Control of Blood Pressure Flashcards
MAP = ? x ?
MAP = CO x TPR
what do the arterial baroreceptors measure?
stretch –> blood pressure
where can the arterial baroreceptors be found?
in the aortic arch and at the bifurcation of the common carotid arteries
in cases of low blood pressure will the baroreceptors fire more or less?
less
when do arteries stretch more - with high or low blood pressure?
high
below which mean arterial pressure are the arterial baroreceptors ‘silent’?
< 40 mmHg
above which mean arterial pressure are the arterial baroreceptors saturated?
> 120 mmHg
which nerve do the arterial baroreceptors in the aortic arch use to travel to the brain?
vagus
which nerve do the arterial baroreceptors in the carotid sinus use to travel to the brain?
glossopharyngeal
where does info from both sets of arterial baroreceptors travel to in the brain?
medullary cardiovascular centres
if blood pressure is too high, what do the medullary cardiovascular centres do?
increase parasympathetic action on sinoatrial node (via vagus) –> increase heart rate
if blood pressure is too high, what do the medullary cardiovascular centres do?
increase sympathetic action on sinoatrial node –> increase heart rate
on ventricles –> increase contractility
on blood vessels –> venoconstriction and arteriolar constriction
what other inputs do the medullary cardiovascular centres have?
cardiopulmonary centres central chemoreceptors chemoreceptors in muscle joint receptors higher centres
does gravity reduce venous return?
not necessarily
what is the first event in the valsalva manoeuvre?
increase in thoracic pressure is transmitted through to aorta
what is the second event in the valsalva manoeuvre?
increase in thoracic pressure leads to decreased venous return, decreased end diastolic volume, decreased stroke volume, decreased cardiac output and decreased mean arterial pressure
what is the third event in the valsalva manoeuvre?
decreased mean arterial pressure is detected by baroreceptors which initiate a reflex increase in cardiac output and increase in total peripheral resistance
what is the fourth event in the valsalva manoeuvre?
decrease in thoracic pressure is transmitted through to aorta
what is the fifth event in the valsalva manoeuvre?
venous return is restored so stroke volume increases, but reflex effects are still wearing off
what is the sixth event in the valsalva manoeuvre?
everything returns to normal
is long term control of blood pressure mediated by the arterial baroreceptors?
nope
which three hormone systems are involved in long term control of blood pressure?
renin - angiotensin - aldosterone system antidiuretic hormone (ADH / vasopressin) atrial natriuretic peptide and brain natriuretic peptide
where is renin produced?
juxtaglomerular apparatus of the kidney
what triggers renin production?
decreased mean arterial pressure detected by the cardiopulmonary centres –> sympathetic action on juxtaglomerular apparatus
decreased distension of afferent arterioles
decreased delivery of Na+/Cl+ through the tubule
what does renin do?
converts angiotensinogen to angiotensin I
what does angiotensin I do?
not a lot really, just gets converted to angiotensin II
what converts angiotensin I to angiotensin II?
angiotensin converting enzyme (ACE)
what does angiotensin II do?
stimulates release of aldosterone
increases release of ADH
vasoconstriction –> increased total peripheral resistance
where is aldosterone produced?
adrenal cortex
what does aldosterone do?
increases Na+ reabsorption in loop of Henle –> reduces diuresis, increases plasma volume
what does antidiuretic hormone do?
increases water permeability of the collecting duct –> reduces diuresis, increases plasma volume
increases thirst
vasoconstriction
where is ADH synthesised?
hypothalamus
where is ADH released?
posterior pituitary
what triggers ADH release?
decrease in blood volume (from cardiopulmonary centres)
increase in osmolarity of interstitial fluid (osmoreceptors in hypothalamus)
angiotensin II
where are ANP and BNP produced?
myocardial cells in the atria (ANP) and ventricles (BNP)
what triggers ANP and BNP release?
increased distension of atria and ventricles
what do ANP and BNP do?
increase excretion of Na+ (natriuresis)
inhibit release of renin
acts on medullary cardiovascular centres to reduce mean arterial pressure
what percentage of hypertension patients have secondary hypertension?
5-10%
