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Specialized Cells

cells uniquely suited to perform a particular function

Epithelial Tissue

includes glands and tissues that cover interior and exterior body surfaces.

Connective Tissue

provides support for the body and connects its parts.

Nervous Tissue

transmits nerve impulses throughout the body.

Muscle Tissue

enables the body to move, along with the bones.


groups of tissues that perform a particular job in an organism.

organ systems

groups of organs that perform closely related functions.


the process by which organisms keep internal conditions relatively constant despite changes in external environments.

Feedback inhibition

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.

cell body

largest part of a typical neuron; contains the nucleus and much of the cytoplasm.


the bushy, branching extensions of a neuron that receive messages and conduct impulses toward the cell body.


long nerve fiber that conducts away from the cell body of the neuron

myelin sheath

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.

resting potential

electrical charge across the cell membrane of a resting neuron.

action potential

a neural impulse; a brief electrical charge that travels down an axon changing the charge from negative to positive.


the minimum level of stimulation required to trigger a neural impulse.


location at which a neuron can transfer an impulse to another cell.


chemicals used by a neuron to transmit an impulse across a synapse to another cell.


three layers of connective tissue in which the brain and spinal cord are wrapped.

cerebrospinal fluid

fluid in the space between the meninges that acts as a shock absorber that protects the central nervous system.


the largest part of the brain; controls conscious thought and stores memories.


the "little brain" attached to the rear of the brainstem; it helps coordinate voluntary movement and balance.

brain stem

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.


quick automatic response to a stimulus.

sensory receptors

detect changes in the environment and stimulate neurons to send nerve impulses to the brain.


the adjustable opening in the center of the eye through which light enters.


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.

semicircular canals

three canals within the inner ear that contain specialized receptor cells that generate nerve impulses with body movement.

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