Regulation of blood pressure and flow Flashcards
baroreceptors
detect changes in MAP and regular bp short term
what regulates bp long term
kidneys
location of baroreceptors
carotid sinuses and aortic arch
what type of walls are they located in
thin walls that can be stretched by pressure
how do they detect changes in pressure
baroreceptor nerve endings are sensitive to stretch and pressure
rate of baroreceptor nerve firing proportional to
magnitude and changes in MAP
are baroreceptors positive or negative feedback
negative
where do baroreceptors signal to
medulla oblonglata
medulla oblongata regulates
Heart rate
stroke volume
diameter
which nervous system do baroreceptors mainly work with
autonomic
sympathetic
incr MAP
parasympathetic
decr MAP
adrenaline
increase MAP
angiotensin II and vasopressin
increase MAP
how do symp nerves work
mediated by noradrenaline via B adrenergic receptors
a1 adrenergic receptors in arterioles ( except skeletal muscle which is a2 adrenergic)
increase cardiac output and peripheral resistance
how do parasympathetic nerves work
mediated by ach by muscarinic receptors
inhibit heart rate
causes of hypotension
loss of blood (hemorrhage)
loss of salts: burns and sweating, diarrhoea and vomiting
stress- fainting
orthostasis
standing up
associated with a drop in mean blood pressure
why does orthostasis occur and how does the cardiovascular system compensate?
standing and effect of gravity leads to blood pooling in legs
reduced blood vol and lowering of central venous pressure
reduced venous return, reduced end diastolic pressure, reduced SV and reduced blood pressure
baroreceptor reflex will compensate
how do baroreceptor respond to lower arterial pressure
lower firing of baroreceptors
local flow is regulated by what sorts of factors
local, neuronal, hormonal
local factors which control arterioles dilation and constriction
myogenic response
metabolites
autocoids
endo cells
myogenic response
vasoconstriction of arterioles caused by stretch of smooth muscle
brain, kidney heart
vasodilation induces by metabolites
O2 decr
CO2 incr
H+, adenosine, K+, osmolarity incr
autocoids
released as result of inflammation and bleeding
inflammation leads to vasodilation eg via histamine
bleeding leads to constriction
endothelial cells
release local factors ( paracrine)
nitric oxide and prostacyclin- dilation
endothelin 1 - constriction
incr metabolic activity leads to (local)
active hyperemia
reduced blood flow in organ leads to (local)
flow auto regulation
active hyperemia sequence
incr metabolic activity of organ
decr O2, incr metabolites in organ isf
arteriolar dilation in organ
incr blood flow to organ
flow autoregulation sequence
decr arterial pressure in organ
decr blood flow to organ
decr O2, incr metabolites, decr vessel wall stretch in organ
arteriolar dilation in organ
restoration of blood flow towards normal in organ
neural control of arterioles in skin
room temp: arterioles constricted by moderate symp activity
cold, fear or loss of blood: symp activity incr and arterioles vasoconstrict. divert blood to essential organs
incr body temp: symp activity decr and arterioles vasodilation
blood flow to skin incr to cool
hormones involved in arterioles vasoconstriction and dilation
angiotensin II
vasopressin
atrial natriuretic peptide
angiotensin II
vasoconstriction
renin- angiotensin system
vasopressin
vasoconstriction
posterior pituitary gland
atrial natriuretic peptide
vasodilation
cardiac atria
a1 adrenergic receptors
cause vasoconstrict in response to noradrenaline and adrenaline
B1 adrenergic receptors in skeletal muscle
cause vasodilation in response to adrenaline and noradrenaline
i’m exercise you need to
boost O2 uptake and co2 removal ( incr Co)
increase blood flow to muscles, heart and skin (changes peripheral resistance)
stabilise arterial bp (despite changes in co and peripheral resistance)
What is the first thing the brain does during exercise
switches off baroreceptors
resets upwards so they don’t have opposing effects
blood flow during exercise
divert to muscles, skin and heart by vasodilation of arterioles
decr to essential organs by vasodilation of arterioles
Symp and Parasymp output during exercise
Decr parasymp output to heart
incr symp output to heart
incr symp output to veins
What happens to the CVS during exercise?
Slight drop in TPR
LArge incr CO
SO overall MAP incr
MAP = CO x TPR
CO incr a lot because HR and SV incr
local responses during exercise
contraction skeletal muscle, leading to vasodilation of arterioles to skin and muscle
Why does TPR decr
incr sympathetic and local responses lead to vasodilation of arterioles to skin and muscle
(see useful diagram)
local control involves
vasoconstriction and vasodilation
