A&P ch.27 Fluid, Electrolytes, and Acid-Base Balance
Name three hormones that play a major role in adjusting fluid and electrolyte balance in the body...
ADH, aldosterone, and natriuretic peptides (ANP and BNP)
List the components of extracellular fluid (ECF) and intracellular (ICF)...
interstitial fluid plasma other body fluids the intracellular fluid (ICF) is the cytosol of the cell
What are the three major buffer systems in body fluids? How does each system work?
1). Phosphate buffer system: consists of H2PO4-, a weak acid that in solution reversibly dissociates into a hydrogen ion and HPO4(2-). This plays a relatively small role in regulating the PH of the ECF because the ECF contains far higher concentration of bicarbonate ions than phosphate ions; however it is important in buffering the pH of the ICF 2). Protein buffer system: these depend on the ability of amino acids to respond to changes in pH by accepting or releasing hydrogen ions. If the pH rises, the carboxyl group of the AA dissociates to release a hydrogen ion; if the pH drops, the AA accepts an additional hydrogen ion to form an amino ion NH3+ and the carboxylate ion can accept a hydrogen ion to form a carboxyl group. Plasma proteins contribute to the buffering capabilities of the blood; inside cells, protein buffer systems stabilize the pH of the ECF by absorbing extracellular hydrogen ions or exchanging intracellular hydrogen ions for extracellular potassium. 3). Carbonic acid-Bicarbonate buffer system: most carbon dioxide generated in tissues is covered to carbonic acid, which dissociates into a hydrogen ion and a bicarbonate ion. Hydrogen ions released by dissociation of organic or fixed acids combine with bicarbonate ions, elevating PCO2; additional CO2 is lost at the lungs.
What effect would a decrease in the pH of body fluids have on respiratory rates?
A decrease in pH accompanies and increase in the partial pressure of CO2. Chemoreceptors sensitive to pCO would stimulate the respiratory centers of the medulla oblongata, resulting in an increase in the respiratory rate
As a person ages, the glomerular filtration rate and the number of function nephrons decreases. What effect would these changes have on pH regulation?
A decrease in the GFR and the number of function nephrons reduces the body's ability to regulate pH through renal compensation
In a protein buffer system, if the pH increases...
A hydrogen ion is released and a carboxylate ion is formed
Osmoreceptors in the hypothalamus monitor the osmotic concentration of the ECF and secrete ______ in response to higher osmotic concentrations...
ADH
Changes in the pH of body fluids are compensated for by all of following except
An increase in urine output... changes are compensated for... the carbonic acid-bicarb buffer system the phosphate buffer system changes in the rate and depth of breathing protein buffers
Calcium homeostasis primarily reflects...
An interplay among reserves in the bones, the rate of absorption, and the rate of excretion
Why should a person with fever drink plenty of fluids?
Because for each degree Celsius the body temperature increase above normal, daily water loss increases by 200 mL
Why can prolonged vomiting produce metabolic alkalosis...
Because large amounts of stomach hydrochloric acid are lost from the body. More acid is then formed by the parietal cells of the stomach. The H+ that are released are produced by the dissociation of carbonic acid and exchange of bicarb ions with chloride ions from the blood. The alkaline tide of released bicarbonate ions increases the blood pH, leading to metabolic alkalosis
Metabolic alkalosis occurs when...
Bicarbonate ion concentrations become elevated
How do respiratory and renal mechanisms support the buffer systems?
By recreating or absorbing hydrogen ions, controlling the excretion of acids and bases, and by generating additional buffers
The MOST important factor affecting the pH of body tissues is the concentration of...
Carbon Dioxide
Identify four physiologically important cations and two important anions in the extracellular fluid...
Cations: Sodium Potassium Calcium Magnesium Anions: Phosphate Chloride
Define dehydration...
Decrease in the water content of the body that developed when water losses outpace water gains, and this threatens homeostasis
Respiratory acidosis develops when the blood pH is...
Decreased due to an increased blood pCO2 level
The most recent advise from medical and nutritional experts is to monitor one's intake of salt so that it does not exceed the amount needed to maintain a constant ECF volume. What effect does excessive salt ingestion have on BP?
Excessive salt intake causes an increase in total BV and BP due to an obligatory increase in water absorption across the intestinal lining and recall of fluid from the ICF.
How would a prolonged fast affect the body's pH?
Fatty acids are catabolized, producing large numbers of ketone bodies, which are organic acids that decrease the blood pH (this decreased pH would eventually lead to ketoacidosis)
Differentiate among fluid balance, electrolyte balance, and acid-base balance, explain why each is important to homeostasis...
Fluid balance is a state in which the amount of water gained each day is equal to the amount lost to the environment. It is vital that the water content of the body remain stable, because water is an essential ingredient of cytoplasm and accounts for about 99% of ECF volume. Electrolyte balance exists when there is neither a net gain nor a net loss of any ion in body fluids. It is important that the ionic concentrations in body water remain within normal limits; if levels of calcium or potassium become too high, for instance, cardiac arrhythmias can develop. Acid-base balance exists when the production of hydrogen ions precisely offsets their loss. The pH of body fluids must remain within a relatively narrow range; variations outside the range can be life threatening
What are fluid shifts? What is their function, and what factors can cause them?
Fluid shifts are rapid water movements between the ECF and ICF that occur in response to increases or decreases in the osmotic concentration of the ECF. Such water movements dampen extreme shifts in electrolyte balance
Identify the four hormones that mediate major physiological adjustments affecting fluid and electrolyte balance. What are the primary effects of each hormone?
Four major hormones involved in fluid and electrolyte balance are... 1). ADH-stimulates water conservation by the kidneys and stimulates the thirst center 2). Aldosterone-determines the rate of sodium reabsorption and potassium secretion along the DCT and collecting system of the kidney 3). Natriuretic peptides (ANP and BNP)- reduce thirst, promote loss of sodium and water by the kidneys, and block the release of ADH and aldosterone
The osmotic concentration of the ECF decreases if an individual gains water without a corresponding?
Gain of electrolytes
Drinking a solution hypotonic to the ECF causes the ECF to?
Increase in the volume and become hypotonic to the ICF
The primary components of the extracellular fluid are...
Interstitial fluid and plasma
Define edema...
Movement of abnormally large amounts of water from plasma into interstitial fluid
The principal anions in the ICF are...
Phosphate and proteins (Pr-)
Which is more dangerous, disturbances of sodium balance or disturbances of potassium balance?
Potassium ion imbalances are more dangerous than sodium ion imbalances because they can lead to muscle weakness or paralysis when blood concentrations are too low, and to cardiac arrhythmias when levels are too high. Disturbances in sodium balance, by contrast, produce dehydration or tissue edema.
Describe a fluid shift...
Rapid movement of water between ECF and ICF in response to an osmotic gradient
When the pH of body fluids begins to decrease, free amino acids and proteins will...
Release a hydrogen from the amino group
What is the difference between metabolic acidosis and respiratory acidosis? What can cause these conditions?
Respiratory acidosis, which results from abnormally high level of CO2 (hypercapnia), is usually caused by hypoventilation. Metabolic acidosis, which occurs when bicarbonate ion levels decrease, can result from overproduction of fixed to organic acids, impaired ability to secrete H+ ions by the kidneys and severe bicarbonate losses
Differentiate between respiratory compensation and renal compensation...
Respiratory compensation is a change in the respiratory rate that help stabilize the pH of the ECF. Increasing or decreasing the rate of respiration alters pH by decreasing or increasing the PCO2. When the PCO2 decreases the pH increases, when the PCO2 increases the pH decreases. Renal compensation is a change in the rate of hydrogen and bicarbonate ion secretion or reabsorption in response to changes in plasma pH. Tubular hydrogen ion secretion results in the diffusion of bicarbonate ions into the ECF
Differentiate between respiratory and metabolic disorders that disturb acid-base balance...
Respiratory disorders result from abnormal CO2 removal by the lungs and its generation in other tissues. Metabolic disorders are caused by the generation of organic or fixed acids by conditions affecting the concentration of bicarbonate ions in the ECF.
Exercise physiologists recommend that adequate amounts of fluid be ingested before, during, and after exercise. Why is fluid replacement during extensive sweating important?
Since sweat is usually hypotonic, the loss of fluid volume is primarily from the interstitial space, which leads to a decrease in plasma volume and an increase in the hematocrit. Severe dehydration can cause the blood viscosity to increase substantially, resulting in an increased workload on the heart, ultimately increasing the probability of heart failure
Why must tubular fluid in nephrons be buffered?
So that it can contain more H+ without decreasing the pH below approximately 4.5, at which point H+ secretion cannot continue because the H+ concentration gradient becomes too steep. The hydrogen ions would leak out of the tubule as fast as they are pumped in
Why does prolonged sweating increase plasma sodium ion levels...
Sweat is a hypotonic solution with lower sodium concentration than ECF. Sweating causes a greater loss of water than of sodium, increasing plasma sodium ion levels.
After the age of 40, does the total body water content increase or decrease...
Total body water content gradually decreases with age
Define and given an example of... volatile acid fixed acid organic acid which represents the greatest threat to acid-base balance? why?
Volatile- acids that can leave solution and enter the atmosphere, such as carbonic acid Fixed- acids that do not leave solution, such as sulfuric acid Organic- Acids produced during metabolism, such as lactic acids and ketones Volatile acids are the greatest threat because of the large amounts generated by normal cellular processes.
What effect would being in the desert without water for a day have on the osmotic concentration of your blood plasma...
You would lose fluid through perspiration, urine formation, and respiration. As a result, the osmotic concentration of your blood plasma (and other body fluids) would increase.
See question number four on page 1048...
a). carbonic acid (H2CO3-) b). bicarbonate ion (HCO3-) c). sodium bicarbonate (NaHCO3)
Identify the three interrelated processes essential to stabilizing body fluid volumes...
fluid balance electrolyte balance acid-base balance
Identify the body's three major buffer systems...
phosphate buffer system protein buffer system carbonic acid- bicarb buffer system
What effect would drinking a half-gallon of distilled water have on ADH levels?
temporarily decrease your blood osmolarity (osmotic concentration). This decrease in osmolarity would lead to a decrease in the level of ADH in your blood, because ADH release is triggered by increases in osmolarity
