Fluid Balance and CV Control

Question 1

Osmolality of ECF can be decreased by:

Answer 1

increase in water intake

Question 2

Osmolality of ECF can be increased by:

Answer 2

• decrease in water intake
• increased sweating
• increased Na⁺ intake

Question 3

2 mechanisms to restore ECF osmolality

Answer 3

1. kidney mechanisms involving ADH:
   
   • regulate amount of water excreted in urine
2. brain mechanisms:
   
   1. regulate amount of water and Na⁺ that are ingested

Question 4

Where are the osmoreceptors located in the hypothalamus?

Answer 4

• within the anteroventral wall of the 3^rd ventricle (AV3V region)
  
  • including the:
    
    • Organum Vasculosum of the Lamina Terminalis (OVLT)
    • Subfornical Organ (SFO)
    • within the Median Preoptic Nucleus (MPO)

Question 5

Osmoreceptor neurons project to the _____________ & ___________ of the hypothalamus.

Answer 5

Supraoptic Nucleus (SON) & Paraventricular Nucleus (PVN)

Question 6

Steps of Osmotic Homeostasis Kidney Mechanism

Answer 6

1. osmoreceptor neurons from MPO, SFO, and OVLT synapse with ADH neurons at the PVN and SON
2. these ADH neurons project axons to the Posterior Pitutiary (neurohypophysis)
3. when stimulated, ADH secreted into blood at that site

Question 7

What happens to the osmoreceptor neurons when plasma osmolality increases (decreased water intake, etc.)?

Answer 7

osmoreceptor neurons shrink due to water leaving osmotically & passing into the ECF

-leads to activation of the ADH neurons in the PVN/SON & ADH secretion

Question 8

Action of ADH at Kidney

Answer 8

• acts via V2 receptors
• increases water reabsorption by Collecting Duct:
  • result = concetrates urine to help restore ECF osmolality

Question 9

What enzymes converts Angiotensinogen to ANGI?

Answer 9

Renin

Question 10

What enzymes converts ANGI to ANGII?

Answer 10

ACE

Question 11

Primary Control Point of Regulation of ANGII Synthesis

Answer 11

Renin