Which of the following is not an example of a negative homeostatic mechanism in the human body?
Increasing heart rate and force of contraction when blood pressure falls.
Secreting insulin after a meal to return blood sugar concentration to normal.
Retention of fluid leads to retention of more fluid.
Shivering when body temperature falls below normal.
The Correct Answer is C
This is because it is an example of a positive feedback loop, which amplifies the change and moves the system away from its normal state.
A negative feedback loop is a mechanism that reverses a deviation from the set point and maintains homeostasis.
Choice A is wrong because increasing heart rate and force of contraction when blood pressure falls is a negative feedback loop that restores blood pressure to normal.
Choice B is wrong because secreting insulin after a meal to return blood sugar concentration toward normal is a negative feedback loop that regulates glucose levels.
Choice D is wrong because shivering when body temperature falls below normal is a negative feedback loop that increases heat production and raises body temperature.
Normal ranges for blood pressure are 90/60 mmHg to 120/80 mmHg, for blood glucose, are 70 mg/dL to 140 mg/dL, and for body temperature are 36.5°C to 37.5°C or 97.7°F to 99.5°F.
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Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is D
Explanation
Exocrine glands secrete through ducts or tubes to the body’s exterior.
For example, sweat glands, salivary glands, and liver are exocrine glands.
Choice A is wrong because exocrine glands do not only secrete salts, but also other substances such as enzymes, mucus, and sebum.
Choice B is wrong because exocrine glands do not secrete hormones at all.
Hormones are secreted by endocrine glands, which are ductless glands that release their products directly into the bloodstream.
Choice C is wrong because exocrine glands do not secrete into the bloodstream, but onto an epithelial surface such as the skin or the gastrointestinal tract.
Only endocrine glands secrete into the bloodstream.
Correct Answer is D
Explanation
The pulmonary circuit sends oxygen-poor blood to the lungs, where it is oxygenated and returned to the heart.
This is distinguished from the systemic circuit, which sends oxygen-rich blood to the tissues and returns oxygen-poor blood to the heart.
Choice A is wrong because it confuses the pulmonary circuit with the systemic circuit. The pulmonary circuit does not send blood to the tissues but to the lungs.
Choice B is wrong because it only describes part of the pulmonary circuit.
The pulmonary circuit sends oxygen-poor blood to the heart, but only after it has been oxygenated in the lungs.
Choice C is wrong because it confuses the pulmonary circuit with the systemic circuit. The pulmonary circuit does not bring blood from the tissues but from the heart.
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