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Key Terms Chapter 17: The Endocrine System

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    62668
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    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 produces mineralocorticoids and glucocorticoids
    adrenal glands
    endocrine glands located at the top of each kidney that are important for the regulation of the stress response, blood pressure and blood volume, water homeostasis, and electrolyte levels
    adrenal medulla
    inner layer of the adrenal glands that plays an important role in the stress response by producing epinephrine and norepinephrine
    adrenocorticotropic hormone (ACTH)
    anterior pituitary hormone that stimulates the adrenal cortex to secrete corticosteroid hormones (also called corticotropin)
    alarm reaction
    the short-term stress, or the fight-or-flight response, of stage one of the general adaptation syndrome mediated by the hormones epinephrine and norepinephrine
    aldosterone
    hormone produced and secreted by the adrenal cortex that stimulates sodium and fluid retention and increases blood volume and blood pressure
    alpha cell
    pancreatic islet cell type that produces the hormone glucagon
    angiotensin-converting enzyme
    the enzyme that converts angiotensin I to angiotensin II
    antidiuretic hormone (ADH)
    hypothalamic hormone that is stored by the posterior pituitary and that signals the kidneys to reabsorb water
    atrial natriuretic peptide (ANP)
    peptide hormone produced by the walls of the atria in response to high blood pressure, blood volume, or blood sodium that reduces the reabsorption of sodium and water in the 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 and secreted by the parafollicular cells (C cells) of 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 the glycoprotein thyroglobulin
    cortisol
    glucocorticoid important in gluconeogenesis, the catabolism of glycogen, and downregulation of the immune system
    cyclic adenosine monophosphate (cAMP)
    second messenger that, in response to adenylyl cyclase activation, triggers a phosphorylation cascade
    delta cell
    minor cell type in the pancreas that secretes the hormone somatostatin
    diabetes mellitus
    condition caused by destruction or dysfunction of the beta cells of the pancreas or cellular resistance to insulin that results in abnormally high blood glucose levels
    diacylglycerol (DAG)
    molecule that, like cAMP, activates protein kinases, thereby initiating a phosphorylation cascade
    downregulation
    decrease in the number of hormone receptors, typically in response to chronically excessive levels of a hormone
    endocrine gland
    tissue or organ that secretes hormones into the blood and lymph without ducts such that they may be transported to organs distant from the site of secretion
    endocrine system
    cells, tissues, and organs that secrete hormones as a primary or secondary function and play an integral role in normal bodily processes
    epinephrine
    primary and most potent catecholamine hormone secreted by the adrenal medulla in response to short-term stress; also called adrenaline
    erythropoietin (EPO)
    protein hormone secreted in response to low oxygen levels that triggers the bone marrow to produce red blood cells
    estrogens
    class of predominantly female sex hormones important for the development and growth of the female reproductive tract, secondary sex characteristics, the female reproductive cycle, and the maintenance of pregnancy
    exocrine system
    cells, tissues, and organs that secrete substances directly to target tissues via glandular ducts
    first messenger
    hormone that binds to a cell membrane hormone receptor and triggers activation of 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 a cell membrane hormone receptor that initiates the next step in a second messenger system upon activation by hormone–receptor binding
    general adaptation syndrome (GAS)
    the human body’s three-stage response pattern to short- and long-term stress
    gigantism
    disorder in children caused when abnormally high levels of GH prompt excessive growth
    glucagon
    pancreatic hormone that stimulates the catabolism of glycogen to glucose, thereby increasing blood glucose levels
    glucocorticoids
    hormones produced by the zona fasciculata of the adrenal cortex that influence glucose metabolism
    goiter
    enlargement of the thyroid gland either as a result of iodine deficiency or hyperthyroidism
    gonadotropins
    hormones that regulate the function of the gonads
    growth hormone (GH)
    anterior pituitary hormone that promotes tissue building and influences nutrient metabolism (also called somatotropin)
    hormone
    secretion of an endocrine organ that travels via the bloodstream or lymphatics to induce a response in target cells or tissues in another part of the body
    hormone receptor
    protein within a cell or on the cell membrane that binds a hormone, initiating the target cell response
    hyperglycemia
    abnormally high blood glucose levels
    hyperparathyroidism
    disorder caused by overproduction of PTH that results in abnormally elevated blood calcium
    hyperthyroidism
    clinically abnormal, elevated level of thyroid hormone in the blood; characterized by an increased metabolic rate, excess body heat, sweating, diarrhea, weight loss, and increased heart rate
    hypoparathyroidism
    disorder caused by underproduction of PTH that results in abnormally low blood calcium
    hypophyseal portal system
    network of blood vessels that enables hypothalamic hormones to travel into the anterior lobe of the pituitary without entering the systemic circulation
    hypothalamus
    region of the diencephalon inferior to the thalamus that functions in neural and endocrine signaling
    hypothyroidism
    clinically abnormal, low level of thyroid hormone in the blood; characterized by low metabolic rate, weight gain, cold extremities, constipation, and reduced mental activity
    infundibulum
    stalk containing vasculature and neural tissue that connects the pituitary gland to the hypothalamus (also called the pituitary stalk)
    inhibin
    hormone secreted by the male and female 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 the cellular uptake and utilization of glucose, thereby decreasing blood glucose levels
    insulin-like growth factors (IGF)
    protein that enhances cellular proliferation, inhibits apoptosis, and stimulates the cellular uptake of amino acids for protein synthesis
    leptin
    protein hormone secreted by adipose tissues in response to food consumption that promotes satiety
    luteinizing hormone (LH)
    anterior pituitary hormone that triggers ovulation and the production of ovarian hormones in females, and the production of testosterone in males
    melatonin
    amino acid–derived hormone that is secreted in response to low light and causes drowsiness
    mineralocorticoids
    hormones produced by the zona glomerulosa cells of the adrenal cortex that influence fluid and electrolyte balance
    neonatal hypothyroidism
    condition characterized by cognitive deficits, short stature, and other signs and symptoms in people born to women who were iodine-deficient during pregnancy
    norepinephrine
    secondary catecholamine hormone secreted by the adrenal medulla in response to short-term stress; also called noradrenaline
    osmoreceptor
    hypothalamic sensory receptor that is stimulated by changes in solute concentration (osmotic pressure) in the blood
    oxytocin
    hypothalamic hormone stored in the posterior pituitary gland and important in stimulating uterine contractions in labor, milk ejection during breastfeeding, and feelings of attachment (also produced in males)
    pancreas
    organ with both exocrine and endocrine functions located posterior to the stomach that is important for digestion and the regulation of blood glucose
    pancreatic islets
    specialized clusters of pancreatic cells that have endocrine functions; also called islets of Langerhans
    paracrine
    chemical signal that elicits a response in neighboring cells; also called paracrine factor
    parathyroid glands
    small, round glands embedded in the posterior thyroid gland that produce parathyroid hormone (PTH)
    parathyroid hormone (PTH)
    peptide hormone produced and secreted by the parathyroid glands in response to low blood calcium levels
    phosphodiesterase (PDE)
    cytosolic enzyme that deactivates and degrades cAMP
    phosphorylation cascade
    signaling event in which multiple protein kinases phosphorylate the next protein substrate by transferring a phosphate group from ATP to the protein
    pineal gland
    endocrine gland that secretes melatonin, which is important in regulating the sleep-wake cycle
    pinealocyte
    cell of the pineal gland that produces and secretes the hormone melatonin
    pituitary dwarfism
    disorder in children caused when abnormally low levels of GH result in growth retardation
    pituitary gland
    bean-sized organ suspended from the hypothalamus that produces, stores, and secretes hormones in response to hypothalamic stimulation (also called hypophysis)
    PP cell
    minor cell type in the pancreas that secretes the hormone pancreatic polypeptide
    progesterone
    predominantly female sex hormone important in regulating the female reproductive cycle and the maintenance of pregnancy
    prolactin (PRL)
    anterior pituitary hormone that promotes development of the mammary glands and the production of breast milk
    protein kinase
    enzyme that initiates a phosphorylation cascade upon activation
    second messenger
    molecule that initiates a signaling cascade in response to hormone binding on a cell membrane receptor and activation of a G protein
    stage of exhaustion
    stage three of the general adaptation syndrome; the body’s long-term response to stress mediated by the hormones of the adrenal cortex
    stage of resistance
    stage two of the general adaptation syndrome; the body’s continued response to stress after stage one diminishes
    testosterone
    steroid hormone secreted by the male testes and important in the maturation of sperm cells, growth and development of the male reproductive system, and the development of male secondary sex characteristics
    thymosins
    hormones produced and secreted by the thymus that play an important role in the development and differentiation of T cells
    thymus
    organ that is involved in the development and maturation of T-cells and is particularly active during infancy and childhood
    thyroid gland
    large endocrine gland responsible for the synthesis of thyroid hormones
    thyroid-stimulating hormone (TSH)
    anterior pituitary hormone that triggers secretion of thyroid hormones by the thyroid gland (also called thyrotropin)
    thyroxine
    (also, tetraiodothyronine, T4) amino acid–derived thyroid hormone that is more abundant but less potent than Tand often converted to T3 by target cells
    triiodothyronine
    (also, 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 chronically reduced levels of a hormone
    zona fasciculata
    intermediate region of the adrenal cortex that produce hormones called glucocorticoids
    zona glomerulosa
    most superficial region of the adrenal cortex, which produces the hormones collectively referred to as mineralocorticoids
    zona reticularis
    deepest region of the adrenal cortex, which produces the steroid sex hormones called androgens
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