Endocrine System and Hormones – Vocabulary Review

A comprehensive set of vocabulary flashcards covering major glands, hormones, and key concepts from the endocrine-system lecture notes.

Endocrine gland

A ductless gland that secretes hormones into the extracellular fluid for transport in the bloodstream.

Exocrine gland

A gland that releases its secretions into ducts leading to body surfaces or cavities.

Hormone

A chemical messenger released by endocrine glands that alters the activity of specific target cells or organs.

Homeostasis

The maintenance of a relatively constant internal environment despite external fluctuations.

Steroid hormone

A lipid-soluble hormone derived from cholesterol that diffuses through cell membranes to bind intracellular receptors.

Protein hormone

A water-soluble hormone composed of long chains of amino acids that binds to membrane receptors.

Amine hormone

A water-soluble hormone formed from a modified amino acid (e.g., adrenaline).

Lipid-soluble hormone

Hormone that can cross the phospholipid bilayer and activate receptors inside the cell (e.g., steroids).

Water-soluble hormone

Hormone that binds to receptors on the cell membrane and uses secondary messengers inside the cell.

Target cell

A cell that bears specific receptors and can be influenced by a particular hormone.

Target organ

An organ whose physiological activity is altered by a given hormone.

Hormone receptor

A specific protein that binds a particular hormone, initiating a cellular response.

Saturation (receptors)

Condition in which all available receptors are bound; additional hormone produces no further effect.

Secondary messenger

An intracellular signaling molecule activated by a hormone-receptor interaction on the membrane.

Enzyme amplification

Cascade process where one hormone molecule triggers production/activation of thousands of enzyme molecules.

Hormone clearance

Removal and breakdown of hormones (mainly in liver and kidneys) after they have exerted their effects.

Negative feedback

Regulatory mechanism where a hormone’s effects counteract the original stimulus that triggered its release.

Hypothalamus

Brain region linking nervous and endocrine systems; controls pituitary secretions and basic homeostatic functions.

Pituitary gland (Hypophysis)

Small endocrine gland beneath the brain; consists of anterior and posterior lobes influencing many other glands.

Infundibulum

Stalk connecting the hypothalamus to the pituitary gland, containing blood vessels and nerve fibres.

Anterior lobe (Adenohypophysis)

Front portion of pituitary that synthesizes and secretes its own hormones under hypothalamic control.

Posterior lobe (Neurohypophysis)

Rear portion of pituitary that stores and releases hormones produced in the hypothalamus.

Releasing factor

Hypothalamic hormone that stimulates secretion of a specific anterior pituitary hormone.

Inhibiting factor

Hypothalamic hormone that decreases secretion of a specific anterior pituitary hormone.

Follicle-stimulating hormone (FSH)

Anterior pituitary hormone that stimulates ovarian follicle growth and sperm production.

Luteinising hormone (LH)

Anterior pituitary hormone that triggers ovulation, corpus luteum formation, and testosterone secretion.

Growth hormone (GH)

Anterior pituitary hormone that promotes body growth and protein synthesis.

Thyroid-stimulating hormone (TSH)

Anterior pituitary hormone that stimulates thyroid gland to produce thyroid hormones.

Adrenocorticotropic hormone (ACTH)

Anterior pituitary hormone that stimulates adrenal cortex hormone release.

Prolactin (PRL)

Anterior pituitary hormone that initiates and maintains milk production in females.

Oxytocin (OT)

Posterior pituitary hormone that causes uterine contractions and milk ejection.

Antidiuretic hormone (ADH) / Vasopressin

Posterior pituitary hormone that promotes water reabsorption in kidneys and, at higher levels, vasoconstriction.

Pineal gland

Small brain gland that secretes melatonin and helps regulate sleep–wake cycles.

Melatonin

Pineal hormone whose secretion is stimulated by darkness and inhibited by light, influencing sleep patterns.

Thyroid gland

Neck gland producing thyroxine, triiodothyronine, and calcitonin to regulate metabolism and calcium levels.

Thyroxine (T4)

Less-active, longer-lasting thyroid hormone that increases metabolic rate; converted to T3 in tissues.

Triiodothyronine (T3)

More active thyroid hormone that raises metabolism and heat production.

Calcitonin

Thyroid hormone that lowers blood calcium and phosphate by inhibiting bone resorption and kidney reabsorption.

Parathyroid glands

Usually four small glands on thyroid’s posterior surface that secrete parathyroid hormone.

Parathyroid hormone (PTH)

Hormone that raises blood calcium and increases phosphate excretion.

Thymus

Chest gland that secretes thymosins and is essential for T-lymphocyte maturation.

Thymosins

Group of thymic hormones that stimulate development and maturation of T-lymphocytes.

Adrenal medulla

Inner region of adrenal gland that secretes adrenaline and noradrenaline for fight-or-flight responses.

Adrenaline (Epinephrine)

Adrenal medulla hormone that prepares body for emergency (fight-or-flight) situations.

Noradrenaline (Norepinephrine)

Adrenal medulla hormone similar to adrenaline; notably increases heart rate and force.

Adrenal cortex

Outer region of adrenal gland that produces corticosteroids such as aldosterone and cortisol.

Aldosterone

Adrenal cortical hormone that increases sodium reabsorption and potassium excretion by kidneys.

Cortisol

Adrenal cortical hormone that promotes normal metabolism and helps body withstand stress.

Pancreas

Mixed gland with exocrine digestive function and endocrine islets of Langerhans producing insulin and glucagon.

Islets of Langerhans

Clusters of pancreatic endocrine cells containing alpha and beta cells that secrete glucagon and insulin.

Insulin

Beta-cell pancreatic hormone that lowers blood glucose by enhancing cellular uptake and storage.

Glucagon

Alpha-cell pancreatic hormone that raises blood glucose by stimulating glycogen and fat breakdown.

Gonads

The testes and ovaries, producing gametes and sex hormones.

Androgens (e.g., Testosterone)

Male sex hormones that develop and maintain male characteristics and support sperm production.

Oestrogens

Female sex hormones that promote female characteristics and regulate menstrual cycle.

Progesterone

Ovarian hormone that prepares uterus for pregnancy and mammary glands for lactation.