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

This vasodilation is dependent on the endothelium and factors inside the endothelium. The intracellular calcium levels are raised by endothelium-dependent vasodilators such as acetylcholine. NO is formed as a result of this, which is an endothelial-derived relaxing factor. Now NO moves to the vascular smooth muscles to cause its vasodilating effect

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 enzymes are enzymes that are continuously synthesized whether suitable substrate is available or not.

Induced enzymes are enzymes that can only be detected after a certain substance (inducer) has been added.

Because Constitutive enzymes are constantly produced, they have a greater chance to be influenced by pathology than the temporary induced enzyme.

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

Septic shock results when infectious organisms that are found in the bloodstream induce a profound inflammatory response and then causes haemodynamic decompensation. The components that are found in the bacteria, such as cytokines, can lead to the formation of iNOS in macrophages, smooth muscles, etc. If the NO is widespread it then results in severe hypotension, shock and death.

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?

NOS enzyme inhibitors are released by the body, this binds competitively to the arginine binding site in NOS, thus arginine cannot be converted to NO.

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

NO that is released can, due to its role in Prostaglandin synthesis, have an iflammatory response when there is an injury or infection. This causes erythema (redness of the skin), vascular permeability and oedema (acute inflammation).

advantage: NO and peroxynitrates that are formed during inflammation are important microbicides.

disadvantage: an overproduction of NO can lead to tissue damage, psoriasis lesions, etc. It can also influence disease pathology.

In which possible neurological and psychiatric diseases is NO involved? 

Parkinson's disease, stroke and amyotrophic lateral sclerosis.