WATER AND BODY FLUIDS Lecture 4 and 5
Three Basic Processes in urine formation
∙ Glomerular filtration
o where the blood is filtered by the nephron by the glomerulus into the Bowman’s capsule
∙ Tubular reabsorption
o Materials that need to be in the blood are reabsorbed into the blood stream through osmosis and with carrier mediated transport
o Renal threshold the maximum amount of solute that can be transported using carrier mediated transport
o After this point glucose, blood proteins, ketone bodies and bile among other things should not be in the filtrate
∙ Tubular Secretion
o Removal of waste through renal tubule to be excreted in urine
o Hydrogen, Potassium and other selected solutes
o When worrying about renal failure the kidneys fail to properly secrete solutes so things like potassium intake need to be closely monitored
∙ Hypothalamus has the thirst center which regulates fluid intake
∙ Vasopressin/ Antidiuretic hormone reduce the amount of fluid lost in the urine o ADH released when the body has higher demand for water and creates more concentrated urine
o Alcohol inhibits ADH
Taking apart electrolytes
∙ Primary extracellular ions are Na+(cation) and Cl(anion)
∙ Primary intracellular ions are K+(cation) and HPO42(anion)
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∙ Hypoprefix meaning low
∙ Hyper prefix meaning high
∙ Natpertaining to sodium
∙ Kal pertaining to potassium
∙ Phos pertaining to phosphate Don't forget about the age old question of What is the role of public health in the identified health issues in your community?
∙ Aldosterone stimulates sodium reabsorption and prevents excessive loss of sodium o Helps maintain the small acceptable range of sodium in the blood
o Reabsorption of sodium causes excretion of potassium
∙ Acids are proton DONORS
∙ Bases are proton ACCEPTORS
∙ Blood has a narrow pH range in which life can be sustained of 7.357.45 o Alkalosis pH too high in blood
Respiratory too much CO2 expulsion
Metabolic too much acid is lost
o Acidosis pH too low in blood
Respiratory too much CO2 retention
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∙ Buffers help maintain narrow pH goal and avoid pH fluctuation
o Bicarbonate is the most important
H2CO3H+ + HCO3
Carbonic acid Hydrogen ions and bicarbonate
Used to avoid excess CO2 in the blood (acidosis)
Acidic blood is neutralized with secretion of hydrogen ions and alkaline blood is neutralized with bicarbonate
o Phosphate and plasma proteins act as buffers as well