A receptor is a cell (or a group of cells) in a sense organ which is sensitive to a particular type of stimulus such as light, sound, smell, taste, heat, pressure, etc. The different sense organs contain receptors for detecting different stimuli.
When receptors do not work properly, the environmental stimuli are not able to create nerve impulses and the body does not responds.
When receptors are damaged, the external stimuli transferring signals to the brain are not felt.
For example,
(i) During fever, taste buds do not work properly and as a result, taste of the food eaten is not felt properly thus enzyme secretion is also affected.
(ii) When a person is suffering from a cold, the nostrils are filled with mucus. Then smell of the surrounding is not felt properly. This is due to interruption in reacting to the sense of smell by the olfactory receptor.
(iii) When skin receptors are damaged, and we accidentally touch a hot object, then our hands might get burnt as the damaged receptor cannot perceive the external stimuli of heat and pain.