Describe the interplay between kidney functions

• Na⁺ & H₂O Balance : Managed by transporters and channels in different nephron segments :

  • Proximal tubule : NHE & SGLT ( Na⁺ ) , Aquaporin ( H₂O )

  • Loop of Henle : NKCC ( Na⁺, ascending ) , AQP ( H₂O , descending )

  • Distal tubule : NCC , ENaC ( Na⁺ )

  • Collecting duct : ENaC ( Na⁺ ) , AQP ( H₂O )

• Blood Volume Regulation: Achieved by controlling H₂O reabsorption via Na⁺ handling.

• Blood Pressure Control: Interdependent with blood volume and sodium-water balance.

Define the general components of blood pressure regulation

• Setpoint : Target blood pressure

• Sensor : Baroreceptors ( acute ) , kidneys ( chronic )

• Signal

  • Acute : Sympathetic nervous system

  • Chronic : Hormonal signals ( e.g., RAAS )

• Effectors

  • Cardiovascular system ( heart , vessels )

  • Kidneys , adrenal glands , pituitary , hypothalamus

Define the renal-specific components of blood pressure regulation

• Setpoint : Renal perfusion pressure and [ NaCl ] at the macula densa

• Sensor : Juxtaglomerular ( JG ) apparatus :

  • Macula densa cells : Detect luminal NaCl

  • Granular cells : Detect perfusion pressure

• Signal : Renin secretion

• Effectors ( intra-renal ) :

  • Afferent arteriole ( vasoconstriction )

  • Distal tubule & collecting duct ( ↑ Na⁺ & H₂O reabsorption )

Describe the downstream effects of renin

1. Renin converts angiotensinogen → Angiotensin I ( Ang I )

2. ACE converts Ang I → Angiotensin II ( Ang II )

3. Angiotensin II effects :

   • Vasoconstriction of peripheral vasculature

   • ↑ Aldosterone from adrenal cortex ( → ↑ Na⁺/H₂O reabsorption )

   • ↑ ADH from pituitary ( → ↑ H₂O reabsorption )

   • Renal effects : Afferent arteriole constriction , ↑ Na⁺ & H₂O retention

List the targets of hypertensive drugs