Homeostasis

Negative feedback is far more common in maintaining homeostasis than is positive feedback.

It refers to negative feedback. Positive feedback is also possible (but rare); nevertheless, choice A is the best answer.

The effector produces the effect that it is directed to by the integrating centre. That direction is passed along the efferent (or outgoing) pathway.

Homeostasis tends to respond to a detected change with “negative feedback”. The duodenum requires an alkaline environment, so the arrival of acidic chyme would result in a response that causes duodenal pH to rise. By closing the pyloric sphincter, the alkaline pancreatic juice and alkaline brush border secretions will have time to restore duodenal pH to the required level of about 7.4.

The hypothalamus would respond in a way that opposed the rise in osmotic pressure. Releasing more ADH would make the distal convoluted tubules of the nephrons to become more permeable to water. This would allow more water to be reclaimed from the filtrate which would act against the osmotic pressure of the plasma from rising further. It would also stimulate thirst.

Homeostasis tends to result in a response that opposes the detected change. So something would happen to promote the loss of heat from the body. The evaporation of sweat from the skin will produce a cooling effect on the superficial tissues. The other choices would generate more heat or decrease heat loss.

Homeostasis is derived from words that mean remaining similar and standing still and refers to physiological conditions remaining more or less the same.