Negative and positive feedback Knowledge-Based Practice

Questions

1. 1.

   In a physiological negative feedback loop, what causes the activity of the effector to decrease once the controlled variable begins returning to normal?

   • A) The gradual reduction of the initiating stimulus as the variable approaches the set point lowers receptor signaling to the control center.
   • B) The control center detects effector exhaustion and permanently raises the variable's target set point.
   • C) The effector triggers an antagonistic positive feedback cycle that suppresses its own functional output.
   • D) The sensory receptors undergo complete sensory adaptation after a fixed interval, terminating communication.
2. 2.

   In homeostatic regulation governed by negative feedback, how is a physiological variable maintained relative to its set point?

   • A) It is held at an absolutely fixed, unvarying numerical value through continuous and constant effector activity.
   • B) It fluctuates within a narrow, predictable range around the set point in a state of dynamic equilibrium.
   • C) It progressively deviates further from the set point until an external event halts the response.
   • D) It oscillates between extreme physiological thresholds because effectors can only function at maximum capacity.
3. 3.

   How does a physiological positive feedback loop typically achieve termination in a healthy organism?

   • A) Sensory receptors spontaneously reverse their electrical polarity to decrease effector activity.
   • B) The control center permanently adjusts the internal set point to match the heightened physiological level.
   • C) Effector tissues deplete their metabolic reserves until cellular activity ceases entirely.
   • D) A specific culminating event occurs that eliminates the initial stimulus driving the loop.
4. 4.

   In homeostatic regulation, how does the response produced by an effector in a negative feedback mechanism fundamentally differ from that in a positive feedback mechanism?

   • A) A negative feedback mechanism amplifies the initial stimulus, whereas a positive feedback mechanism diminishes it.
   • B) A negative feedback mechanism opposes the initial change from a set point, whereas a positive feedback mechanism reinforces the change.
   • C) A negative feedback mechanism operates without a control center, whereas a positive feedback mechanism requires hormonal regulation.
   • D) A negative feedback mechanism continuously destabilizes internal conditions, whereas a positive feedback mechanism maintains a dynamic equilibrium.
5. 5.

   Which of the following physiological processes operates through a positive feedback mechanism rather than a negative feedback loop?

   • A) The amplification of uterine contractions stimulated by oxytocin during childbirth
   • B) The secretion of insulin by the pancreas to lower elevated blood glucose levels
   • C) The activation of sweating and vasodilation in response to an increase in body temperature
   • D) The release of parathyroid hormone to restore declining blood calcium concentrations

Answers and step-by-step solutions appear after you finish the test.