Question

Positive feedback mechanisms are used to maintain homeostasis. Describe the positive feedback regulation, the contractions of labor, and answer the questions below in great detail. (8 pts)

For positive feedback:

What is the variable? (0.5 pt)

What is the normal range? (0.5 pt)

Which conditions may change the variable? (0.5 pt)

How the changes to be detected? (1 pt)

What is/are the response(s)? (1 pt)

What is the final effect? (0.5 pt)

Answer 1

Homeostasis is the maintenance of a stable environment of a body.In human body there are many conditions to be maintained like body temperature,pressure,glucose levels,levels of nutrients etc.This is maintained by feedback loops when a response to change in environment occurs.There is Positive feedback regulations and Negetive feedback regulation.

In positive feedback regulation mechanism, the output of a particular response changes in such a way that it increases or stimulates the output further.Here a deviation from normal range of any condition is not reversed ,but results in amplifying the change and the original stimulus is suppressed. An example of positive feedback regulation is the childbirth at full term.During childbirth growth of fetus causes a stretch in uterine walls and is detected by stretch receptors.This results in the release of a hormone called oxytocin that makes contractions in the uterine muscles.As the labor is near more oxytocin is secreted which in a positive feedback loop stimulates the secretion of prostaflandins from fetal membranes that even increases the contractions.This positive loop continues to trigger the secretion of these hormones and finally sum of these changes initiates regular contractions that becomes more powerful and frequent.This cycle is stopped only when the baby is born.This explains the positive feedback regulation.

In homeostasis variable is a parameter that is affected by the feedback regulation.In positive feedback the variable is the stimulus that is triggering the changes and is further affected by the changes.In the example of child birth the variable is the tension in cervical tissue.

A normal range is a parameter in which fluctuations below or above a certain value is not considered significant.If the value  fluctuates negetive or positive feedback regulation occurs.For example  the body temperature,pressure etc. In positive feedback is normal only if there is an end point in the loop.

The conditions that may change the variable includes body temperature,blood glucose levels ,water levels.In positive feedback loop the condition is a response of a nerve or tissue to stimulate a variable and finally stop the stimuli when it is no longer needed.In child birth the condition that changes the variable is the fetal growth.

In order to detect a change in internal or external environment there are receptors in the body that can detect a change in the environment.These receptors responds to specific stimulus and any change leads to an electric impulse and thus changes in hormonal activities.Thus the brain signals an effector to respond to stimuli using a negetive or positive loop.In child birth the change is detected by stretch receptors.

The responses in homeostasis feedback mechanisms includes nervous responses from the nervous system or chemical responses from the endocrine system.In the example of childbirth the response was the release of oxytocin hormone.

The final effect is a change in the conditions that caused the regulation mechanism.The change is either maintaining the levels back in the normal range in negetive feedback loops or the end of a particular stimuli in positive loop.In the example of child birth the birth of the child ended the loop.