Endocrine System Key Terms

Vocabulary flashcards covering the key terms, glands, hormones, and functional mechanisms of the Endocrine System based on the provided lecture notes.

Hormones

Chemicals secreted by the endocrine system that function as chemical messages traveling through the bloodstream.

Target cells

Cells that possess specific receptors for hormone binding.

Endocrine glands

Ductless glands that release hormones into interstitial fluid, where they can enter the bloodstream.

Exocrine glands

Glands with ducts that carry their secretions to body cavities, the lumen of an organ, or the outer surface of the body.

Hormone sensitivity

The degree of responsiveness of a target cell to a hormone, regulated by up-regulation or down-regulation of receptor counts.

Down-regulation

A decrease in target cell receptors in response to high hormone levels, making the cell less sensitive.

Up-regulation

An increase in target cell receptors in response to limited hormone levels, making the cell more sensitive.

Circulating hormones

Hormones that enter the blood and travel throughout the body.

Local hormones

Hormones that act on the cell that produced them (autocrines) or on a nearby cell (paracrines).

Autocrines

Local hormones that act directly on the cell that produced them.

Paracrines

Local hormones that act on nearby cells.

Water-soluble hormones

A class of hormones unable to penetrate the lipid membrane of the target cell.

Steroid hormones

Lipid-soluble hormones that diffuse through the lipid membrane into the nucleus, forming a hormone-receptor complex that turns genes on or off.

Humoral stimulus

A chemical change in the blood that causes hormone secretion, such as blood $Ca^{2+}$ levels regulating parathyroid hormone.

Hormonal stimulus

A secretion mechanism where one hormone stimulates another endocrine gland to release a hormone.

Pituitary gland

An endocrine gland controlled by the hypothalamus that secretes hormones that control other endocrine glands.

Hypothalamus

The brain region identified as the master gland that synthesizes 9 different hormones and controls the pituitary gland.

Releasing hormones

Hormones produced by the hypothalamus that trigger hormone production by other endocrine glands, particularly influencing the pituitary gland.

Infundibulum stalk

The stalk that connects the hypothalamus to the pituitary gland.

Somatotrophic cells

Cells of the anterior pituitary that produce growth hormone.

Gonadotrophic cells

Anterior pituitary cells that produce follicle-stimulating hormone (FSH) and luteinizing hormone (LH).

Tropic hormones

Anterior pituitary hormones that act specifically on other endocrine glands.

Hypophyseal portal system

A vascular system carrying blood from the capillaries of the hypothalamus to the capillaries of the anterior pituitary.

Growth hormone (GH)

Anterior pituitary hormone that regulates bone and skeletal muscle growth, regulates metabolism, promotes lipid breakdown, and reduces glucose uptake by liver cells.

Thyroid-stimulating hormone (TSH)

Anterior pituitary hormone that stimulates the thyroid gland to produce T3 and T4.

Follicle-stimulating hormone (FSH)

Gonadotropin produced by anterior pituitary gonadotrophic cells that targets ovaries in females (initiating follicle development and estrogen secretion) and testes in males (stimulating spermatogenesis).

Luteinizing hormone (LH)

Gonadotropin that stimulates testosterone production in males, and in females triggers ovulation, corpus luteum formation, progesterone secretion, and works with FSH to stimulate estrogen.

Oxytocin

Hormone synthesized by the hypothalamus and stored/released by the posterior pituitary that enhances uterine contractions during childbirth and milk ejection from mammary glands.

Antidiuretic hormone (ADH)

Hormone synthesized by the hypothalamus and stored/released by the posterior pituitary that causes the kidneys to return more water to the blood, reducing urine output.