 18

the group of nerves that controls voluntary muscles

Front 19

autonomic nervous system

Back 19

the group of nerves that conrols involuntary muscles

Front 20

reflex

Back 20

an automatic response that occurs very rapidly and without conscious control

Front 21

concussion

Back 21

a bruiselike injury of the brain that occurs when the soft tissue of the cerbrum bumps against the skull

Front 22

cornea

Back 22

the clear tissue that covers the front of the eye

Front 23

pupil

Back 23

the opening through which light enters the eye

Front 24

iris

Back 24

the circular structure that surrounds the pupil & regulates the amount of light entering the eye

Front 25

lens

Back 25

the flexible structure that focuses light that has entered the eye

Front 26

retina

Back 26

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

Front 27

nearsightedness

Back 27

the condition in which nearby objects canbe seen clearly but distant objects are blury

Front 28

farsightedness

Back 28

the condition in which distant objects are seen clearly but nearby objects are blury

Front 29

eardrum

Back 29

the membrane that seperates the outer ear from the middle ear, & that vibrates when sound waves strike it

Front 30

cochlea

Back 30

a snail shaped tube in the inner ear lined with sound receptors; nerve impulses are sent from the cochlea to the brain

Front 31

semicircular canal

Back 31

stuctures in the inner ear that are responsible for the sense of balance

Front 32

drug

Back 32

any chemical that cause change in a persons behavior or body

Front 33

drug abuse

Back 33

the deliberate misuse of drugs for purposes other than appropriate medical ones

Front 34

tolerance

Back 34

a state in which a drug user, after repeatedly taking a drug, needs larger & larger doses of the drug to produce the same effect

Front 35

withdrawal

Back 35

a period af adjustment that occurs when a drug dependent person stops taking the drug

Front 36

stimulant

Back 36

a drug that speeds up body processes

Front 37

depressant

Back 37

a drug that slows down the activity of the central nervous system

Front 38

anabolic steroid

Back 38

synthetic chemicals that are similar to hormones produced in the body that may increase muscle size and cause mood swings

Front 39

alcoholism

Back 39

a disease in which a person is both physically addicted to and emotionally dependent on alcohol