Integrated Cardiac Function

Question 1

Venous input must equal cardiac output because the systems are in _______.

Answer 1

Venous input must equal cardiac output because the systems are in series.

Question 2

Cardiac output is typically______.

Answer 2

5 liters/ min

Question 3

What are the equations for CO & MAP.

Answer 3

MAP = CO x TPR = (HR x SV) x TPR
-CO (HR & SV) & TPR are independent variables & MAP is dependent variable

CO = HR x SV
-HR & SV are independent variables & CO is dependent variable

Question 4

CO is regulated by intrinsic & extrinsic mechanisms, what does this mean?

Answer 4

Intrinsic = local to the heart. Starlings law, ionic potentials, contractility.

Extrinsic = extra-cardiac. Neuronal, hormonal, baroreceptors, chemoreceptors, symp & parasymp stimulation

Question 5

Describe the neurotransmitter, receptor, second messenger & effects of sympathetic stimulation to the heart.

Answer 5

neurotransmitter: norepi
receptor: B1 pacemaker

second messenger: increase cAMP

effects: tachycardia & increase contractility, positive inotrophy & chronotropy = increase stroke volume & cardiac ouput
mnemonic: alpha adrenergic vasoconstriction. norepi increases BP by vasoconstricting arterioles (increases resistance) via a1 receptor to increase TPR.

B2 receptors dilate the bronchioles in the lung

Question 6

Describe the neurotransmitter, receptor, second messenger & effects of parasympathetic stimulation to the heart.

Answer 6

neurotransmitter: Ach
receptor: M2 pacemaker

second messenger: decrease cAMP

effects: bradycardia & decrease contractility (lesser effect), negative inotrophy & chronotropy = decrease stroke volume & cardiac ouput

Question 7

If you decrease your end-systolic volume, you increase _______.

Answer 7

Stroke volume

SV = EDV - ESV

Certain drugs act on the heart by increasing contractility & shift pressure v volume curve to the left & increase SV by decreasing ESV

Question 8

In myocardial local ishemia, the Na/KATPase will not work well because there is lack of

Answer 8

ATP

No ATP because no O2 made via oxidative metabolism

Question 9

Cardiac output is _______ proportional to Oxygen consumption. Discuss this.

Answer 9

directly

Cardiac output (normally 5-6 L/min) is the volume of blood pumped by the heart into the aorta each minute. The cardiac output is the same into the aorta and into the pulmonary artery because the systemic and pulmonary circuits are in series. (Note that cardiac output is not the sum of the flows into the aorta and pulmonary arteries.)

At a normal cardiac output, the entire blood volume moves around the body once each minute. If cardiac output falls below about one third of normal, the functions of all the cells will be impaired due to hypoxia. Hypoxia is a condition in which the amount of oxygen in the tissues is insufficient for their metabolic needs.

During exercise, cardiac output increases in proportion to the amount of work performed, and also in proportion to the increased consumption of oxygen by the muscles.

The relationship between cardiac output and oxygen consumption is linear. This linear relationship accounts for many of the effects of
physiological variables on cardiac output noted.
During maximally strenuous exercise, cardiac output may rise six-fold to 36 L/min, or even higher in trained athletes.

See graph pg. 110

Question 10

Discuss some factors that increase & decrease CO

Answer 10

see pgs. 111-112

Question 11

A blood transfusion shifts the vascular function curve ______ & a positive inotropic effect shifts the cardiac function (starling) curve ______.

Answer 11

A blood transfusion shifts the vascular function curve right & a positive inotropic effect shifts the cardiac function (starling) curve up and to the left.

see pg. 113

Question 12

Discuss mean systemic filling pressure hypothetical state

Answer 12

If we stop the heart from beating, there is no flow (cardiac output or venous return = 0) & the pressure it will have will equal the peripheral venous pressure in the elastic veins.

Question 13

Men systemic filling pressure _____ in a transfusion since we are filling elastic vessels with more volume.

Answer 13

Men systemic filling pressure increases in a transfusion since we are filling elastic vessels with more volume.

Question 14

In a hemmorage, we give transfusions for 2 reasons, what are they?

Answer 14

1) We increase @ restore the blood pressure
2) It also gives an increase in venous return (venous return = cardiac output) which increases cardiac output

see pg. 113

Question 15

ARTERIOLAR vasodilatation shifts the vascular function curve __ & ARTERIOLAR vasoconstriction shifts it ___, which represents a change on the y axis of venous return or CO. Arteriolar vasoconstriction or vasodilation ______ MSFP (mean systemic filling pressure) on the ____ axis because the blood volume has not changed. Therefore, MSFP ______ with increases & decreases in blood volume.

Answer 15

ARTERIOLAR vasodilatation shifts the vascular function curve up & ARTERIOLAR vasoconstriction shifts it down, which represents a change on the y axis of venous return or CO. Arteriolar vasoconstriction or vasodilation do not change MSFP point on the X axis because the blood volume has not changed (mean systemic filling pressure). Therefore, MSFP increases & decreases with increases & decreases in blood volume.

see pg. 114

Question 16

ARTERIOLAR _______ shifts blood from the arterial side to the venous side & increases venous return.

ARTERIOLAR ______ shifts blood from the venous side to the arterial side & decreases venous return.

Answer 16

ARTERIOLAR Vasodilation shifts blood from the arterial side to the venous side & increases venous return.

ARTERIOLAR vasoconstriction shifts blood from the venous side to the arterial side & decreases venous return

Arteriolar resistance traps blood in the arterial side & MAP increases due to increased volume in the arterial side that we took from the venous side.

see pg. 114

Question 17

Discuss the cardiovascular response to exercise.

Answer 17

Contracting muscles rhythmically open and close venous flap valves, thereby promoting increased VR (venous return) = mechanical pump, especially in the legs.

A transient increase in RAP (right atrial pressure) increases EDV (end-diastolic volume & pressure) and increases SV and CO, in accordance with Starling’s Law of the Heart.

An overall decrease in TPR due to conditions of local hypoxia, hypercapnea, and acidemia in working muscle, usually the legs, causes arteriolar vasodilation* and prevents MAP from rising too much (there is arteriolar vasoconstriction like in all sympathetic responses, but the vasodilation response is greater than vasoconstriction in exercise so TPR decreases). CO = MAP/ TPR, decreasing TPR allows an increase in CO without increasing MAP too much (or arteries would explode).

Remember that the vasodilatation is of the arterioles of the working muscle & there is vasoconstriction in the non working muscle. The effect of larger vasodilatation shifts blood to the venous side which increases CO.

The decrease in MAP shown on the flow chart above is only transient, as MAP DOES increase during exercise. Sympathetic drive during exercise increases HR and contractility, with accompanying increases in SV and CO.

See pg. 115

Question 18

What are the 3 things that shift the cardiac function curve up? What shifts occur in the venous return curve & why?

Answer 18

1) HR
2) SV
3) Increase in contractility/ inotropy

4) The venous return curve also shifts upward due to increased arteriolar vasodilation in working muscle, but mostly due to venous contraction (veniconstriction increases MSFP, that is, the same amount of venous blood is now in a smaller vessel)!

During exercise with maximal sympathetic stimulation, VR (venous return) and CO both increase to a higher match point, without much change in RAP.

Sympathetic venoconstriction increases MSFP because the blood volume is now contained in a smaller cardiovascular system. Note that the veins contain a much larger quantity of blood than do the arterioles, so that venoconstriction increases MSFP whereas arteriolar vasoconstriction has only a negligible or no effect in altering MSFP.

These all occur during exercise

see graph pg. 116

Question 19

Spinal anesthesia inhibits sympathetic drive, resulting in veno_____, ______ peripheral venous pressure, _____ venous return and lower CO.

Answer 19

Spinal anesthesia inhibits sympathetic drive, resulting in venodilation, lower peripheral venous pressure, lower VR and lower CO.

Question 20

Rest of this lecture is on EKG.

Answer 20

-

Question 21

The T wave corresponds to ventricular repolarization, which occurs during ______ ejection. The P wave coincides with atrial systole, which continues during the ____interval. The QRS complex is caused by ventricular excitation, which is followed by ______. The ST segment encompasses_______.

Answer 21

The T wave corresponds to ventricular repolarization, which occurs during reduced ejection. The P wave coincides with atrial systole, which continues during the PR interval. The QRS complex is caused by ventricular excitation, which is followed by isovolumic contraction and rapid ejection. The ST segment encompasses isovolumic contraction and persists through rapid ejection.

Question 22

The third heart sound (S3) occurs during _____ and is caused by sudden tensing and reverberation of the ventricular walls. Although usually a sign of underlying pathology in adults, it is a normal finding in _______. Ventricular filling and S3 occur during ____stole, not repaid ejection.

Answer 22

The third heart sound (S3) occurs during ventricular filling and is caused by sudden tensing and reverberation of the ventricular walls. Although usually a sign of underlying pathology in adults, it is a normal finding in children. Ventricular filling and S3 occur during diastole, not repaid ejection.

Whereas a right-axis deviation does not necessarily correlate with a heart sound. Regurgitant valves produce murmurs, not heart sound.

Question 23

Decreased afterload would ______ the stroke volume by decreasing the end-systolic volume, as seen on a pressure-volume loop. Decreasing preload or contractility would _____ stroke volume. A negative inotropic agent would decrease contractility and _____. A negative chronotropic agent would decrease heart rate.

Answer 23

Decreased afterload would increase the stroke volume by decreasing the end-systolic volume, as seen on a pressure-volume loop. Decreasing preload or contractility would decrease stroke volume. A negative inotropic agent would decrease contractility and stroke volume. A negative chronotropic agent would decrease heart rate.

Question 24

An increase in preload of the left ventricle, with all other parameters remaining constant, would increase which of the following?

Answer 24

End diastolic volume

Question 25

The t-wave is associated with ventricular ______ that occurs just prior to relaxation of ventricular tension, before the dichrotic notch, before the opening of the mitral valve, and before the left ventricular pressure and the aortic pressure reach their diastolic values.

Answer 25

The t-wave is associated with ventricular repolarization that occurs just prior to relaxation of ventricular tension, before the dichrotic notch, before the opening of the mitral valve, and before the left ventricular pressure and the aortic pressure reach their diastolic values.

Question 26

Isovolumic left ventricular contraction closely follows ventricular depolarization signaled by the beginning of the ______. The second heart sound is due to the closure of the aortic valve, which occurs during ______ of the left ventricle. The v wave of the jugular pulse is associated with ______ filling and emptying, which occurs during ventricular relaxation. Isotonic contractions involve shortening and are not ______.

Answer 26

Isovolumic left ventricular contraction closely follows ventricular depolarization signaled by the beginning of the QRS complex. The second heart sound is due to the closure of the aortic valve, which occurs during relaxation of the left ventricle. The v wave of the jugular pulse is associated with atrial filling and emptying, which occurs during ventricular relaxation. Isotonic contractions involve shortening and are not isovolumic.

Question 27

When do heart sounds occur?

Answer 27

Heart sounds are the noises generated by the beating heart and the resultant flow of blood through it. Specifically, the sounds reflect the turbulence created when the heart valves snap SHUT.

Question 28

1) The match point on the intersection of the curves represents when cardiac output and venous return are equal @ denote?
2) The mean circulatory pressure refers to the pressure when the heart is ______.

Answer 28

1) resting cardiac output and central venous pressure.

2) stopped

Question 29

What would shift the cardiac output curve up?

Answer 29

Increases in contractility, heart rate, and stroke volume would shift the cardiac function curve upwards.

Question 30

Atrial _____ would yield an S4 heart sound.

Answer 30

Atrial hypertrophy would yield an S4 heart sound.

Question 31

Preload is the ____tolic pressure. Decreased afterload would increase the stroke volume by decreasing the ______ volume.

Answer 31

Preload is the end-diastolic pressure. Decreased afterload would increase the stroke volume by decreasing the end-systolic volume.