• What do you understand by the term “endothelium-dependent” vasodilation?  Explain.

It means endothelium controls vascular tone in  a paracrine fashion , by secreting diffusible soluble mediators able to act on physically contiguous cells.

• When we talk about the NOS enzyme, what is meant by “constitutive” and “inducible” enzymes and what are the pathological and physiological implications thereof?

Constitutive  means continuous transcription of gene , and constitutive enzymes are enzymes that are produced independently and are regarded as house keeping.

Inducible means that the presence of an inducer causes an increase in gene expression enzymes are adaptive enzymes used for breaking down in the cell.

• Explain how NO contributes to the fatal pathology of septic shock

This physiological production of NO is important for blood pressure regulation and blood flow distribution. thus hyperproduction of NO by the inducible form of NO synthase (iNOS) may contribute to the hypotension, cardio-depression and vascular hypo-reactivity in septic shock.

• Which autacoids’ mechanism of action depends on effects on the guanylyl cyclase-cGMP system?

Nitric oxide

• NO may be toxic to the cell.  Which mechanisms are available to the body to counter this detrimental effect of NO?

Arginase is an enzyme in the urea cycle that hydrolyses L-Arginine to urea. It suppresses nitric oxide production through various mechanism.

• Name a way in which NO can act pro-inflammatory.  Give examples of where it will have advantages or disadvantages

NO is considered as a pro-inflammatory mediator that induces inflammation due to over production in abnormal situations.

Advantage- it play a role in immune protection , if there are invasive foreign pathogens during inflammatory response , cells respond by production NO to boost the immune.

Disadvantage- affects apoptosis and cell death.

• In which possible neurological and psychiatric diseases is NO involved?

Major depression , schizophrenia ,bipolar