Control of body fluid volume and osmolality Flashcards
1
Q
Where are prostaglandins synthesised?
A
- Cortex of kidneys
- Medullary interstitial cells
- Collecting duct epithelial cells
- Synthesis stimulated by a decrease in effective circulating volume
2
Q
What are the effects of prostaglandins?
A
- Release of vasodilators
- Renin release
3
Q
What does a decreased circulating volume result in?
A
- Decreased venous return
- This then causes decreased cardiac output
4
Q
What are the consequences of decreased venous return?
A
- Detected by atrial stretch receptors
- This increases ADH release
- More water is reabsorbed in the kidneys
- Circulating volume increases
5
Q
What are the consequences of decreased cardiac output?
A
- Decreased BP sensed by baroreceptors
- Causes increase in sympathetic tone
- CO and peripheral resistance increase
6
Q
Decreased CO also causes decreased blood flow to kidneys. What are the consequences of this?
A
- Decreased hydrostatic pressure in capillaries and increased renin release
- Both cause increased Na+ tubular reabsorption
- This increases renal H2O retention and circulating volume
7
Q
Outline the function of atrial naturetic peptide?
A
- Inhibits Na+/K+ ATPase and closes ENac channels
- Reduces Na+ reabsorption
- Na+ and water excretion by kidney is increased
- Vasodilates afferent arterioles and increases GFR
- Inhibits aldosterone secretion
- Inhibits ADH release
- Decreases renin release
8
Q
When is ANP produced?
A
- Produced by cardiac atrial cells in response to an increase in ECF volume
9
Q
How does BP affect the reabsorption of Na+?
A
- High BP causes higher hydrostatic pressure and lower osmotic pressure in capillaries
- This causes less reabsorption of Na+
