Chapter 16

adrenal gland

An endocrine gland that lies atop a kidney; consisting of the inner adrenal medulla and the outer adrenal cortex.

circadian rhythm

Biological rhythm with a 24-hour cycle.

hormone

Chemical signal produced by one set of cells that affects a different set of cells.

pheromone

Chemical signal released by an organism that affects the metabolism or influences the behavior of another individual of the same species.

gonadotropic hormone

Chemical signal secreted by the anterior pituitary that regulates the activity of the ovaries and testes; principally, follicle-stimulating hormone (FSH) and luteinizing hormone (LH).

second messenger

Chemical signal such as cyclic AMP that causes the cell to respond to the first messenger—a hormone bound to a receptor protein in the plasma membrane.

first messenger

Chemical signal, such as a peptide hormone, that binds to a plasma membrane receptor protein and alters the metabolism of a cell because a second messenger is activated.

ovary

Female gonad that produces eggs and the female sex hormones.

estrogen

Female sex hormone that helps maintain sex organs and secondary sex characteristics.

progesterone

Female sex hormone that helps maintain sex organs and secondary sex characteristics.

thymosin

Group of peptides secreted by the thymus gland that increases production of certain types of white blood cells.

gonad

Organ that produces gametes; the ovary produces eggs, and the testis produces sperm.

adrenal cortex

Outer portion of the adrenal gland; secretes mineralocorticoids, such as aldosterone, and glucocorticoids, such as cortisol.

cyclic adenosine monophosphate (cAMP)

ATP-related compound that acts as the second messenger in peptide hormone transduction; it initiates activity of the metabolic machinery.

diabetes mellitus

Condition characterized by a high blood glucose level and the appearance of glucose in the urine, due to a deficiency of insulin production and failure of cells to take up glucose.

pituitary dwarfism

Condition in which an affected individual has normal proportions but small stature; caused by inadequate growth hormone.

simple goiter

Condition in which an enlarged thyroid produces low levels of thyroxine.

Addison disease

Condition resulting from a deficiency of adrenal cortex hormones; characterized by low blood glucose, weight loss, and weakness.

myxedema

Condition resulting from a deficiency of thyroid hormone in an adult.

acromegaly

Condition resulting from an increase in growth hormone production after adult height has been achieved.

Cushing syndrome

Condition resulting from hypersecretion of glucocorticoids; characterized by thin arms and legs and a "moon face," and accompanied by high blood glucose and sodium levels.

congenital hypothyroidism

Condition resulting from improper development of the thyroid in an infant; characterized by stunted growth and mental retardation.

endocrine gland

Ductless organ that secretes (a) hormone(s) into the bloodstream.

thyroid gland

Endocrine gland in the neck that produces several important hormones, including thyroxine, triiodothyronine, and calcitonin.

pineal gland

Endocrine gland located in the third ventricle of the brain; produces melatonin.

pituitary gland

Endocrine gland that lies just inferior to the hypothalamus; consists of the anterior pituitary and posterior pituitary.

exophthalmic goiter

Enlargement of the thyroid gland accompanied by an abnormal protrusion of the eyes.

renin

Enzyme released by kidneys that leads to the secretion of aldosterone and a rise in blood pressure.

exocrine gland

Gland that secretes its product to an epithelial surface directly or through ducts.

cortisol

Glucocorticoid secreted by the adrenal cortex that responds to stress on a long-term basis; reduces inflammation and promotes protein and fat metabolism.

leptin

Hormone produced by adipose tissue that acts on the hypothalamus to signal satiety.

oxytocin

Hormone released by the posterior pituitary that causes contraction of uterus and milk letdown.

aldosterone

Hormone secreted by the adrenal cortex that decreases sodium and increases potassium excretion; raises blood volume and pressure.

epinephrine

Hormone secreted by the adrenal medulla in times of stress; adrenaline.

adrenocorticotropic hormone (ACTH)

Hormone secreted by the anterior lobe of the pituitary gland that stimulates activity in the adrenal cortex.

follicle stimulating hormone (FSH)

Hormone secreted by the anterior pituitary gland that stimulates the development of an ovarian follicle in a female or the production of sperm in a male.

prolactin (PRL)

Hormone secreted by the anterior pituitary that stimulates the production of milk from the mammary glands.

parathyroid hormone (PTH)

Hormone secreted by the four parathyroid glands that increases the blood calcium level and decreases the blood phosphate level.

atrial natriuretic hormone (ANH)

Hormone secreted by the heart that increases sodium excretion and, therefore, lowers blood volume and pressure.

glucagon

Hormone secreted by the pancreas that causes the liver to break down glycogen and raises the blood glucose level.

insulin

Hormone secreted by the pancreas that lowers the blood glucose level by promoting the uptake of glucose by cells, and the conversion of glucose to glycogen by the liver and skeletal muscles.

antidiuretic hormone (ADH)

Hormone secreted by the posterior pituitary that increases the permeability of the collecting ducts in a kidney.

calcitonin

Hormone secreted by the thyroid gland that increases the blood calcium level.

thyroxine (T4)

Hormone secreted from the thyroid gland that promotes growth and development; in general, it increases the metabolic rate in cells.

luteinizing hormone (LH)

Hormone that controls the production of testosterone by interstitial cells in males and promotes the development of the corpus luteum in females.

prostaglandin

Hormone that has various and powerful local effects.

melatonin

Hormone, secreted by the pineal gland, that is involved in biorhythms.

adrenal medulla

Inner portion of the adrenal gland; secretes the hormones epinephrine and norepinephrine.

pancreas

Internal organ that produces digestive enzymes and the hormones insulin and glucagon.

thymus gland

Lymphatic organ, located along the trachea behind the sternum, involved in the maturation of T lymphocytes in the thymus gland. Secretes hormones called thymosins, which aid the maturation of T cells and perhaps stimulate immune cells in general.

testes

Male gonads that produce sperm and the male sex hormones.

androgen

Male sex hormone (e.g. testosterone).

testosterone

Male sex hormone that helps maintain sexual organs and secondary sex characteristics.

pancreatic islets

Masses of cells that constitute the endocrine portion of the pancreas.

parathyroid gland

Masses of cells that constitute the endocrine portion of the pancreas.

positive feedback

Mechanism in which the stimulus initiates reactions that lead to an increase in the stimulus.

chemical signal

Molecule that brings about a change in a cell, tissue, organ, or individual when it binds to a specific receptor.

norepinephrine

Neurotransmitter of the postganglionic fibers in the sympathetic division of the autonomic system; also, a hormone produced by the adrenal medulla.

steroid hormone

One of a group of hormones derived from cholesterol.

hypothalamic-inhibiting hormone

One of many hormones produced by the hypothalamus that inhibits the secretion of an anterior pituitary hormone.

hypothalamic-releasing hormone

One of many hormones produced by the hypothalamus that stimulates the secretion of an anterior pituitary hormone.

hypothalamus

Part of the brain located below the thalamus that helps regulate the internal environment of the body and produces releasing factors that control the anterior pituitary.

anterior pituitary

Portion of the pituitary gland controlled by the hypothalamus and that produces six types of hormones, some of which control other endocrine glands.

posterior pituitary

Portion of the pituitary gland that stores and secretes oxytocin and antidiuretic hormone, which are produced by the hypothalamus.

tetany

Severe twitching caused by involuntary contraction of the skeletal muscles due to a calcium imbalance.

thyroid-stimulating hormone (TSH)

Substance produced by the anterior pituitary that causes the thyroid to secrete thyroxine and triiodothyronine.

growth hormone (GH)

Substance secreted by the anterior pituitary; controls size of individual by promoting cell division, protein synthesis, and bone growth.

melanocyte-stimulating hormone (MSH)

Substance that causes melanocytes to secrete melanin in lower vertebrates.

anabolic steroid

Synthetic steroid that mimics the effect of testosterone.

glucocorticoid

Type of hormone secreted by the adrenal cortex that influences carbohydrate, fat, and protein metabolism; see cortisol.

mineralocorticoid

Type of hormone secreted by the adrenal cortex that regulates water-salt balance, leading to increases in blood volume and blood pressure.

peptide hormone

Type of hormone that is a protein, a peptide, or derived from an amino acid.