Physiology Review Slides Lec. 18

Question 1

Mechanism of ADH Release

Answer 1

• Starts with an INCREASE in EC Fluid osmolarity
• > Osmoreceptor cells in ANT. Hypothalamus

——> Action Potential

———> Release of ADH (POST. Pituitary)

Question 2

Fxn of ADH

Answer 2

Increase WATER Reabsorption

Question 3

Where is ADH Formed?

Answer 3

In Magnocellular Neurons in the

1. Supra-Optic Nuclei
2. Para-Ventricular Nuclei

Question 4

Requirements for forming Concentrated urine

Answer 4

• Presence of ADH

- High Osmolarity of Renal MEDULLA

Question 5

The purpose of the Countercurrent Multiplier System?

Answer 5

To create a CONCENTRATION gradient for ADH to work

Question 6

Max concentration of Urine

Answer 6

1200 - 1400 mOsm/L

Question 7

When there is a Large EXCESS of water in the body, how much can the Kidneys excrete? What will be the concentration be?

Answer 7

• 20 Liters/day

- 50 mOsm/L

Question 8

What is the Obligatory Urine volume

Answer 8

0.5L/day

Question 9

Fxn of the Osmoreceptor-ADH Feedback Mechanism

Answer 9

To control EC Fluid SODIUM Concentration and Osmolarity

Question 10

Why is the [ ] gradient limited to 200mOsm in the Tubule?

Answer 10

Because of the PARACELLULAR diffusion of ions back INTO the Tubule.