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HES 105 > week 12 > Flashcards

week 12 Flashcards

1
Q

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

A

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

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2
Q

define cardiac output (Q)

A

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

Q = HR x SV

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3
Q

define heart rate (HR):

A

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

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4
Q

define stroke volume (SV)

A

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

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5
Q

define venous return (VR)

A

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

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6
Q

how can we increase cardiac output (Q)?

A

increase HR
increase SV
increase HR and increase SV

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7
Q

define diastole and end-diastolic volume (EDV)

A

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

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8
Q

define systole and end-systolic volume (ESV)

A

systole: contraction phase, when cardiac ejection occurs

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

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9
Q

how do we calculate SV

A

EV = EDV - ESV

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10
Q

how do we increase SV

A

increase EDV
decrease ESV

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11
Q

what is an ejection fraction and how do we calculate it

A

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

EF = SV/EDV x 100 (in %)

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12
Q

copy down the first slide on page 5 of cardiac output

A
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13
Q

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

A
  • 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

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14
Q

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

A
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15
Q

what is HR regulated by?

A

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
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16
Q

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

A
  • 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
17
Q

what influences a persons resting HR?

A

genetics, age and endurance training status

18
Q

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

A

typical resting HR: 60-100 bpm

lower: bradycardia
higher: tachycardia

19
Q

what determines a persons HR max?

A

genetics and age

20
Q

what is SV influenced by

A

preload, contractility and afterload

21
Q

define preload

A

amount of stretch in ventricle/muscle cells

preload is more or less synonymous with EDV

22
Q

define contractility

A

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

23
Q

define afterload

A

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

24
Q

what determines ESV

A

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

25
Q

copy down first slide on page 9 of cardiac output

A
26
Q

what are some factors that influence contractility

A

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

27
Q

what are some factors that influence preload?

A

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

28
Q

what is the main determinant of afterload

A

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

29
Q

what effect do vasodilation and vasoconstriction have on VR

A

vasodilation: decreased VR
vasoconstriction: decreased VR

30
Q

copy down second slide on page 11 of cardiac output

A
31
Q

what are metabolites and what do they do

A

metabolites are products of metabolism like CO2, H+ and La-

they cause vasodilation in the vascular beds where they appear

32
Q

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

A
33
Q

copy down both slides on page 15 of cardiac output

A
34
Q

what are the two plausible theories that explain cardiovascular drift

A
  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

  1. 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

35
Q
A

HES 105 (16 decks)

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