Which one of the following is an example of negative feedback loop in humans?
1. Secretion of sweat glands and constriction of skin blood vessels when it is too hot.
2. Constriction of skin blood vessels and contraction of skeletal muscles when it is too cold.
3. Secretion of tears after falling of sand particles into the eye.
4. Salivation of mouth at the sight of delicious food.

All the following regarding regulation of a physiological function by either a neurotransmitter or a hormone are true except:

1. Target cells must have specific receptor proteins with which these molecules combine.
2. When these molecules bind to target cells, specific sequences of changes must occur.
3. There must be an "off-switch" that will stop the induced changes.
4. Second messengers will always be involved in the response of the target cell.

Assertion: Hormone pathways involved in homeostasis typically involve negative feedback and are often paired.
Reason: Negative feedback helps restore a pre existing state.

1. Both assertion and reason are true and the reason is the correct explanation of the assertion.
2. Both assertion and reason are true but the reason is not the correct explanation of the assertion.
3. Assertion is true but reason is false.
4. Both assertion and reason are false.