cardiovascular system Flashcards
(84 cards)
the pumping action of the heart is called bulk flow- what does bulk flow distribute?
ions , water and CO2- pH, osmolarity and body water
heat- body temp
hormones, various substrates- metabolism
what is a typical stroke volume at rest?
60-80ml
what is the arrangement between the pulmonary and systemic circuits, does their arrangement increase or decrease resistance to flow?
systemic and pulmonary are in SERIES flow
series= higher total resistance
ie r=1+1
what is the arrangement of flow in the systemic system, does this arrangement increase or decrease overall resistance to flow?
systemic blood can flow through a choice of paths, these paths are arranged in parallel.
parallel = lower total resistance
r=1/2+1/2
what is the relationship between resistance, flow and pressure?
blood flow= change in blood pressure/ resistance to flow
*resistance dependent on the radius of the tube
where is most of your blood volume located?
about half of your blood at any point is sitting in your venous system
what occurs to pulse pressure as you move further away from the heart?
further from the heart=dampening of pulse pressure
elasticity of the arteries helps to dampen this
determinants of blood pressure (equation)
MABP= CO x TPR
primary structure and role of the aorta and large arteries
high pressure vessels, drives blood through the systemic system
lots of smooth muscle and connective tissue
primary structure and role of smaller arteries and arterioles?
resistance vessels
control of these vessels determines the volume of flow through that circulation
wrapped in smooth muscle to accomidate these changes (vasoconstriction/dilation)
primary structure and function of capillaries
exchange vessels
single layer of endothelial cells so nutrients can be easily transferred
primary structure and function of veins and venules
primary reservoir- abilities to hold the blood. Thin walled and large lumen, elastic layers allowing them to stretch
what makes up cardiac cells (discuss the two types)
- contractile myocardial cells- form bulk of cells in the atria and ventricles. Attatched via intercalated disks, gap junctions allow electrical signals to spread rapidly. all myocardial cells contract with every heart beat. actin and myosin= striated appearance
- nodal tissue (SA and AV node) 1% of cardiac cells, small round cells with no contractile proteins, for generating action potentials, gap junctions are present.
what rate does the SA node generate action potentials?
100-110 action potentials per min
what is the action potential conduction speed through atrial muscle compared to ventricular muscle
atrial muscle= 0.5ms-1
ventricular myocardium= 0.5ms-1
at what speed does the action potential conduct though the bundle branches (purkinje system) and why is it important its at this rate?
5ms-1
want to get the two ventricles to contract at the same time so the signal needs to travel to them quickly
why is the action potential conducted slowly through the av node? what rate is it conducted?
slowly at av node because we want to delay the signal so the ventricles will contract after the atria for effective ejection of blood.
AV node conduction= 0.05ms-1
what does the resting membrane potential of nodal and myocardial cells depend upon?
high resting permability to potassium
Pk lower in nodal tissue then myocardial cells and RMP is more negative
RM P of SA nodal cells is unstable
what is the pacemaker potential?
nodal tissue- pacemaker cells, no true resting membrane potential, they have a pacemaker potential which is a slow steady depolarisation.
lower permeability for potassium and an increasing permeability to sodium= gradual decrease in RMP
at threshold voltage calcium channels open and a ‘slow ap’ occurs
ventricular cells resting membrane potential
they have a higher potassium permeability therefore a more negative resting membrane potential (stable RMP)
depolarisation= opening of voltage gated sodium channels (due to a signal).
much faster process that requires a stimulus
how can we increase size of contraction in the cardiac cells?
cant recruit more cardiac cells as they all contract with every beat, but we can increase the amount of calcium.
more calcium= stronger contraction
why does tetanus not normally occur in heart muscle?
Has a long absolute and relative refractory period- these prevent the re-excitation of the heart muscle during the contraction period
depolarisation moving towards a lead results in a ___ wave
positive
depolarisation away from a lead results in a ____ wave
negative