Control of Blood Volume Flashcards
What is responsible for the long term regulation of blood pressure?
Regulation of kidney function to control the body’s fluid volume
How do the kidneys control the body’s fluid volume?
Renal body-fluid feedback system:
- when arterial pressure increases, urine output increases and vice versa
- due to increased ECF increasing blood volume, cardiac output, and total peripheral resistance
What are the 2 determinants of the regulation of blood pressure?
- renal output curve for salt and water
- level of salt and water intake
What effect does increasing water and salt intake on MABP graph?
If renal output for water and salt remained the same, then you would have a new equilibrium point and a new MABP
What is the equilibrium point for water and salt intake on MABP?
where MABP is maintained for long-term
Explain the effect modifying kidney function will have on MABP graph?
- steeper slope of renal output, less increase in MABP for increase in water and salt intake
- equilibrium point does not change much
Where is ADH released from?
Pituitary gland
What triggers the release of ADH?
- increase in osmotic pressure (hypothalamic osmoreceptors)
- hypovolaemia (decrease atrial baroreceptor firing rate)
- hypotension (decrease in arterial baroreceptor firing to increase sympathetic activity)
- angiotensin II
Explain the action of ADH
- increases blood volume by increasing water permeability in renal collecting ducts and decreases urine output
- in severe hypovolemic shock can cause reflex vasocontriction to increase total peripheral resistance
What is renin?
a proteolytic enzyme released from the kidneys
What triggers renin release?
- sympathetic nerve activation (baroreceptor feedback)
- renal artery hypotension
- decreased sodium in distal tubules
Explain RAAS regulation of blood volume
- blood volume decreases
- baroreceptor rate decreases
- signals MCVC centre
- activates renal sympathetic nerves
- increases kidney renin output
- decreases urine formation
Explain RAAS regulation of blood pressure
- decreased BP
- renin release from juxtoglomerular cells
- renin cleaves substrate to form angiontensin I
- converted by enzyme in the lungs to angiotensin II
- acts directly on kidneys to constrict renal arteries decreases blood flow
- also causes release of aldosterone from adrenal glands to increase sodium and water reabsorption
- also stimulates release of ADH
What is the atrial-natriuretic hormone
28 amino acid peptide stored in muscle cells of atria
What triggers the release of the atrial-natriuretic hormone?
- stretch of the atria
- helps oppose effects of RAAS system and can help counteract volume overload