The Heart as a Pump Flashcards
What are 4 functions of the cardiovascular system?
- transport nutrients to cells and tissues
- transport waste products away from cells and tissues
- transport hormones throughout the body
- help maintain extracellular environment (homeostasis)
What are the 2 components of the cardiovascular system?
- heart (pump)
2. blood vessels
Which side of the heart pumps blood to the pulmonary circulation?
The right side of the heart
Which side of the heart pumps blood to the systemic circulation?
The left side of the heart
What are valves?
flexible flaps of fibrous (connective) tissue
Which valves are the semilunar valves?
pulmonary and aortic valves
Which valves are the AV valves?
tricuspid and mitral valves
Which ventricle has a higher pressure?
left ventricle
What is the importance of the chordae tendineae and papillary muscles?
prevents valve from bulging backwards/valve eversion/prolapse during ventricular systole
What is the function of the intercalated discs?
it is a junction between membranes of adjacent cells that allows ions to diffuse from one cell cytosol to another (allows for AP spread)
What are the 3 major types of cardiac muscle?
- atrial and ventricular muscle (strong contractions “work horse”)
- excitatory cells (pacemaker or nodes)
- conductive cells (fibers, branches, bundles)
When are the coronary arteries perfused?
during diastole
As aortic pressure declines, coronary blood flow…
declines
Describe what happens during atrial systole
atria depolarization, atria contract, blood volume increases in ventricle, aortic pressure decreased
Describe what happens during isovolumic contraction
ventricle depolarizes, AV valve close, ventricular pressure increasing to overcome aortic pressure, when ventricular pressure overcomes aortic pressure, aortic valve opens at end of isovolumic contraction, S1 heart sound from AV valves closing
Describe what happens during ejection
ventricular volume decreases d/t ventricle contracting and ejecting blood to the aorta, ventricular systole, aortic pressure increases at first and then begins to decrease towards end of ejection phase, ventricle repolarization begins at end of ejection
Describe what happens during isovolumic relaxation
aortic valve closes (recoil and flow back - dicrotic notch), ventricular pressure drops, S2 from semilunar valves, ventricular repolarization (relax)
Describe what happens during diastole
AV valve opens, ventricles begin to increase in volume
How does aortic balloon pump impact coronary artery blood flow?
balloon pump increases aortic pressure near coronary ostia (increases coronary artery perfusion)
How does tachycardia impact coronary artery blood flow?
tachycardia reduces diastolic filling time, which reduces cardiac output and increases the duration of compressed coronary arteries
What are coronary artery dilators?
adenosine
nitric oxide
metabolism waste products (CO2, H+, K+)
What are coronary artery constrictors?
NE acting at alpha 1 adrenergic receptors
Endothelin
Thromboxane A2
How does SNS stimulation effect coronary perfusion?
Increase SNS = increased coronary blood flow
increase alpha 1 AR mediated VSMC constriction BUT
increase beta 1 AR mediated (cardiac) metabolite activity –> increased metabolism waste products –> local metabolites –> dilatation
How does beta blockers effect coronary perfusion?
paradoxically increase coronary blood flow
slows HR, increases duration of diastole, and increase diastolic filling (autoregulation)
What happens during ischemia?
Lactic acid builds up, acidification (H+), glycolysis stops, cardiomyocyte dies
What is stroke work output of the heart?
it is the amount of energy that the heart converts to work during each heartbeat
it comes in two energy forms: volume/pressure work, kinetic work
What is preload?
tension on ventricular muscle at onset of contraction due to volume loading (venous return), left ventricular end diastolic pressure (how full the ventricle is and how stretched), volume of blood pumped by the ventricle
What is the medical significance of the Frank Starling mechanism?
the heart can pump out any extra volume that it gets filled with (no backup of blood)
What is afterload?
tension in wall of left ventricle when aortic valve opens (diastolic BP), resistance against which the ventricle pumps, wall stress in the left ventricle when blood is being ejected (LVP)
hypertensive patients have increased systemic vascular resistance and afterload = stress on the heart
Afterload increases when ventricular wall stress…
increases!
example: aortic stenosis increases P
HTN increases P
increased SVR increases P
Explain the heart failure SWO curve in terms of volume, pressure, and reduction in area under the curve
the shift in volume to the right d/t more volume in ventricle leading to overstretching and less tension, decreased ability to eject effectively
Explain inotropy (cardiac contractility)
for a given ventricular muscle length, there is more Ca2+ = stronger contraction (empties more thoroughly) = decreases ESV
Explain length-tension of contraction
for a given Ca2+ concentration, the ventricular muscle length is longer = stronger contraction
increase preload = increase EDV
empties the extra volume but doesn’t empty more thoroughly (ESV same)
Describe kinetic work
kinetic work = kinetic energy of blood flow (work required to accelerate blood to the velocity of ejection
in aortic stenosis - kinetic work may increase because the CSA through the stenosed aorta is less which means the velocity of ejection will be much higher for a given flow rate
The flow of blood through the aorta is going to be determined by …
the cardiac output
flow should be constant under normal circumstances
Velocity is inversely proportional to..
CSA
as aortic CSA reduces then velocity will increase when flow is constant
regurgitated blood can compromise
cardiac output
