Physiology Kidney Regulation

Which parts of the nephron respond to regulatory hormones?

• distal convoluted tubule

• collecting duct

Osmolarity gradient in cortex

300 mOsm/L

Osmolarity gradient in Outer Medulla

600 mOsm/L

Osmolarity gradient in Inner Medulla/ Bottom of Loop of Henle

1200 mOsm/L

Glomerular filtration rate

the rate at which blood is filtered through the glomeruli into the Bowman’s capsule

Anti-diuretic hormone

• ADH released by hypothalamus based on signals from stretch receptors in aorta, carotid sinus, and osmoreceptors in CNS

How does ADH affect permeability?

increases permeability of CD in kidneys, retaining more water

How do ADH and BP interact with other?

• if BP high →hypothalamus inhibited, less ADH so more water leaves in urine

• if BP drops, hypothalamic stimualted, more ADH, less water leaves in urine, (extra fluid) blood volume and pressure increases

Renin

• released by JGA if blood pressure drops

• converts andiotensinogen to angiotensin I

Where is angiotensinogen produced?

in liver and is already in blood plasma for renin to convert

Angiotensin Converting Enzyme

converts angiotensin I to angiotensin II (active form)

Where is angiotensin found?

endothelial capilaary walls

• primarily in lungs

What 3 things does angiotensin II does?

1. stimulates thirst centers in brain (dipsogenic response)

2. causes peripheral vasoconstriction

3. stimulates release of aldosterone from adrenal gland

What does aldosterone do in the angiotensin-aldosterone system?

stimulates resorption of sodium in DCt

Atrial Natriuretic Hormone

• if blood volume too great, stretch receptors stimulate release of this hormone

• inhibits sodium reabsorption in DCT so more sodium is lost in urine

• reduction in sodium content in blood, reduces blood volume and pressure

What are the three major buffer system?

1. bicarbonate

2. ammonia

3. phosphate

Where is plasma pH regulated?

distal tubules and collecting duct

Bicarbonate Buffer: A-type cells

• CO2 from blood enters cell

• inside cells, carbonic anhydrase forces CO2 +H20→proton plus HCO3

• active protein pumps pump H ions out into urine

• apical

Bicarbonate Buffer: B-type cells

• CO2 from blood enters cell

• inside cells, carbonic anhydrase forces CO2 +H20→proton plus HCO3

• active protein pumps pump H ions into bloodstream

• basolateral

Why buffer urine?

• low solubility at low pH = risk of kidney stones and gout

• slightly acidic urine inhibits bacterial growth

What is main nitrogenous wastes in humans?

urea

How does the body get rid of urea?

• kidney filters it from blood

• waste leaves body in liquid form as urine