Flashcards: Volume regulation: Blood pressure and the kidneys (Physiology)

❀ Extracellular fluid volume is sensed through changes in renal sodium and water excretion.

❀ Sensor: Atrial stretch receptors, arterial baroreceptors, afferent arteriole NaCl delivery to the distal tubule (DT).

❀ Effector: Renin-angiotensin-aldosterone system (RAAS) for sodium retention, atrial natriuretic peptide (ANP) for sodium excretion.

❀ The body maintains balance between intake and output of sodium in the extracellular fluid by ensuring that intake is approximately equal to output.

❀ Atrial stretch receptors, arterial baroreceptors, and afferent arteriole NaCl delivery to the distal tubule (DT) are involved in sensing changes in ECF volume.

❀ The renin-angiotensin-aldosterone system (RAAS) retains sodium, while atrial natriuretic peptide (ANP) promotes sodium excretion.

RAAS is activated by:

❀ Reduced renal perfusion

❀ Increased sympathetic activity Both are interpreted as a fall in blood volume.

Aldosterone secretion is increased by:

❀ Activation of RAAS

❀ Increased plasma potassium ([K+]) levels.

❀ Most of the filtered salt and water is reabsorbed in the proximal tubule (PT), with this fraction increasing with Renin-Angiotensin-Aldosterone System (RAAS) activity.

❀ A much smaller, variable fraction is reabsorbed from the distal tubule (DT) and collecting duct (CD).

❀ Reabsorption of sodium and solute-free water are separated processes.

❀ Aldosterone-mediated sodium reabsorption increases plasma osmolarity, which is then adjusted by pure water reabsorption via the Antidiuretic Hormone (ADH) system.

❀ The result is increased sodium and water in extracellular fluid (ECF) with little or no change in plasma sodium concentration or osmolarity.

Aldosterone acts on principal cells lining the collecting duct by:

❀ Increasing Na/K ATPase activity.

❀ Increasing expression of ENaC channels on the luminal membrane.

This results in increased sodium reabsorption and increased potassium secretion.

Aldosterone acts on intercalated cells of the collecting duct by:

❀ Increasing H+ ATPase activity.

This results in increased hydrogen ion secretion and increased bicarbonate reabsorption.

❀ Principal cells are specialized cells lining the renal tubules, particularly the collecting ducts, involved in electrolyte transport, particularly sodium and potassium.

❀ Intercalated cells are specialized cells found in the renal tubules, particularly the collecting ducts, involved in acid-base regulation by secreting hydrogen ions (H+) and reabsorbing bicarbonate ions (HCO3-).

❀ ENaC stands for Epithelial Sodium Channel.

Conn's syndrome is:

❀ Primary hyperaldosteronism.

Conn's syndrome is often due to:

❀ Adenoma (tumour) of the adrenal cortex.

Liddle's syndrome is characterized by:

❀ A rare, genetic gain-of-function mutation in the epithelial sodium channel (ENaC).

Liddle's syndrome leads to:

❀ Increased renal sodium retention.

❀ Increased extracellular fluid volume (ECFV).

❀ Increased blood pressure (BP).

Liddle's syndrome is associated with:

❀ Low renin levels.

❀ Low aldosterone levels.

Renal artery stenosis is characterized by:

❀ Abnormal narrowing of the blood vessel supplying the kidney.

Renal artery stenosis leads to:

❀ Reduced blood flow to the stenotic kidney.

Renal artery stenosis results in:

❀ Increased renin production.

Addison's disease and adrenal failure involve:

❀ Progressive failure of the adrenal cortex, resulting in insufficient production of cortisol and aldosterone.