Haemodynamics Flashcards
What is the equation for SV?
SV = EDV - ESV
Central venous pressure affects the passive filling of the ventricles and hence EDV or ESV?
EDV
Aortic pressure affects the ejection of blood from the left ventricle and hence EDV or ESV?
ESV
HR is only influenced by the sympathetic system. True or false?
False - sympathetic and parasympathetic
What is meant by preload?
The volume of blood in the ventricle after diastole (EDV) - the stretch of the ventricular muscle
What is meant by afterload?
The resistance the left ventricle must overcome to circulate blood
What is cardiac output?
The amount of blood pumped out of the heart in a minute
What is stroke volume?
The amount of blood pumped out of the heart per beat
The greater the afterload, the less energy needed for ventricular contraction. True or false?
False - the more energy needed
Arterial pressure is directly proportional to flow resistance of the vascular network. True or false?
True
How can flow resistance be controlled?
By changes in vessel diameter - i.e. constriction/relaxation
Poiseuille’s law describes flow resistance in an entire branch. True or false?
False - an individual vessel or tube
What two things determine blood viscosity?
Haematocrit
Protein content
As protein content and haematocrit levels in blood increase, viscosity increases. True or false?
True
Do longer vessels have more or less resistance than shorter ones?
More resistance
Changes in vascular resistance are rarely due to changes in vessel length. Why?
Because vessel length doesn’t change - only when a person grows
What happens to resistance as diameter of a vessel decreases?
Resistance increases
As the number of vessels in series with each other increases, what happens to resistance?
It increases
As the number of vessels within a section (parallel) increases, what happens to resistance?
It decreases
When flow is sequential, i.e. from one vessel to the next, the total resistance is approx. equal to the total resistance of the biggest diameter vessel. True or false?
False - equal to resistance of smallest diameter vessel
What is resistance equal to when the flow is distributed to vessels of similar diameter in parallel?
total resistance of a single vessel divided by the number of vessels
In a branching network, both the flow and pressure drop through each section. True or false?
False - pressure drops but flow is the same
Why are arterioles the critical section of circulation for determining TPR?
Because they have a small diameter and small number relative to capillaries so they exert greatest resistance
They are the smallest diameter vessel lined by smooth muscle
MAP is greater than CVP. True or false?
True
The difference between MAP and CVP is the pressure gradient that drives blood through the systemic circuit. True or false?
True
What is the equation for CO?
CO = MAP / TPR
What is meant by compliance, in relation to vessels?
Measure of the ability of blood vessels to stretch as the pressure inside them rises
Arteries have high compliance. True or false?
False - they have a thick muscular wall and low compliance
Veins have a thin muscle wall. Does this mean compliance will be high or low?
High as they are very stretchable
What is meant by critical closing pressure?
When arterial pressure falls below 20mmHg, tension in the artery wall collapses the vessel and flow shuts down
In a person at rest, the systemic arteries contain the most amount of blood. True or false?
False - systemic veins do
A pharmacological agent that selectively constricts arteriolar smooth muscle increases both afterload and preload. True or false?
False - increases afterload without affecting preload. (constriction increases resistance to flow)
A pharmacological agent that selectively constricts venous smooth muscle increases afterload without affecting preload. True or false?
False - increases preload, without affecting afterload
Vasoconstriction in large veins decreases venous return pressure in ventricles (preload). True or false?
False - increases
Vasoconstriction of large veins increases EDV. True or false?
True
Does vasoconstriction of large veins increase or decrease stroke volume?
Increase
Constriction of veins has a huge effect on flow resistance. True or false?
False - veins are large