Control Of Blood Pressure And Hypertenison Flashcards
What is hypertension?
Sustained increase in blood pressure
What is BP measured in?
mmHg (millimetres of mercury)
What is the normal / ideal adult blood pressure?
90/60 mmHg to 120/80mmHg
What is classified as Stage 1 hypertension?
BP > 140/90 mmHg
What is classified as stage 2 hypertension?
BP > 160/100 mmHg
What is classified as severe hypertension?
BP > 180 systolic
Or
BP > 110 diastolic
What is primary hypertension?
When the cause of the hypertension is unknown
What is secondary hypertension?
The cause of the hyper tension can be defined
Give some examples of conditions causing secondary hypertension?
Renovascular disease
Chronic renal disease
Hyperaldosteronism
Cushing’s syndrome
What can hypertension damage?
Heart
Vasculature
What conditions can damage to the heart and vasculature cause?
Heart failure
Myocardial infarction
Stroke
Renal failure
Retinopathy
Which chamber of the heart is usually affected with hypertension and what happens to it?
Left ventricle
Left ventricular hypertrophy
How can hypertension lead to an atrophic kidney?
Hypertension increases the risk of atheromas (degeneration of artery wall due to formation of fatty plaques and scar tissue)
Renal artery stenosis develops (renal artery narrowed)
Reduced blood flow to kidney makes it atrophic
What is the equation of cardiac output?
CO = SV x HR
Cardiac output = Stroke volume x Heart Rate
What is the equation for mean arterial blood pressure? (In terms of CO and TPR)
Mean arterial BP = CO x TPR
Mean arterial Blood Pressure = Cardiac Output x Total Peripheral Resistance
What is the equation relating blood pressure to blood flow and resistance?
BP = Blood flow x resistance
What is the mechanism which is responsible for short term blood pressure regulation?
Baroreceptor reflex
How does the baroreceptor reflex adjust cardiac output?
Changes sympathetic and parasympathetic inputs to the heart
How does the baroreceptor reflex alter total peripheral resistance?
Adjusts level of sympathetic input to the blood vessel (a1 receptors = less stimulation by noradrenaline)
What adrenoreceptor is important in the sympathetic input of blood vessels?
What is the neurotransmitter that binds to it?
A1 (Alpha 1)
Noradrenaline
Where are the baroreceptors located that are important in the baroreceptor reflex?
Carotid sinus
Aortic arch
What happens in the baroreceptor reflex when mean arterial pressure is increased?
Baroreceptors stretch
Fire action potentials to medulla
Medulla reduces sympathetic stimulation of heart and blood vessels and increases parasympathetic stimulation of the heart
Bradycardia and vasodilation counteract inc in mean arterial pressure
What is the baroreceptor reflex good for?
Rapid changes in BP
NOT LONG TERM
What are the 4 neurohumoral pathways that control circulating blood volume therefore CONTROLLING BLOOD PRESSURE?
MEDIUM/LONG Term control of BP
Renin-angiotensin-aldosterone system (RAAS)
Sympathetic nervous system
Antidiuretic hormone (ADH)
Atrial natriuretic peptide (ANP)
How does the RAAS regulate (increase) blood pressure?
Hypovolaemia or Hypotension detected (Baroreceptors/reduced renal perfusion)
Renin produced/released from kidney
Angiotensinogen —> Angitotensin I —> Angiotensin II —> Increase in BP and blood volume
What is the function of Renin produced by the kidney?
Cleaves Angiotensinogen to Angitensin I
How is Angiotensin I cleaved to Angiotensin II?
ACE enzymes in the lungs
What parts of the body does Angiotensin II act on to increase blood pressure and increase blood volume?
Arterioles
Adrenal cortex (indirectly the kidney nephron)
Posterior pituitary (Indirectly the nephron)
What effect does Angiotensin II have on the Arterioles to help increase blood pressure?
Vasoconstriction
What effect does Angiotensin II have on the adrenal cortex and how does this increase blood pressure or blood volume?
Stimulates aldosterone production
Aldosterone stimulates Na+/K+ pump expression in the nephron
More Na+ reabsorbed back into blood (water follows the Na+) at expense of K+ being lost, increases the volume of water in the blood increasing BP
What effect does Angiotensin II have on the posterior pituitary and how does this increase blood pressure or blood volume?
Angiotensin II stimulates production of ADH
ADH acts on collecting duct (kidney)
Increases translocation of aquaporins into the collecting duct of nephron
More water reabsorbed back into blood
Increases blood volume/pressure
What part of the kidney is renin released from?
Juxtaglomerular granule cells
What factors stimulate renin release for the juxtaglomerular granule cells?
Reduced NaCl delivery to kidney
Reduced kidney perfusion pressure
Sympathetic stimulation of the juxtglomerular granule cells
There are 2 angiotensin II receptors AT1 and AT2, which receptor does most of the action occur at?
What type of receptor is this?
AT1
G protein coupled receptor
Where is bradykinin normally found and what is its affect?
Lungs
Vasodilator
Lowers blood pressure
What is the effect of ACE on bradykinin?
Breaks it down
Inhibits its affect of vasodilation by breaking it down into peptide fragments
How can ACE Inhibitors cause Hypotension and a cough?
If ACE inhibited Bradykinin accumulates (not broken down) causing Vasodilation
Also causes cough
What are some examples of ACE Inhibitors?
Captopril
Lisinopril
Perindopril
Enalapril
What is the role of the sympathetic nervous system in increasing BP?
Reduces renal blood flow:
-Reduces GFR by vasoconstriction of arterioles
-Less Na+ and therefore water excreted
Stimulates renin release from Juxtoglomerular granule cells, INC Ang II levels, INC aldosterone = INC Na+ reabsorption = INC water reabsorption
What is the role of ADH in BP?
Acts to INC blood volume therefore INC BP
How does ADH increase BP?
INC translocation of aquaporins in collecting duct
Stimulates Na+ reabsorption (Na+/K+/Cl- co-transporter) water follows Na+
How does Atrial Natriuertic peptide (ANP) affect BP?
Decreases BP
How does Atrial Natriuretic peptide (ANP) reduce BP?
Promotes Na+ excretion (inhibits Na+ reabsorption)
Therefore increases water excretion reducing blood vol/pressure
Vasodilation of afferent Arteriole
Where is ANP synthesised and stored?
Atrial cardiac myocytes
When is ANP released from atrial myocytes?
When stretched a lot, more ANP is released
What happens with ANP when BP is low/ low blood volume (Hypovolaemia)?
Atrial cells stretched less
Less stretch inhibits ANP release
What is the role of Prostaglandins in BP?
Vasodilators
Act as a buffer to excessive vasoconstriction
Important when Ang II is high
How does dopamine affect BP?
Decreases BP
Vasodilation + INC renal blood flow
Reduces reabsorption of NaCl (more water lost)
Inhibits Na+/K+ ATPase in PCT
How can Renovascular disease cause Secondary Hypertension?
Renal artery stenosis (occlusion of renal artery) reduces perfusion pressure in that Kidney
Renin produced
RAAS activated
Other Kidney also has vasoconstriction and Na+ retention, more ADH made by posterior pituitary, More water retained
How does Renal parenchymal disease cause Secondary Hypertension?
Loss of vasodilator substances
Na+ and water retention due to inadequate Glomular filtration
What are parenchymal cells?
The functional tissue/cells of an organ (not the connective tissue)
What is Conn’s syndrome?
Adrenal tumour secreting aldosterone
What effect does Conn’s syndrome have on the body and why?
Elevated aldosterone
Hypertension
Hypernatraemia
Hypokalaemia
What is Cushing’s syndrome?
Excess secretion of Cortisol
What effect does Cushing’s syndrome have on BP and why?
At high [cortisol] can act on aldosterone receptors increasing Na+ retention, water retention and K+ excretion
What is a tumour of the adrenal medulla called the secretes Catecholamines?
Phaeomochromocytoma (produces noradrenaline and adrenaline)
How is a Phaeochromocytoma treated?
Alpha blockers + Beta blockers
Alpha blocker = Phenoxybenzamine
Beta blocker = Bisoprolol
How can you non-pharmacologically try and treat hypertension?
Exercise
Diet
Reduce Na+ intake (salt)
Reduce alcohol intake
How can you treat hypertension by targeting the RAAS?
ACE inhibitors
Angiotensin II receptor antagonists
How do ACE inhibitors treat hypertension?
Prevent conversion of Ang I to Ang II
Prevents the vasoconstriction action it has and prevents the release of aldosterone
What are some Angiotensin II receptor blockers? (Block action of Angiotensin II)
Losartan
Valsartan
Temisarta
How does an L-type Ca2+ channel blocker act as a vasodilator?
Reduces Ca2+ entry into vascular smooth muscle
Relaxation of vascular smooth muscle
What is an example of an L-type Ca2+ channel blocker?
Verapamil
What affect does a drug which is an A1 receptor blocker have on the body?
Blocks A1 receptors on vascular smooth muscle
Reduces sympathetic tone by not allowing noradrenaline to bind
Vasodilation
Can led t postural hypotension
What is an example of a drug which is an A1 receptor blocker?
Doxazosin
How do diuretics treat hypertension?
Increased water excretion in urine
What is spironolactone?
Aldosterone antagonist (Diuretics)
What do Thiazide diuretics inhibit?
Na/Cl co-transporter
How do Beta blockers treat hypertension?
Block B1 receptor
This is in the heart
Prevents noradrenaline binding
Heart rate reduced
Heart contraction strength reduced