Chapter 20 Outline Anatomy Review: Urinary system structure Kidney structure Nephron structure Renal corpuscle Filtration membrane Granular juxtaglomerular cells Macula densa Adrenal gland Hypothalamus Posterior pituitary Physiology terms to know before class: Filtration Reabsorption Secretion Excretion Osmolarity Baroreceptors Osmoreceptors Vasopressin / ADH Renin Angiotensinogen Angiotensin I ACE Angiotensin II Aldosterone Atrial natriuretic peptide pH Acidosis Alkalosis Hyperventilate Hypoventilate Compensation 1
Fluid & Electrolyte Homeostasis Maintenance of electrolytes Key electrolytes H + & HCO 3 - : pH Ca 2+ : hemostasis, muscle function, neurotransmitter release Na + : drives water balance, excitatory cell membrane potentials, 2 ⁰ active transport 630 g filtered/day 3.2 g excreted/day 99.5% reabsorbed Hypernatremia → plasma osmolarity increases H 2 O may will move out of cells, cells, including brain cells, may shrink Hyponatremia → plasma osmolarity is decreased, H 2 O will move into cells, cells, including brain cells, may swell K + : neuron function, excitatory cell membrane potentials Hypokalemia → resting membrane potential becomes more negative Hyperkalemia → resting membrane potential becomes less negative Initially easy to depolarize but can’t repolarize and are less excitable Cl - : water balance associated with exocrine gland secretions, respiratory watery saline layer HPO 4 -2 : involved in pH balance Maintenance of cell volume Requires regulation of ECF Osmolarity Water follows solutes ↑ ECF [solutes] → ↑ ECF osmolarity → ↓ cell volume or ↓ ECF [solutes] → ↓ ECF osmolarity → ↑ cell volume ∆ cell volume can impact cell function Brain: cells shrink - dehydration headaches, confusion, unconsciousness Brain: cells swell - ↑ volume & pressure in cranium, decreased blood flow Some cells can maintain cell volume by adjusting their ICF [solutes] Nephron tubule cells in hyperosmotic medulla Some cells use changes in cell volume as a signal Liver cells modify glycogen production and glycogenolysis based on cell swelling or shrinking, respectively Integration of systems Heart and lungs – neural control, give fast responses Renal system – endocrine & neuroendocrine control, slower but longer term responses Example: blood volume & pressure 2
Water Balance Mass balance: water intake = water excretion Intake: drinking, food, metabolism of food Excretion: urine, feces, sweat, exhalation, skin evaporation Regulated water loss: urine, sweat , feces Insensible water loss: exhalation, skin evaporation Kidneys Excretion of water when in excess: dilute urine produced Diuresis: production of hyposmotic urine → removal of excess water Reabsorption of water when limited: concentrated urine produced Production of hyperosmotic urine → reabsorption & conservation of water 180 L filtered/day 1.8 L excreted per day 99% reabsorbed Osmolarity of the renal interstitium & glomerular filtrate Interstitium Renal cortex Renal medulla Nephron tubules Proximal Descending limb
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