Midterm 1 - Heart as a Pump

Question 1

denervated heart rate

Answer 1

pace follows the SA node intrinsic rhythm

Question 2

main control for heart rate regulation

Answer 2

sympathetic/adrenal medulla and parasympathetic by modulating the length of potential drift in autorhytmic cells

Question 3

what is stroke volume

Answer 3

volume of blood ejected per contraction

Question 4

how to calculate stroke volume

Answer 4

End-diastolic volume - end-systolic volume

Question 5

primary determinants of stroke volume

Answer 5

EDV = preload
ESV = afterload

Question 6

what is the EDV/preload

Answer 6

volume of blood present in the ventricles at the end of diastole

Question 7

what is the EDV/preload linked to

Answer 7

the work imposed on ventricles prior to contraction

Question 8

what is the ESV/afterload

Answer 8

residual volume of blood contained in ventricle after systole

Question 9

what does the ESV/afterload depend on

Answer 9

the impedance to ejection of blood from ventricles

Question 10

what are forces that prevent blood to eject

Answer 10

resistance
turbulence

Question 11

what is the result of an increase in EDV

Answer 11

increase in stroke volume

Question 12

what does an increase in EDV alter

Answer 12

cardiac peformance via the Frank Starling law of the heart

Question 13

what is the frank starling law of the heart

Answer 13

as preload is increased, the contractility of the heart is increased which increases stroke volume

Question 14

what does the increase in stretch of cardiac muscle fibers at the end of diastole induce

Answer 14

increase in contractility by enhancing binding of Ca++ to troponin-C

Question 15

what occurs with EDV under resting condition

Answer 15

EDV stretches cardiac muscle to sub-optimal levels

Question 16

why does stretching the cardiac muscle beyond optimum not occur

Answer 16

the pericardium

Question 17

what is the main factor affecting preload (EDV)

Answer 17

venous return

Question 18

what happen during increased venous return

Answer 18

increased EDV

Question 19

what happens during decreased venous return

Answer 19

decreased EDV

Question 20

what is venous return dependent on

Answer 20

the pressure difference between large veins and right atrium

Question 21

Factors involved with venous return

Answer 21

skeletal muscle pump
respiratory activity/pump
blood volume
autonomic nervous system

Question 22

how does the skeletal muscle pump work

Answer 22

muscle contraction squeezes veins which push blood towards heart

Question 23

how does the respiratory pump work

Answer 23

inspiration

Question 24

what is inspiration

Answer 24

construction of diaphragm

Question 25

what does the inspiration in the respiratory pump do

Answer 25

increases abdominal pressure which transfers to abdominal veins and creates low pressure in the thoracic cavity where the vena cava is - promoting venous return

Question 26

what does increased blood volume result in

Answer 26

elevated venous return

Question 27

what does the ANS do to venous return

Answer 27

veins contain smooth muscles innervated by sympathetic fibers, and an increase in APs in nerve fibers results in contraction –> increased pressure in vein –> increased venous return

Question 28

what is a factor affecting afterload (ESV)

Answer 28

resistance to flow the ventricles encounter during ejection

Question 29

what happens to afterload during exercise

Answer 29

indirectly controlled by the heart contractility (higher contractility = lower ESV)

Question 30

what is the main determinant for afterload during rest

Answer 30

arterial vasomotor tone (arterial vascular resistance) = total peripheral resistance

Question 31

what is total peripheral resistance

Answer 31

arterial blood pressure

Question 32

what does measuring blood pressure indicate

Answer 32

afterload

Question 33

how to calculate blood pressure

Answer 33

cardiac output x arterial resistance