Module 2 The Endocrine System

Lesson Summary

Self-regulated by the hypothalamus/pituitary complex, the endocrine system utilizes tropic hormones such as releasing hormone from the hypothalamus and ACTH, TSH, and hGH from the anterior pituitary to stimulate other endocrine glands, such as the adrenal gland and thyroid gland, to produce their hormones. Negative feedback shuts off the tropic hormones when levels of hormones by the target glands reach correct amounts. Disruption in the level of a hormone can cause serious effects on physiological function such as urine production, growth, and metabolic rate.

Lesson Glossary

acromegaly: a condition brought about by excessive secretion of human growth hormone in an adult; hands, feet and nose widen and become enlarged, jaw protrudes, voice becomes husky, barrel chest may develop, sweat glands enlarge, heart enlarges, high blood pressure may develop, enlarged tissues press on nerves, especially the optic nerves causing loss of vision, particularly in the outer fields, and pressure on the brain causes severe headaches; there is an increased likelihood of developing diabetes mellitus

anterior pituitary: an endocrine gland consisting of secretory cells which synthesize and secrete several hormones directly into the bloodstream

diabetes insipidus: a condition caused by lack of ADH which results in excessive production of very dilute urine; ADH may be produced in insufficient quantities by the hypothalamus or the posterior pituitary may fail to release it into the bloodstream when a tumor develops

gigantism: a condition where a person produces excess hGH during childhood, resulting in a height of 8 feet or more

hypothalamus: region of the brain located below the cerebral hemispheres and thalamus, and just above the pituitary gland; functions in maintaining homeostasis, and is especially important in coordinating the endocrine and nervous systems; secretes hormones of the posterior pituitary as well as releasing hormones which regulate the anterior pituitary

neurosecretory cells: specialized nerve cells in the hypothalamus that extend into the posterior pituitary and secrete ADH and oxytocin into the posterior pituitary and subsequently into the bloodstream

pituitary dwarfism: a condition where a person does not produce enough hGH during childhood resulting in short stature

posterior pituitary: an extension of the hypothalamus composed of nervous tissue that secretes hormones produced in the hypothalamus into the bloodstream; consists of a temporary storage site for hormones produced in the hypothalamus

releasing hormones: sometimes called releasing factors; hormones produced by neurosecretory cells in the hypothalamus that stimulate or inhibit the secretion of hormones by the anterior pituitary

tropic hormones: chemical messengers (hormones) that have another endocrine gland as their target; hormones that stimulate other glands to produce their secretions

vasopressin: also called antidiuretic hormone