control of cardiac output Flashcards

1
Q

Frank-Starling law of heart allows heart to increase / decrease stroke volume as

A

volume of VR changes

 Increased VR produces increased myocardial stretch which increases SV and HR

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2
Q

As metabolism changes –

SVR has to change

A

 Increased metabolism – Decreased arteriole constriction - Increased tissue flow
 Only way this works is if the body maintains a constant MAP

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3
Q

With nervous control, baroreceptors etc. kept

A

the MAP constant thus allowing CO to change appropriately with the change in SVR and metabolism

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4
Q

without nervous control

A

MAP decreases as SVR deceases with a small change in CO

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5
Q

Highest rate of metabolism from birth to about

A

10 years of age

 ≈ 4.0 L/min/m2

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6
Q

Decrease CI with age due to

A

decreasing muscle mass and overall decrease in activity

 ≈ 2.4 L/min/m2 @ 80 years

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7
Q

Normal Values

A

Healthy young male: CO = 5.6 L/minute  Healthy young female: CO = 4.9 L/minute
 Average for CO for resting adult: 5.0 L/min  Average weight: 70 kg  Average surface area: 1.7 m2  Average cardiac index: 3 L/min/m2

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8
Q

Levels of Cardiac Effectiveness

A

 Normal  Normal levels of nervous tone
 Hypereffective  Increased levels of CO
 Caused by:  Increased levels of nervous tone (sympathetic)  Hypertrophy
 Increased levels CO result from changes in contractility and HR
 Hypoeffective  Decreased levels of CO  Variety of problems (see list pg 231 of Guyton)

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9
Q

max co normal

A

Normal conditions (normal ANS tone)  RESTING VALUES: RAP = 0 mmHg  CO = 5 L/min  MAX VALUES: RAP ≥ 4 mmHg  CO = 13 L/min

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10
Q

max co hypereffective heart (nervous)

A

MAX VALUES: RAP ≥ 4 mmHg  CO = 25 L/min

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11
Q

max co Hypereffective heart (hypertrophy)

A

Increased muscle mass 50 to 75%
 Increase max CO 60 to 100%
 MAX VALUES: RAP ≥ 4 mmHg  CO = 30-40 L/min
 Max value represents summation of nervous response and hypertrophy

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12
Q

Factors That Alter External Pressure

A

Cyclic changes in respiration  Breathing against negative pressure
 Shifts curve to left  Positive pressure breathing
 Shifts curve to right  Opening thoracic cage
 Intrapleural pressure = 0 mmHg. Shifts curve to right 4 mmHg
 Cardiac tamponade

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13
Q

increased cvp

A

Cardiac output
 Venous return
 More volume leaves the central venous compartment than enters so CVP begins to. Will continue until back at equilibrium
 CVP driven to value where CO and VR are equal
 CO & VR stabilize where two function curves intersect

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14
Q

Cardiac function curve can shift

A

Change in cardiac effectiveness

 Change in external pressure

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15
Q

Venous function curve can shift

A

Change in mean systemic filling pressure

 Change in venous resistance

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16
Q

ventricle diastole Vo C R

A

30,24,0

17
Q

arteries Vo C R

A

600,2,1

18
Q

arterioles Vo C R

A

100,0,13

19
Q

capillaries Vo C R

A

250,0,5

20
Q

central venous compartment Vo C R

A

80,4,0

21
Q

entire circuit Vo C R

A

3560,140,20