Endocrine System: Vocabulary Flashcards

Vocabulary-style flashcards covering key terms and definitions from the endocrine system lecture notes.

Endocrine system

Glands, tissues, and cells that secrete hormones; enables internal communication essential for coordinating cell activities.

Hormones

Chemical messengers that coordinate activities of other cells and tissues.

Exocrine glands

Glands with ducts that secrete onto an epithelial surface or mucosa (external secretions).

Endocrine glands

Glands with no ducts that release hormones into the bloodstream to act internally.

Hypothalamus

Brain region that regulates primitive functions and many pituitary activities.

Pituitary gland

Endocrine gland connected to the hypothalamus; has anterior (adenohypophysis) and posterior (neurohypophysis) lobes.

Infundibulum

Stalk that connects the hypothalamus to the pituitary.

Sella turcica

Bony cavity in the sphenoid bone that houses the pituitary.

Anterior pituitary (adenohypophysis)

Front lobe of the pituitary that produces multiple hormones regulated by hypothalamic hormones.

Posterior pituitary (neurohypophysis)

Back lobe of the pituitary; stores and releases OT and ADH produced in the hypothalamus.

Hypothalamic releasing and inhibiting hormones

Hormones (e.g., GnRH, TRH, CRH, GHRH, PIH, somatostatin) that regulate anterior pituitary secretion.

Oxytocin (OT)

Hypothalamus-produced hormone stored in the posterior pituitary; stimulates labor contractions and milk ejection; promotes bonding.

Antidiuretic hormone (ADH, vasopressin)

Hormone from the hypothalamus stored in the posterior pituitary; promotes water retention by the kidneys.

Gonadotropin-releasing hormone (GnRH)

Hypothalamic hormone that stimulates release of FSH and LH from the anterior pituitary.

Thyrotropin-releasing hormone (TRH)

Hypothalamic hormone that stimulates release of TSH from the anterior pituitary.

Corticotropin-releasing hormone (CRH)

Hypothalamic hormone that stimulates release of ACTH from the anterior pituitary.

Growth hormone-releasing hormone (GHRH)

Hypothalamic hormone that stimulates release of growth hormone from the anterior pituitary.

Prolactin-inhibiting hormone (PIH)

Inhibits prolactin release from the anterior pituitary.

Somatostatin

Inhibits release of GH and TSH from the anterior pituitary.

Growth hormone (GH)

Promotes cell growth and division; secreted by the anterior pituitary; regulated by GHRH and somatostatin.

Follicle-stimulating hormone (FSH)

Stimulates ovarian follicle development and sperm production; influences ovarian estrogen secretion.

Luteinizing hormone (LH)

Stimulates ovulation, corpus luteum formation, and testosterone secretion.

Thyroid-stimulating hormone (TSH)

Stimulates thyroid hormone production (T3 and T4) by the thyroid.

Adrenocorticotropic hormone (ACTH)

Stimulates adrenal cortex to secrete glucocorticoids.

Prolactin (PRL)

Postpartum hormone that stimulates milk production by the mammary glands.

Growth hormone–releasing factor (IGF-1)

A hormone produced mainly by the liver; mediates many growth-promoting effects of GH (often referred to as IGF-1).

IGF-1 (insulin-like growth factor 1)

Hormone produced primarily by the liver that mediates GH effects on growth.

Thyroid gland

Largest endocrine gland; produces T3 and T4; has follicles with colloid and parafollicular C cells that secrete calcitonin.

Triiodothyronine (T3)

Active thyroid hormone that increases metabolic rate.

Thyroxine (T4)**

Thyroid hormone that is converted to T3; increases metabolic rate.

Calcitonin

Hormone from parafollicular cells that lowers blood calcium by inhibiting bone resorption.

Parathyroid hormone (PTH)

Raises blood calcium; promotes calcitriol synthesis; increases calcium absorption and bone resorption.

Adrenal glands

Glands atop kidneys with adrenal cortex and adrenal medulla that regulate stress responses and metabolism.

Adrenal medulla

Inner core of the adrenal gland; secretes catecholamines (epinephrine and norepinephrine) during stress.

Adrenal cortex

Outer tissue of the adrenal gland; has zones that produce mineralocorticoids, glucocorticoids, and androgens.

Zona glomerulosa

Outer adrenal cortex zone that secretes mineralocorticoids (e.g., aldosterone).

Zona fasciculata

Middle adrenal cortex zone that secretes glucocorticoids (e.g., cortisol).

Zona reticularis

Inner adrenal cortex zone that secretes glucocorticoids and androgens.

Pancreatic islets (Islets of Langerhans)

Endocrine clusters in the pancreas containing alpha, beta, delta, and PP cells.

Alpha cells

Islet cells that secrete glucagon to raise blood glucose.

Beta cells

Islet cells that secrete insulin (and amylin) to lower blood glucose.

Delta cells

Islet cells that secrete somatostatin to modulate other islet hormones.

Pancreatic polypeptide (PP) cells

Islet cells that secrete pancreatic polypeptide; modulates pancreatic secretions after meals.

Glucagon

Hormone from alpha cells that raises blood glucose by promoting gluconeogenesis and glycogenolysis.

Insulin

Hormone from beta cells that promotes glucose uptake and storage; lowers blood glucose.

Somatostatin (islet)

Inhibits insulin and glucagon release; delays nutrient absorption.

Hyperglycemic hormones

Hormones that raise blood glucose (e.g., glucagon, GH, epinephrine, norepinephrine, cortisol, corticosterone).

Hypoglycemic hormone

Hormone that lowers blood glucose (principally insulin).

Gonads

Ovaries and testes; have endocrine and exocrine functions; produce gonadal steroids.

Ovarian hormones

Estradiol, progesterone, and inhibin; regulate female reproduction and cycles.

Testicular hormones

Testosterone and inhibin (also weaker androgens); regulate male reproduction and sperm production.

Pineal gland

Gland that secretes melatonin (and serotonin) and helps regulate circadian rhythms; undergoes involution after puberty.

Thymus

Gland involved in endocrine, lymphoid, and immune functions; maturates T cells; secretes thymopoietin, thymosin, thymulin; involutes after puberty.

Melatonin

Hormone from the pineal gland; regulates circadian rhythms and sleep; has other wide-ranging roles.

Cholecalciferol (vitamin D3) precursor

Skin-produced precursor to vitamin D activated by UV light.

Angiotensinogen

Liver prohormone; precursor to angiotensin II, a regulator of blood pressure.

Erythropoietin (EPO)

Kidney hormone that stimulates red blood cell production.

Calcitriol

Active vitamin D produced in kidneys; increases calcium absorption.

Renin

Renin-angiotensin system enzyme from kidneys; helps regulate blood pressure.

Atrial natriuretic peptide (ANP)

Heart hormone that lowers blood pressure and volume.

Brain natriuretic peptide (BNP)

Heart hormone that lowers blood pressure and volume; marker for heart stress.

Hormone classes: steroids, monoamines, peptides

Three chemical classes of hormones: steroids (from cholesterol), monoamines (from amino acids), and peptides (chains of amino acids).

Steroid hormones

Derived from cholesterol; include cortisol, aldosterone, estrogens, and testosterone.

Monoamines

Hormones derived from single amino acids (biogenic amines) such as epinephrine, norepinephrine, thyroid hormones.

Peptide hormones

Hormones made from short or long chains of amino acids (e.g., insulin, GH, ACTH).

Thyroid hormone synthesis (MIT/DIT)

Process of iodide uptake and iodination (MIT/DIT) to form T3/T4 within thyroglobulin.

Proinsulin

Precursor to insulin; cleaved to insulin and connecting peptide (C-peptide) before secretion.

receptor specificity and saturation

Receptors bind only specific hormones; saturation occurs when all receptors are occupied.

Up-regulation

Increase in receptor number, increasing target-cell sensitivity to hormone.

Down-regulation

Decrease in receptor number, reducing target-cell sensitivity.

Synergistic effects

Two or more hormones work together to produce a greater effect.

Permissive effects

One hormone enhances the response to a second, subsequent hormone.

Antagonistic effects

One hormone opposes the action of another.

Hormone clearance (MCR)

Removal of hormones from the blood by liver/kidney; defines hormone half-life.

Stress (GAS)

A disruption of homeostasis triggering a three-stage response: alarm, resistance, exhaustion.

Alarm reaction (GAS)

Initial fight-or-flight response with norepinephrine and epinephrine; glycogenolysis and BP rise.

Stage of resistance (GAS)

Cortisol-dominated phase supporting alternative energy sources via gluconeogenesis.

Stage of exhaustion (GAS)

Prolonged stress leading to fat/protein depletion, immune compromise, potential death.

Hyposecretion

Insufficient hormone release.

Hypersecretion

Excessive hormone release.

Hypoparathyroidism

Low PTH; hypocalcemia; possible tetany; often after thyroid surgery.

Hyperparathyroidism

Excess PTH; hypercalcemia; bone resorption; risk of kidney stones.

Cushing syndrome

Excess cortisol; hyperglycemia, hypertension, muscle weakness, edema; fat redistribution.

Androgenital syndrome (AGS)

Masculinization effects; elevated androgens; often with cortisol excess.

Type 1 diabetes mellitus

Autoimmune destruction of pancreatic beta cells; low insulin; treated with insulin.

Type 2 diabetes mellitus

Insulin resistance; obesity/age/race risk factors; managed with lifestyle, meds, sometimes insulin.

Diabetic complications

Neuropathy, retinopathy, nephropathy, cardiovascular disease, poor wound healing.