Cardio Flashcards
Which is the site of highest resistance in the cardiovascular?
The arterioles
Flow is predicted by Reynolds number.how it is determined?
When Reynolds number is increased > ^tedency for turbulence >audible vibrations:bruits
Factors:
#^velocity:narrowing of the vessel>low A>^υ
(υ=Q/A)
#low viscosity :anemia>low hematocrit
What’s the site of largest total cross sectional and surface area?
The capillaries
What does the capillaries wall consist of?
A single layer of endothelial cells and a basal lamina
No muscle layer
Where is the unstressed volume?
It is the blood volume contained in the veins
What is the velocity of blood at the wall of the vessel?
Zero
Hence,shear is highest at the wall
Where does the largest decrease in pressure occur?
Across the arterioles
Paorta=100mmHg
Parteriol=50mmHg
How does elastic tissue affect the compliance of blood vessels?
They are inversely related.
Compliance=capacitance=distensibility
The greater the amount of elastic tissue ,the higher the elastance(STIFFNESS ),the lower the compliance
C=V/P. Capacitance decreases with age
How is pulse pressure determined?
Which is its most important determinant?
It is the difference between systolic an diastolic pressure
It is proportional to arterial compliance
The most important determinant of PP is stroke volume
Name 5cases in which we have ^pulse pressure…
#hyperthyroidism #aortic regurgitation #obstructive sleep apnea #aortic stiffness #exercise
Name 4cases in which we have low pulse pressure…
#aortic stenosis #cardiogenic shock #cardiac tamponade #HF
Which segment of the ECG is isoelectric?
The ST segment where the ventricles are Depolarized
What does T-wave inversion indicate?
Recent MI
What does U-wave suggest?
Hypokalemia
Bradycardia
The intrinsic rate of phase 4 depolarization is fastest in…
SA>AV>Hiss,Purkinje
The speed of conduction is highest in…
Purkinje > atria>ventricles>AV node
How is mean arterial pressure determined?
MAP=2/3D+1/3S
How is the resistance of blood vessels determined?
How does the pattern of the vessel and it’s branches affect the resistance?
in series:
R=8ηl/πr^4
#in parallel series:
¥the total resistance is less than any individual artery
¥in each parallel ,we have the same pressure,but only a fracture of. blood flow
¥each vessel receives the same blood flow
¥as blood flows the pressure decreases(ΔΡ=Q*R> ΔΡ ^>Ρarterioles is lower)
When the heart rate increases which part of the cardiac circle is preferentially shortened?
Diastole because there is less filling time>low CO
How can myocardial oxygen demand be increased?
C:contractility
A:afterload
R:heart rate
D:diameter of ventricle(^wall tension)
Wall tension=pressureradius/2wallthichness
How is ejection fraction determined?
Which is approximate number?
EF. (Ποσοτικοποιηση του contractility)
EF=SV/EDV=EDV-ESV/EDV
It is approximately 55%
How does HF affect EF?
EF is lower in systolic HF
EF is normal in diastolic HF
In the myocardial action potential for Hiss/Purkinje/ventricles/atria which ion causes the rapid upstroke and depolarization?
Voltage gated Na channels open
In the myocardial action potential for Hiss/Purkinje/ventricles/atria what is the cause of myocyte contraction?
At the plateau phase we have Ca influx(L-channels of dihydropyridine )
And K effluent.myocyte contraction occurs due to Ca-induced-Ca release from the SR through ryanodine receptors.
In the pacemaker action potential of the SA and AV nodes what is the cause of spontaneous depolarization during diastole?
It is due to If channels (funny current),responsible for the mixed inward of K and Na at phase 4.Its slope determines HR(chronotropic effect)
In the pacemaker action potential of the SA and AV nodes what is the cause of the upstroke?
It is due to the opening of voltage gated Ca channels.
The amount of inward Ca molecules determines conduction velocity.in the AV node>PR interval
^inward Ca>^velocity>short PR
How is chronotropic effect determined?
Rate of phase 4 depolarization->HR
proportional to the number of Ifunny channels
+:^HR-sympathetic β1
-:lowHR-parasympathetic M
How is dromotropic effect determined?
It determines the conduction velocity(in the AV)->PR
It is proportional to Ca inward
+:sympathetic,β1>short PR
-:parasympathetic ,M2>long PR
Which parts of the heart have parasympathetic Vagal innervation?
SA,atria,AV
What are the low resistance paths between cells in cardiac muscle?
The gap junctions>rapid electrical spread
What are three factors that increase contractility(intotropy)?
^HR>high rate of firing act.pot.>more Ca is stored in the SR
#sympathetic stimulation:
▶️^inward of Ca:keeps Ca channels open for more t at the
Plateau phase
▶️phosphorylation of phiospholamban>^CaATPSR
#glycocods:inhibit NaKATP>^NAi>lows efflux of Ca
Give 5examples that decrease contractility
#β1blockers(low cAMP) #HF with systolic dysfunction #Acidosis #Hypoxia/hypercapnia #Non-dihydropyridine Ca channel blocker
Give two pharmacological examples that decrease afterload and preload
Nitroglycerin>venodilator>low preload
Hydralazine>vasodilato>low afterload
Equation of stroke volume SV
SV=EDV-ESV
CO equations
CO=SV*HR
CO=O2consumption/O2pulm.vein-O2pulm.art
CO=MAP/TPR
Stroke work equation
Stroke work=Aortic pressure*SV
Which are the Jugular venous pulse(JPV) waves?
α:atrial contraction
c:RV contraction(closed tricuspid valve bulging into atrium)
x:descent,atrial relaxation[absent in tricuspid regurgitation]
v:^right atrial pressure due to filling against closed tricuspid valve(billing)
ψ:descent,RA emptying into RV
What is the Cushing reaction?
^intracranial pressure cause compression of the cerebral blood vessels>cerebral ischemia>^Pco2>vasomotor center increases sympathetic outflow>^perfusion pressure(hypertension)>^stretch>peri feral reflex baroreceptor induced>bradycardia
Triad #hypertension #bradycardia #respiratory depression
What are the factors that increase Pc,favoring filtration?
#Arteriolar dilation #venous constriction #increase venous/arterial pressure #HF #NO
What are the factors that increase πi favoring filtration?
Inadequate lymphatic function
What are the factors that increase πc favoring absorption?
Dehydration
What are the factors that decrease πc favoring filtration?
#liver disease #nephrotic syndrome #malnutrition
What are the factors that increase Kf favoring filtration?
#burn #infections #toxins #histamine(dilation of the arteries,constriction of the veins) #cytocins
Acts on prostaglandins in the vascular system
Prostacyclin. ➡️vasoconstriction
E-prostaglandin
Thromboxane A2 ➡️vasodilation
F-prostaglandin
What are the 2causes of orthostatic hypotension?
#volume depletion #impaired baroreceptor reflex(individuals with sympatholytic agents)
On an ECG with ventricular extrasystoles ,what is the effect on SV?whatis the effect on the next normal ventricular contraction?
Pulse pressure decreases(inadequate ventricular filling time)>decreased stroke volume
The next contraction will have an increased pulse pressure due to increased contractility(^Ca!!!)
2 P waves preceding each QRS complex at the ECG indicates…
That the conduction velocity through the AV node must be decreased
The greatest pressure decrease in the circulation occurs across the arterioles because…
They have the greatest resistance (low r>^R>^ ΔP)
What’s the act of propranolol?
It is adrenergic antagonist that blocks β1 β2 receptors>low HR+contractility>lowCO
