GLOSSARY

ACTH HORMONE -- A hormone secreted by the pituitary which stimulates the adrenal cortex.

ACETYLCHOLINE -- excitatory chemical transmitter released at synapses and at neuromuscular junctions.

ACTION POTENTIAL -- the complete reversal of the resting potential characterized by an influx of positive ions into the neuron and an expulsion of negative ions.

ADRENAL GLAND -- an endocrine gland that functions in metabolism (adrenal cortex) and in physiological mechanisms of stress (adrenal medulla).

AFFERENT FIBER -- neural fiber that carries impulses from the peripheral nervous system to the central nervous system.

ASSOCIATION NEURON -- a neuron which connects different parts of the central nervous system.

AXON -- an anatomical subdivision of the neuron that carries the neural impulse to a muscle, gland, or another neuron's dendrite..

CEREBELLUM -- part of the brain which acts to smooth and coordinate muscular movement.

CEREBRAL HEMISPHERE -- half of the cerebrum.

CORTEX -- the part of the brain involved in higher mental functions. Also called cerebral cortex.

CRITICAL THRESHOLD VALUE -- the intensity at which an action potential is generated (may refer either to a stimulus or an excitatory potential

DENDRITE -- anatomical sub division of the neuron that carries an excitatory potential to the cell body.

EFFECTOR -- muscle or a gland.

EFFERENT FIBER -- neural fiber that carries impulses from the central nervous system to the peripheral nervous system and effectors..

ENDOCRINE GLAND -- any gland that releases secretions directly into the bloodstream.

EXOCRINE GLAND -- any gland that secretes fluids via a duct onto a selected body surface.

GONADS -- endocrine glands that function to maintain sexual behavior.

HOMEOSTASIS -- the tendency of the body to maintain a balance among internal physiological conditions.

HORMONES -- fluids secreted by glands of the endocrine system.

HYPOTHALAMUS -- a structure in the brain that functions in the expression of emotion, in wakefulness, hunger, thirst, and sexuality.

INHIBITION -- any influence that decreases the probability that an action potential will be generated.

ION -- a charged particle.

MEDULLA -- a structure in the brain stem that controls vital functions such as heart rate, breathing, and blood pressure.

PITUITARY GLAND -- an endocrine gland that functions in growth and in control of other glands.

PROJECTION AREA -- areas of the cortex where sensory fibers terminate.

PROPRIOCEPTION -- a sense that tells us the spatial position of parts of the body.

RECEPTOR -- a specialized structure that transforms a stimulus into an excitatory potential.

RESTING POTENTIAL -- the difference in ionic concentration between fluids inside the cell membrane (relatively negative) and fluids outside the cell membrane (relatively positive) when the neuron is not conducting.

RETICULAR ACTIVATING SYSTEM (RAS) -- a network of neurons that acts as a nonspecific relay for all sensory stimuli bound for the cortex.

SOMATOTROPIC HORMONE -- a hormone secreted by the pituitary gland.

SOMESTHETIC -- having to do with the senses of the skin and of kinesthesis.

SYNAPSE, SYNAPTIC JUNCTION -- the point at which an excitatory or an inhibitory potential may be transferred from the axon of one neuron to the dendrite of another.

TSH (THYROID-STIMULATING HORMONE) -- a hormone, secreted by the pituitary gland, that stimulates the thyroid gland.

THALAMUS -- a structures in the brain that acts as a specific relay for sensory Impulses bound for the cortex.

THYROID -- an endocrine gland that acts to accelerate metabolism.

THYROXINE -- hormone secreted by the thyroid gland.

October 9, 1999