Quiz 20

Why should you love your kidney and treat it right?

Because it controls blood pressure Because it determines blood viscosity Because it prevents anemia - The kidney detects low blood oxygen levels and blood pressure. When blood oxygen is too low (anemia), it releases erythropoietin (EPO), a hormone that increases red blood cell production. The more red blood cells produced, the greater the blood viscosity. When blood pressure is too high, the kidney can correct the problem by producing more urine. Urine is really just filtered blood and so with increased urine production, there is less blood volume and therefore less blood pressure. What is very amazing about this pressure/urine volume relationship is that it can work independently of hormones as a simple pressure filter. The higher the pressure, the more urine produced; the more urine made, the lower the blood volume will drop and therefore further reduce blood pressure. This is a life long mechanism for regulating blood pressure. Of course this can work in reverse such that if blood pressure is too low, less urine is made and blood volume with rise (coupled with some fluid intake as well).

Why are women more prone to bacterial infections of the urinary tract than men?

Because women have shorter urethras - With the much shorter urethras in women, contaminating bacteria from the external world can move into the urinary tract. Inflammation of the urinary tract attempts to combat the bacteria, causing pain. Bacteria can also move into the bladder or even up the ureters to cause kidney infections.

Compare this image to the baseline in Model 1. How would GFR change in this image relative to baseline? (Left artery larger than right)

GFR would increase

Compare this image to the baseline in Model 1. How would glomerular hydrostatic pressure change in this image relative to baseline? (Left artery larger than right)

Glomerular hydrostatic pressure would increase

Why must GFR be kept at a constant level?

So that you filter your blood to remove wastes So that you can maintain blood pressure So that you can maintain the proper ion concentration in your blood - A balanced rate of glomerular filtration ensures that your blood gets filtered at a rate which your nephron tubules can work with the filtrate inside of them. If the GFR is too high, the filtrate passes through the nephron too fast and solutes (& water) do not get reclaimed (reabsorbed). If GFR is too low, too much volume get reabsorbed and waste products do not leave the body. Maintaining blood composition and volume factor into the maintenance of blood pressure. You must maintain an appropriate rate of glomerular filtration to constantly adjust your blood levels of ions and wastes. If you do not filter your blood, body pH is not maintained and ionic composition changes. These in turn affect cellular functions such that neurons may not fire or the heart may not beat. Enzymes in the body also need a steady environment in which to work.

Which of the following will be the response of the nephron to increase filtrate formation in response to too little filtrate flowing past the distal convoluted tubule?

The afferent arteriole will dilate

Using this image (Model 3 from worksheet), what factor decreases GFR the most?

severe blood loss

When blood pressure or blood volume are too high, ____ will be released and will stimulate the kidney to ____ GFR so that blood volume & pressure will decline.

ANP; increase

Using Model 3, why does increasing blood plasma protein concentration impact GFR the way it does?

It increases glomerular colloid osmotic pressure, thus decreasing GFR