week 12

Question 1

what is the formula for calculating Q (cardiac output)?

Answer 1

Q = 100 x (VO2 / [CaO2 - CvO2])

Question 2

define cardiac output (Q)

Answer 2

the volume of blood pumped out of the left ventricle in 1 min (L/min)

Q = HR x SV

Question 3

define heart rate (HR):

Answer 3

the number of cardiac cycles or beats per min (beats/min or bpm)

Question 4

define stroke volume (SV)

Answer 4

the volume of blood pumped out of the left ventricle in one heart beat (mL)

Question 5

define venous return (VR)

Answer 5

the volume of blood coming back into the heart in 1 min (not always equal to Q)

Question 6

how can we increase cardiac output (Q)?

Answer 6

increase HR
increase SV
increase HR and increase SV

Question 7

define diastole and end-diastolic volume (EDV)

Answer 7

diastole: the relaxation phase when cardiac filling occurs

EDV: the amount of blood in the ventricles at the end of diastole - what is in the ventricle at the end of filling

Question 8

define systole and end-systolic volume (ESV)

Answer 8

systole: contraction phase, when cardiac ejection occurs

ESV: amount of blood in the ventricle at the end of systole - at the end of ejection

Question 9

how do we calculate SV

Answer 9

EV = EDV - ESV

Question 10

how do we increase SV

Answer 10

increase EDV
decrease ESV

Question 11

what is an ejection fraction and how do we calculate it

Answer 11

proportion of blood in the ventricle that is ejected with each beat

EF = SV/EDV x 100 (in %)

Question 12

copy down the first slide on page 5 of cardiac output

Question 13

why is Q one of the most important determinants of VO2 max and of endurance performance?

Answer 13

• the ability to match Q to metabolic demands has huge implications for health and general function
• training adaptations to Q have implications for both performance and for health

to understand what happens to Q during acute and chronic exercise, we need to know what happens to HR, EDV, and ESV and WHY

Question 14

copy down first slide on page 6 of cardiac output!!!

Question 15

what is HR regulated by?

Answer 15

HR is regulated by the autonomic nervous system (ANS)

• cardioacceleratory (SNS) and cardioinhibitory (PSNS) centers in the medulla
• direct innervation of SA node by accelerator nerve and vagus nerve - increases or decreases firing rate
• HR can be increased via increased SNS outflow, decreased PSNS outflow, or both

Question 16

what is the balance of SNS/PSNS outflow from the cardiovascular control center influenced by?

Answer 16

• mvmt via motor cortex + proprioceptors
• emotions via hypothalamus
• body temp via hypothalamus
• metabolic activity in muscles via metaboreceptors
• circulating O2, CO2, and H+ via chemoreceptors
• arterial BP via baroreceptors
• venous return via RA stretch receptors

Question 17

what influences a persons resting HR?

Answer 17

genetics, age and endurance training status

Question 18

what is the typical resting HR and what is it called when someone is below or above that?

Answer 18

typical resting HR: 60-100 bpm

lower: bradycardia
higher: tachycardia

Question 19

what determines a persons HR max?

Answer 19

genetics and age

Question 20

what is SV influenced by

Answer 20

preload, contractility and afterload

Question 21

define preload

Answer 21

amount of stretch in ventricle/muscle cells

preload is more or less synonymous with EDV

Question 22

define contractility

Answer 22

the amount of force produced during contraction (at a given period)

contraction force is established by contractility of muscle fibers and is enhanced when cells are stretch towards optimum length by higher preload

Question 23

define afterload

Answer 23

force opposing ventricular ejection (what the heart needs to overcome to pump blood into the aorta)

Question 24

what determines ESV

Answer 24

ESV is determined by the balance between the force of contraction and the force the heart is pumping against (afterload). ESV will be lower with increased contraction force and decreased afterload

Question 25

copy down first slide on page 9 of cardiac output

Question 26

what are some factors that influence contractility

Answer 26

movement, emotions, body temp, local metabolites, arterial BP, venous return, SNS/PSNS outflow, etc... accelerator and vagus nerves also innervate the myocardium therefore factors that influence SNS/PSNS outflow from the medulla also influence contractility SNS - increased contractility = + inotropic effect PSNS - decreased contractility = - inotropic effect

Question 27

what are some factors that influence preload?

Answer 27

the same factors that affect SNS outflow from medulla also trigger release of E/NE into bloodstream this causes venoconstriction throughout body which increases venous BP b/c the same amount of fluid is now squeezed into smaller vessels this squeezing encourages blood to flow back to the heart, increasing VR. VR influences preload which is more or less synonymous with EDV venous BP is also influenced by blood volume b/c the more fluid in a vessel, the higher the pressure. blood volume influences arterial BP for the same reason. venous return is enhanced by the skeletal muscle pumps b/c muscle contractions helps pump blood back towards the heart. valves prevent backflow preload is also influenced by the amount of time available to get blood into the ventricle which is determined by HR

Question 28

what is the main determinant of afterload

Answer 28

BP is the main determinant of afterload BP is influenced by vascular resistance (= resistance encountered by blood flowing through vessels) increased VR = increased afterload decreased VR = decreased afterload VR is influenced by length of blood vessels, viscosity of blood, and diameter of blood vessels. Vessel diameter is the only one we can cahnge in the short term

Question 29

what effect do vasodilation and vasoconstriction have on VR

Answer 29

vasodilation: decreased VR vasoconstriction: decreased VR

Question 30

copy down second slide on page 11 of cardiac output

Question 31

what are metabolites and what do they do

Answer 31

metabolites are products of metabolism like CO2, H+ and La- they cause vasodilation in the vascular beds where they appear

Question 32

write down and memorize second slide on page 12 of cardiac output

Question 33

copy down both slides on page 15 of cardiac output

Question 34

what are the two plausible theories that explain cardiovascular drift

Answer 34

1. driven by increased HR - HR increases - since Q is regulated, SV decreases to maintain Q HR increases over time bc - increased body temp - hypothalamus signals cardioacceleratory center - SNS outflow to SA node 2. driven by decreased SV - SV decreases - since Q is regulated, HR increases to maintain Q SV drops over time bc - thermoregulatory response - increased skin blood flow to dump heat - eventual dehydration - due to sweat lost and resp losses