Which of the following would slow down gas exchange between the blood and alveolar air?
A decrease in membrane thickness
An increase in alveolar surface area
An increase in membrane thickness
A decrease in nitrogen solubility
An increase in respiratory rate
The Correct Answer is C
A. A decrease in membrane thickness: Thinner respiratory membranes allow gases to diffuse more rapidly between alveolar air and blood. A decrease in thickness enhances gas exchange rather than slowing it.
B. An increase in alveolar surface area: A larger surface area provides more sites for diffusion, improving the efficiency of gas exchange. This change accelerates, rather than impedes, oxygen and carbon dioxide transfer.
C. An increase in membrane thickness: Thickening of the alveolar-capillary membrane, as occurs in conditions like pulmonary fibrosis or edema, increases the diffusion distance. This slows down the movement of oxygen and carbon dioxide between alveoli and blood, reducing gas exchange efficiency.
D. A decrease in nitrogen solubility: Nitrogen is largely inert and not actively exchanged in the lungs. Changes in its solubility have minimal effect on oxygen or carbon dioxide diffusion, so it does not significantly slow gas exchange.
E. An increase in respiratory rate: A higher respiratory rate enhances the ventilation of alveoli and maintains the concentration gradient for diffusion. This actually promotes faster gas exchange rather than slowing it.
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Correct Answer is E
Explanation
. Chloride:Chloride ions participate in the chloride shift, helping maintain electrical neutrality as bicarbonate ions move out of red blood cells, but they do not directly stimulate oxygen unloading.
B. Potassium:Potassium ions are primarily involved in maintaining cellular membrane potential. They are not generated by CO₂ in RBCs and do not directly influence oxygen release from hemoglobin.
C. Nitrogen:Nitrogen is largely inert in the blood and does not participate in acid-base reactions or oxygen unloading. It is not generated from CO₂ metabolism in red blood cells.
D. Sodium:Sodium ions contribute to plasma osmolarity and fluid balance but are not produced within RBCs as a result of CO₂ addition and do not affect hemoglobin’s oxygen affinity.
E. Hydrogen:The addition of CO₂ to blood forms carbonic acid, which dissociates into bicarbonate and hydrogen ions. The increase in hydrogen ions lowers pH within RBCs, promoting the Bohr effect and stimulating hemoglobin to release more oxygen to the tissues.
Correct Answer is C
Explanation
A. Diastolic:Diastolic pressure is the lower number in a blood pressure reading. It represents the pressure in the arteries when the heart is relaxed between beats, not the higher value.
B. Repolarization:Repolarization refers to the process of cardiac muscle cells returning to a resting electrical state after contraction. It is not directly measured in a blood pressure reading.
C. Systolic:Systolic pressure is the higher number in a blood pressure reading. In this example, 110 mmHg represents the arterial pressure when the ventricles contract, pushing blood into the arteries.
D. Depolarization:Depolarization is the process by which cardiac cells generate an action potential to initiate contraction. It is an electrical event and does not correspond to the numeric values of blood pressure.
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