Regulation

Water/Ion Balance

• this lesson will cover water and ions and their concentrations in our blood/plasma
• too much water = swelling = hypertension
• not enough water = shriveling = hypotension
• high ion concentrations will draw water to that area by osmosis (more water reabsorbed into our bodies)
• low ion concentrations will have a higher water concentration to begin with, but will need to gain more ions to be within the "normal" range for our body (more ions reabsorbed by our body

Two Main Hormones

• Vasopressin (ADH) - increases water in the blood
• Aldosterone - increases ions in the blood

Vasopressin (ADH)

• important for water reabsorption
• secreted from posterior pituitary, made by hypothalamus
• stimulated by receptors found in the walls of arteries that can tell when the walls are stretched or not.
• ADH released when there is not enough water in the blood ––> no stretch detected in artery walls
• binds to receptors on collecting tubule cells and causes aquaporin to be put into the membrane
• dysfunction results in diabetes

Aldosterone

• important for ion reabsorption (Na+ and K+)
• secreted from the adrenal gland
• regulated by negative feedback
• also partly regulated by renin - a hormone made at the beginning of the nephron

1. aldosterone binds to a receptor on a cell in the ascending loop of Henle
2. receptor sends a signal to make more Na+ and K+ channels
3. channels are made and put into the cells so more Na+ and K+ can return to the blood

Big Picture Summary

• ex. when you drink alcohol, the alcohol actually inhibits the function of ADH -–> less water is reabsorbed back into the body = more water in urine ––> thats why you have to pee all the time!

Rein-Angiotensin-Aldosterone System (RAAS)

• activated by low blood pressure (BP) aka hypotension
• kidneys sense the low BP and RAAS begins

1. Sensors determine low blood pressure and renin enzyme is made in juxta-glomerular cells
2. think "just a step away" from the glomerulus
3. Renin is released into the blood and heads to the liver
4. Angiotensinogen acts in Renin and turns it into angiotensin l
5. Angiotensin l moves through the blood stream to the area of the lungs, where it meets angiotensin converting enzyme (ACE)
6. ACE turns angiotensin l into angiotensin ll

• ion reabsorption in the kidneys (nephron)
• activation of the sympathetic nervous system
• making aldosterone
• vasoconstriction ––> causing increased blood pressure
• stimulates secretion of ADH ––> decreases urine output

Extra Activity...

• Where is the hormone made?
• Where is the hormone secreted from?
• Stimulators?
• Inhibitors?
• Action?