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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Related Questions
Correct Answer is B
Explanation
A hormone is a secreted molecule that is carried in the bloodstream to where it acts on target cells that bear specific receptors for that hormone.
This definition is consistent with the dictionary and encyclopedia sources.
Choice A is wrong because it contradicts the definition of a hormone.
Hormones are not just any secreted molecules, but ones that have specific effects on cells with matching receptors.
Correct Answer is C
Explanation
The endocrine system may have a longer-lasting effect than the nervous system because the hormones it produces can circulate in the bloodstream for a long time and affect many organs and tissues.
The nervous system, on the other hand, uses nerve impulses and neurotransmitters for communication, which are faster but more short-lived.
Choice A is wrong because the endocrine system is essential to life.
It regulates many vital functions such as metabolism, growth, reproduction, mood, sleep, and blood pressure.
Choice B is wrong because the endocrine system takes longer than the nervous system to deliver its messages.
The hormones have to travel through the bloodstream to reach their target cells, while the nerve impulses can travel along the nerve fibers at high speeds.
Choice D is wrong because the endocrine system does use receptors.
The hormones bind to specific receptors on the target cells to trigger a response.
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