Exam 1: Lecture 5, Antihypertensive drugs I Flashcards
What can go wrong with heart simplified
Hypertension = issue with pipes
Heart failure = issues with the mechanical pump
Cardiac Arrhythmia = issues with the electrical drive of the pump
Flow of blood through the heart
Deoxygenated blood enters RA via SVC and IVC
Blood flows through tricuspid valve when RA pressure > RV pressure…valve closes when opposite
RV contracts = increase RV pressure = blood flows through pulmonary valve into pulmonary artery
Pulmonary artery carries blood to lungs where it gets oxygenated
Oxygenated blood moves from pulmonary vein into LA
When LA pressure > LV pressure then blood flows through mitral (bicuspid) valve into LV. closes when opposite
LV contraction pushes blood through the aortic valve into aortic arch
** Left and Right side beat at the same time **
Resting pressure in the left heart is…..
higher than that in the right heart
Cardiac output is…
L/Min
Formula is CO = SV X HR
SV = L/beat HR = beats/min
Stroke Volume formula….
EDV - ESV = SV
EDV (End diastolic volume ~ 120ml)
ESV (End systolic volume ~ 50ml)
What is preload?
stretch of a single cardiomyocyte at end of ventricular filing ( max volume = max stretch)
Not measured in living animals due to invasive procedure
can be approximated by EV or EDP (End diastolic pressure)
Volume to approximate preload is measured by ultrasound but its difficult in children, during tachycardia or a anomalous heart anatomy…why?
Because the heart beats too fast and you are assuming there is uniformity in ventricle size and shape.
What is afterload?
The “load” against which the left ventricle ejects blood
increase afterload due to increase aortic pressure and/or increase vascular resistance
increased afterload leads to increase ESV and decreased SV
What does the Frank-Starling curve show?
the relationship between SV and LVEDP(Left Ventricle End Diastolic pressure, ie “Preload”)
Starling’s law of heart
The more the heart fills, the more it pumps
What is compliance?
The ability of a heart chamber or a blood vessel to expand when filed with blood
nonlinear at higher pressure due to elastic properties
Compliance of Arteries vs Veins
veins have ~10-20 X > compliance than arteries
can accommodate larger change in volume with smaller change in pressure
decreased arterial compliance associated with increased arterial BP
What is blood pressure?
pressure of blood pushing against blood vessel walls
Normal blood pressure?
<120 systolic
<80 diastolic
Where does greatest drop in circulating pressure occur?
Arterioles due to parallel tubes
