Integration of Cardiac Function

Question 1

what receptors are used for sympathetic and parasympathetic effects upon the heart and what are their second messengers?

Answer 1

SNS- beta1 adrenergic receptors (increase cAMP)

PNS- M 2 muscarinic receptors (decrease cAMP)

Question 2

what are the two intrinsic mechanisms or regulating cardiac output?

Answer 2

starlings law- increased volume=increased contractility

membrane potentials and therefore ionic concentrations

Question 3

what are the extrinsic mechanisms of regulation of cardiac output?

Answer 3

neuronal and hormonal signaling

Question 4

why is the cardiac output the same into the aorta and into the pulmonary artery?

Answer 4

because the two circuits are in series

Question 5

graphically what is the difference between cardiac output and oxygen consumption?

Answer 5

linear

Question 6

what eight factors increase cardiac output?

Answer 6

fever, exercise, anxiety, body weight, pregnancy, hyperthyroidism, chronic anemia and hypoxia

Question 7

what five factors decrease cardiac output?

Answer 7

sleep, aging, severe anoxia, acute hemorrhage and heart disease

Question 8

what is histotoxic hypoxia?

Answer 8

tissue poisoning that causes the tissues to be less able to use oxygen

Question 9

why does cardiac output have varying responses to hypoxia and severe anoxia?

Answer 9

because severe anoxial causes oxygen deprivation in the heart and decreases cardiac output

Question 10

what is the effect of hypertension on cardiac output?

Answer 10

it is unaltered

Question 11

what are the only two ways to produce a different steady state match of CO?

Answer 11

changing the cardiac function curve or the vascular function curve

Question 12

during exercise what happens to the body’s vasculature and what is the overall effect?

Answer 12

there is arteriolar and venous vasoconstriction. the overall effect is functionally increasing venous return by the venous constriction

Question 13

how does muscle contraction promote venous return?

Answer 13

by pumping venous blood past valves towards the heart

Question 14

why is there an overall decrease in peripheral resistance to blood flow during exercise?

Answer 14

because local hypoxia, hypercapnea and acidemia promote vasodilation and prevent MAP from increasing too much

Question 15

what happens to the mean systemic filling pressure during an increase and a decrease in sympathetic stimulation?

Answer 15

increase- increase in MSFP and decrease with a decrease in sympathetic stimulation

Question 16

what happens to cardiac output and venous return during exercise? does a difference in central venous pressure cause this?

Answer 16

both increase, however here is not an increase in CVP

Question 17

what does depolarization and repolarization look like on an EKG?

Answer 17

depolarization is a bump on the graph in the positive y axis while repolarization is a bump in the negative region of the graph

Question 18

what does the P wave of the electrocardiogram correspond to?

Answer 18

atrial depolarization

Question 19

what does the QRS complex correspond to in the EKG?

Answer 19

ventricular depolarization

Question 20

what does the T wave in the EKG correspond to?

Answer 20

ventricular repolarization

Question 21

why is the T wave of the EKG inverted?

Answer 21

because the ventricles repolarize from the epicardium towards the endocardium (opposite of depolarization)

Question 22

why can’t atrial repolarization be seen in EKG?

Answer 22

because it is obscured by ventricular depolarization

Question 23

what depolarizations occur during the PR interval?

Answer 23

the SA node, atria, AV node, the His bundle, the bundle branches and the purkinji fibers

Question 24

why do the depolarization of the AV node, AV bundle, bundle branches and Purkinje fibers not appear on the EKG?

Answer 24

because they do not generate voltages large enough to be detected

Question 25

what does the ST segment correspond to in the action potential of the ventricular myocardium?

Answer 25

the plateau phase

Question 26

what is produced by the upstroke of all of the ventricular action potentials?

Answer 26

the QRS complex

Question 27

what segments are contained in ventricular diastole?

Answer 27

the TP segment and the PR interval

Question 28

when does most ventricular filling occur? how does this correspond to atrial contraction?

Answer 28

ventricular filling occurs mostly in early diastole and atrial contraction occurs at the end of ventricular diastole

Question 29

what does atrial contraction contribute to preload?

Answer 29

produces only a small rise in ventricular volume and pressure (both sides of the heart)

Question 30

when does atrial diastole occur and what happens to the atrial pressure during this time?

Answer 30

it occurs during ventricular diastole and the atrial pressure increases

Question 31

why is there a fall in ventricular pressure even after the mitral and tricuspid valves open?

Answer 31

because the forward momentum of blood into the ventricle expands them and drops the pressure simultaneously

Question 32

how does blood flow into the aorta continue during systole even though there are times when aortic pressure is greater than ventricular pressure?

Answer 32

because the forward momentum continues the flow even though there is a deceleration of flow until it stops and closes the aortic valve

Question 33

what is the relationship of the P wave and atrial contraction?

Answer 33

the P wave precedes atrial contraction

Question 34

what happens to flow at the dichrotic notch?

Answer 34

the decrease of the pressure gradient causes the reversal of flow

Question 35

what does the R wave coincide with?

Answer 35

the onset of ventricular contraction

Question 36

how many sounds are produced by the heart? which ones can be heard with a stethoscope?

Answer 36

4 | closure of the AV valves and closure of the semilunar valves

Question 37

when does the T wave occur with respect to blood flow?

Answer 37

during the second half of the ejection phase

Question 38

what six factors affect stroke volume?

Answer 38

atrial filling pressure, ventricular filling time, ventricular compliance, heart rate (increase causes a decrease in diastole time), preload and afterload

Question 39

what is the timing of the right and left atria? the ventricles?

Answer 39

the right atrium contracts prior to the left atrium | the left ventricle contracts prior to the right

Question 40

how does the amount of time that the pulmonary valve is open compare to the aortic valve?

Answer 40

the aortic valve is open for less time even though the left ventricle contracts earlier because there is an increased time of isovolumetric contraction because aortic pressure is higher

Question 41

what two sounds are not normally heard in adults?

Answer 41

ventricular diastolic filling and atrial contraction