| word | definition |
| Central Nervous System | the division of the nervous system consisting of the brain and spinal cord |
| peripheral nervous system | the division of the nervous system consisting of allof the nerves located outside the central nervous system |
| brain | the part of the central nervous system that is locted in the skull and controls most function in the body |
| spinal cord | the thick column of nervous tissue that links the brain to most of the nerves in the peripheral nervous system |
| cerebrum | The part of the brain that interprets input from the senses, controls movement, and carries out complex mental processes. |
| cerebellum | THe part of the brain that coordintates the actions of the muscles and helps maintain balance. |
| brain stem | The part of the brain that lies between the cerebellum and spinal cord and controls the body's involuntary actions. |
| somatic nervous system | the goup of nerves in the peripheral nervous system that controls voluntary action |
| autonomic nervous systemm | The group of nerves in the peripheral nervous system that controls involuntary actions. |
| reflex | an automatic response that occurs rabidly and without conscious control |
| concussion | a bruiselike injury of the brain that occurs when the soft tissue of the brain collide against the skull |
| synapse | the junction where one neuron can transfer an impulse to the next structure |
| sensory neuron | a neuron that picks up stimuli from the internal or external environment and converts each stimulus into a nerve impulse |
| nerve | a bundle of nerve fibers |
| motor neuron | a neuron that sends an impulse to a muscle, or gland, causing the muscle or gland to react |
| interneuron | a neuron that carries nerve impulses from one neuron to another |
| axon | a threadlike extension of a neuron that carries nerve impulses away from the cell body |
| dendrite | a threadlike extension of a neuron that carries nerve impulses toward the cell body |
| stimulus | any change or signal in the environment that can make an organism react in some way |
| neuron | a cell that carries information through the nervous system |
| nerve impulse | the message carried by a neuron |
| response | what the body does in reaction to a stimulus |
| cornea | the clear tisse that cover the front of the eyes |
| pupil | the opening through which light enters the eyes |
| iris | the cirular stucture that surrounds the pupil and regulates the amount of light entering the eye |
| lens | the flexible stucture that focuses light that has entered the eye |
| retina | the layer or receptor cells at the back of the ey on which an image is focused |
| nearsightedness | the condition in which a person can see mearby objects clearly |
| farsightedness | the condition in which a person can see distant object clearly |
| eardrum | the membrane that separates the outer ear from the middle ear, and that vibrates when sound waves strike it |
| cochlea | a snail-shaped tube in the inner ear that is lined with receptor cells that respond to sound |
| semicircular canal | structures in the inner ear that are responsible for the sense of balance |