KIDNEY'S ROLE IN HOMEOSTASIS

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KIDNEY'S ROLE IN HOMEOSTASIS por Mind Map: KIDNEY'S ROLE IN HOMEOSTASIS

1. ACID/BASE BALANCE

1.1. Acid/base homeostasis and pH regulation are vital in proper physiological functioning of the body. This requires a balance between the concentrations of acids and bases in the blood. PH measures Hydrogen ions (H+) in the body's fluids. The pH scale measures how acidic or basic a substance is, and can ranges from 0-14. A pH of 7 is neutral. A pH <7 is acidic. A pH > 7 is basic.

1.1.1. The Kidney's mechanisms for regulating acid/base balance are bicarbonate (HCO3-) reabsorption, H+ secretion. Acids dissociate into H+ to lower pH, while bases dissociate into OH- to raise pH. Buffers can absorb these excess ions to maintain pH. These processes mainly occur in the Proximal Tubule, Distal Tubule and collecting ducts

1.1.1.1. Increased pH in the body (alkalosis) is due to heavy loss of acid in the body or by increased levels of bicarbonate.

1.1.1.1.1. Common causes include: vomiting, gastric suctioning, hypokalemia, hypercalcemia

1.1.1.1.2. Signs and symptoms: dizziness, dysrhythmias, numbness and tingling of fingers and toes.

1.1.1.2. Decreased pH in the body (acidosis) Acidosis occurs when the blood is too acidic due to too little bicarbonate

1.1.1.2.1. Acidosis has several symptoms, including headache and confusion, individual can become lethargic and easily fatigued

1.1.1.2.2. Common causes include:starvation, diabetic keto acidosis, renal failure, use of drugs

1.1.1.3. Buffers:

1.1.2. pH scale

2. BLOOD PRESSURE CONTROL

2.1. In low blood pressure

2.2. When blood pressure is low the kidneys , cells in the Juxtaglomerular apparatus (JGA) in the kidneys release the enzyme, Renin. This is the initial step in a system called Renin-Angiotensin-Aldosterone System (RAAS) Renin converts angiotensinogen (which is produced in the liver) to the hormone angiotensin I. An enzyme called angiotensin-converting enzyme (ACE) metabolizes angiotensin I into angiotensin II. Angiotensin II causes vasoconstriction of the efferent arteriole in the glomerulus. The constriction means that the blood entering the glomerulus has aharder time leaving because the exit is much smaller than the entrance.This increases the GFR, which in turn raises blood pressure

2.2.1. In high blood pressure cells in the JGA send a negative feedback signal to stop the release of renin therefore also stopping the RAAS

2.3. Angiotensin II also stimulates the release of the hormone aldosterone in the adrenal glands, which causes the renal tubules to retain sodium and water and excrete potassium. Angiotensin II and aldosterone work together to raise blood volume, blood pressure and sodium levels to restore the balance of sodium, potassium, and fluids.

2.3.1. RAAS

3. WASTE EXCRETION

3.1. Urine formation is an important process used by body to rid itself of metabolic wastes and toxins through the kidneys

3.1.1. Urine formation starts in the Glomerulus where water and substances in the blood (electrolytes, glucose, fatty acids, amino acids) pass from the capillaries into the Bowman’s capsule through filtration. The filtrate (the fluid that has passed through the membrane which also includes waste) moves from the glomerular capsule further into the nephron

3.1.2. The filtrate flows into a duct in the nephron called the renal tubule. As it moves, the needed substances and some water are reabsorbed through the tube wall into nearby capillaries.

3.1.3. At the same time, a process called secretion occurs where waste ions and hydrogen pass from the capillaries into the renal tubule. The secreted ions together with remaining filtrate become urine. Nitrogenous wastes excreted in urine include urea, creatinine, ammonia, and uric acid. The urine flows out of the tubule into the collecting duct the through the renal pelvis, into the ureter and down the bladder.

3.1.3.1. High levels of waste products in the body can be toxic and deadly. Dialysis may be needed if a person’s kidney function is poor and can no longer remove toxic wastes

3.1.3.2. Signs and symptoms of urea build up: Weakness, exhaustion, confusion, nausea, vomiting, loss of appetite, high blood pressure

3.1.4. The kidneys not only dispose of wastes but they prevent the body becoming dehydrated. Water is reabsorbed into the blood stream by osmosis; thus maintaining homeostasis

4. FLUID/ELECTROLYE BALANCE

4.1. The kidneys help maintain electrolyte concentrations by filtering electrolytes and water from blood, returning some to the blood, and excreting excess into the urine. Electrolyte imbalances can occur from dehydration/over-hydration

4.1.1. Sodium

4.1.1.1. Normal range 135-145mmol/L.. 65% of sodium is actively reabsorbed in the Proximal tubule. When blood volume or sodium concentration becomes too low, the sensors in the body trigger mechanisms to increase blood volume. The adrenal glands secrete the hormone Aldosterone which causes the kidneys to retain sodium and to excrete potassium. This then causes the release of Antidiuretic hormone (ADH), which causes water to be retained, therefore balancing Na+ and H2O to restore plasma volume.

4.1.1.1.1. Hyponatremia causes: Kidney disease resulting in muscle wasting, adrenal insufficiency, GI losses, increased sweating,use of diuretics,syndrome of inappropriate ADH

4.1.1.1.2. Hypernatremia causes: ingestion of large amounts of concentrated salt solutions, excess aldosterone secretion, diabetes insipidus, water deprivation

4.1.2. Potassium

4.1.2.1. Potassium (K+) is filtered in the Glomerulus and almost completely reabsorbed in the proximal tubule and the loop of Henle. Potassium is necessary for the normal functioning of cells, nerves, and muscles. Normal range 3.5-5.0 mmol/L

4.1.2.1.1. Hypokalemia causes: use ot potassium- wasting diuretics, Diarrhea, vomitting, GI losses, alkalosis, polyuria, extremem sweating

4.1.2.2. Most of the body’s potassium is located inside the cells. Once potassium is absorbed, it circulates to the kidneys, where it is regulated through process of active secretion and absorption in the distal tubule and collecting ducts

4.1.2.2.1. Aldosterone is a hormone involved in potassium control in the body. High potassium serum levels stimulate cells of the distal tubule and collecting ducts of the nephron, activating sodium/potassium pumps which pumps 3 sodium ions out of cell and 2 potassium ions into the cell. This results in reabsorption of sodium and water into the blood and secretes potassium ions into the urine.

4.1.3. Calcium

4.1.3.1. Approximately 65% of calcium is passively reabsorbed from the Proximal tubule

4.1.4. Magnesium

4.1.4.1. About 25% is actively absorbed in the Proximal tubule.

5. References:

5.1. Lehnhardt, A., & Kemper, M. J. (2010). Pathogenesis, diagnosis and management of hyperkalemia. Pediatric nephrology (Berlin, Germany), 26(3), 377-84.

5.2. The Renin-Angiotensin System and Blood Pressure Control. (n.d.). Retrieved March 8, 2019, from http: //ukrocharity.org/kidney- disease/ the-renin-angiotensin-system- and-blood-pressure-control

5.3. Aldosterone. (n.d.). Retrieved March 08, 2019, from Aldosterone - an overview | ScienceDirect TopicsScienceDirectElsevierRELX Group

5.4. Potter, P. A., Perry, A.G., Stockert, P.A., & Hall, A.M. (Eds.). (2014). Canadian fundamentals of nursing (5th Cdn. ed.) (J. C. Ross-Kerr, M. J. Wood, B. J. Astle & W. Duggleby, Cdn. Adapt.). Toronto, ON: Elsevier Canada.

5.5. Counts, C. S. (2015). Core curriculum for nephrology nursing. Pitman, NJ: American Nephrology Nurses Association.