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

An increase in blood flow stimulates endothelial-dependent vasodilation by increasing the shear stress on the endothelium, in both conduction and resistance vessels.

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

Constituent enzymes are enzymes synthesized by a constant level and constant amounts, so these enzymes are produced in constant quantities without taking into account the concentration of the substrate or the physiological requirements.

An induced enzyme is affected by the presence of an inducer which leads to an increase in gene expression. The concentration of such enzymes increases drastically when a substrate is added.

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

Endotoxin components from the bacterial wall along with endogenously generated tumor necrosis factor and other cytokines induce the synthesis of iNOS in macrophages, neutrophils, T cells as well as hepatocytes, smooth muscle cells, endothelial cells and fibroblasts. This widespread generation on NO results in exaggerated hypotension, shock and in some cases death.

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

Nitric oxide (NO)

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

Scavengers of superoxide anion such as superoxide dismutase may protect NO, enhancing its potency and prolonging its duration of action. Nitrate tolerance.

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

When your body reacts to infection or even injury it leads to the activation of leukocytes and release of inflammatory mediators. which leads to an increase in iNOS levels in leukocytes. The NO produced is an important microbial agent. It helps the immune system to reach the infected area, but also has a disadvantage because it causes vasodilation.

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

Parkinson's disease, stroke and amyotrophic lateral sclerosis.