lecture 9 - cardiac cycle Flashcards
define cardiac cycle
Cardiac cycle – the cardiac cycle is the series of coordinated events that occur during one complete heartbeat
define systole and diastole
Systole – the pressure that is exerted by the blood on the blood vessel walls during a ventricular contraction
Diastole – the arterial blood pressure that is reached during or because of diastole, the lowest level of a given cardiac cycle. Is when the heart is relaxed which allows it to fill with blood.
the phases of the cardiac cycle
atrial diastole
atrial systole
ventricular filling
isovolumetric contraction
ventricular ejection
isovolumetric relaxation
the phases of the cardiac cycle - atrial diastole (quiescent period)
when the atria relax and fill with blood from the lungs (left atrium) and the body (right atrium)
the phases of the cardiac cycle - atrial systole
when the atria contract and pump blood into the ventricles
the phases of the cardiac cycle - ventricular filling (systole)
when the valves open and the blood flows into the ventricles from the atria
the phases of the cardiac cycle - isovolumetric contraction (ventricular systole)
when the ventricles contract but the valves are closed do there is no change in volume
the phases of the cardiac cycle - ventricular ejection (ventricular diastole)
when the valves open and blood is pumped out of the ventricle into the aorta (left ventricle) and the pulmonary artery (right ventricle)
the phases of the cardiac cycle - isovolumetric relaxation
when the ventricle relax, but the valves are closed so there is not change in volume
Relate the electrical events represented on an electrocardiogram (ECG or EKG) to the normal mechanical events of the cardiac cycle.
P wave – the first small upward deflection, represents depolarization of the atria
QRS complex – Q is a small negative deflection, R is a large positive deflection, and S is a small negative deflection following the R wave. This all symbolizes the depolarization of the ventricles.
T wave – is a smooth asymmetrical, upward deflection that occurs after the QRS complex, is the repolarization of the ventricles
The electrical events on an ECG directly correspond with what is shown for mechanical events of the cardiac cycle
Explain how atrial systole is related to ventricular filling.
The Atrial systole represents the final phase of ventricular filling where the atria will contract and actively push the remaining blood in the ventricles.
Relate the opening and closing of specific heart valves in each phase of the cardiac cycle to pressure changes in the heart chambers and the great vessels (i.e., blood vessels entering and leaving the heart).
During the cardiac cycle, heart valves open and close based on pressure differences between the heart chambers and the great vessels, allowing blood to flow in one direction only; when the pressure in a chamber becomes higher than the pressure in the vessel connected to it, the valve between them opens, and when the pressure reverses, the valve closes, ensuring unidirectional blood flow
Relate the opening and closing of specific heart valves in each phase of the cardiac cycle to pressure changes in the heart chambers and the great vessels - atrioventricular
Open during ventricular diastole: When the pressure in the atria is higher than the pressure in the ventricles, the AV valves open, allowing blood to flow from the atria into the ventricles.
Close during ventricular systole: As the ventricles contract, their pressure rises above the atrial pressure, causing the AV valves to close and preventing backflow
Relate the opening and closing of specific heart valves in each phase of the cardiac cycle to pressure changes in the heart chambers and the great vessels - semilunar
Open during ventricular systole: When the pressure in the ventricles exceeds the pressure in the aorta and pulmonary artery, the semilunar valves open, allowing blood to be ejected from the heart.
Close during ventricular diastole: As the ventricles relax, pressure in the aorta and pulmonary artery becomes higher than the ventricular pressure, causing the semilunar valves to close and prevent backflow
Relate the opening and closing of specific heart valves in each phase of the cardiac cycle to pressure changes in the heart chambers and the great vessels - ventricular systole
contraction
Early Systole (Isovolumetric Contraction): All valves are closed, ventricular pressure rapidly increases, causing the AV valves to close tightly.
Ventricular Ejection: Once ventricular pressure exceeds the pressure in the aorta and pulmonary artery, the aortic and pulmonary valves open, allowing blood to be ejected
Relate the opening and closing of specific heart valves in each phase of the cardiac cycle to pressure changes in the heart chambers and the great vessels - ventricular diastole
relaxation
Isovolumetric Relaxation: All valves are closed, ventricular pressure rapidly drops, causing the semilunar valves to close.
Ventricular Filling: When ventricular pressure falls below the pressure in the atria, the AV valves open, allowing blood to flow into the ventricles
Relate the heart sounds to the events of the cardiac cycle.
specifically the “lub” (S1) and “dub” (S2) sounds, are directly related to the closing of the atrioventricular valves (mitral and tricuspid) during ventricular contraction (systole) for “lub” (S1), and the closing of the semilunar valves (aortic and pulmonary) at the end of ventricular contraction, marking the beginning of ventricular relaxation (diastole) for “dub” (S2) - essentially, the heart sounds are audible vibrations created by the turbulent blood flow as the valves close during the cardiac cycle
Define systolic and diastolic blood pressure and interpret a graph of aortic pressure versus time during the cardiac cycle.
Systolic – the top number which shows the pressure exerted on the artery walls when the heart is actively contracting
Diastole – the bottom number which shows the pressure the arteries put on the heart when it is relaxed and filling with blood
interpreting systolic and diastolic on a graph
- The peak or highest point on the graph represents the systolic, the lowest point on the graph represents the diastolic.
Compare and contrast pressure and volume changes of the left and right ventricles during one cardiac cycle.
the left ventricle experiences significantly higher pressure changes compared to the right ventricle due to its responsibility for pumping blood throughout the systemic circulation, while both ventricles generally undergo similar volume changes, with the left ventricle having slightly larger volumes due to its larger size; essentially, the left ventricle generates much greater pressure to pump blood against higher resistance, while the right ventricle pumps blood at lower pressure into
why does the left ventricular tend to have more pressure on it
- essentially the left has higher pressure because it is sending blood to the entire body, whereas the right only pumps to the lungs so it has less resistance or pressure on it.
Given the heart rate, calculate the length of one cardiac cycle.
60 seconds/heart rate (bpm)
Ex: 70bpm would give 60/70 = 0.86 seconds for a full cycle
Define cardiac output (CO) and state its units of measurement.
refers to the volume of blood pumped by the heart per minute, and is typically measured in liters per minute (L/min)
Calculate cardiac output, given stroke volume and heart rate.
CO = stroke volume X heart rate
Predict how changes in heart rate (HR) and/or stroke volume (SV) will affect cardiac output (CO).
if either heart rate (HR) or stroke volume (SV) increases, then cardiac output (CO) will also increase; conversely, if either HR or SV decreases, then CO will decrease as well
Describe the concepts of ejection fraction and cardiac reserve.
“Ejection fraction” refers to the percentage of blood that is pumped out of the heart’s left ventricle with each contraction, essentially measuring how efficiently the heart is pumping blood.
“cardiac reserve” represents the difference between the heart’s resting pumping ability and its maximum potential to pump blood when needed, indicating how much extra capacity the heart has to respond to increased demands like exercise.
Define end diastolic volume (EDV) and end systolic volume (ESV)
EDV = the volume of blood in a ventricle at the end of the filling phase (diastole) which represents then max amount of blood in the ventricle before a contraction begins
ESV = the volume of remaining blood in a ventricle at the end of the contraction phase (systole), this is the amount of blood left after the ventricle has pumped out as much as possible.
SV = the difference between end-diastolic and end-systolic (the volume ejected with each heart beat)
calculate stroke volume (SV) given values for EDV and ESV.
Calculating stroke volume: SV= EDV - ESV
venous return
the volume of blood that returns to the heart per unit of time.
The ability of an area to store large or small volumes of blood can affect this
preload
- the stretch of the muscle cells before contraction; the blood remaining in the left ventricle at the end of diastole causing it to stretch
the pressure on the ventricular muscle at the end of diastole, this is when the heart is still filling. (left ventricular end-diastolic pressure). the resting cells are normally shorter than optimal
Is affected by changes in venous tone and blood volume (stretches it)
an increase in EDV=increase in SV
afterload
the pressure the heart must work against to pump blood out of the ventricles - the pressure the ventricles have to overcome; the amount of resistance or force that occurs when the heart ejects blood from the left ventricle
Can be affected by the amount of vascular resistance present
high bp = high ESV = low CV
Explain how venous return affects end diastolic volume (EDV), end systolic volume (ESV), and stroke volume (SV).
Effect on EDV: Increases with increased venous return, as more blood fills the ventricle during diastole. Effect on ESV: Indirectly decreases ESV by increasing EDV and therefore, stroke volume. Effect on SV: Increases with higher venous return due to increased EDV
Explain how afterload affects end diastolic volume (EDV), end systolic volume (ESV), and stroke volume (SV).
Afterload primarily impacts end systolic volume (ESV), where increased afterload leads to a higher ESV and decreased SV, as the heart struggles to eject blood against greater resistance. When afterload increase there is an increase in EDV.
- afterload primarily impacts end systolic volume (ESV), where increased afterload leads to a higher ESV and decreased SV, as the heart struggles to eject blood against greater resistance
Explain how preload affects end diastolic volume (EDV), end systolic volume (ESV), and stroke volume (SV).
An increase in preload causes a increase in EDV. A change in preload primarily affects stroke volume by altering the EDV. Increased preload leads to a larger stroke volume without changing the ESV. An increase in preload leads to a direct increase in stroke volume.
Describe the role of the autonomic nervous system in the regulation of cardiac output
The autonomic nervous system (ANS) plays a crucial role in regulating cardiac output by controlling the heart rate and force of contraction through its two branches: the sympathetic nervous system (SNS), which increases cardiac output by accelerating heart rate and enhancing myocardial contractility, and the parasympathetic nervous system (PNS), which decreases cardiac output by slowing down the heart rate; essentially allowing the body to adjust cardiac output based on situational demands like exercise or rest.
preload
contractility
afterload
preload - directly influences the end diastolic volume. If preload increases so does EDV and the opposite is also true
contractility
is increasing the force at which the chamber squishes; the force required to eject blood from the left ventricle
- the more it does this the more the SV goes down because there is less in the heart. The more blood that is ejected the lower the ESV and the higher the SV
After load
The pressure the hear must work against to pump blood out of the ventricles
