Cardiovascular Physiology Flashcards
What do the waveforms on an EKG mean?
P wave: Atrial depolarization
PR interval: AV conduction
QRS complex: Ventricular depolarization
QT interval: (timing) 0.4 seconds
T wave: Ventricular repolarization
What are the factors that determine cardiac output?
CO = HR x SV
Heart rate regulation:
Parasympathetic: Decreases
Sympathetic: Increases
Stroke volume regulation:
Preload: End Diastolic Volume (volume in ventricle after diastole, aka the amount of blood that enters the ventricle)
Afterload: Resistance the ventricles must overcome to circulate the blood.
Contractility: How hard the myocardium must contract for a given preload.
Describe mechanical events of the heart and how are they related to electrical events?
When do S1 and S2 take place?
Systole: Ventricular Contraction
Diastole: Ventricular Relaxation.
P wave: Firing of SA node. Atrial Depolarization, resulting in atrial contraction. Blood goes into ventricles. Pressure in Atrium thus falls, closing AV valves. This is S1, also marking the beginning of Systole.
QRS complex: Ventricular Depolarization, causing ventricular contraction. Semilunar valves remain closed briefly until isovolumetric contraction.
S-T duration: Rapid Ejection Phase: After isovolumetric contraction, pressure increases and blood spills into Aorta.
T wave: Ventricular Repolarization: Reduced ejection. Eventually, semilunar valves close, producing S2, also marking the end of Systole and beginning of Diastole, where Isovolumetric relaxation takes place.
What is the relationship of edema to capillary dynamics?
Edema caused by: Increased filtration due to increased blood pressure / increased capillary permeability, or Decreased reabsorption, or obstruction of lymphatic drainage.
For example, Capillary hydrostatic pressure (CHP) increases, or Tissue Oncotic pressure decreases. Inbalance of filtration - reabsorption causes edema.
How is the RAAS involved in the regulation of MAP?
Decreased MAP causes decreased renal perfusion pressure which stimulates release of renin which converts angiotensinogen to angiotensin I —(ACE)—> angiotensin II which:
o Causes vasoconstriction, thus increasing TPR and MAP
o Release of aldosterone, thus increases Na+/Water reabsorption, and increased blood volume, thus increasing MAP
What is the relationship of cardiac output to venous return?
Identical (can’t pump out more than you get in)
Being in a closed loop system, CO must equal VR when averaged over time unless blood is accumulating in the systemic or pulmonary circulations
What information can be derived from cardiac function curves and venous return curves?
Cardiac function curve describes relationship between right atrial pressure and cardiac output. CO depends on preload and cardiac contractility but is also affected by blood volume and vascular tone
o Shifts upwards (counter clockwise) with physical exercise and vascular resistance
o Shifts downward (clockwise) with damaged heart muscles/decreased cardiac performance
Venous return x axis = mean systemic pressure
