SAQ: Blood flow and atherosclerosis

Question 1

Shear Stress and Laminar Shear stress

Answer 1

• Shear is a frictional dragging force exerted on the vessel wall by the blood moving through the lumen
• LSS is a strong unidirectional form of shear
• Occurs in undisturbed fluid flow

Question 2

Mechanotransduction

Answer 2

• Spatially decentralised mechanism
• Force applied to wall changes tension in cytoskeleton
• Mechanically coupled to a variety of sensors eg c-Src

Question 3

c-Src

Answer 3

• Tyrosine kinase mechanosensor
• Promotes eNOS expression
• Also stabilises its mRNA via two divergent pathways

Question 4

eNOS

Answer 4

• Oxidises arginine (with CFs: BH4, NADPH)
• Citrulline and NO formed
• NO diffuses to local VSM

Question 5

NO

Answer 5

Suppresses

• Leukocyte adhesion
• VSMC migration/proliferation
• Platelet recruitment

Activates

• Guanylyl cyclase
• GTP -> cGMP
• Signalling cascade -> relaxation of VSM