Negative and positive feedback Knowledge-Based Download PDF

Questions

1. 1.

   When arterial blood pressure rises above normal homeostatic levels, the baroreceptor reflex triggers physiological changes that decrease heart rate and promote vasodilation. In the context of homeostatic feedback mechanisms, why is this response classified as negative feedback?

   • A) It amplifies the initial increase in arterial stretch to rapidly push the cardiovascular system past a critical threshold.
   • B) It permanently resets the baseline cardiovascular set point to match the newly elevated arterial pressure.
   • C) It initiates an escalating series of contractions that depend entirely on an external anatomical event to terminate.
   • D) It produces an effector output that reverses the direction of the initial disturbance toward the homeostatic set point.
2. 2.

   In human physiology, how does a negative feedback mechanism maintain a regulated variable in a state of dynamic equilibrium?

   • A) By holding the variable at a perfectly fixed, unvarying numerical value under all conditions
   • B) By permanently inactivating cellular receptors once the target set point is achieved
   • C) By stimulating effectors to increase their activity proportionally with every deviation above baseline
   • D) By producing continuous corrective adjustments that cause the variable to fluctuate within a narrow range around a set point
3. 3.

   Unlike negative feedback mechanisms that naturally self-stabilize near a set point, how is a healthy physiological positive feedback cascade typically brought to an end?

   • A) By an outside or culminating event that abruptly eliminates the stimulus driving the cycle
   • B) By the gradual resetting of the control center's homeostatic set point to a higher baseline
   • C) By the effector generating an opposite, inhibitory output each time the variable deviates
   • D) By the metabolic depletion of all biochemical receptors involved in sensing the deviation
4. 4.

   In human homeostasis, which statement best describes the fundamental operational difference between negative feedback and positive feedback mechanisms?

   • A) Negative feedback amplifies deviations from a physiological set point, whereas positive feedback diminishes the response to maintain balance.
   • B) Negative feedback counteracts deviations from a physiological set point, whereas positive feedback reinforces the deviation to drive a process toward completion.
   • C) Negative feedback relies exclusively on endocrine hormones, whereas positive feedback relies entirely on neural signaling pathways.
   • D) Negative feedback is triggered only when a variable drops below its set point, whereas positive feedback is triggered only when a variable rises above its set point.
5. 5.

   Which of the following physiological processes is regulated primarily by a positive feedback mechanism rather than a negative feedback mechanism?

   • A) Regulation of blood glucose concentration by insulin and glucagon
   • B) Uterine contractions during childbirth amplified by oxytocin release
   • C) Maintenance of core body temperature through shivering and sweating
   • D) Osmoregulation of blood plasma through antidiuretic hormone secretion