Ch. 17 Key Terms

acromegaly

Disorder in adults caused when abnormally high levels of GH trigger growth of bones in the face, hands, and feet.

adenylyl cyclase

Membrane-bound enzyme that converts ATP to cyclic AMP, creating cAMP as a result of G-protein activation.

adrenal cortex

Outer region of the adrenal glands, consisting of multiple layers of epithelial cells and capillary networks that produce mineralocorticoids and glucocorticoids.

adrenal glands

Endocrine glands located at the top of each kidney that regulate the stress response, blood pressure and blood volume, water homeostasis, and electrolyte levels.

adrenal medulla

Inner layer of the adrenal glands that produces epinephrine and norepinephrine, playing an important role in the stress response.

adrenocorticotropic hormone (ACTH)

Anterior pituitary hormone that stimulates the adrenal cortex to secrete corticosteroid hormones.

alarm reaction

The short-term stress or fight-or-flight response of stage one of the general adaptation syndrome, mediated by hormones epinephrine and norepinephrine.

aldosterone

Hormone produced by the adrenal cortex that stimulates sodium and fluid retention, increasing blood volume and blood pressure.

alpha cell

Pancreatic islet cell type that produces the hormone glucagon.

angiotensin-converting enzyme

Enzyme that converts angiotensin I to angiotensin II.

antidiuretic hormone (ADH)

Hypothalamic hormone stored by the posterior pituitary that signals the kidneys to reabsorb water.

atrial natriuretic peptide (ANP)

Peptide hormone produced by the atria walls that reduces sodium and water reabsorption in kidneys and promotes vasodilation.

autocrine

Chemical signal that elicits a response in the same cell that secreted it.

beta cell

Pancreatic islet cell type that produces the hormone insulin.

calcitonin

Peptide hormone produced by the thyroid gland that functions to decrease blood calcium levels.

chromaffin

Neuroendocrine cells of the adrenal medulla.

colloid

Viscous fluid in the central cavity of thyroid follicles containing thyroglobulin.

cortisol

Glucocorticoid important in gluconeogenesis, catabolism of glycogen, and downregulation of the immune system.

cyclic adenosine monophosphate (cAMP)

Second messenger that triggers a phosphorylation cascade in response to adenylyl cyclase activation.

delta cell

Minor cell type in the pancreas that secretes the hormone somatostatin.

diabetes mellitus

Condition caused by destruction or dysfunction of beta cells or cellular resistance to insulin, resulting in high blood glucose levels.

diacylglycerol (DAG)

Molecule that activates protein kinases, initiating a phosphorylation cascade.

downregulation

Decrease in the number of hormone receptors, typically due to chronically high levels of a hormone.

endocrine gland

Tissue or organ that secretes hormones into the blood and lymph without ducts.

endocrine system

Cells, tissues, and organs that secrete hormones as a primary or secondary function.

epinephrine

Primary catecholamine hormone secreted by the adrenal medulla in response to short-term stress.

erythropoietin (EPO)

Protein hormone secreted in response to low oxygen levels that triggers red blood cell production.

estrogens

Class of female sex hormones important for female reproductive health and secondary sex characteristics.

exocrine system

Cells and tissues that secrete substances directly to target tissues via glandular ducts.

first messenger

Hormone that binds to a cell membrane receptor and activates a second messenger system.

follicle-stimulating hormone (FSH)

Anterior pituitary hormone that stimulates the production and maturation of sex cells.

G protein

Protein associated with cell membrane hormone receptors that initiates the next step in a second messenger system.

general adaptation syndrome (GAS)

The body's three-stage response pattern to short- and long-term stress.

gigantism

Disorder in children caused by abnormally high levels of GH that leads to excessive growth.

glucagon

Pancreatic hormone that stimulates the breakdown of glycogen to glucose, increasing blood glucose levels.

glucocorticoids

Hormones produced by the zona fasciculata of the adrenal cortex influencing glucose metabolism.

goiter

Enlargement of the thyroid gland due to iodine deficiency or hyperthyroidism.

gonadotropins

Hormones regulating the function of the gonads.

growth hormone (GH)

Anterior pituitary hormone promoting tissue building and influencing nutrient metabolism.

hormone

Secretion of an endocrine organ that travels through the bloodstream to induce a response in target cells.

hormone receptor

Protein within a cell or on the cell membrane that binds a hormone, initiating a response.

hyperglycemia

Abnormally high blood glucose levels.

hyperparathyroidism

Disorder caused by overproduction of PTH, resulting in elevated blood calcium.

hyperthyroidism

Clinically abnormal elevated thyroid hormone levels; characterized by increased metabolic rate.

hypoparathyroidism

Disorder caused by underproduction of PTH, leading to abnormally low blood calcium levels.

hypophyseal portal system

Network of blood vessels enabling hypothalamic hormones to travel to the anterior pituitary.

hypothalamus

Region functioning in neural and endocrine signaling, located below the thalamus.

hypothyroidism

Clinically low level of thyroid hormone in the blood, characterized by low metabolic rate.

infundibulum

Stalk connecting the pituitary gland to the hypothalamus containing vasculature and neural tissue.

inhibin

Hormone secreted by gonads that inhibits FSH production by the anterior pituitary.

inositol triphosphate (IP3)

Molecule that initiates the release of calcium ions from intracellular stores.

insulin

Pancreatic hormone that enhances cellular glucose uptake, decreasing blood glucose levels.

insulin-like growth factors (IGF)

Proteins enhancing cellular proliferation and inhibiting apoptosis.

leptin

Protein hormone secreted by adipose tissues that promotes satiety.

luteinizing hormone (LH)

Anterior pituitary hormone triggering ovulation and testosterone production.

melatonin

Hormone secreted in response to low light that induces drowsiness.

mineralocorticoids

Hormones produced by the adrenal cortex influencing fluid and electrolyte balance.

neonatal hypothyroidism

Condition characterized by cognitive deficits and short stature due to maternal iodine deficiency.

norepinephrine

Secondary catecholamine hormone secreted by the adrenal medulla in response to stress.

osmoreceptor

Hypothalamic sensory receptor stimulated by changes in blood solute concentration.

oxytocin

Hypothalamic hormone important in stimulating uterine contractions and milk ejection.

pancreas

Organ important for digestion and regulation of blood glucose, with exocrine and endocrine functions.

pancreatic islets

Clusters of pancreatic cells with endocrine functions, also called islets of Langerhans.

paracrine

Chemical signal that elicits a response in neighboring cells.

parathyroid glands

Glands embedded in the posterior thyroid gland producing parathyroid hormone (PTH).

parathyroid hormone (PTH)

Hormone produced by parathyroid glands in response to low blood calcium levels.

phosphodiesterase (PDE)

Cytosolic enzyme that deactivates cAMP.

phosphorylation cascade

Signaling event where multiple protein kinases transfer a phosphate group from ATP.

pineal gland

Endocrine gland secreting melatonin, regulating the sleep-wake cycle.

pinealocyte

Cells of the pineal gland that produce and secrete melatonin.

pituitary dwarfism

Disorder in children caused by abnormally low levels of GH, leading to growth retardation.

pituitary gland

Organ that produces, stores, and secretes hormones in response to hypothalamic stimulation.

PP cell

Minor pancreatic cell type that secretes pancreatic polypeptide.

progesterone

Female sex hormone important for regulating the female reproductive cycle.

prolactin (PRL)

Hormone promoting development of mammary glands and production of breast milk.

protein kinase

Enzyme initiating a phosphorylation cascade upon activation.

second messenger

Molecule activating a signaling cascade in response to hormone binding on a receptor.

stage of exhaustion

Stage three of general adaptation syndrome; the body's long-term stress response.

stage of resistance

Stage two of general adaptation syndrome; continued response to stress after stage one.

testosterone

Steroid hormone important for sperm maturation and male reproductive development.

thymosins

Hormones produced by the thymus important for T cell development.

thymus

Organ involved in T cell development, particularly active during infancy and childhood.

thyroid gland

Large endocrine gland responsible for synthesis of thyroid hormones.

thyroid-stimulating hormone (TSH)

Anterior pituitary hormone that triggers secretion of thyroid hormones.

thyroxine (T4)

Amino acid-derived thyroid hormone more abundant but less potent than T3.

triiodothyronine (T3)

Amino acid-derived thyroid hormone that is less abundant but more potent than T4.

upregulation

Increase in the number of hormone receptors typically in response to reduced levels of a hormone.

zona fasciculata

Intermediate adrenal cortex region producing glucocorticoids.

zona glomerulosa

Most superficial adrenal cortex region producing mineralocorticoids.

zona reticularis

Deepest adrenal cortex region producing androgens.