Circulation of blood Flashcards
function of cardiovascular system
to maintain an ADATPTABLE supply of blood to tissues to supply nutrients and signalling molecules
and to remove waste products
how are nutrients exchanged in the cardiovascular system
via capillary exchange
pressure differentals are generated across tissues to allow exchange
what is haemodynamics
the physics of blood flow
what are the 2 major factors blood flow is dependant on?
pressure diff between point A and B (driving force)
resistance to flow (also controls rate)
equation for blood flow
change in pressure/resistance
basically darcy’s law
what are 3 things that affect resistance
viscosity
vessel length
vessel radius (most important out of these 3 factors)
why does vessel radius cause sm of a difference in flow
flow proportional to r^4
so small diff in radius hugely affects the flow
e.g. is the radius in a vessel is 2x bigger than the other
then resistance = 16x less
so flow = 16x greater
how does vessel length increase resistance
more vessel coming into contact w/ blood
more of it to get through
so if vessel length = 1
flow = 1
if vessel length = 2
flow = 1/2
how does blood viscosity affect resistance
more viscous = more resistant = less flow
e.g. if haematocrit or protein content is quite high, then more viscous blood
what does the hagen-poiseuille formula tell us?
flow is directly proporional to r^4
and that resistance is affected by blood viscosity, vessel length and vessel radius
dw dont need to know formula
ehich vessel is rate of blood flow highest in?
elastic arteries
if lumen is biggest in vena cava, then why is blood flow highest in the aorta?
flow not only dependent on radius, even tho flow DP to r^4
but, pressure vry important
if pressure in venae cava is the lowest, the how is the rate of blood flow high?
vry little rsistance, vry large lumen
which part of the heart has the ability to generate most pressure (how much in mmHg) and why is this important
left ventricle (100-140mmHg)
needs to pump to rest of body
how is blood pressure maintained in the systemic circ
elastic arteries can act as ‘pressure resovoirs’
how can elastic arteries act as pressure reservoirs
when heart pumps, arteries fill with blood
when heart relaxes and blood moves through, theres elastic recoil that helps push the blood further
to see how pressure differs in each part of the CV system see onenote for diagram
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which artery is BP measured at
brachial artery
what is the top and bottom numbers in a BP reading representing
top = systolic pressure = max pressure
bottom = diastolic pressure = min pressure
what is considered ideal blood pressure
systolic= 90-120
diastolic = 60-80
what is considered ideal blood pressure
systolic= 90-120 (120-140 GP might advise excersice etc)
diastolic = 60-80
what is mean arterial pressure
mean pressure over course of one contraction
not jsut average of the two numbers cuz the heart is in diastole for longer, so value skewed towards diastolic BP
diastolic pressure + 1/3 of pulse pressure
see onenote for BP values diagram
what is pulse pressure
diff between systolic and diastolic pressure
what type of cells are at the sinoatrial node, and how do they work?
pacemaker cells
spontaneously depolarise w/o need for oustside nerve input
what does the 100msec delay through the AV node allow for?
atrial contraction
pathway of the electrical impulse
sinoatrial node
via internodal pathways
atrioventricular node
AV bundle
down the septum
through bundle branches
into ventricular myocardium through Purkinje fibres
see onenote
what does an ECG detect
electrical activity across the heart
an amalgamation of all the action potentials occuring in the heart
what does the P wave represent
atrial depolarisation (systole)
memb potential goes up, +ve deflection
what does the QRS complex represent
ventricular depolarisation (systole)
(during this time, repolarisation of atria also happenening, but cant see it as is masked by ventricular events)
what does T wave show
ventricular repolarisation - (diastole)
see onenote for all diagrams in comparison to heart activity
what are 3 mechanical events taht happen during the cardiac cycle
contraction inc chamber pressure
blood flows from high pressure to low pressure
valves open and close due to pressure gradients
what is isovolumic contraction
when it contracts but volume stays the same
happens in ventricle during ventricular systole, until the pressure surpasses the aortic pressure, blood will stay in ventricles
what causes the dicrotic notch
elastic recoil when the aortic valve shuts which causes pressrue to rise slightly
pressure and volume relations, see all notes in onenote
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