Module 18: Endocrine System

hormone

a molecule that is released in one part of the body but regulates the activity of cells in other parts of the body

circulating hormone

most endocrine hormones; pass from the secretory cells that make them into interstitial fluid and then into the blood

paracrine hormone

local hormone that acts on neighboring cells

autocrine hormone

local hormone that acts on the same cell that secreted them; receptors receive hormone from its own cell

lipid soluble hormones

class of hormones including steroid hormones, thyroid hormones, and nitric oxide; most are bound to transport proteins; receptors are located inside target cells

water soluble hormones

class of hormones including amine hormones, peptide and protein hormones, and eicosanoid hormones; circulate in blood plasma in a "free" form (not attached to other molecules); receptors are part of the plasma membrane of target cell (not inside cell)

Hypothalamus

Small region of the brain below the thalamus; major link between nervous and endocrine systems; cells here synthesize at least 9 different hormones; important role in regulation of all aspects of growth, development, metabolism, homeostasis

Pituitary gland

Pea-shaped structure attached to hypothalamus by the infundibulum (stalk); secretes seven different hormones; split into two parts, anterior and posterior

Anterior pituitary

gland that releases hormones (hGH, TSH, PRL, ACTH, FSH, LH, MSH) when stimulated by RELEASING HORMONES and suppressed by INHIBITING HORMONES from the hypothalamus

Posterior pituitary

gland does NOT synthesize hormones, but STORES and RELEASES two hormones (oxytocin and ADH)

Tropic hormones

hormones that act on other endocrine glands

human growth hormone (hGH)

hormone secreted by the anterior pituitary that increases protein synthesis, causing growth of bones and skeletal muscles, enhances lipolysis in adipose tissue, resulting in increased use of released fatty acids for ATP production by body cells

thyroid stimulating hormone (TSH)

hormone secreted by the anterior pituitary that stimulates the synthesis and secretion of T3 and T4 by the Thyroid gland

follicle stimulating hormone (FSH)

hormone secreted by the anterior pituitary that stimulates development and maturation of ovarian follicles, stimulates follicular cells of the ovary to secrete estrogens; stimulates sperm production in males

luteinizing hormone (LH)

hormone secreted by the anterior pituitary that stimulates ovulation in females, testosterone production in males

prolactin (PRL)

hormone secreted by the anterior pituitary that stimulates milk production by mammary glands

oxytocin

hormone produced by the hypothalamus and stored/secreted by the posterior pituitary that enhances contraction of smooth muscle cells in wall of uterus; stimulates milk ejection from mammary glands in response to suckling infant; has actions with brain that foster parental caretaking behavior toward offspring

Antidiuretic hormone (ADH)

hormone produced by the hypothalamus and stored/secreted by the posterior pituitary that conserves body water by decreasing urine production - causes kidneys to return more water to the blood; secretion inhibited by alcohol; decreases water lost by inhibiting sweating and causes constriction of arterioles, which increase BP

T3 (triiodothyronine) and T4 (thyroxine)

hormones that increase basal metabolic rate, increase body temperature (calorigenic), stimulate protein synthesis, increase use of glucose and fatty acids for ATP production, stimulate lipolysis, regulate development and growth of nervous tissue and bones

Calcitonin

Hormone produced by the thyroid gland; can decrease levels of calcium in the blood by inhibiting the action of osteoclasts, the cells that break down bone extracellular matrix

Parathyroid hormone

Hormone that is the major regulator of the levels of CALCIUM, magnesium, and phosphate ions in the blood; INCREASES number and activity of OSTEOCLASTS -> elevated bone resorption -> releases Ca2+ and phosphates into blood; also affects kidneys - slows rate at which Ca2+ is lost from blood into urine, and promotes formation of calcitriol

Aldosterone

The major mineralocorticoid hormone secreted by zona glomerulosa of adrenal cortex; regulates homeostasis of Na+ and K+ and helps adjust blood pressure and blood volume by adjusting fluid levels

Cortisol

The major glucocorticoid hormone secreted by zona fasciculata to regulate metabolism and resistance to stress; stimulates protein breakdown, glucose formation, lipolysis, resistance to stress, anti-inflammatory effects, and depression of immune responses

Androgens

Hormones produced by the adrenal cortex that assist in early growth of axillary and pubic hair in both sexes; function as precursors to estrogens after menopause

Epinephrine and Norepinephrine

Hormones produced by the adrenal medulla that enhance the effects of the sympathetic nervous system (fight or flight responses)

Alpha cells

Cells of the pancreas that secrete glucagon in response to low blood glucose

Beta cells

Cells of the pancreas that secrete insulin in response to high blood glucose

Glucagon

Hormone produced by the pancreas to raise blood glucose levels by accelerating breakdown of glycogen into glucose by the liver

Insulin

Hormone produced by the pancreas to lower blood glucose by accelerating transport of glucose into cells

Type 1 diabetes

Immune system destroys the pancreatic beta cells, leading to little or no production of insulin at pancreas

Type 2 diabetes

Long term metabolic disorder characterized by Insulin resistance and high blood sugar

estrogen

primary sex hormone produced by ovaries

testosterone

primary sex hormone produced by testes

thymus

gland that produces hormones involved in maturation of T-lymphocytes of the immune system

melatonin

Hormone secreted by pineal gland involved in setting of the body's biological clock; more is liberated during darkness than in light - promotes sleepiness

Diabetes insipidus

Dysfunction with the posterior pituitary; due to defects in ADH receptors or an inability to secrete ADH; symptoms include excretion of large volumes of urine, dehydration, thirst

goiter

Enlarged thyroid gland; associated with hypothyroidism or inadequate dietary iodine

Cushings syndrome

Hypersecretion of cortisol by adrenal cortex; tumor of adrenal gland that secretes cortisol

Addisons disease

Hyposecretion of glucocorticoids and aldosterone