Endocrine System Review Flashcards

Vocabulary practice flashcards covering endocrine structures, mechanisms, pathways, and hormones based on Anatomy & Physiology II lecture materials.

Autocrines

Chemicals that exert their physiological effects on the exact same cells that secreted them.

Paracrines

Locally acting chemicals that affect surrounding cells other than those that secreted them.

Hormones

Long-distance chemical messengers secreted by cells into extracellular fluids that travel through blood to regulate target cell metabolic functions.

Eicosanoids

Biologically active lipids derived from arachidonic acid (such as prostaglandins, leukotrienes, and thromboxanes) that exhibit local hormone-like activity.

Permissiveness

A hormonal interaction pattern in which one hormone cannot exert its full physiological effect on a target cell without another hormone being present.

Synergism

A hormonal interaction pattern where more than one hormone produces the same effect on a target cell, resulting in an amplified combined effect.

Antagonism

A hormonal interaction pattern in which one or more hormones oppose the specific action of another hormone.

Up-regulation

An adaptive response in target cell activation where target cells produce a greater number of receptors in response to low hormone concentrations.

Down-regulation

An adaptive mechanism where target cells lose receptors in response to high hormone concentrations to prevent overstimulation.

Humoral Stimuli

Hormone release triggered directly by changing concentrations of ions or nutrients in the blood, such as low blood $\text{Ca}^{2+}$ stimulating parathyroid hormone release.

Neural Stimuli

Hormone secretion prompted directly by nerve fiber impulses, such as preganglionic sympathetic fibers stimulating the adrenal medulla.

Hormonal Stimuli

Hormone secretion stimulated by tropic hormones released from other endocrine glands, such as hypothalamic hormones regulating anterior pituitary release.

Neurohypophysis

The posterior region of the pituitary gland plus the infundibulum stalk, composed of neural tissue that stores and releases oxytocin and ADH.

Adenohypophysis

The anterior lobe of the pituitary gland, composed of glandular tissue that synthesizes and secretes six major hormones ($GH$, $TSH$, $ACTH$, $FSH$, $LH$, and $PRL$).

Hypophyseal Portal System

A vascular network consisting of a primary capillary plexus, hypophyseal portal veins, and a secondary capillary plexus that delivers hypothalamic tropic hormones directly to the anterior pituitary.

Hypothalamic-Hypophyseal Tract

A neuronal pathway connecting hypothalamic nuclei (paraventricular and supraoptic) to the posterior pituitary for transporting synthesized neurohormones.

Oxytocin

A peptide hormone synthesized in the hypothalamic paraventricular nuclei and released by the posterior pituitary that stimulates uterine contractions during labor and milk ejection in lactating females.

Antidiuretic Hormone (ADH)

A neurohormone synthesized in the supraoptic nuclei of the hypothalamus and stored in the posterior pituitary that acts on kidney tubules to prevent urine formation and conserve body water.

Diabetes Insipidus

A metabolic condition caused by ADH deficiency, resulting in the production of massive amounts of dilute, odorless urine accompanied by intense thirst.

Syndrome of Inappropriate ADH Secretion (SIADH)

A disorder caused by ADH hypersecretion, presenting with fluid retention, reduced blood solute concentration, weight gain, and brain edema.

Growth Hormone (GH)

An anterior pituitary hormone secreted by somatotropic cells that promotes tissue growth, protein synthesis, and fat mobilization; also known as somatotropin.

Insulin-like Growth Factors (IGFs)

Somatomedin proteins produced by liver, muscle, bone, and cartilage in response to growth hormone that indirectly mediate GH's growth-promoting actions.

Gigantism

A clinical condition caused by hypersecretion of growth hormone during childhood while epiphyseal growth plates remain open.

Acromegaly

A disorder resulting from excessive growth hormone secretion in adults following epiphyseal plate closure, characterized by enlargement of extremities and facial features.

Thyroid-Stimulating Hormone (TSH)

A tropic hormone produced by the anterior pituitary that stimulates normal development and secretion of the thyroid gland; also called thyrotropin.

Adrenocorticotropic Hormone (ACTH)

A tropic hormone released from the anterior pituitary in response to CRH that prompts the adrenal cortex to synthesize and secrete corticosteroids; also called corticotropin.

Follicle-Stimulating Hormone (FSH)

A gonadotropin secreted by the adenohypophysis that promotes gamete (egg or sperm) production in the gonads.

Luteinizing Hormone (LH)

A gonadotropin that induces ovulation and sex hormone release in females, and stimulates interstitial cells to produce testosterone in males.

Prolactin (PRL)

An anterior pituitary hormone that stimulates milk production in breast tissue, regulated positively by PRH and negatively by dopamine (PIH).

Thyroxine (T4)

The main hormone secreted by thyroid follicles, containing two tyrosine molecules with four bound iodine atoms.

Triiodothyronine (T3)

The highly active form of thyroid hormone produced at target tissues from $T_4$, containing two tyrosines with three bound iodine atoms.

Cretinism

Congenital hypothyroidism in children resulting in growth retardation, mental sluggishness, delayed puberty, and enlarged tongue.

Myxedema

Hypothyroidism in adults characterized by a low basal metabolic rate, cold intolerance, lethargy, and potential goiter development under iodine deficiency.

Graves Disease

An autoimmune hyperthyroid condition where abnormal antibodies mimic TSH, raising metabolic rate, heart rate, nervousness, and causing exophthalmos.

Calcitonin

A peptide hormone produced by parafollicular (C) cells of the thyroid gland that lowers blood calcium levels in children by inhibiting osteoclasts.

Parathyroid Hormone (PTH)

A peptide hormone released by chief cells of the parathyroid glands that increases blood $\text{Ca}^{2+}$ levels by activating osteoclasts and enhancing renal calcium reabsorption.

Zona Glomerulosa

The outermost cortical layer of the adrenal gland, responsible for synthesizing mineralocorticoids (chiefly aldosterone).

Zona Fasciculata

The middle layer of the adrenal cortex, responsible for synthesizing glucocorticoids (chiefly cortisol).

Zona Reticularis

The innermost layer of the adrenal cortex, responsible for producing gonadocorticoids (chiefly weak androgens like DHEA).

Aldosterone

The primary mineralocorticoid produced by the adrenal cortex that regulates $\text{Na}^+$ balance by reducing sodium excretion and stimulating kidney reabsorption.

Renin-Angiotensin Mechanism

A hormonal regulatory system where kidney-derived renin initiates a cascade converting angiotensinogen to angiotensin II, stimulating aldosterone release.

Cortisol

The primary glucocorticoid hormone secreted in response to stress that promotes gluconeogenesis and elevates blood levels of glucose, fatty acids, and amino acids.

Cushing's Disease

A pathological state caused by excessive glucocorticoids, causing persistent hyperglycemia, bone loss, and immune suppression.

Addison's Disease

A hyposecretory disorder of the adrenal cortex involving deficient levels of both mineralocorticoids and glucocorticoids.

Adrenal Medulla

The inner core of the adrenal gland composed of nervous tissue and chromaffin cells that secrete epinephrine and norepinephrine under sympathetic stimulation.

Glucagon

A 29-amino-acid polypeptide hormone produced by pancreatic alpha ($\alpha$) cells that acts as a hyperglycemic agent by promoting glycogenolysis and gluconeogenesis.

Insulin

A 51-amino-acid protein hormone secreted by pancreatic beta ($\beta$) cells that lowers blood glucose by stimulating cellular glucose uptake, glycogen synthesis, and fat storage.

Polyuria

A classic sign of diabetes mellitus characterized by abnormally large urine output due to osmotic diuresis.

Polydipsia

Excessive, continuous thirst arising from severe dehydration; one of the three cardinal signs of diabetes mellitus.

Polyphagia

Excessive hunger and food consumption driven by cellular starvation; one of the three cardinal signs of diabetes mellitus.

Hyperinsulinism

An excess secretion of insulin leading to hypoglycemia, anxiety, disorientation, and potential loss of consciousness.

Melatonin

An amine hormone secreted by the pineal gland that regulates circadian rhythms and body processes showing daily variations.

Atrial Natriuretic Peptide (ANP)

A cardiac hormone produced in response to elevated blood pressure or volume that lowers blood sodium, volume, and blood pressure by inhibiting aldosterone release.

Leptin

A hormone produced by adipose tissue that targets hypothalamic centers to induce satiety and enhance energy expenditure.

Erythropoietin (EPO)

A glycoprotein hormone released by the kidneys that signals red blood cell production within the bone marrow.