Module 2

Module 2—The Endocrine System

Lesson Summary

 

In this lesson you explored the following focusing question:

• Who is the boss of the endocrine system, and how is the control of the endocrine system managed?

Self-regulated by the hypothalamus-pituitary complex, the endocrine system utilizes tropic hormones, such as releasing hormones 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 reduces the secretion of the tropic hormones when the levels of hormones secreted by the target glands reach correct amounts. Disruption in the level of a hormone can cause serious effects on physiological functions, such as urine production, growth, and metabolic rate.

 

You may choose to review the hormones of this lesson by watching all of “The Hypothalamus and Pituitary Gland: The Master Complex.”

 

Lesson Glossary

 

Consult the glossary in the textbook for other definitions that you may need to complete your work.

 

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 that 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 tumour develops.

 

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

 

hypothalamus: the 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 co-ordinating the endocrine and nervous systems; secretes hormones of the posterior pituitary as well as releases hormones that 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: hormones produced by neurosecretory cells in the hypothalamus that stimulate or inhibit the secretion of hormones by the anterior pituitary; sometimes called releasing factors

 

vasopressin: also called antidiuretic hormone (ADH)

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