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70 Cards in this Set
- Front
- Back
The volume of blood ejected by EACH ventricle per unit of time is the definition of?
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Cardiac Output
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What is the measurement of Cardiac Output at rest?
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5-6 L/min
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What are the percentages of Cardiac Output for:
Brain Cardiac Muscle Kidneys |
Kidneys: 20-25%
Brain: 13% Cardiac Muscle: 4% |
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What is normal heart rate?
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80 bpm
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What is the difference for the SV in the ventricles?
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Usually the same for both ventricles
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Which ventricle is Cardiac Output usually referring to?
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Left Ventricle
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What is the normal SV?
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70-80 mL/systole
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What 3 factors is the SV affected by?
If these remain constant, what is SV determined by? |
Venous Return
Peripheral Resistance Autonomic Nervous System If all those remain constant, Force of Contraction determines SV. (Basis of Frank-Starling Law) |
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What happens to the SV and CO if the HR increases between 90-140 bpm ?
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CO increases proportionally
SV will decrease due to less filling time |
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If the HR increases beyond 140 bpm, how does Cardiac Output respond?
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It will now decrease because the SV decreases faster than the increase in HR.
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Will the heart automatically eject ALL the blood that enters it over a broad range of volume?
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Yes, ALL of it.
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What makes it possible for the heart to automatically eject ALL the blood that eneters it over a broad range of volume?
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The striated nature of the cardiac muscle.
It's force of contraction is proportional to the degree of stretch (up to a limit!....!!...!!!!!) |
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What is the force of contraction of the cardiac muscle proportional to?
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Degree of Stretch
Length of the Ventricular Muscle Fibers |
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What does the proportionality of the force of contraction with the length of the ventricular muscle fibers imply?
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That ALL the extra blood resulting from increased venous return is pumped out.
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What determines the initial LENGTH of the Ventricular Muscle Fibers ?
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The quantity of blood in the ventricles just prior to their contraction. This is called the End Diastolic Volume.
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What determines the degree of TENSION of the cardiac muscle when it begins to contract?
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The Pre-load, which is determined by the End Diastolic Volume.
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According to the Frank-Starling Law, what does any change in the Venous Return have a direct effect on?
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Stroke Volume and therefore, the Cardiac Output
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What is the pathway of an increase in venous return?
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Increased Venous Return = Increase in strength of contraction = increased SV = Increased CO
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Does increasing the Blood Pressure have a similar effect as an increase in the Venous return on Cardiac Output?
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Yes, but indirectly.
Increased BP = Increased Resistance = Decreased SV = Increased EDV = Increased strength of myocardial contraction = Increased SV = Increased CO |
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After the initial adjustment by the Frank-Starling Law, what takes over and begins to regulate the strength of contraction (and thus Cardiac Output)?
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Homeometric Regulation takes over the heart so the muscular stretch returns to normal.
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Does the metabolism of the myocardium depend on the degree of stretch of the myocardium?
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No
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What are the valves called between the Atrium and Ventricles?
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Cuspid Valves
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What are the valves called between Ventricles and great Arteries?
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Semi-Lunar Valves
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What is the cause for the heart Lub-Dup sounds?
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Closing of heart valves.
The first sound is the closure of the Cuspid valves, and the second with a higher frequency is due to the closure of the Semi-lunar valves. |
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What are the leaflets of the valves covered with?
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Endothelial Tissue
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What are the divisions between the cusps called?
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Commissures
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What two things do the Chordae Tendinae anchor together? What is this meant to prevent?
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The A-V valves (cuspid) have their ventricular surface anchored to the Ventricular wall.
This prevents blood reflux (heart murmur) |
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The Cardiac cycle is marked from where to where?
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Beginning of one cycle (THE END OF SYSTOLE when both atria are being filled with returning blood, and all valves are closed) to the beginning of the next
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How is each cardiac cycle initiated?
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By SPONTANEOUS generation of an action potential in the SA node.
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What is the pathway from the beginning of the Action potential in the Atria?
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A-V node
Bundle of HIS Bundle Branches Purkinje Fibers FInally all the cardiac fibers |
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In regards to the Action Potential, what contributes to effective ventricular filling?
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The delay of the impulse going from the atria to the ventricles
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What is the function of the conductive system's Specialized Muscle Tissue?
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Impulse generation and transmission.
(NOT CONTRACTION) |
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How fast are all the 4 components of the cardiac cycle accomplished?
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Less than 1 second, due to the HR being ~70 bpm
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What type of process is the opening and closing of the valves?
What determines this? |
It is a Passive Process.
This is determined by the Pressure Gradient across them. |
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What prevents the closure of the AV valves and helps with ventricular filling?
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Atrial Contraction, as soon as the intraventricular pressure is higher than the atrial pressure.
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Does atrial contraction increase the ventricular pumping efficiency?
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Yes, by 40-50%
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Can the heart function effectively without the aid of Atrial Contraction increasing the Ventricular Pumping Efficiency?
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Yes
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What are the 4 phases of Systole and Diastole?
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Systole: Contraction Phase (I) & Ejection Phase (II)
Diastole: Relaxation Phase (III) & Filling Phase (IV) |
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List the 3 phases of ventricular pumping during Systole
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1. Isometric Contraction
2. Rapid Ejection 3. Reduced Ejection |
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List the 5 phases of ventricular pumping during Diastole
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1. Protodiastole
2. Isometric Contraction 3. Rapid Inflow 4. Diastasis 5. Atrial Systole |
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What are the sensors that respond to distension of the artery wall as a result of increased blood pressure?
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Baroreceptors
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Where do the Baroreceptors send impulses to?
What happens as a result? |
Cardiac Center - Medulla Oblongata - specifically the cardioinhibitor center.
This results in the activation of the Parasympathetic System. |
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When the Baroreceptors activate the PNS in the Medulla Oblongata, what are the effects on the heart?
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Decreased:
HR and Contraction Cardiac Output Blood Pressure |
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Where are the Baroreceptors located and what are they innervated by?
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Aortic Arch: Called the Aortic Sinus, innervated by the Vagus.
Carotid Artery: Called the Carotid Sinus, located at the bifurcation of each common carotid, innervated by the Carotid Sinus Nerves (Nerves of Herring) |
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How does the heart respond to a decrease in blood pressure?
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The SNS acts through a cardioacceleration center
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How do Chemoreceptors differ from Baroreceptors?
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Chemoreceptors don't respond to changes in pressure, rather by changes in the concentration of pO2 and pCO2 in the blood.
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Where are the Chemoreceptors located?
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Aortic Bodies: Scattered in the tissue between the Aorta and the Pulmonary Arteries.
Carotid Bodies: Immediately close to the bifurcation of each common carotid artery. |
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What is the term for the value that adjusts the cardiac output to the individual person's body size by representing blood flow relative to a square meter of body surface area?
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Cardiac Index
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What is the normal adult range for Cardiac Index?
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4.2 L/min/m2
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State the equation for Cardiac Index
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Cardiac Index = Cardiac Output / Body surface area
(Body Surface Area = (Height x Weight) / 3600) |
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The amount of blood that passes a given point in the circulation in a given period of time is called?
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Blood Flow (change in Pressure / Resistance)
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The rate of blood flow is expressed in what Law?
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Poiseulle's Law
Proving the diameter is the most important factor in determining blood flow. |
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What is the term describing the impediment to blood flow, and what is the term describing the measure of the blood flow through a vessel for a given deltaP?
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Resistance is impediment to blood flow
Conductance is the measure of the blood flow through a vessel for a given change in Pressure. |
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When the cardiac system is working properly, the atria contract how much sooner than the ventricles?
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1/6th second
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What ability of the myocardium causes automatic rhythmical discharge and contraction?
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Capacity of Self-Excitation
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Which fibers of the heart represent the capability of Self-Excitation to the greatest extent?
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The fibers of the conductive system with the SA node
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What is the potential for the SA fibers between discharges compared to the Ventricular muscle fibers?
What is the reason for the difference? |
SA fibers = -55 -> -60mV
Ventricular fibers = -85 -> -90mV Due to the SA fibers being naturally leaky to Na+. |
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What are the 3 types of membrane channels that play an important role in causing the voltage changes of the action potential?
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1. Fast Na+ Channels
2. Slow Ca2+/Na+ Channels 3. Potassium Channels |
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Which membrane ion channel is responsible for bringing the membrane back to its resting level?
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Potassium Channels
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Which membrane ion channel is responsible for the response to the spike-like onset of the action potential in the ventricular muscle?
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Fast Na+ Channels
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Which membrane ion channel is responsible for the plateau of the ventricular action potential?
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Slow Ca2+/Na+ Channels
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Which channels are permanently closed at the S-A node? Which are open?
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Fast Na+ Channels are closed.
Slow Ca2+/Na+ Channels are open. |
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What does the high extracellular Na+ and high (-) intracellular charge do to the Na+ ions?
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It gives them a tendency to leak into the cell.
Naughty Sodium. |
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How do the Slow Ca2+/Na+ Channels get activated at the S-A node? What does this result in?
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The gradual leaking of Na+ into the SA node cells causes a further increase of the potential from -55mV to -40mV.
-40mV is the Threshold Voltage of the SA node. Once it reaches -40mV, the Slow Ca2+/Na+ Channels are activated, allowing entrance of Ca2+ and Na+. This results in an Action Potential. |
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What is the Threshold Voltage of the S-A fibers?
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-40mV.
This is generated from Na+ leaking into the cells. |
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What is the cause of the Self-Excitation of the S-A fibers?
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The natural leakiness of the Na+ in the SA fibers causes their Self-Excitation.
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How long after opening do the Slow Ca2+/Na+ Channels close? What is happening at the almost at the same time?
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It takes only 100-150ms for the Slow Ca2+/Na+ Channels to close.
Many K+ Channels open at the same time, forcing more K+ outside the cell. |
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What are the results of the K+ travelling out the cell?
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A temporary excess of (-) charge inside the cell.
Hyperpolarization, which initially carries the resting membrane potential down to -55 to -60mV at the end of the Action Potential. |
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How is Rhythmicity possible in a Cardiac Action Potential?
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It's never (-) enough to keep all the channels closed.
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Where do the action potentials spread to, following the S-A node?
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Through the fused surrounding muscle fibers
To the entire Atrial mass Eventually to the A-V node |