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Anatomy & Physiology II Unit Eight Osmosis Solute - substance that is dissolved in a medium (solvent) Solvent - substance (usually liquid) that dissolves a solute Solution - mixture of solutes dissolved in a solvent Concentration - ratio of solute to solvent Osmosis Isotonic solution *concentration of solutes outside the cell is equal to the concentration inside the cell Hypertonic solution *concentration of solutes outside the cell is greater than the concentration inside the cell Osmosis Hypotonic solution *concentration of solutes outside the cell is less than the concentration inside the cell The selectively permeable character of the cell membrane functions to maintain isotonic conditions in the body Animal Cell Osmosis Aaaaaaaaaaaaa Aaaaaaaaaaaaa Aaaaaaaaaaaaa Aaaaaaaaaaaaa Aaaaaaaaaaaaa Aaaaaaaaaaa Aaaaaaaaaaaaa aaaaaaaaaaaaa Lysed Aaaaaaaaaaaaa Aaaaaaaaaaaaa Aaaaaaaaaaaaa Aaaaaaaaaaaaa Aaaaaaaaaaaaa Aaaaaaaaaaa Aaaaaaaaaaaaa Aaaaaaaaaaaaa aaaaaaaaaaaaa Crenated Osmosis Diffusion - the movement of a substance from an area of high concentration to an area of low concentration Osmosis - the diffusion of water - the movement of water to an area of high solute concentration Osmosis Diffusion Semipermeable membrane Osmosis Osmosis Osmolarity is the total concentration of all solute particles in a solution Osmolarity is expressed in osmoles (one mole of solute in one liter of water) Very small concentrations are expressed in milliosmoles (0.001osmol) Osmosis Osmotic pressure is created by the movement of water toward a higher solute concentration Molecules that dissociate will exert a greater osmotic pressure than those that do not Therefore, the higher the solute concentration, the higher the osmotic pressure Osmosis Many body systems create high solute concentrations so as to produce higher osmotic pressure Movement of water into and out of cells with selectively permeable membranes is driven by osmotic gradients Osmosis Milliequivalency is the expression of solute concentration that takes into consideration the effect of the ion valence charge on the osmotic pressure Osmotic Effects of Solutes Electrolytes (ions) are solutes that easily dissociate, carry a charge and can conduct an electrical current Electrolytes may be monoatomic or polyatomic Osmotic Effects of Solutes Electrolytes are the most numerous solutes in body fluids, but constitute the least in weight Electrolytes exert a powerful affect on the osmolarity of body fluids and the body’s water content and distribution Osmotic Effects of Solutes Electrolytes also play a large role in the regulation of acid/base balance and in determining charge difference across cell membranes Osmotic Effects of Solutes Nonelectrolytes are solutes that do not have a charge (neutral) Nonelectrolytes are typically larger covalently bonded molecules such as glucose, urea and other organics Osmotic Effects of Solutes Nonelectrolytes do not dissociate, so they do not carry charges Nonelectrolytes are fewer in number, but constitute the majority of the weight of solutes Therefore, nonelectrolytes have less effect on osmotic pressure Fluid Balance Balance of body fluids means that fluid intake should equal fluid output In addition, the fluid gained or lost must be added to or taken from the right compartment (ICF or ECF) Fluid Balance Fluid Balance As has been seen, electrolyte concentrations in the different compartments must also be stringently maintained Electrolytes attract water through osmosis, therefore a loss of fluids results in the loss of electrolytes Fluid & Electrolyte Balance ICF 65% of body fluids Major electrolytes K+ Mg2+ HPO43- ECF 35% of body fluids Major electrolytes Na+ Ca2+ Cl- Fluid Balance The three structures that play the major role in fluid and electrolyte balance are: * brain (hypothalamus) * kidneys * adrenal glands Regulation of Fluid Intake volume of ECF Decreased or Increased osmolarity of ECF Increased volume of ECF which decreases osmolarity of ECF Hypothalamus Decrease saliva Creates thirst Drink fluids Hypothala mic and Kidney Regulatio n of Fluids and Electrolyt Adrenal Gland Regulation of Fluids and Electrolyt Imbalances of Prominent Electrolytes Sodium (Na+) + most abundant ion in the ECF + normal ECF concentration is 143mEq/L Imbalances of Prominent Electrolytes Sodium (Na+) + functions in fluid balance, nerve impulse transmission & muscle contractions + regulated by aldosterone, cortisol & estrogen Imbalances of Prominent Electrolytes Hypernatremia + ECF concentration above 145mEq/L + symptoms include edema, hypertension & weight gain + caused by excessive sodium intake or inadequate H2O intake Imbalances of Prominent Electrolytes Hyponatremia + ECF concentration below 130mEq/L + symptoms include headaches, hypotension, shock, tachycardia & disorientation + caused by excessive H2O loss Imbalances of Prominent Electrolytes Potassium (K+) + most abundant ion in the ICF + normal ECF concentration is 5mEq/L Imbalances of Prominent Electrolytes Potassium (K+) + functions in nerve impulse transmission, muscle contractions & enzyme cofactor + regulated by aldosterone and pH balance Imbalances of Prominent Electrolytes Hyperkalemia + ECF concentration above 5.5mEq/L + symptoms include muscle weakness, bradycardia & cardiac arrest + caused by renal failure or severe burns Imbalances of Prominent Electrolytes Hypokalemia + ECF concentration below 3.5mEq/L + symptoms include muscle weakness, disorientation, fatigue & cardiac arrest + caused by excessive H2O loss Imbalances of Prominent Electrolytes Calcium (Ca2+) + normal ECF concentration is 5mEq/L + functions in blood clotting, muscle contractions, insulin secretion, bone structure, cardiac function & neurotransmitter release Imbalances of Prominent Electrolytes Calcium (Ca2+) + regulated by calcitonin, parathyroid hormone (PTH) & estrogen Imbalances of Prominent Electrolytes Hypercalcemia + ECF concentration above 5.8mEq/L + symptoms include kidney stones, constipation, nervous depression or coma Imbalances of Prominent Electrolytes Hypercalcemia + caused by excessive vitamin D or sun exposure, parathyroid tumor, osteoporosis or prolonged immobility Imbalances of Prominent Electrolytes Hypocalcemia + ECF concentration below 4.5mEq/L + symptoms include muscle tremors, weakened heart & increased clotting time Imbalances of Prominent Electrolytes Hypocalcemia + caused by low vitamin D intake, high protein diet, diarrhea or burns Hormone Actions and Imbalances Aldosterone is produced by the adrenal cortex under the influence of angiotensin II It functions to increase the reabsorption of Na+, which increases the secretion of K+ Hormone Actions and Imbalances The reabsorption of Na+ leads to the passive reabsorption of H2O Secretion of aldosterone is triggered by decreased blood volume or pressure, decreased Na+, increased K+ or excessive stress Hormone Actions and Imbalances Hormone Actions and Imbalances Aldosteronism (Conn’s disease) ~ caused by hypersecretion of aldosterone ~ results in increased Na+ retention and increased K+ secretion Hormone Actions and Imbalances Aldosteronism (Conn’s disease) ~ symptoms include muscle weakness, hypertension, edema & renal dysfunction ~ treated with cortex suppressing drugs or tumor removal Hormone Actions and Imbalances Addison’s disease ~ caused by hyposecretion of mineralocorticoids (aldosterone) & glucocorticoids (cortisol) ~ results decreased Na+ and increased K+ Hormone Actions and Imbalances Addison’s disease ~ symptoms include muscle weakness, hypotension, skin pigmentations & dehydration ~ treated with hormone replacement therapy Hormone Actions and Imbalances Antidiuretic hormone (ADH) is produced by the hypothalamus and stored & released by the posterior pituitary gland It functions to increase the conservation of H2O Hormone Actions and Imbalances H2O conservation increases blood volume and therefore blood pressure Secretion of ADH is stimulated by low blood volume, low blood pressure or increased Na+ levels Hormone Actions and Imbalances Hormone Actions and Imbalances Diabetes insipidus ~ caused by hyposecretion of ADH ~ results in the failure to conserve H2O Hormone Actions and Imbalances Diabetes insipidus ~ symptoms include persistent thirst and large amounts of dilute urine ~ treated with monitored and controlled fluid intake Hormone Actions and Imbalances Calcitonin is produced by the thyroid in response to high blood Ca2+ levels It functions to decrease blood Ca2+ levels and increases bone deposition Hormone Actions and Imbalances Parathyroid hormone (PTH) is produced by the parathyroid glands in response to low blood Ca2+ levels It functions to increase blood Ca2+ levels and decreases bone mass Hormone Actions and Imbalances Estrogen is produced and secreted by the gonads and adrenal glands It functions in reproduction and has aldosterone-like affects Hormone Actions and Imbalances Cortisol is produced and secreted by the adrenal cortex in response to ACTH & CRH It functions in the promotion of gluconeogenesis & depressing the inflammatory response Hormone Actions and Imbalances Cushing’s disease ~ caused by hyposecretion of cortisol ~ results in high blood glucose concentration and Na+ & H2O retention Hormone Actions and Imbalances Cushing’s disease ~ symptoms include hyperglycemia, easy bruising, edema, hypertension & poor wound healing ~ treatment is directed by the underlying cause Hormone Actions and Imbalances Insulin is produced and secreted by the beta cells of the pancreas in response to elevated blood glucose levels It functions in stimulating cellular uptake of glucose and the formation of glycogen Hormone Actions and Imbalances Diabetes mellitus ~ caused by malfunctions of the insulin process ~ results in high blood glucose concentration Hormone Actions and Imbalances Diabetes mellitus ~ symptoms excessive urine output, dehydration, excessive thirst & hunger accompanied by weight loss ~ there are two forms – Type I and Type II Hormone Actions and Imbalances Diabetes mellitus - Type I ~ insulin dependent ~ caused by the destruction of the beta cells ~ treatment through insulin injections Hormone Actions and Imbalances Diabetes mellitus - Type II ~ insulin independent ~ caused by reduced insulin production or the failure of body cell insulin receptors ~ treatment through diet, exercise & weight control Buffers Remember – a buffer is a chemical system that resists large changes in pH by taking up or giving off H+ Therefore, a buffer is a homeostatic mechanism that helps to regulate the pH of blood and other body fluids Buffers The pH range of blood is 7.357.45 It is extremely important that blood stay in this narrow range, making buffering systems necessary Buffers The body has two types of buffering systems: < chemical < physiological Buffers A chemical buffer is a substance that removes or releases H+ from a system by binding to them or releasing them Chemical buffers are found in the blood of the circulatory system Buffers A physiological buffer is a system that stabilizes pH by controlling the body’s output of acids, bases & CO2 The two systems that act as physiological buffers are the respiratory and urinary systems Chemical Buffers The bicarbonate buffering system CO2 + H2O H2CO3 HCO3- + H+ The phosphate buffering system H2 PO4- HPO42- + H+ Chemical Buffers The protein buffering system - COOH - COO- + H+ OR - NH2 + H+ - NH3+ Physiological Buffers The respiratory system is a two to three times stronger buffering system than chemical buffers It is directly involved with the bicarbonate buffering system CO2 + H2O H2CO3 HCO3- + H+ Physiological Buffers The urinary system is most powerful buffering system in the body H+ are secreted from the blood into kidney tubules where they bind with HCO3-, HPO42- or ammonia Physiological Buffers The bound and free H+ are then excreted in the urine The kidneys also control blood pH with the reabsorption of HCO3The removal of free H+ is what makes this buffering system so powerful Physiological Buffers When either physiological system is interrupted, it can cause major pH abnormalities Depending on the cause, pH can raise or lower outside the normal blood pH range Physiological Buffers Respiratory acidosis - occurs when the blood pH drops below 7.35 - CO2 increases in the blood - caused by trauma, illness, hypoventilation, pulmonary disease or barbiturate overdose Physiological Buffers Metabolic acidosis - occurs when the blood pH drops below 7.35 - increased levels of metabolic acids - caused by starvation, low dietary carbohydrates, diarrhea, strenuous exercise or excessive alcohol Physiological Buffers Respiratory alkalosis - occurs when the blood pH rises above 7.45 - CO2 decreases in the blood - caused by hyperventilation or aspirin overdose Physiological Buffers Metabolic alkalosis - occurs when the blood pH rises above 7.45 - decreased metabolic acids in the blood - caused by constipation, prolonged emesis or overdosing on alkaline drugs Buffering Overview Buffering Overview Application Situations Read through the following hypothetical situations and determine how the body will respond or why a therapy was used Be sure to think through the physiological reasons Application Situation One Michael works as a construction worker. He is in the hot sun many hours a day. As a result he loses water and salt by perspiration. How does his body maintain homeostasis? Application Situation one answer The elevation of blood osmolarity will cause the hypothalamus to stimulate the posterior pituitary to release more ADH causing the kidneys to excrete less urine The hypothalamus will also make him thirsty, causing him to drink a lot of liquids Application Situation one answer The loss of sodium and water will stimulate the adrenal glands to secrete more aldosterone, causing the kidneys to reabsorb more sodium Application Situation Two Rachel urinates several times each day but is able to sleep through the night without the need to urinate. What is the explanation? Application Situation Two answer The kidneys produce less urine when she is asleep because the hypothalamus causes the posterior pituitary to secrete more ADH during sleep Because the body systems slow down during sleep there is less metabolic water produced Application Situation Three Cynthia has had diarrhea for the past two weeks. Her potassium level is only 25% of the normal value. Why is her potassium so low? Application Situation Three answer Due to the diarrhea, she has lost a large amount of fluid and with this fluid she has lost potassium She will need to be given potassium immediately or her heart may develop arrhythmias and stop beating Application Situation four Melissa has been unable to eat anything following her surgery. Her doctor has ordered an IV of D5W. Why did he do this? Application Situation four answer The fluid in the D5W will replace fluid she will naturally lose The dextrose (glucose) will provide an energy source for her body while she recuperates Application Situation five Dr. Quack has told Betty she needs to flush the poisons out of her body. He has been giving her an IV of distilled water twice a week. What are the risks to Betty of this treatment? Application Situation five answer Distilled water is hypotonic to blood cells Many of the red blood cells will lyse creating a burden on the liver and spleen to cleanse the blood Lower numbers of red blood cells would lead to oxygen deficiencies and anemia Application Situation Six David has had a severe head trauma. There is swelling on his brain. His doctor has ordered an IV of 20% glucose. Why did he do this? Application Situation Six answer The 20% glucose solution is hypertonic This solution will attract fluid from the brain into the blood, carrying away from the swollen area Application Situation Seven Pablo has a history of hypertension. His doctor has placed Pablo on a low salt diet. What is the rationale for the low salt diet? Application Situation Seven answer Large amounts of salt makes Pablo’s blood hypertonic This hypertonic condition will cause fluids to move from interstitial spaces into the blood, creating more volume and therefore more pressure
