cardiovascular system design Flashcards
what are the two circulations in series in the cardiovascular system?
pulmonary and systemic circulations
how is blood flow divided within the pulmonary and systemic circulations?
blood flows entirely into and out of the pulmonary circulation
in the systemic circulation flow is divided between tissues in paralell
what is resistance to flow determined by?
blood vessels
what is capacitance?
the amount of blood stored in a certain location
what percentages of blood lie in the systemic circulation, the heart and the pulmonary vessels?
84% systemic, 7% in heart and 9% in pulmonary vessels
where does most of the blood reside?
venous vessels
how are vessels distinguished?
physical dimensions, morphological characteristics and function
what are all heart chambers, valve leaflets and vessels lined with?
endothelial cells (regulators)
what does myogenic mean?
that the stimulation of pumping is not recieved from the nervous system, but from the heart muscle itself
where is the central control of BP and contractility?
the heart
explain systole and diastole?
systole- when the heart is most contracted and the semilunar valves are opened
diastole- when the heart is most open and the tricuspid and mitral valves are open
explain the rout of blood in one full cycle.
deoxygenated blood returns to right atrium-> right ventricle->pulmonary circulation
oxygenated blood returns from the pulmonary veins to the left atrium->left ventricle->systemic circulation
how is heart contraction made more efficient?
contraction of individual cells occur at regular intervals, valves must open fully but not leak, muscle contractions must be forceful and ventricles must fill adequately during diastole
what is cardiac output?
the quantity of blood pumped into the aorta by the heart per unit time (also the amount that flows through the circulation)
CO=SV (stroke volume)x HR (heart rate)
what is the typical cardiac output for a resting individual with normal heart function?
5 L/min
what are the major determinants of stroke volume?
ventricular preload, ventricular afterload and myocardial contractility
what controls the heart rate?
the autonomic nervous system
what is sterling’s law of the heart?
cardiac output is determined almost entirely by the rate of venous return
what controls local blood flow and therefore blood return?
peripheral tissue (heart automatically pumps this incoming blood into the arteries to continue the flow
how does the heart know to pump with greater force?
if the heart is more stretched from an increased volume of inflowing blood (larger the ventricular end diastolic volume, the larger the stroke volume
what is the consequence of arteriolar vasoconstriction via smooth muscle?
increase in peripheral resistance
what is the consequence of venous vasoconstriction via smooth muscle?
reduced venous volume and increase in cardiac output
how is blood flow to capillary beds controlled?
by precapillary sphincters
what is the trend of internal diameter of blood vessels?
the aorta and venae cavea are approximately the same sizes while the intermediate vessels are progressively smaller. capillaries are about the diameter of a RBC
what is the trend of wall thickness of blood vessels?
veins are thinner than arteries all together but they are progressively thinner as diameter gets smaller
what is the trend of number of blood vessels?
larger vessels have fewer numbers while smaller vessels increase in number
what is the trend of cross sectional area of blood vessels?
veins have a larger cross sectional area in general. capillaries have the largest cross sectional area and larger vessels have the least.
what is the consequence of cross sectional area on flow velocity in blood vessels?
where there is a smaller cross sectional area, there is a faster blood flow
how does blood pressure change through the vascular system?
blood pressure changes with diastole and systole only in the arteries and areterioles. from there, blood pressure is lost progressively
where is the highest vascular resistance in the body? what does this cause?
arterioles
this causes the larges drop in mean arterial pressure
does the heart generate constant flow or constant pressure?
pressure
what is the formula for pressure?
P= rho(density) x g(acceleration due to gravity) x h (height)
how is medical blood pressure gauged?
relative to atmospheric pressure
what is the mean arterial pressure?
average pressure over the entire cardiac cycle
MAP= DP (diastolic)+ 1/3 PP (pulse pressure)
what is the pulse pressure?
the difference between the systolic and diastolic pressures
what do systolic pressure and diastolic pressure indicate?
s- the highest arterial pressure reached during heart contraction
d- the lowest arterial pressure reached during heart relaxation
what is the normal diastolic pressure, systolic pressure, pulse pressure and mean arterial pressure?
SP/DP= 120/80mmHg
PP=40mmHg
MAP= 93mmHg
waht is the dichrotic notch?
a small dip in blood pressure caused by back filling of the aortic valve as it closes
what method do doctors typically use to take blood pressure and how is it done?
ausculatory method
when the external pressure from the cuff is greater than systolic pressure, there is no blood flow. as pressure is lowered, blood flow is restored and the clinician can hear the turbulence. as pressure is further reduced the fluctuations increase making louder sounds from more turbulence. when the pressure is below diastolic, the flow is laminar and is silent
describe the direct method to measure blood pressure
an arterial blood catheter is passed retrograde for pressures in arteries and left ventricle while a venous catheter is passed antegrade to get the pressures in veins and the right side of the heart
what parts of circulation cannot be measured with direct blood pressure? what is used instead?
pulmonary venous and left atrial pressures
use pulmonary capillary wedge pressure
how is the pulmonary artery catheterized?
it is passed from a systemic vein through the right heart into the pulmonary artery
how is vascular pressure calculated?
a balloon on a pulmonary artery catheter is expanded until vascular pressure equilibrates beyond the balloon. the wedge pressure at the tip of the catheter is a measure of the pulmonary venous and left atrial pressure
what is another calculation of mean arterial pressure?
MAP= CO (cardiac output)x TPR (total peripheral resistance)
what are two conditions that must be met by the mean arterial pressure?
it must drive blood flow without damaging organs
how is MAP controlled short term and how is it detected?
by altering cardiac output and peripheral resistance (mostly)–neurally and hormonally
detected by baroreceptor reflex
how is peripheral resistance changed?
regulation of vasomotor tone
how is long term control of MAP achieved?
altering blood volume by the kidneys
