Endocrine System: Parathyroid and Calcium Homeostasis; Adrenal Glands

Vocabulary flashcards covering the parathyroid glands, PTH, calcitriol, calcitonin, calcium physiology, and adrenal gland anatomy and hormones.

Parathyroid glands

Glands on the posterior surface of the thyroid; usually four; secrete parathyroid hormone (PTH).

Parathyroid hormone (PTH)

Hormone that raises plasma Ca2+ by three actions: stimulate calcitriol production, mobilize Ca2+ from bone, and enhance renal Ca2+ reabsorption (indirectly increasing intestinal Ca2+ absorption).

Ca2+-sensing receptor

Receptor that monitors plasma Ca2+ levels and triggers PTH release when Ca2+ falls.

Calcitriol (1,25-dihydroxycholecalciferol; vitamin D3)

Primary hormone that enhances Ca2+ uptake; promotes renal Ca2+ reabsorption; helps mobilize Ca2+ from bone; production regulated by PTH.

Calcitonin

Hormone released when plasma Ca2+ increases; decreases bone resorption.

Calcium (Ca2+)

Mineral with roles in bone/teeth matrix, extracellular fluid functions (neurotransmitter release, heart and smooth muscle contraction, blood coagulation, tight junction maintenance, neuronal excitability), and intracellular signaling (muscle contraction and second messengers).

Extracellular matrix

Calcified matrix of bone and teeth.

Extracellular Ca2+ functions

Supports neurotransmitter release, myocardial and smooth muscle contraction, acts as a cofactor in coagulation, helps cement tight junctions, and influences neuronal excitability.

Intracellular Ca2+

Ca2+ inside cells; drives muscle contraction and serves as a signal in second messenger pathways.

Adrenal glands

Glands located atop the kidneys; composed of an outer cortex and inner medulla.

Adrenal medulla

Inner region of the adrenal gland; hormones include epinephrine and norepinephrine (part of the sympathetic response).

Adrenal cortex

Outer region of the adrenal gland; secretes corticosteroids (mineralocorticoids and glucocorticoids) and androgens.

Epinephrine

Hormone produced by the adrenal medulla; part of the fight-or-flight response (sympathetic activation).

Norepinephrine

Hormone produced by the adrenal medulla; works with epinephrine in the fight-or-flight response.