Question

Which is an example of positive feedback?
A) Seasonal growth
B) Vessel diameter and blood pressure
C) Allosteric inhibition of enzymes
D) Both A and B.

Answer 1

Hint:A feedback mechanism is a loop system in which the system responds to a perturbation.The retort may be in the same direction that is positive feedback or in the opposite direction which is negative feedback.

Complete answer:
Positive feedback is a method in which the end products of an action result in more of that action to occur in a feedback loop. This amplifies the unique action. It is contrasted with negative feedback, which is when the end results of an action hold back that action from enduring to occur. These mechanisms are brought into being in many biological systems. An important example of positive feedback is the process of labor and childbirth.
Parts of a Positive Feedback Loop
>Stimulus : A stimulus is something that disrupts the body’s homeostasis. An injury or an infection are examples of stimuli. They affect the normal processes in the body.
>Sensor : A sensor detects the alteration in homeostasis. Example, nerve cells in the cervix perceive pressure placed on it from the head of the fetus during labor. Nerve impulses from a sensor will pass through to the control center.
>Control Center : A control center is the part of the body that responds to the variation and takes action. The pituitary gland which is located near the brain, is the control center in many feedback loops. It produces many diverse hormones, such as oxytocin, growth hormone, and antidiuretic hormone (ADH), in response to stimuli.
>Effector : Effector is any organ or a cell that eventually responds to the stimulus. For example in labor, the end outcome of the positive feedback loop is that the uterus contracts. In this situation, the uterus is the effector organ.
These four parts are also seen in negative feedback loops, but the end result is different because in negative feedback the effector organs work to delay the process that caused them to activate. Positive feedback loops do not go on forever. They are eventually stopped by negative feedback loops once the process they were used for is complete.
The growth of many organisms is seasonal, depending on variation in temperature, light, and food availability. A growth model proposed by Somers is one of the most broadly used models to describe seasonal growth.

So the correct answer for this is option (A) seasonal growth.

Note:Positive feedback occurs to raise the change or output. The result of a reaction is amplified to make it occur more speedily. Negative feedback occurs to decrease the change or output. The result of a reaction is reduced to carry the system back to a stable state.