1. Aldosterone
Physiology 3
Hannah Lim

2. To increase blood pressure
Main purpose
To increase blood pressure

3. Structure

4. Cortex of adrenal glands above the kidneys
Where does it come from?
Cortex of adrenal glands above the kidneys

5. How does body sense low BP?

6. How does it work? urine blood
Goal: Increase Na+ and water reabsorption in blood to increase vessel pressure

7. Goal: Bring in Na+ from urine into the bloodstream through different channels

8. Three main functions
Create Na+/K+ pump to drive K+ ions into the principal cell of collective duct.
Creates K+ channels on the apical surface of the principal cell to allow K+ to flow through passive transport to the urine
Creates Na+ channels on the apical surface of the principal cell to allow Na+ from the urine into the principal cell, then through the Na+/K+ pump into the blood.
High concentration of Na+ in blood causes osmosis to occur, so water from the urine will come into the blood
Increased stroke volume = Increased blood pressure

9. Aldosterone - steroid pathway
DNA binding protein

10. What else does it do? Removes excess protons from blood
H2O + CO2 → H2CO3 ⇒ H+ + HCO3-
Goal: Reduce free protons in blood to prevent acidosis

11. How do leftover protons escape cell?
Proton pump
Sodium proton pump
Potassium proton pump H+ H+
Na+ H+ K+
Goal: Get rid of leftover protons in alpha intercalated cell through pumps that also power the aldosterone pathway to increase blood pressure

12. How does aldosterone “know” when to be released?
2 alternative triggers:
Angiotensin II activates adrenal glands
High potassium levels in blood
How does aldosterone “know” when to be released?

13. Renin Angiotensin Aldosterone Pathway

14. High Potassium Levels in Blood

15. Thanksgiving Anecdote
Grandpa had blood pressure 190/88 and was severely dizzy when he stood up. He regularly takes 3 medications, 1. Beta blocker, 2. Ca+2 channel blocker, 3. Angiotensin II receptor blocker. He took the beta blocker again when we arrived, but it did nothing to lower his blood pressure. Angiotensin II receptor blocker would have worked because it would have intercepted the cascade:
Blood vessels would not constrict.
Aldosterone would not be stimulated to increase Na+ and water reabsorption in the blood.

17. Significance
Understanding the pathways in physiology can allow you to think on the spot during emergencies. Often times, people take medications blindly, but you now have the knowledge to think critically before putting yourself, or the ones you love, in danger.