the process by which organisms keep internal conditions relatively constant despite changes in external environments.
negative feedback. the process in which a stimulus produces a response that opposes the original stimulus.
cells that transmit impulses, or the electrical signals that are messages carried by the nervous system.
the bushy, branching extensions of a neuron that receive messages and conduct impulses toward the cell body.
a layer of fatty tissue segmentally encasing the fibers of many neurons; enables vastly greater transmisssion speed of neural impulses as the impulse hops from one node to the next.
a neural impulse; a brief electrical charge that travels down an axon changing the charge from negative to positive.
chemicals used by a neuron to transmit an impulse across a synapse to another cell.
fluid in the space between the meninges that acts as a shock absorber that protects the central nervous system.
the "little brain" attached to the rear of the brainstem; it helps coordinate voluntary movement and balance.
the part of the brain that lies between the cerebellum and spinal cord that controls the body's involuntary actions.
the brain's sensory switchboard, located on top of the brainstem; it directs messages to the sensory receiving areas in the cortex and transmits replies to the cerebellum and medulla.
a neural structure lying below the thalamus; directs eating, drinking, body temperature; helps govern the endocrine system via the pituitary gland, and is linked to emotion.
detect changes in the environment and stimulate neurons to send nerve impulses to the brain.
The transparent structure behind the pupil that changes shape to help focus images on the retina.
the light-sensitive inner surface of the eye, containing the receptor rods and cones plus layers of neurons that begin the processing of visual information.
retinal receptors that detect black, white, and gray; necessary for peripheral and twilight vision, when cones don't respond.
retinal receptor cells that are concentrated near the center of the retina and that function in daylight or in well-lit conditions. The cones detect fine detail and give rise to color sensations.
A coiled, bony, fluid-filled tube in the inner ear through which sound waves trigger nerve impulses.