Assume you have been chewing a piece of bread for 5 or 6 minutes. How would you expect its taste to change during this time? Why?
The bread will begin to taste sweet as some of the starch is broken down into sugar due to the chemical digestion of carbohydrates by salivary amylase.
How does the respiratory system influence the buffer system of the body?
The respiratory system maintains a constant bicarbonate level in thebloodstream by outgassing carbon dioxide. In the event of a respiratory problem the bicarbonate system might not be a constant.
Humans can survive for a period of time without water thanks to the ability of the kidneys to produce concentrated urine. Briefly explain what factors allow this to happen.
Facultative water reabsorption depends on the presence of antidiuretic hormone. In the presence of ADH, the pores of the collecting tubule enlarge and the filtrate loses water by osmosis as it passes through the medullary regions of increasing osmolarity. Consequently, water is conserved and urine becomes concentrated. The water that passes through these regions is reabsorbed by the body in order to prevent dehydration.
What is bile and where is it produced? What is its digestive function? Where is it stored and concentrated?
Bile is a watery solution containing bile salts, bile pigments, cholesterol, neutral fats, phospholipids, and a variety of electrolytes. It is produced in the liver. Its digestive function is to emulsify fats. It is stored and concentrated in the gallbladder.
Identify and describe the operation of the three major chemical buffers of the body.
The bicarbonate buffer system (carbonic acid plus sodium bicarbonate) acts to tie up the hydrogen ions released by a strong acid, thus converting it to a weaker acid, which lowers the pH only slightly. For a strong base, the carbonic acid will be forced to donate more H+ to tie up the OH- released by the base, with the net result of replacement of a strong base by a weak one. Again the pH rise is very small. The phosphate buffer system, composed of the sodium salts of dihydrogen phosphate and monohydrogen phosphate, acts in a similar fashion to the bicarbonate system. NaH2PO4 acts as a weak acid; Na2HPO4 acts as a weak base. Hydrogen ions released by strong acids are tied up in weak acids; strong bases are converted to weak bases. Amino acids of the protein buffer system release H+when the pH begins to rise by dissociating carboxyl groups, or bind hydrogen ions with amine groups to form NH3+ when the pH falls.
Explain the role of aldosterone and ADH in sodium and water balance.
Aldosterone targets the distal tubule and collecting duct and enhances sodium-ion reabsorption so that very little leaves the body in urine. Aldosterone also causes increased water reabsorption because, as sodium is reabsorbed, water follows it back into the blood if there is an ample supply of ADH in the blood. ADH makes the DCT and CD premeable to water by causing the instillation of aquaporins in the walls of the tubular cells.
List and describe three pressures operating at the filtration membrane, and explain how each influences net filtration pressure.
Glomerular hydrostatic pressure (GHP) is the chief force pushing water and solutes across the filtration membrane. The higher the GHP, the more filtrate is pushed across the membrane. Glomerular osmotic pressure of plasma proteins in the glomerular blood, and capsular hydrostatic pressure exerted by fluids in the glomerular capsule, drive fluids back into the glomerular capillaries. The net filtration pressure equals glomerular hydrostatic pressure minus (glomerular osmotic pressure plus capsular hydrostatic pressure)
Helen is a 62-year-old smoker. Her physician has diagnosed her as having emphysema that has caused her to hypoventilate. She is tired and sedentary. Besides having difficulty breathing, what other condition is contributing to her tiredness?
Helen is suffering from respiratory acidosis because she is retaining too much carbon dioxide. Her shallow breathing, due to the damage to her lungs from the disease, is the cause. In order to release the carbon dioxide, one must be able to breathe normally (deep breathing would be optimal).
Ellen, a 47-year-old woman who has suffered kidney disease for several years, has been diagnosed with proteinuria. Her legs and feet are so swollen that she has difficulty walking. Her hands and her left arm are also swollen. What is proteinuria, and could this condition be playing a role in her swollen limbs?
Proteinuria is a condition in which the permeability of the glomerular capillaries is increased to such an extent that large amounts of plasma proteins (mostly albumin) pass into the glomerular filtrate and are excreted in the urine. If the condition is severe, the loss of plasma proteins may decrease osmotic pressure substantially. When this happens there is a tendency for fluid to leave the systemic blood vessels and enter the tissue space. This is the reason for Ellen's swollen limbs.
While having a physical examination, a young male informed his doctor that at age 8 he had lobar pneumonia and pleurisy in his left lung. The physician decided to measure his VC. Describe the apparatus and method used for taking this measurement. Define the following terms used in the description of lung volumes: TV, IRV, ERV, RV, and VC.
His vital capacity (VC) was measured using a spirometer. As he breathed into a mouthpiece, a hollow bell, inverted over water, was displaced, giving a graphic recording on a rotating drum. Tidal volume (TV) is the amount of air that moves into and out of the lungs with normal breathing. Inspiratory reserve volume (IRV) is the amount of air that can be forcibly inhaled beyond the tidal volume. The expiratory reserve volume (ERV) is the amount of air that can be evacuated from the lungs over and above a tidal expiration. Residual volume (RV) is the amount of air that remains in the lungs even after the most strenuous expiration. Vital capacity (VC) is the total amount of exchangeable air.
A smoker sees his doctor because he has a persistent cough and is short of breath after very little exertion. What diagnosis will the doctor make and what can he person expect if he does not quit smoking?
The person is suffering from chronic bronchitis, which causes the dyspnea and coughing. If he does not stop smoking, he can expect frequent pulmonary infections, more coughing, and progressively more severe dyspnea (all symptoms of chronic obstructive pulmonary disease). Ultimately, he can expect to develop hypoxemia, CO2 retention, and respiratory acidosis. He may develop emphysema or lung cancer.