What term describes the condition where the body becomes hypersensitive due to insufficient ligand exposure?

• A. Down Regulation
• B. Up Regulation
• C. Desensitization
• D. Receptor blockage

Answer: (B)

The term that describes the condition where the body becomes hypersensitive due to insufficient ligand exposure is known as up regulation. In this scenario, when there is a lack of sufficient ligands (such as hormones or neurotransmitters) that bind to their respective receptors, cells may respond by increasing the number of receptors on the cell surface. This adaptive mechanism aims to enhance sensitivity to the low levels of available ligand, making the cells more responsive.

This process is particularly relevant in situations where the natural levels of stimulants are decreased, such as during chronic exposure to low hormone levels. The increase in receptors allows for improved signal detection when ligands do become available, thereby promoting better physiological responses despite the initial deficiency in ligand availability.

In contrast, down regulation refers to a decrease in receptor number or sensitivity due to prolonged exposure to a high concentration of ligands, leading to decreased cellular responsiveness. Desensitization involves a temporary state of reduced response to a continuous stimulus, while receptor blockage typically pertains to scenarios where a receptor is obstructed by an antagonist or another molecule that prevents natural ligands from binding.