Question

1. As determined in this laboratory exercise, beverages of varying tonicities altered plasma osmolarity. How would the changes in plasma osmolarity and plasma volume you discussed earlier affect the Starling Forces for the Net Glomerular Filtration Pressure and therefore glomerular filtration rate?

Answer 1

Starling’s law of the heart says that increased plasma volume will increase blood pressure throughout the body. The increased blood volume with its higher blood pressure will go into the afferent arteriole and into the glomerulus, resulting in increased GFR. Also, with low blood volume due to dehydration will have a decreased GFR.

Pressure changes within the afferent and efferent arterioles that go into and out of the glomerulus itself will also impact GFR. Vasodilation in the afferent arteriole and vasconstriction in the efferent arteriole will increase blood flow (and hydrostatic pressure) in the glomerulus and will increase GFR.