
Introduction:
Positive feedback is a physiological phenomenon in which a change in the system’s internal condition generates a response in the same direction as the cause of the change. In other words, positive feedback intensifies a physiological condition.

Answer to Problem 1E
Solution:
The correct answer is option (e).
Explanation of Solution
Explanation/justification for the correct answer:
During childbirth, the uterus undergoes contractions in order to push the fetus out of the cervix. This is aided by the action of the hormone oxytocin. It is known that uterine contractions during parturition induce the production of oxytocin. Oxytocin functions to intensify these contractions and help the fetus to move out of the cervix with ease. Hence, oxytocin sets up a positive feedback loop by increasing the uterine contraction. So, the correct answer is option (e).
Explanation for the incorrect answer:
Option (a) states that in conditions of increased acidity suppresses the cells lining the stomach walls to produce more acid. This is an example of negative feedback as the response to the change is in reverse direction to the cause. So, this is an incorrect option.
Option (b) states that a rise in blood pressure Triggers the elimination of water in the urine, which reduces blood pressure. This is an example of negative feedback as the response to the change is in reverse direction to the cause. So, this is an incorrect answer.
Option (c) states that an risein the concentration of H+in blood causes an risein excretion in urine. This is a case of negative feedback as elimination in urine reduces the concentration of H+in blood. Hence this option is incorrect.
Option (d) states that an risein carbon dioxide concentration in the blood Triggers breathing, which increases the rate at which carbon dioxide is eliminated from the body. Elimination reduces the carbon dioxide concentration in blood hence it is negative feedback. So this option is incorrect.
Among the given options option (e) Contraction of the uterus push the fetus against the cervix that triggers the release of oxytocin in the bloodstream; oxytocin the Triggers stronger contraction of the uterus. is an example of positive feedback.
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Chapter 1 Solutions
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