blood pressure control (short/long term) Flashcards
importance of regulating mean arterial pressure
allows evaluation of how well blood flows through your body and whether it’s reaching all major organs
regulated by changes in CO and systemic vascular resistance
components and function of arterial baroreceptor reflex
homeostatic mechanism - helps maintain blood pressure at nearly constant levels - responsible for short term control of arterial blood pressure
baroreceptors located in the carotid sinus and the aorta detect changes in blood pressure and relate info back to cardio centres in the brain
provides rapid negative feedback loop
identify other inputs to medullary cardiovascular centres
cardiopulmonary receptors - sensing central blood volume
central chemoreceptors - sensing arterial pCO2 and pO2
chemoreceptors in muscle - sensing metabolite conc.
joint receptors - sensing joint movement
higher centres - hypothalamus and cerebral cortex
explain relationship between CO, TPR, and MAP
MAP = CO x TPR
importance of coordinated control of CVS system using response to exercise as eg
describe effects of changes in posture on CVS system
transition from supine to standing tends to cause a drop in blood pressure of at least 20mmHg systolic and 10mmHg diastolic
postural hypotension
person’s blood pressure abnormally drops as they go from sitting or lying down to standing position
postural hypotension
describe effect of Valsalva manoeuvre on CVS system
increased thoracic pressure is transmitted through aorta
increased thoracic pressure reduces filling pressure from veins, which therefore decreases VR, EDV, SV, CO, MAP
reduced MAP detected by baroreceptors which initiates reflex increase in CO and TPR
at end of manoeuvre, decrease in thoracic pressure is transmitted through to aorta - hence drop
VR is restored so SV increases
eventually, back to normal…
cardiopulmonary (arterial) baroreceptors
located in atria, ventricles and pulmonary vessels
stretch receptors stimulated by change of arterial wall when pressure changes
medullary cardiovascular centres
baroreceptors
mechanoreceptors located in blood vessels near heart that provide brain with info pertaining to blood volume and pressure, by detecting level of stretch on vascular walls
as blood volume increases, vessels stretched and firing rate of baroreceptors increase
recognise role of kidneys in regulating plasma volume and therefore BP
renal counter-current system creates very high osmolarity outside collecting duct
control over Na+ transport determines how big that osmotic gradient is
control over permeability of collecting duct to water determines if water follows that osmotic gradient or not
hence, can control amount of water lost in urine, and how much retained
identify receptors involved in sensing plasma volume
osmoreceptors baroreceptors
renin-angiotensin-aldosterone hormone system mechanism – long term control of BP
angiotensin ii stimulates release of aldosterone from adrenal cortex, which increases Na+ reabsorption in loop of Henle, therefore, reducing diuresis and increasing plasma volume
also increases release of ADH from pituitary which increases water permeability of collecting duct, therefore reducing and increases plasma volume and sense of thirst
angiotensin
peptide hormone causes vasoconstriction and an increase in BP
also stimulates release of aldosterone from adrenal cortex to promote Na+ retention by kidneys
renin
produced from juxtaglomerular
converts angiotensinogen to angiotensin i - which is then converted by ACE to angiotensin ii
angiotensin converting enzyme (ACE)
catalyses conversion of angiotensin i to angiotensin ii
aldosterone
steroid hormone released by adrenal glands - adrenal cortex
controls balance of water and salts in kidney by keeping Na+ in and releasing K+ from body
too much can cause high BP and build-up of fluid in body tissues
angiogenesis
formation of new blood vessels
involves migration, growth and differentiation of endothelial cells , which line inside wall of blood vessels
controlled by chemical signals in body
atrial and brain natriuretic peptide
small peptide secreted by heart, myocardial cells in atria and ventricles respectively, upon atrial stretch and high systemic BP
tends to decrease MAP
increases excretion of Na+ (natriuresis)
inhibits release of renin
acts on medullary CV centres to reduce MAP
antidiuretic hormone
produced in brain, causes kidney to release less water, decreasing amount of urine produced
juxtaglomerular cells
granular cells - in the kidney that synthesise, store and secrete enzyme renin
specialised smooth cells mainly in walls of afferent arterioles (some in efferent) that deliver blood to glomerulus
vasoconstrictor on TPR
increases TPR
