Question

Which one of the following is an example of negative feedback loop in humans ?

• A. Constriction of skin blood vessels and contraction of skeletal muscles when it is too cold
• B. Secretion of tears after falling of sand particles into the eye
• C. Salivation of mouth at the sight of delicious food
• D. Secretion of sweat glands and constriction of skin blood vessels when it is too hot

Answer 1

The correct option is A Constriction of skin blood vessels and contraction of skeletal muscles when it is too cold

• Negative feedback is a reaction that induces a decrease in function.
• It occurs in response to some kind of stimulus. In the case of heat regulation in the human body, when the temperature of the body falls from the normal level (less than 37°C), blood vessels start to constrict (vasoconstriction) for holding heat.
• Skeletal muscles start to contract, which produces a shivering effect that increases the level of heat production. It is an example of the negative feedback system.

So the correct option is A.