Endocrine System and Hormones Vocabulary Flashcards

Vocabulary flashcards covering key endocrine terminology, gland structures, mechanisms of hormone action, and secreted hormones based on the lecture notes.

Exocrine glands

Glands that secrete into a duct that carries the secretion to the body surface or to one of the body cavities, such as sweat glands, mucous glands, salivary glands, and glands of the alimentary canal.

Endocrine glands

Ductless glands that secrete hormones into the surrounding extracellular fluid, which then usually pass into capillaries to be transported by the blood.

Hormones

Chemicals secreted by endocrine glands and transported in the blood that change cell functioning by altering the type, activities, or quantities of proteins produced.

Target cells

Particular groups of cells that possess the specific receptors required to bind and be influenced by a given hormone.

Target organs

Particular organs containing cells with the correct receptors for a specific hormone.

Steroid hormones

Lipid-soluble hormones (such as oestrogen, progesterone, cortisol, and aldosterone) that bind to transport proteins in blood and diffuse across cell membranes to combine with receptor proteins in the cytoplasm or nucleus.

Protein and amine hormones

Water-soluble, non-lipid-soluble hormones that attach to receptor proteins in the target cell membrane, triggering a secondary messenger substance inside the cell.

Enzyme amplification

A cascading process where a single hormone molecule triggers a multi-step pathway, increasing reacting molecules at each step and resulting in the activation or manufacture of thousands to billions of enzyme molecules.

Hormone clearance

The process of shutting off hormone action by breaking down hormone molecules in target cells, liver, or kidneys, followed by excretion in bile or urine.

Hypothalamus

An almond-sized structure at the base of the brain below the thalamus that connects the nervous and endocrine systems and regulates basic functions like body temperature, water balance, and heart rate.

Releasing factors

Factors secreted by the hypothalamus that travel through blood vessels to the anterior pituitary lobe to stimulate hormone secretion.

Inhibiting factors

Factors secreted by the hypothalamus that travel through blood vessels to the anterior pituitary lobe to slow down hormone secretion.

Pituitary gland (Hypophysis)

A vital gland located under the hypothalamus, measuring about $13\,\text{mm}$ in diameter, joined to the hypothalamus by the infundibulum and consisting of an anterior and posterior lobe.

Infundibulum

The stalk joining the pituitary gland to the hypothalamus, containing blood vessels supplying the anterior lobe and nerve fibres extending to the posterior lobe.

Gonadotropins

Hormones released by the anterior pituitary gland that affect the gonads, specifically ovaries and testes; includes FSH and LH.

Follicle-stimulating hormone (FSH)

An anterior pituitary hormone that stimulates follicle development in female ovaries and sperm production and maturation in male testes.

Luteinising hormone (LH)

An anterior pituitary hormone that works with FSH to induce ovulation and form the corpus luteum in females, and stimulates interstitial cells in male testes to secrete male sex hormones.

Growth hormone (GH / Somatotropin)

An anterior pituitary hormone that stimulates body growth (especially the skeleton) by increasing cellular uptake of amino acids and protein synthesis.

Thyroid-stimulating hormone (TSH / Thyrotropin)

An anterior pituitary hormone that stimulates the production and release of hormones from the thyroid gland.

Adrenocorticotropic hormone (ACTH / Adrenocorticotropin)

An anterior pituitary hormone that controls the production and release of hormones from the adrenal cortex.

Prolactin (PRL / Lactogenic hormone)

An anterior pituitary hormone that works with other hormones to initiate and maintain milk production in females.

Posterior lobe of the pituitary gland (Neurohypophysis)

The rear lobe of the pituitary gland that stores and releases oxytocin and antidiuretic hormone produced in special nerve cells of the hypothalamus.

Oxytocin (OT)

A hormone produced in the hypothalamus and released by the posterior pituitary that stimulates uterine contractions during labour and milk release from mammary glands during breastfeeding.

Antidiuretic hormone (ADH / Vasopressin)

A hormone produced in the hypothalamus and released by the posterior pituitary that causes kidneys to return water from forming urine to the blood, retaining body fluid.

Pineal gland

A small gland found deep inside the brain that decreases in size after puberty and secretes melatonin to regulate sleep patterns.

Melatonin

A hormone secreted by the pineal gland that regulates sleep patterns; its production is stimulated by darkness and inhibited by light.

Thyroid gland

A two-lobed gland located in the neck below the larynx that secretes thyroxine ($\text{T}_4$), triiodothyronine ($\text{T}_3$), and calcitonin.

Thyroxine ($\text{T}_4$)

A thyroid hormone based on two tyrosine molecules with four attached iodine atoms; accounts for approximately $80\%$ of thyroid hormone production, is less active than triiodothyronine, and controls body metabolism.

Triiodothyronine ($\text{T}_3$)

A highly active thyroid hormone based on two tyrosine molecules with three attached iodine atoms, accounting for approximately $20\%$ of thyroid hormone production.

Calcitonin

A hormone secreted by C-cells in the thyroid gland that lowers blood calcium and phosphate concentrations by reducing kidney reabsorption and bone breakdown.

Parathyroid glands

Usually four small, pea-sized glands located on the rear surface of the thyroid lobes that secrete parathyroid hormone.

Parathyroid hormone (PTH / Parathormone)

A hormone secreted by the parathyroid glands that increases calcium levels in the blood and promotes phosphate excretion in the urine.

Thymus

A chest gland located above the heart and behind the sternum that secretes thymosins and shrinks after puberty.

Thymosins

A group of hormones secreted by the thymus that influence the maturation of disease-fighting cells called T-lymphocytes.

Adrenal glands

A pair of endocrine glands located above each kidney, each consisting of an inner adrenal medulla and an outer adrenal cortex with distinct functions and structures.