Kidneys Role in Homeostasis

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Kidneys Role in Homeostasis par Mind Map: Kidneys Role in Homeostasis

1. Regulation of Blood Ionic Composition

1.1. help regulate blood levels of ions such as: sodium, potassium, calcium, chloride, phosphate

1.1.1. Sodium Na+: 135 - 145 major solute in extracellular fluids that determines the osmolarity of extracellular fluids Antidiuretic Hormone (ADH) Atrial Natriuretic Peptide (ANP)

1.1.2. Potassium K+: 3.5-5.0 mEq/L important for maintaining membrane potential of nerves and muscles Alderstone

1.1.3. Calcium Ca+: 4.5-5.5 mEq/L important for bone density, blood clotting, neurotransmitter release, maintenance of muscle tone, and excitability of nervous and muscle tissue Parathyroid Hormone (PTH)

1.1.4. Magnesium Mg+: 1.3 - 2.1 mEq/L - important for normal neuromuscular activity, synaptic transmission and myocardial functioning - secretion of PTH depends on Mg+ - Kidneys excrete magnesium in response to hypercalcemia - Kidneys reabsorb magnesium in response to hypocalcemia

1.1.5. Phosphate Phosphate: 1.7 - 2.6 mEq/L - important intracellular ions - an importnat buffer of H+ in body fluids snd urine - structural components of bone and teeth PTH inhibits reabsorption of phosphate while stimulating reabsorption of calcium by renal tubular cells

1.1.6. Chloride Cl: 95 - 105 mEq/L - most prevalent ion in ECF - governs the extent of water loss in urine ADH helps regulate chloride balance in body fluids

2. Regulation of Blood Volume

2.1. adjust blood volume by conserving or eliminating water in urine

2.1.1. Increase of blood volume = increase in blood pressure

2.1.2. Decrease of blood volume = decrease in blood pressure

3. Regulation of Blood pH through Acid-Base Balance

3.1. pH: 7.35 - 7.45

3.2. Protein Buffer System

3.2.1. - most abundant buffer system in intracellular fluid - proteins are composed of amino acids, organic molecules that contain at least one carboxyl group (-COOH) and one amino group (-NH2) carboxyl releases H+ which then reacts with any OH- to form water free amino group will act as a base by combining with H+

3.3. Carbonic Acid - Bicarbonate Buffer System

3.3.1. excrete hydrogen ions into the urine and conserve bicarbonate ions - Bicarbonate ion (HCO3-) can act as a weak base - Carbonic Acid (H2CO3) can act as weak acid H+ + HCO3- --> H2CO3 (Carbonic Acid) --> dissociates to water and carbon dioxide. CO2 is then released by the lungs H2CO3 --> H+ + HCO3-

3.4. Phosphate Buffer System

3.4.1. - composed of H2PO4 (dihydrogen phosphate ion) and HPO42- (mono hydrogen phosphate) - phosphate are major anions in intracellular fluid and minor ones in ECF - Dihydreogen phosphate ion acts as a weak acid and is capable of buffering strong bases - Monohydrogen phosphate ion is capable of buffering the H+ released by strong acids by acting as a weak base OH- + H2PO4 --> H2O + HPO42- H+ + HPO42- --> H2PO4 -

4. Regulation of Blood Pressure

4.1. Hypertension: activates ANP

4.1.1. Increased ANP = decreasing blood pressure - peripheral vasodilation - dieresis (increase in urine output) - natriuresis (increase in excretion of Na+ in urine)

4.2. Hypotension: secrete enzyme renin, which activates the renin-angiotensin-aldoesterone pathway and releases ADH

4.2.1. Increased renin = increased blood pressure - peripheral vasoconstriction - decreased urine formation - increased cardiac output - increased tubular water reabsorption - increased blood volume

5. Maintenance of Blood Osmolarity

5.1. separately regulates loss of water and loss of solutes in the urine

5.1.1. Blood Osmolarity: 285 mOsm/liter - Sodium is the main ion that keeps the body at a constant osmotic level - Increase in Na+ in ECF can lead to hypertension and oedema - Decrease in Na+ in ECF can lead to hypotension and dehydration when osmolarity is low, ADH is suppressed when osmolarity is high, ADH is released so kidneys can resorb water

5.1.2. clear urine, no unpleasant odour

6. Production of Hormones

6.1. Aldosterone

6.1.1. released by the adrenal cortex with the activation of the renin-angiotensin-aldosterone system that stimulates the collecting ducts to reabsorb more Na+ and Cl- and secrete more K+

6.2. Antidiuretic Hormone (ADH)

6.2.1. is a vasopressin. Released by the posterior pituitary, it regulates water reabsorption by increasing water permeability of principal cells in the last part of the distal convoluted tubule an throughout the collecting duct it is stimulated by an increase of osmotic pressure of plasma and interstitial fluid and decrease in blood volume

6.3. Atrial Natriuretic Peptide (ANP)

6.3.1. - it inhibits reabsorption of Na+ and water in the proximal convoluted tubule and collecting duct - suppresses secretion of Aldosterone and ADH stimulated by the stretching of the atria cells in the heart

6.4. Parathyroid Hormone (PTH)

6.4.1. released by the parathyroid glands. Stimulates cells in the early distal convoluted tubules to absorb more Ca+ - Inhibits phosphate reabsorption in proximal convoluted tubules which promotes phosphate excretion stimulated by Hypocalcemia

6.5. Calcitriol

6.5.1. Calcitriol - activates Vitamin D, which regulates calcium homeostasis

6.6. Erythropoietin

6.6.1. - created by erythropoietin producing cells of the kidney - maintain normal red blood cell count and precent anemia stimulated by hypoxia

7. Regulation of Blood Glucose

7.1. Gluconeogenesis

7.1.1. - release glucose into the blood to help maintain normal blood glucose surpassed by insulin activated by catecholamines

7.2. Glucose Uptake

7.2.1. - uptake glucose from circulation to satisfy energy needs

7.3. Glucose Reabsorption

7.3.1. - tubular reabsorption of glucose by facilitated diffusion in proximal tubule -importnat in events of hyperglycaemia

7.4. Blood Glucose: 4.0 to 7.0 mmol/L

8. Excretion of Wastes and Foreign Substances

8.1. collected in the collecting tubule and excreted through the urinary bladder

8.1.1. Excess ions: sodium, potassium, calcium, magnesium, chloride, bicarbonate, phosphate and ammonium

8.1.2. Metabolic wastes: urea, creatine, uric acid, nitrogenous waste

8.1.3. Drug Metabolites: most pharmacological agents are detoxified in liver and then excreted through the kidney

9. References

9.1. Counts, S. (Ed.). (2015). Core curriculum for nephrology nursing (6th ed.). Pitman, NJ: American Nephrology Nurses Association. Thomas, N. (Ed.). (2014). Renal nursing (4th ed.). Hoboken, NJ: Wiley Blackwell. Tortora, G. & Derrickson, B. (2012). Principles of Anatomy & Physiology (13th ed.). Danvers, MA: John Wiley & Sons, Inc.