| A | B |
|---|
| irritability | the ability of a cell or an organism to respond to a stimulus |
| impulse | message carried by a nerve cell |
| receptors | specialized structures that can detect a stimulus; sense organs |
| effectors | a muscle or a gland that responds to a stimulus |
| stimulus | any factor that triggers an impulse |
| brain | a group of specialized cells that coordinate and control and organism |
| neuron | a nerve cell |
| cell body | cyton; part of a neuron that contains the nucleus |
| dendrites | part of a neuron specialized to receive impulses |
| axon | part of the neuron; carries impulses away from the cyton |
| Schwann cells | cells that surround the axon and help form the myelin sheath |
| myelin | layers of white fatty substance produced by some Schwann cells |
| synapse | the gap between two neurons |
| nerves | bundles of axons joined by connective tissue |
| sensory neurons | carry impulses toward the brain and spinal cord |
| motor neurons | carry impulses from the brain and spinal cord to the effectors |
| interneurons | relay impulses between neurons |
| thalamus | a relay center between various parts of the brain and the spinal cord |
| hypothalamus | controls body temperature, blood pressure and emotions |
| pons | a relay station linking the spinal cord, medulla oblongata, cerebrum and cerebellum |
| cerebrum | the largest part of the brain; divided into two hemispheres |
| corpus callosum | nerve fibers that bridge the two hemispheres of the brain |
| cerebellum | part of the brain; controls all voluntary activity and some involuntary activity |
| medulla oblongata | part of the brain; continuous with the spinal cord; c ontrols all involuntary activities |
| spinal cord | the cord of nervous tissue in vertebrates |
| somatic n.s. | part of the peripheral n.s that contains sensory and motor neurons that connect the cns to skeletal muscles, skin and sense organs |
| autonomic n.s | a division of the peripheral n.s. consisting of motor fibers from the brain and spinal cord that serve the internal organs; not under voluntary action |
| parasympathetic n.s. | slows down various body systems |
| sympathetic | speeds up various body systems |
| reflex | an involuntary response to a stimulus; does not involve the brain |
| nearsighted | vision problem caused by the eyeball being too long |
| farsighted | a vision problem caused by the eyeball being too short |
| rods | responsible for black and white vision |
| cones | responisble for color vision |
| cerebral cortex | the outer layer of the cerebrum |
| reflex arc | the pathway the impulse travels in a reflex |
