Blood pressure regulation Flashcards
(38 cards)
What systems are responsible for short and long term control of blood pressure?
short- baroreceptor reflex
mid- mechanical
long- RAAS system, sympathetic nervous system, ADH, ANP
Why can the baroreceptor reflex not correct sustained changes in blood pressure?
because the stretch threshold for firing will change and reset
What 3 things stimulate release of renin ?
- reduced NaCl delievery to macular denser cells distal tubule (less Na+ means lower blood volume)
- reduced perfusion to kidneys (indicates low blood volume, detected by baroreceptors in afferent arteriole
- Sympathetic stimulation to JGA
Where is renin released from?
the granular cells of the afferent arteriole
What makes up the juxtaglomerular apparatus?
- granular cells on afferent arteriole
- macular denser cells on distal tubule
What does renin do?
Converts angiotensinogen from liver into angiotensin 1
Where is ACE released from and what does it do?
- from lungs
- converts angiotensin 1 into angiotensin 2
What are the effects of activated angiotensin 2 GPCRs?
- vasoconstriction
- aldosterone release
- ADH release (increase water retention and thirst sensation)
- noradrenaline release
- increased Na+ reabsorbtion
What does aldosterone do?
- stimulates Na+ reabsorbtion in principal cells of collecting ducts
- by activating apical Na+ and K+ channels and Na/K/ATPase channels
How does ACE alone help increase blood pressure?
It breaks down bradykinin which is a vasodilator (so you get less vasodilation)
ACE inhibitors therefor can help decrease blood pressure, name an ACE inhibitor and explain why ACE inhibitors cause a dry cough?
ramapril (aptopril, lisinopril, perindopril, enalapril)
bradykinin accumulates causing brochoconstriction (so you cough)
How does sympathetic stimulation cause long term increase in blood pressure?
- It decreases renal blood flow so RAAS is activated
- stimulates the Na/H exchanger and Na/K/ ATPase pump so more Na resorbtion
- It stimulates renin release directly
How does ADH increase blood pressure?
- stimulates thrist sensation
- stimulates Na/K/Cl transporter so more water reabsorbed into blood
- stimulates vasoconstriction
How do the natriuetic peptides (ANP and BNP) change blood pressure?
- They’re released on atrial or ventricular distension (BP too high), so aim to reduce BP
- By vasodilation and inhibiting Na+ resorbtion
When are prostaglandins released and what is their effect on BP?
- When angiotenisin 2 too high and acute inflammation
- cause vasodilation and less Na+ reabsorbtion
- cause BP to drop
What effect does dopamine have on BP and how?
- decreases BP
- By causing vasodilation of afferent vessels (increased perfusion deactivates RAAS)
- Causes general vasodilation
What is hypertension?
A sustained increase in blood pressure above 140/90
What is the difference between primary and secondary hypertension?
primary- unknown cause (poss genetic, envromental ect)
secondary- something else is causing the hypertension (very rare)
Name some secondary causes of hypertension
- Renovascular disease- occulsion of renal artery causing decreased blood flow and so RAAS activated
- Renal parenchymal disease- cause unclear, loss of vasodilatory substances, then water retention due to poor filtration
- Adrenal causes
What are the adrenal causes of hypertension?
conns syndrome- adenoma secretes aldosterone
cushings syndrome- high glucocorticosteroids causing Na+ and water retention
I
Describe the impacts of hypertension
- increased afterload causes LV hypertrophy (leads to heart failure) and more demand of 02 (leads to MI)
- damages arterioles which leads to atherclerosis and weak vessels which leads to stroke, retinopathy, renal failure and aneyrism
How can hypertension be treated non- pharamacologically?
- exersize
- diet modification
- decreased salt intake
- decreased fat intake
How can hypertension be treated by drugs?
- ACE inhibitors and angiotension2 receptor antagonists decrease RAAS
- L type ca2+ channel blockers and a receptor blockers cause vasodilation
- diuretics to decrease Na+ resorbtion and so blood volume
- Beta blockers to decrease HR and contractability
How can mean arterial pressure be calculated?
SVx HRx TRP or systolic- 1/2 (pulse pressure) Or Diastolic + 1/3 ( pulse pressure)
