Water Balance, pH, and Blood Pressure PDF

The Kidney: Regulator of Water, pH, and Blood Pressure  Recall: The Kidney Main functions: Filtering blood (Yesterday’s lesson) Maintaining water balance Regulating pH Controlling blood pressure Composed of over 1 mi...

The Kidney: Regulator of Water, pH, and Blood Pressure  Recall: The Kidney Main functions: Filtering blood (Yesterday’s lesson) Maintaining water balance Regulating pH Controlling blood pressure Composed of over 1 million nephrons (functional units)  Introduction to Osmotic Pressure Osmotic pressure is the force required to prevent water movement across a semipermeable membrane. It's driven by differences in solute concentration between two solutions. The greater the water concentration, the greater the osmotic pressure difference between the two sides. Importance: Crucial for understanding cellular processes and bodily functions.  Osmoregulation in the Human Body The active regulation of osmotic pressure in bodily fluids. Regulation of water and solute concentrations in the body Purpose: Maintains proper fluid balance and cellular function. Key organs involved: Kidneys Hypothalamus Pituitary gland Hormones: Antidiuretic hormone (ADH) Aldosterone Processes: Water reabsorption Ion regulation Urine concentration  Osmotic Challenges and Adaptations Hypotonic environments: Challenge: Cell swelling Adaptation: Contractile vacuoles (in some organisms) Hypertonic environments: Challenge: Cell shrinkage Adaptation: Accumulation of organic solutes Human examples: Sweating and dehydration Consuming salty foods Altitude changes Importance of maintaining osmotic balance for: Nerve function Muscle contraction Nutrient transport  Osmoregulation: Basics Regulation of water and solute concentrations in the body Importance: Maintain cellular function Prevent dehydration or over-hydration Role of kidneys: Fine-tune water balance through urine production  Osmoregulation: Antidiuretic Hormone (ADH) Also known as vasopressin Released by the posterior pituitary gland Function: Increases water reabsorption in the kidneys Regulated by: Blood osmotic pressure Blood volume If blood volume is lower and more concentrated osmotic pressure is high. This stimulates the release of ADH which stimulates the kidneys to increase reabsorption  Maintaining Water Balance Kidneys adjust urine concentration based on body's needs Mechanisms: ADH-mediated water reabsorption Selective permeability of collecting ducts Result: Homeostasis of body water content  pH Regulation: Acid-Base Balance Normal blood pH range: 7.35-7.45 Kidneys work with lungs to maintain pH balance Kidney's role: Excrete excess H+ ions Reabsorb or produce bicarbonate (HCO3-)  pH Regulation: Buffering Systems Bicarbonate buffer system: H+ + HCO3- ⇌ H2CO3 ⇌ CO2 + H2O Phosphate buffer system Protein buffer system Kidneys regulate these systems to maintain pH  pH Regulation: Renal Mechanisms Secretion of H+ ions into urine Reabsorption of filtered bicarbonate Production of new bicarbonate Excretion of titratable acids (e.g., phosphates)  Blood Pressure Regulation: Renin-Angiotensin-Aldosterone System (RAAS) Complex hormone system that regulates blood pressure Key components: Renin (produced by kidneys) Angiotensinogen (produced by liver) Angiotensin I and II Aldosterone (produced by adrenal glands)  Blood Pressure Regulation: RAAS Mechanism Low blood pressure detected Kidneys release renin Renin converts angiotensinogen to angiotensin I Angiotensin I converted to angiotensin II Angiotensin II: Constricts blood vessels Stimulates aldosterone release Aldosterone increases sodium and water retention  Blood Pressure Regulation: Other Mechanisms Atrial natriuretic peptide (ANP): Released by heart atria Promotes sodium and water excretion Antidiuretic hormone (ADH): Increases water retention Constricts blood vessels