intro to cardiovascular system Flashcards
what do we need the CVS for
1) Transport for respiratory gases and nutrients.
2) temperature regulation
3) as a signalling system for distributing hormones, information molecules etc to target tissues
4) male hydraulic device
what is t proportional to
x2 (distance squared)
what does the CVS use a combination of
convection and diffusion
what is convection
movement by pressure gradient
how does the heart create this convection current
by creating a pressure difference between arteries and veins
heart cycle
1) superior and inferior vena cave deposits deoxygenated blood into the right atrium
2) blood then goes into the right ventricle
3) blood is then pushed out of the right ventricle via the pulmonary artery into the lungs (under lower pressure to allow good gaseous exchange)
4) - blood gets oxygenated by diffusion -
5) it then comes back to the heart and enters into the left atrium via the pulmonary vein
6) blood is then pumped to left ventricle
7) finally pumped out of left ventricle to the rest of the body under high pressure via the aorta.
what do the opening and closing of the valves depend on
pressure gradients
systole =
contractions (ventricles being emptied of blood)
diastole =
relaxations (ventricles being filled with blood)
What is Cardiac output
volume of blood ejected from the ventricles per minute
cardiac output equation =
SV X HR
what organ’s oxygen supply is relatively in line with how much they need? (they’re output) (3)
- liver
- GI
- muscles
what organ is well perfused
Kidney
what organs are underperfused (2)
- myocardium
- brain
(becomes an issue when there is a clinical problem such as angina e.g. angina / myocardium
CO at rest =
70bpm + 70ml = 5litres/min
CO after exercise =
180bpm + 120ml = 20 litres/min
what are the three main factors controlling cardiac output
1) filling pressure - starling’s law
2) sympathetic/parasympathetic nerves
3) chemical factors
what do sympathetic nerves release and what receptors do they act on (causes increase in heart rate and contractility so CO increases)
NA acting at beta-1-adrenoceptors
what do parasympathetic nerves release and what receptors do they act on (decrease in heart electrical activity at the SAN reducing HR)
Ach acting at M2 receptors
what is blood flow proportional to
pressure across blood vessels - greater pressure means greater flow
what is blood flow is inversely proportional to
resistance - greater resistance means less flow
what is darcey’s law
Blood flow = (pa - pv) / resistance
systemic circulation =
high pressure system
pulmonary circulation =
low pressure system
how do arterioles control arterial BP
by determining total peripheral resistance which changes blood flow
what is parallel circulation
when cardiac output is split up to supply individual areas with blood. - getting first hand oxygenate blood
what is series ‘portal’ circulation
where same blood supply is used between organs e.g. liver receives second hand blood from intestines (contains various nutrients and chemicals from intestines that have been digested)
what are the 4 main functional groups of blood vessels
- elastic vessels
- resistance vessels
- exchange vessels
- capacitance vessels
