Long-term regulation of MAP Flashcards
Why does the pressure in large arteries remain relatively high compared to other blood vessels?
They contain lots of elastic fibres which recoil during diastole meaning there is still some pressure.
What valve helps keep the diastolic pressure above zero in the arteries.
Intact aortic valve.
Which 3 types of hormones/pathways act as effectors for long-term regulation of MAP?
- The renin-angiotensin-aldosterone system (RAAS)
- Natriuretic peptides (NPs)
- Antidiuretic hormones (ADH)
What portion of the total body fluid is taken up by extracellular fluid?
1/3.
What is equation for Extracellular volume (ECFV)?
ECFV= Plasma volume (PV) + Interstitial fluid volume (IFV)
What is interstitial fluid?
The fluid which bathes cells
What compensatory mechanism happens when plasma volume drops? (hint: interstitial fluid)
Compensatory mechanisms shifts fluid from the interstitial compartment to the plasma compartment.
Blood volume and MAP is regulated if ECFV is regulated. True or false?
True.
What two main factors affect extracellular fluid volume?
Water and Na+ excess or deficit
What are the three hormones of the RAAS?
Renin, angiotensin and aldosterone
What does RAAS regulate?
Plasma volume and SVR, hence regulating MAP
Describe the pathway of RAAS.
- Renin is released from granular cells in juxtaglomerular apparatus in kidneys
- stimulating formation of angiotensin I in blood from angiotensinogen
- Angiotensin I is converted to Angiotensin II by the enzyme called angiotensin converting enzyme (ACE) produced by pulmonary vascular endothelium
- Angiotensin II stimulates the release of aldosterone from the adrenal cortex
- Angiotensin II causes systemic vasoconstriction, increasing SVR. Also stimulates thirst and ADH release which contributes to increasing plasma volume
- Aldosterone (a steroid hormone) acts on the kidneys to increase sodium and water retention- increases plasma volume.
Where is renin released from?
From granular cells in juxtaglomerular apparatus in kidneys
What regulates the RAAS?
By mechanisms which stimulate the Renin release:
- renal artery hypotension.
- stimulation of renal sympathetic nerves
- decreased [Na+] in renal tubular fluid.
Decreasing renin release decreases blood pressure.
What is the rate limiting step for RAAS?
The Renin secretion.
What are natriuretic peptides?
Peptide hormones synthesised mainly by the heart (also by brain and other organs)
What do natriuretic peptides do?
Act as vasodilators and cause excretion of salt and water in kidneys, which reduces the blood plasma volume and blood pressure.
Which two hormone pathways are counter-regulatory to one another?
RAAS and natriuretic peptides
What are the two types of natriuretic peptides?
Arterial natriuretic peptide (ANP)- made and stored in atrial muscle cells, released in response to atrial distension
Brain-type natriuretic peptide (BNP)- synthesised by heart ventricles, brain and other organ, also released in response to
volume expansion and increased wall stress of cardiac myocytes
Which form of natriuretic peptides is used to detect suspected heart failure in patients?
BNP.
What is plasma osmolality?
The measure of solute-water balance.
What stimulates ADH release?
Increased (or decreased) plasma osmolality /extracellular fluid volume
What is plasma osmolality monitored by?
osmoreceptors mainly in the brain in close proximity to the hypothalamus
What are antidiuretic hormones (ADH)?
peptide hormones derived from pro-hormone precursors synthesised by the hypothalamus and stored in the posterior pituitary.
