This figure shows the correction of hypoxemia by a negative feedback loop. What should go in the box labeled 1?
Decreased osteoclast activity
Increased osteoblast activity
Secretion of erythropoietin
Secretion of gastroferritin
The Correct Answer is C
Correct answer: C
A. Decreased osteoclast activity: osteoclasts resorb bone and are involved in calcium homeostasis, not the primary sensor/effector for correcting hypoxemia.
B. Increased osteoblast activity: osteoblasts build bone (also related to calcium metabolism), not the mechanism that increases RBC production in response to low O₂.
C. Secretion of erythropoietin: hypoxemia stimulates renal production (secretion) of erythropoietin (EPO), which promotes erythropoiesis in red marrow to raise RBC mass and correct low O₂.
D. Secretion of gastroferritin: gastroferritin (a gastric iron-binding molecule) helps iron handling in the gut but is not the feedback signal used to correct hypoxemia.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
A. Produces plasma hormones: blood does not produce hormones; endocrine organs secrete hormones into the blood. This statement is not a function of blood.
B. Transports a variety of nutrients: this is a function of blood (plasma carries nutrients to tissues).
C. Helps to stabilize the pH of extracellular fluids: this is a function; blood buffers (bicarbonate, proteins) help stabilize pH.
D. Helps to regulate body temperature: this is a function; blood redistributes heat and helps maintain temperature.
E. Participates in the initiation of blood clotting: this is a function; platelets and plasma clotting factors in blood participate in clot formation.
Correct Answer is E
Explanation
A. Thromboplastin: Thromboplastin (tissue factor) initiates the extrinsic coagulation cascade and promotes clot formation; injecting it would increase clotting, not prevent heart attack or stroke.
B. Fibrinogen: Fibrinogen is the soluble precursor that is converted to fibrin during clot formation; giving fibrinogen would support clot formation, not reduce it.
C. Fibrin: Fibrin is the insoluble protein that forms the mesh of a clot; injecting fibrin would directly contribute to clotting.
D. Factor X: Factor X is a key coagulation factor (when activated to Xa it drives thrombin formation); administering it would promote coagulation rather than prevent it.
E. Heparin: Heparin is an anticoagulant that enhances antithrombin activity and reduces clot formation; it is used to prevent or treat thrombosis and reduce risk of heart attack/stroke.
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