physiology Flashcards
main thing driving blood flow is
pressure
main thing driving pressure is
volume and distensibiltiu
pulse pressure
systolic pressure - diastolic pressure
Mean arterial pressure MAP
diastolic + 1/3 pulse pressure
hypertension
greater than or equal to 90 mmHg for diastolic
greater than or equal to 140 mmHg for systolic
can have either or both of these in hypertension
arteries -key properties
elastic
large diameter
resistance in arteries vs arterioles
arteries= big diameter=little resistance arterioles= small diameter=heaps of resistance
active hyperaemia
\wen u e.g. run= increase metabolic activity of tissue= local chemical changes =causing vasodilation
reactive hyperamei
block and then due to physical n chemical changes, get vasodilaiton n massive blood flow
auto regulation of blood flow
increased stretch= increased contraction (constriction)
decreased stretch= decreased contraction (dilation
prostacylcin PGI2
vasodilator
EDHF
vasodilator
endothelial stimulation to get it to vasodilate or vasoconrtstict:
sheer stress of blood flow
laminar flow=vasodilation
turbulent flow= reduced release of vasodialtion
• blood borne factors n subs released from platelets
• Ach , used as a tool –ie used in clinical
bifurication=turbulent flow= blood clot
coronary angiography
for Ach
for Ach
if get vasodilation= endo is healthy
if get vasoconstriction= endo is impaired
coronary angiography
for NTG
for NTG
this is any endothelium-independent vasodilator, so inserting it would be testing function of the smooth muscle
if get vasodilation=smooth musucle fine
NO
vasodilator
veins cos stretchy
big change in volume=small change in pressure
sympathetic effect on veins
increased sympa stim on veins contract muslces makes walls stiff less stretchy/distensible increase venous pressure
things that affect venous return
- venous pressure=increase pressure=increase venous return
- skeletal muscle pump
- resp pump
varicose vein
faulty valves
vascular function
AS U INCREASE RIGHT ATRIAL PRESSURE, YOU DECREASE VENOUS RETURN
the cardiac function
u increase right atrial pressure, U INCREASE END-DIASTOLIC VOLUME AND SO THEREFORE U INCREASE STROKE VOLUME
response to haemorrhage
vasoconstriction
vasodilation\
take home message-fall in cardiac output is due to fall in venous return
Mean Systemic (or circulatory) Filling Pressure (Psf)
pressure everywhere once u’ve stopped your heart
determined mainly by volume of blood and pressure in veins
CO determined by
venous return
MAP
CO x TPR
cardiovascular system as a control system
baroreceptors sensory affernt nerves medullary cardiovascular centre efferent nerves heart, arterioles, veins
baroreceptors
carotid sinus,arch of aorta
baroreceptor reflex
increase in pressure
stretches aorta n carotids
baro increase firing
send message to brain
brain send para message back to heart telling it to slow HR
n decrease sympa message to vessels =vasodilaite=decrease pressure
incrase para
decrease sympa
SHORT TERM REGULATION
cos get adaptation
long term control of MAP is
renin system
• Pressure Diuresis/Natriuresis
RAA system
wen MAP falls, blood flow falls
• Renin released into circulation from juxtaglomerular cells in the kidneys
• This plasma renin converts angiotensin(from liver) to angiotensin 1
• Angiotensin 1 then converted to angiotensin 2 via angiotensin-converting enzyme
• Angiotensin 2 causes vessels to constrict, leading to increased blood pressure
• Angiotensin 2 also stimulates secretion of aldosterone from adrenal cortex. Aldosterone tells kidney to increase reabsorption of sodium n water into blood=increase blood pressure as well
stroke volume
edv-esv
75%
• 75% of the Ca for cardiac contraction comes from the sarcoplasmic reticulum
• 25% comes from ECF – exam question
– Cardiac muscle cell placed in solution with no calcium won’t contract.
cardiac output
volume of blood ejected per min
SA action potential
NA n Ca constantly leaking in
no fast voltage sensitive Na channel
Ca channel open, upward positiveness
K channel open- downwards
tetrodotoxin
blocks fast voltage sensitive Na channel
to increase filtration (pushing fluid out of capillaries)
dilate arterioles
increase systemic arterial pressure
increase venous pressure
to increase reabsorption (pulling fluid back into capillaries)
constrict arterioles
decrease systemic arterial pressure
decrease venous pressure
