1. What do you understand by the term "endothelium-dependent" vasodilation? Explain. 

It refers to the increasing of intracellular Calcium levels in endothelial cells which then leads to the synthesis of Nitric oxide. This NO then diffuses to the smooth muscle resulting in vasorelaxation.

2. When we talk about NOS enzyme, what is meant by "constitutive" and "inducible" enzymes and what are the pathological and physiological implications thereof? 

 Constitutive enzymes: Are enzymes which are synthesised at a constant rate/ level, therefore the enzyme is synthesised in constant amounts regardless of the physiological amounts of the substrate. Constructive enzymes are regulated by calcium. An increase in cytosolic calcium concentrations will trigger the synthesis of NO. 

Inducible enzymes: Are enzymes which are present in minute concentrations in a cell. When a substrate is added this enzyme will increase.  Inducible enzymes are not regulated by Calcium which results in the accumulation of iNOS protein and synthesis of large amounts of NO.

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

Endotoxin components along with endogenously generated TNF and other cytokines induce the synthesis of iNOS in: macrophages, T cells, hepatocytes, smooth muscle cells, endothelial cells and fibroblasts. This wide range of NO generation leads to hypotension, shock and may also resukt in death. 

4. Which autacoids' mechanism of action depends on the guanylyl cyclase - cGMP system?

Nitric Oxide (NO).

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

NO can react with heme and hemoproteins which oxides NO to Nitrate. NO can react with hemoglobin resulting in the transportation of NO throughout the vasculature.

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

NO acts pro-inflammatory as it is an immune regulator. 

Advantage: TH1 cells synthesise NO, which is important with the impaired protective response to injected parasites in animal models after inhibition of iNOS.

Disadvantage: In both acute and chronic inflammatory conditions NO production may magnify tissue injury.

7. In which possible neurological and psychiatric disease is NO involved?

Stroke and Parkinson's disease