PCB 3703 Exam 3 V2 | PCB 3703 Human
Physiology | Actual Q&A with Rationale (PCB3703
Exam 3) | University of Central Florida
1. Which of the following best describes the function of Type II alveolar cells in the human
respiratory system?
A. They provide the primary surface area for gas exchange via diffusion.
B. They act as phagocytes to remove debris and pathogens from the airway.
C. They secrete pulmonary surfactant to reduce surface tension and prevent alveolar
collapse.
D. They form the blood-air barrier with the capillary endothelial cells.
Correct Answer: C
Explanation: Type II alveolar cells are specialized epithelial cells that synthesize and
secrete pulmonary surfactant. This substance reduces the surface tension of the fluid lining
the alveoli, which increases lung compliance and prevents smaller alveoli from collapsing.
Without adequate surfactant, as seen in infant respiratory distress syndrome, the work of
breathing increases significantly.
2. In the oxyhemoglobin dissociation curve, which of the following factors would cause a
rightward shift, indicating a decreased affinity of hemoglobin for oxygen?
A. A decrease in 2,3-bisphosphoglycerate (2,3-BPG) levels.
B. An increase in PCO2, decrease in pH, and increase in temperature.
,C. A decrease in temperature and an increase in blood pH.
D. An increase in fetal hemoglobin concentration.
Correct Answer: B
Explanation: A rightward shift in the oxyhemoglobin dissociation curve signifies that
hemoglobin releases oxygen more readily to the tissues. This is caused by increased
metabolic activity, which produces more CO2, heat, and H+ ions (lowering pH). This
phenomenon is known as the Bohr effect and ensures that active tissues receive more
oxygen during exercise or stress.
3. Under normal physiological conditions, which part of the nephron is responsible for the
reabsorption of 100% of filtered glucose?
A. Proximal convoluted tubule
B. Ascending limb of the Loop of Henle
C. Distal convoluted tubule
D. Collecting duct
Correct Answer: A
Explanation: The proximal convoluted tubule (PCT) is the primary site for the
reabsorption of organic nutrients, including glucose and amino acids. This occurs via
secondary active transport using sodium-glucose linked transporters (SGLT) on the apical
membrane. If blood glucose levels exceed the renal threshold, the transporters become
saturated and glucose will appear in the urine.
, 4. What is the primary stimulus for the central chemoreceptors to increase the rate and depth
of ventilation?
A. A decrease in arterial PO2 below 60 mmHg.
B. An increase in arterial H+ concentration directly.
C. An increase in the concentration of bicarbonate ions in the plasma.
D. A decrease in the pH of the cerebrospinal fluid caused by increased arterial PCO2.
Correct Answer: D
Explanation: Central chemoreceptors located in the medulla oblongata are highly sensitive
to changes in the pH of the cerebrospinal fluid. Carbon dioxide can cross the blood-brain
barrier and react with water to form carbonic acid, which dissociates into bicarbonate and
hydrogen ions. It is the resulting increase in H+ ions in the CSF that directly stimulates the
central chemoreceptors to drive ventilation.
5. Which of the following would occur if the afferent arteriole of a nephron were to constrict
while the efferent arteriole remained unchanged?
A. The hydrostatic pressure in the glomerulus would increase.
B. The filtration fraction would significantly increase.
C. The renal blood flow would increase due to pressure backing up.
D. The glomerular filtration rate (GFR) would decrease.
Correct Answer: D
Physiology | Actual Q&A with Rationale (PCB3703
Exam 3) | University of Central Florida
1. Which of the following best describes the function of Type II alveolar cells in the human
respiratory system?
A. They provide the primary surface area for gas exchange via diffusion.
B. They act as phagocytes to remove debris and pathogens from the airway.
C. They secrete pulmonary surfactant to reduce surface tension and prevent alveolar
collapse.
D. They form the blood-air barrier with the capillary endothelial cells.
Correct Answer: C
Explanation: Type II alveolar cells are specialized epithelial cells that synthesize and
secrete pulmonary surfactant. This substance reduces the surface tension of the fluid lining
the alveoli, which increases lung compliance and prevents smaller alveoli from collapsing.
Without adequate surfactant, as seen in infant respiratory distress syndrome, the work of
breathing increases significantly.
2. In the oxyhemoglobin dissociation curve, which of the following factors would cause a
rightward shift, indicating a decreased affinity of hemoglobin for oxygen?
A. A decrease in 2,3-bisphosphoglycerate (2,3-BPG) levels.
B. An increase in PCO2, decrease in pH, and increase in temperature.
,C. A decrease in temperature and an increase in blood pH.
D. An increase in fetal hemoglobin concentration.
Correct Answer: B
Explanation: A rightward shift in the oxyhemoglobin dissociation curve signifies that
hemoglobin releases oxygen more readily to the tissues. This is caused by increased
metabolic activity, which produces more CO2, heat, and H+ ions (lowering pH). This
phenomenon is known as the Bohr effect and ensures that active tissues receive more
oxygen during exercise or stress.
3. Under normal physiological conditions, which part of the nephron is responsible for the
reabsorption of 100% of filtered glucose?
A. Proximal convoluted tubule
B. Ascending limb of the Loop of Henle
C. Distal convoluted tubule
D. Collecting duct
Correct Answer: A
Explanation: The proximal convoluted tubule (PCT) is the primary site for the
reabsorption of organic nutrients, including glucose and amino acids. This occurs via
secondary active transport using sodium-glucose linked transporters (SGLT) on the apical
membrane. If blood glucose levels exceed the renal threshold, the transporters become
saturated and glucose will appear in the urine.
, 4. What is the primary stimulus for the central chemoreceptors to increase the rate and depth
of ventilation?
A. A decrease in arterial PO2 below 60 mmHg.
B. An increase in arterial H+ concentration directly.
C. An increase in the concentration of bicarbonate ions in the plasma.
D. A decrease in the pH of the cerebrospinal fluid caused by increased arterial PCO2.
Correct Answer: D
Explanation: Central chemoreceptors located in the medulla oblongata are highly sensitive
to changes in the pH of the cerebrospinal fluid. Carbon dioxide can cross the blood-brain
barrier and react with water to form carbonic acid, which dissociates into bicarbonate and
hydrogen ions. It is the resulting increase in H+ ions in the CSF that directly stimulates the
central chemoreceptors to drive ventilation.
5. Which of the following would occur if the afferent arteriole of a nephron were to constrict
while the efferent arteriole remained unchanged?
A. The hydrostatic pressure in the glomerulus would increase.
B. The filtration fraction would significantly increase.
C. The renal blood flow would increase due to pressure backing up.
D. The glomerular filtration rate (GFR) would decrease.
Correct Answer: D
