48_lol_urinary.docx Bio 48 – Human Physiology Biology 48 - Human Physiology Lecture Summary Sheet - Norris Renal Physiology I. Definitions A. Interstitial Fluid B. Plasma C. Urine (waste) II. General Overview III. Physiology A. Body Fluids B. Composition C. Regulation of Water Balance 1. Intake 2. Loss 3. Regulatory Mechanisms a. Intake (via Thirst) b. Loss (via Renal Regulation) IV. Regional Physiology of the Nephron A. Renal Corpuscle 1. Glomerular Filtration a. Renal Clearance (percentage of plasma content that is removed from plasma) renal clearance (ml/min) = urine concentration (mg/ml) x urine flow (ml/min) b. Glomerular Filtration Rate (GFR) c. Renal Blood Flow B. Proximal Convoluted Tubule (PCT) 1. Active Reabsorption a. Transport Maximum b. Renal Threshold 2. Passive Reabsorption 3. Secretion plasma concentration (mg/ml)48_lol_urinary.docx Bio 48 – Human Physiology C. Loop of Henle - Descending Limb D. Loop of Henle - Ascending Limb 1. Thin Segment 2. Thick Segment 3. Counter-Current Multiplier a. Loop of Henle b. Vasa Recta E. Distal Convoluted Tubule (DCT) F. Collecting Duct V. Acid-Base Balance A. Buffers B. Respiratory C. Renal Conservation of HCO3- D. Renal Secretion of H+ VI. Renal Regulation A. Intrinsic (autoregulation) B. Extrinsic (see flow chart) 1. Autonomic Innervation 2. Antidiuretic Hormone (ADH, aka vasopressin) a. Hypothalamic Osmoreceptors b. Posterior Pituitary 3. Aldosterone (renin-angiotensin-aldosterone system) a. Juxtaglomerular Apparatus - Juxtaglomerular Cells (afferent arteriole) - Macula Densa Cells (DCT) 4. Atrial Natriuretic Factor VII. Additional Key Terms / Topics (FYI) acidosis alkalosis colloid osmotic pressure excretion fenestrated filtration micturition natriuresis oncotic pressure osmolarity peritubular fluid podocytes primitive urine reabsorption secretion transport maximum (Tm) vasa recta48_lol_urinary.docx Bio 48 – Human Physiology A. Renal Corpuscle. The glomerulus within the renal corpuscle is the site of filtration. About 1000 ml of blood passes through the glomeruli each minute, of this 125 ml enters Bowman's capsule (called filtrate). Filtration is strictly a mechanical process as blood is filtered through minute pores formed by the fenestrated glomerular capillaries and podocytes of Bowman's capsule. The rate of filtration is influenced by hydrostatic and osmotic pressure differentials between the glomerular capillaries and Bowman's capsule. Hydrostatic pressure is regulated in part by changes in the diameter of the afferent and efferent arterioles. B. Proximal Convoluted Tubule (PCT). Filtrate entering the PCT has about the same osmolarity as plasma but does not contain any large proteins. As much as 80% of the filtrate will be reabsorbed within the PCT. Nearly all nutrients, such as glucose & amino acids are actively reabsorbed. Sodium (Na+) is also actively reabsorbed while chloride (Cl-) and water follow passively. Hydrogen ions (H+) are actively secreted and bicarbonate (HCO3-) is reabsorbed. C. Descending Loop of Henle. The descending limb is impermeable to salt but is freely permeable to water which diffuses out as the tubule descends into an increasingly hypertonic interstitial fluid of the medulla. Consequently the filtrate becomes concentrated within the descending limb. D. Ascend Loop of Henle. The ascending limb is impermeable to water but salts (Na+ & Cl-) are actively reabsorbed contributing to the hypertonicity of the interstitial fluid. The filtrate becomes more dilute as salt is removed but waste molecules remain concentrated within the filtrate. E. Distal Convoluted Tubule (DCT). The DCT is essentially impermeable to water except when aldosterone is present. Under the influence of aldosterone Na+ is reabsorbed and K+ is secreted (water follows Na+ passively). F. Collecting Duct. In the absence of ADH the collecting duct is impermeable to water. In the presence of ADH the collecting duct becomes permeable to water and water is reabsorbed by osmosis as the tubule descends into the increasingly hypertonic interstitial fluid of the medulla.48_lol_urinary.docx Bio 48 – Human Physiology !ANTIDIURETIC HORMONE (ADH) and ATRIAL NATURIETIC HORMONE (stimulatory pathway for ADH, stimulatory pathway for ANH) Volume Osmolarity Volume Baroreceptors Osmoreceptors (hypothalamus) Atia Pressure Diuresis Atrial Naturietic GFR Thirst Hormone (ANH) POSTERIOR PITUITARY ADRENAL CORTEX Antidiuretic Hormone (ADH) (aka vasopressin) RENIN-ANGIOTENSIN-ALDOSTERONE SYSTEM (stimulatory pathway for aldosterone) Plasma Sodium [Na+] Volume Filtrate [Na+] (also decreased filtrate flow) Sympathetic ß adrenergic Macula Densa (DCT) Juxtaglomerular (JG) Cells Renin (enzyme) Angiotensinogen Angiotensin I ACE (angiotensin converting enzyme) Posterior Pituitary Angiotensin II Vasoconstriction Anti-Diuretic Hormone (ADH) ADRENAL CORTEX Plasma Potassium [K] Aldosterone alpha adrenergic constricts afferent arterioles = i GFR Increases permeability of collecting ducts to water (increases water reabsorption) Results in increased blood pressure Aldosterone increases sodium reabsorption (and water) in exchange for potassium and hydrogen ions in the distal convoluted tubules and collecting ducts. ANH decreases sodium (and water) reabsorption from the collecting ducts via inhibition of aldosterone and ADH secretion ADH increases water reabsorption by increasing the permeability of the collecting ducts to water (through addition of water pores) !48_lol_urinary.docx Bio 48 – Human Physiology Study Questions – Renal Physiology: 1. Define “interstitial fluid,” “plasma,” and “urine”. 2. Describe the fluid inputs and outputs associated with the kidneys. 3. Describe the distribution and composition of fluids in the body and the associations between each “compartment”. 4. Describe the different routes of water intake and water loss. 5. Describe the regulatory mechanisms regulating water intake. 6. Describe the anatomical association between the renal blood vessels and the renal tubules (nephron). 7. Name and