Flashcards in Hypertension And The Control Of Blood Pressure Deck (28)
What are some of the features of the baroreceptor reflex?
Nerve endings in the aortic arch, and the carotid sinus are sensitive to stretch, and the increased arterial pressure stretches these receptors, and the decreased pressure stretches less- and works well to control the acute changes in blood pressure
What are the four pathways involved in the control of blood pressure?
The renin- angiotensin- aldosterone system, the symaptheic nervous system, antidiretuic hormone and atrial naturetic peptide
What are the factors that stimulate renin realease?
Reduced NaCl delivery to the distal tubule, reduced perfusion pressure in the kidney which causes the release of renin, and sympathetic stimulation to the JGA increases the release of renin
Where is renin released from?
The granular cells of the afferent arteriole in response to reduced perfusion pressure
What is the juxtaglomeular appartus?
The macula densa, and the granule cells, and the surrounding mesengial cells
What is the reaction proccess of the renin angiotensin aldosterone system?
Angiotensin is catalysed by renin to produce angiotensin I which is catalysed by angitensin converting enzyme to angiotensin II which stimulates vasoconstriction, stimulates Na+ reasportion in the kidneys, and stimulates the release of aldosterone from the adrenal cortex
What are some of the features of the receptors for angitensin II?
AT1 and AT2, but the main actions are via the AT1 receptor and invlude vasoconstriction, stimulation of Na+ reabosrbtion, increased release of Na from the sympathetic nervous system, and the release of aldosterone and hypothalmus increasing the thirst sensation
What are the actions of aldosterone on the kidney?
Acts on the principal cells of the collecting ducts and stimulates Na+ and therefore water reasportion, and activates ENac, and increases the basolateral Na+ extrusion via na/K/ATPase
What are some of the features of angiotensin converting enzyme?
Is known as kinniase II and converts bradykinin to peptide fragements> Bradykinin is a vasodilator and therefore this increases the effects of vasoconstriction
What are some of the actions of the sympatheic nervous system on the kidney?
High levels of sympathetic stimulation reduce the renal blood flow, due to vasoconstriction of the arterioles, and decrease the GFR to decrease the Na+ excretion, and activates the apical Na/H exchanger, stimulates the release of renin and direction sympathetic stimulation acts on the arterioles to reduce the renal blood flow
What is the role of antitdireutic hormone?
Formation of a concentrated urine by retaining water to to control the plasma osmolarity.
What stimulates the realease of ADH?
Stimulated by increases in plasma osmolarity or by severe hypovolemia
What are some of the features of artial natureic peptide?
Promotes Na+ excretion, is synthesised and stored in the atrial myoocytes, and is released from the atrial cells in response to stretch, by the low pressure volume sensors in the atria.
What are the actions of AND?
Causes vasodilation of the afferent ateriole, increased blood flow increases the GFR< also inhibits Na+ reabsorption and the nephron, and acts in the opposite direction to the other neurohormonal regulators, and causes naturesis and the loss of sodium ions
What do prostagladins do?
Act as vasodilators
What do NSAIDS do?
NSAIDs inhibit the cyclo-oxygenase pathway involved in the formation of prostaglandins, and therefore could cause constriction of these important arterioles
How does dopamine interact with the kidneys?
Dopamine is formed locally in the kidney from the circulating L-DOPA, and doapmine receptror are present on renal blood vessels and cells of PCT and TAL, adn the DA causes vasodilation and increases the renal blood flow, and reduces the absorption of NaCL
What are the causes of hypertension?
In around 95% of cases the cause is unknown, other causes include renovascular disease, chronic renal disease, aldosetonism and cushings syndrome
Hoe can renovascular disease caus secondary hypertension?
Occlusion of the renal artery (renal artery stenosis) causes a reduced perfusion pressure in the kidney, this leads to increased production of renin and the activation of the renin angiotensin aldosterone system
How does renal parenchymal disease cause secondary hypertension?
Eariler stage may be a loss of the vasodilator substances, in the later stage there is na+ and water rretnion due to the inadequate filatration, and therefore is a form of volume dependant hypertension
What are some of the examples of adrenal causes of the secondary hypertension?
Cohn s syndrome, which is an aldosterone secreting adenoma, causing hypertension and hypofalemai, cushings sundrome that is an excess secretion of gluocortiod cortisol. And tumour of the adrenal medulla which causes a phaeochromocytoma
What are some of the effects of the increased afterload in hypertension?
This can cuase left ventricular hypertrophy and then heart failure, and an increase in the myocardial oxygen demand which causes myocardial ischameia and a myocardial infarction
What are the effects of the arterial damage that is seen in hypertension?
Can cause atheroscleorisis and weakened vessles which can cause cerebrovascular disease and then stroke, anyersum, neprhoscleoris and renal failure, and retinopathy
Give an example of a drug for treating hypertension that targets the renin angiotensin aldosterone system and exemplify its function?
ACE inhibiotrs prevent the production of Ang II FROM Ang I, they are Amg II receptor antagonists, as ang II is a powerful vasoconstrictor, and has directs actions on the kidney and promote the release of aldosterone
Give examples of some of the vasodilators that can be used in treating hypertension?
L type Ca channle blockers, that reduce the entry of calcium to the vascular smoooth muscle cells and the relaxation of the vascular smooth muscle, adn in principle coul se a1 receptor blockers and these help to reduce the sympatheic tone and therefore cause the realxation of the smooth muscle cells, but could cause postural hypotension
Give some examples of the direutics used to treat hypertension
Thiazide direcutics are used as the reduce the circulating volume, inhibit the n/cl co transporter on the apical membrane of the distal tubule,and other diretutics such as aldosterone antagonists will also reduce the blood pressure
Whhow are beta blockers and hypertension associated?
Beta blockers are not used to treat hypetension, and blocking B1 receptors in the heart will reduce the effects of sympathetic output and reduce the heart rate and the contractility, not used in hypertension alone but if there are other indications such as a previous MI