Renal Hormonal Regulation Lecture

Vocabulary flashcards covering hormones and renal physiology terms from the lecture, suitable for exam review.

Renin–Angiotensin–Aldosterone System (RAAS)

Hormonal cascade activated by low blood pressure/volume that raises blood pressure by increasing Na⁺ and water reabsorption through renin, angiotensin II, and aldosterone.

Angiotensin II

Active peptide formed by ACE; constricts the afferent arteriole, up-regulates Na⁺/H⁺ antiport in the PCT, and stimulates aldosterone release, thereby increasing blood volume and pressure.

Aldosterone

Mineralocorticoid from the adrenal cortex; enhances Na⁺ reabsorption and K⁺ secretion in principal cells of the collecting duct, leading to obligatory water reabsorption.

Antidiuretic Hormone (ADH, Vasopressin)

Posterior pituitary hormone released when plasma osmolarity rises or severe hypovolemia occurs; inserts aquaporins in late DCT/collecting-duct principal cells to promote facultative water reabsorption.

Atrial Natriuretic Peptide (ANP)

Hormone released from atrial myocardium when blood volume is high; inhibits aldosterone and ADH, reduces Na⁺ and water reabsorption, increases urine output, and lowers blood pressure.

Parathyroid Hormone (PTH)

Released by parathyroid glands when blood Ca²⁺ is low; increases Ca²⁺ reabsorption in the early distal convoluted tubule and decreases phosphate reabsorption in the PCT.

Juxtaglomerular Cells

Specialized smooth-muscle cells in the afferent arteriole that detect reduced stretch and secrete renin.

Afferent Arteriole

Vessel bringing blood to the glomerulus; its constriction by angiotensin II lowers GFR.

Renin

Kidney enzyme that converts angiotensinogen to angiotensin I, initiating the RAAS pathway.

Angiotensinogen

Liver-produced plasma protein that is the substrate for renin and precursor to angiotensin I/II.

Angiotensin-Converting Enzyme (ACE)

Enzyme in lung endothelium that converts angiotensin I to angiotensin II.

Proximal Convoluted Tubule (PCT)

First nephron segment where most Na⁺ and obligatory water reabsorption occurs; stimulated by angiotensin II via the Na⁺/H⁺ antiporter.

Sodium–Hydrogen Ion Antiporter

Membrane exchanger in the PCT that reabsorbs Na⁺ in exchange for H⁺; activity is increased by angiotensin II.

Obligatory Water Reabsorption

Water movement that passively follows solute (mainly Na⁺) reabsorption, especially in the PCT; not hormone-regulated.

Principal Cells

Cells of the late DCT and collecting duct that respond to aldosterone and ADH to regulate Na⁺, K⁺, and water balance.

Collecting Duct

Final nephron segment where aldosterone, ADH, and ANP fine-tune Na⁺, K⁺, and water handling before urine exits the kidney.

Facultative Water Reabsorption

Hormone-controlled water reabsorption (primarily via ADH) that adjusts urine concentration based on hydration status.

Aquaporins

Water channels inserted into principal-cell apical membranes by ADH, allowing rapid bulk flow of water.

Osmoreceptors

Hypothalamic neurons that sense small (≈1 %) increases in plasma osmolarity and trigger ADH release.

Diabetes Insipidus

Condition of absent or ineffective ADH action, causing excretion of up to ~20 L/day of very dilute urine.

Hypovolemia

Abnormally low blood volume; severe cases stimulate ADH secretion.

Baroreceptors

Stretch receptors in atrial walls that detect increased volume and promote ANP release.

Suprarenal (Adrenal) Gland

Endocrine gland atop each kidney; its zona glomerulosa secretes aldosterone in response to angiotensin II.

Glomerular Filtration Rate (GFR)

Rate at which plasma is filtered through glomeruli; decreased when angiotensin II constricts the afferent arteriole.

Extracellular Fluid Osmolarity

Solute concentration of plasma and interstitial fluid; a rise is the principal trigger for ADH release.

Sodium–Potassium Pump (Na⁺/K⁺-ATPase)

Basolateral transporter in principal cells whose activity is enhanced by aldosterone, facilitating Na⁺ reabsorption and K⁺ secretion.

Early Distal Convoluted Tubule (DCT)

Nephron segment where PTH increases Ca²⁺ reabsorption.

Vasa Recta

Capillary network surrounding nephron loops and collecting ducts; receives water reabsorbed through aquaporins.

Natriuresis

Excretion of sodium in urine; promoted by ANP.