8. Control of blood volume Flashcards
How is blood volume regulated long term?
Control of body flui volume by the kidneys; renal-body fluid feedback system
What happens to urine production when ArtP increases?
Increase
What happens to urine production when ArtP decreases?
Decreases
What are the primary determinants used to control blood volume?
- Renal output curve for salt and water
- Level of salt and water intake
Draw a flow chart of the process to control blood volume
When is ADH/vasopressin released?
- Increased osmotic pressure
- hypovolemia
- hypotensin
- angiotensin II
Where is ADH released from?
Pituitary gland
What detects an increase in osmotic pressure?
Hypothalamic osmopreceptors
Swell/contract depending on the concentration of solutes in the blood
What do atrial baroreceptors normally inhibit?
ADH release
What does hypovolemia cause?
Decreased baroreceptor firing so increased ADH release
What does hypotension cause?
- Decreased baroreceptor firing
- Increased SNS
- Increased ADH
What does an increase in angiotensin II cause?
Release of ADH
How does ADH increase blood volume?
Increased permeability in renal collecting ducts; stopping the loss of fluid
How does ADH affect urine production?
Decreased urine production
What happens in severe hypovolemic shock?
ADH release = high and causes vasocontriction, which increases TPR
What causes the release of renin?
- Sympathetic nerve activation
- Renal artery hypotension
- Decreased Na+ in kidney distal tubules
Where is renin released from?
Kidney juxoglomerular cells
Where does angiotensin II act?
Acts on resistance vessels increasing TPR
What does angiotensin II cause the release of?
Aldosterone from adrenal gland
How does aldosterone act?
Increased Na+ and water reabsorption
What is ANP? and how does it work?
Atrial-natriuetic hormone, whcih is synthesied and stored in the muscle cells in the atria.
Released in response to the stretching of the atria and helps oppose the effects of the RAAS system (counteracts volume overload)
What can cause hypovolemia?
- Decrease in whole body volume (haemorrhage)
- Decrease in plasma (burns)
- Decrease in sodium (vomitting)
What occurs in hypovolemia intially?
- Decreased SV
- Increased HR
- Decreased CO
- Increased TPR
- Decreased MABP
**Uses CVS mechanisms to compensate
What body mechanisms bridge the gap between the neuronal and RAAS systems in hypovolemia?
- Arteriolar contriction
- Decrease hydrostatic pressure
- Fluid reabsoption
- temporary redistribution
- Decreased renal blood
- Baroreceptors and thirst
What is a result of severe hypovolemia?
Heart Failure
