Endocrine System - Vocabulary Flashcards

Vocabulary flashcards covering key terms from the endocrine system notes.

Endocrine system

A body system that uses hormones to regulate metabolism, growth, and homeostasis, coordinating with the nervous system.

Hormone

A chemical messenger released by endocrine cells into the bloodstream to regulate other cells.

Neurotransmitter

A chemical messenger released at synapses to affect adjacent neurons or muscles.

Direct communication

Signaling via gap junctions; mediators pass between adjacent, connected cells.

Paracrine communication

Local signaling through extracellular fluids; affects nearby cells with receptors.

Endocrine communication

Hormones travel through the bloodstream to distant target cells.

Neural communication

Signaling via synaptic transmission; targets are usually very specific.

Receptor

A protein on or in a cell that binds a specific messenger.

Amine hormone

Hormone derived from a single amino acid (e.g., thyroid hormones, catecholamines, melatonin).

Thyroxine (T4)

Thyroid hormone containing iodine; increases metabolic rate.

Triiodothyronine (T3)

Active thyroid hormone; more potent than T4.

Catecholamine

Amine hormones such as epinephrine, norepinephrine, and dopamine.

Melatonin

Pineal hormone regulating sleep-wake cycles and acting as an antioxidant.

Polypeptide

Short chains of amino acids; a type of peptide hormone.

Protein hormone

Hormone composed of many amino acids, e.g., insulin, growth hormone.

Glycoprotein hormone

Protein hormones with carbohydrate groups; examples: TSH, FSH, LH.

Steroid hormone

Lipid-derived hormones from cholesterol; includes testosterone, estrogen, progesterone, cortisol.

Lipid derivative

Hormone derived from lipids (e.g., calcitriol).

Lipid-soluble hormone

Steroid and thyroid hormones that diffuse through membranes and act intracellularly.

Water-soluble hormone

Peptide and catecholamine hormones that bind surface receptors and use second messengers.

Receptor-hormone complex

For lipid-soluble hormones, the complex forms after binding and can affect gene transcription.

G protein

Membrane protein that relays signals from receptors to enzymes like adenylyl cyclase.

Adenylyl cyclase

Enzyme that converts ATP to cyclic AMP (cAMP) in signal transduction.

cAMP

Secondary messenger that activates protein kinases to alter cell activity.

Negative feedback

Regulatory loop where the response decreases further hormone release.

Positive feedback

Regulatory loop where the response increases hormone release.

Antagonistic hormones

Hormones with opposite effects on a target (e.g., insulin vs glucagon).

Synergistic hormones

Hormones that produce a greater combined effect than separately.

Permissive effect

One hormone enables another to exert its full effect.

Hypothalamus

Brain region providing the highest level of endocrine control and integration with the nervous system.

Hypophyseal portal system

Capillary network linking hypothalamus to the anterior pituitary for releasing/inhibiting hormones.

Neurohypophysis

Posterior pituitary; stores and releases hypothalamic hormones (ADH, oxytocin).

Adenohypophysis

Anterior pituitary; secretes hormones under hypothalamic regulation (RH/IH).

ADH (vasopressin)

Antidiuretic hormone; increases water reabsorption in kidneys.

Oxytocin

Stimulates uterine contractions and milk ejection; also linked to bonding.

TSH

Thyroid-stimulating hormone; stimulates thyroid to release T3/T4.

ACTH

Adrenocorticotropic hormone; stimulates adrenal cortex to release steroids.

FSH

Follicle-stimulating hormone; promotes gamete production; with LH promotes estrogen.

LH

Luteinizing hormone; triggers ovulation and stimulates sex hormones.

Growth hormone (GH)

Promotes growth and protein synthesis; acts on bones and muscles.

Prolactin (PRL)

Stimulates mammary development and milk production.

MSH

Melanocyte-stimulating hormone; increases skin melanin; nonfunctional in adults.

Thyroid gland

Neck gland; produces T3/T4; regulated by TSH; contains follicles and colloid.

Follicle (thyroid)

Thyroid follicle lined by follicle cells surrounding colloid.

Thyroglobulin

Protein synthesized by follicle cells; combines with iodine to form thyroid hormones.

Calcitonin

Thyroid C cells hormone that lowers blood calcium.

Parathyroid hormone (PTH)

Raises blood calcium; antagonistic to calcitonin.

Adrenal cortex

Outer adrenal region; produces steroids (mineralocorticoids, glucocorticoids, androgens).

Mineralocorticoids

Steroids like aldosterone; regulate electrolyte balance.

Aldosterone

Increases Na+ reabsorption in kidneys; helps regulate blood pressure.

Glucocorticoids

Steroids like cortisol; regulate glucose metabolism and stress responses.

Adrenal medulla

Inner adrenal region; secretes catecholamines (epinephrine, norepinephrine).

Epinephrine

Adrenaline; raises blood glucose and prepares body for stress.

Norepinephrine

Noradrenaline; maintains blood pressure and contributes to fight-or-flight.

Pancreas

Organ with endocrine and exocrine functions; contains islets of Langerhans.

Islets of Langerhans

Endocrine cell clusters: alpha (glucagon), beta (insulin), delta (somatostatin), PP (pancreatic polypeptide).

Alpha cells

Produce glucagon to raise blood glucose.

Beta cells

Produce insulin to lower blood glucose.

Delta cells

Produce somatostatin to inhibit insulin and glucagon.

PP cells

Produce pancreatic polypeptide; inhibits gallbladder contraction.

Insulin

Lowers blood glucose by promoting uptake and storage as glycogen/fat.

Glucagon

Raises blood glucose by promoting glycogenolysis and gluconeogenesis.

Pineal gland

Gland in the epithalamus that produces melatonin and regulates circadian rhythms.

Gonads

Ovaries and testes; produce sex hormones and regulate secondary sex characteristics.

Estrogen

Female sex hormone; promotes female secondary characteristics.

Progesterone

Hormone preparing endometrium for implantation and maintaining pregnancy.

Testosterone

Male sex hormone; promotes male characteristics and sperm production.

Placenta

Temporary organ producing hCG to maintain pregnancy and support corpus luteum.

hCG (human chorionic gonadotropin)

Hormone that supports pregnancy by maintaining the corpus luteum.

ANP (atrial natriuretic peptide)

Heart hormone that promotes salt excretion and inhibits aldosterone.

BNP (brain natriuretic peptide)

Heart hormone with similar natriuretic effects as ANP.

EPO (erythropoietin)

Kidney hormone that stimulates red blood cell production.

Renin

Kidney enzyme that activates the angiotensin system to raise BP.

Angiotensin II

Hormone that constricts vessels and raises blood pressure.

FGF23

Bone-derived factor that regulates vitamin D and phosphate handling.

Osteocalcin

Bone-derived hormone that enhances insulin production and sensitivity.

Leptin

Adipose-derived hormone signaling satiety and energy balance.

Cholecalciferol

Vitamin D3 precursor produced by skin; inactive until activated later.

Thymosin

Thymus hormone essential for T lymphocyte development and immune function.

IGF (somatomedin)

Growth factor from liver that mediates growth, especially of bones.

Angiotensinogen

Liver-produced precursor to angiotensin; involved in BP regulation.

Thrombopoietin

Liver-produced hormone that stimulates platelet production.

Hepcidin

Regulates iron homeostasis by inhibiting iron release from cells.