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FHB Exam 1 - Cardiovascular Physiology > Lecture 13 - Cardiac Function > Flashcards

Lecture 13 - Cardiac Function Flashcards

1
Q

What is the Central Venous Pool?

A

Approximate volume in the RIGHT ATRIUM & the great veins in the thorax

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2
Q

What is Venous Return?

A

RATE at which blood returns to the thorax from the PERIPHERAL VASCULAR beds

  • or blood entering CENTRAL VENOUS POOL
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3
Q

What is another way to describe blood ENTERING the central venous pool?

A

VENOUS RETURN

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4
Q

What is Cardiac Output?

A

RATE at which blood leaves Central Venous Pool & is pumped OUT OF the heart

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5
Q

What is the relationship between venous return & cardiac output under normal steady state conditions? What is a situation in which this relationship is not true?

A

Venous return = Cardiac Output

  • if there is a HOLE in the system (stab wound) this relationship is not true –> blood leaves
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6
Q

Where is the majority of blood found?

A

Venous system

  • 60%
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7
Q

Central Line measures what?

A

Clinical indicator of blood returning & being taken out of central venous pool (it measures the pressure gradient formed)

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8
Q

What is the term for the mean pressure that exists in the circulatory system when cardiac output STOPS and the pressures within the vascular system REDISTRIBUTE?

A

Mean Circulatory Pressure

Pmc –> measure of fullness

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9
Q

When is there no pressure gradient for venous return, causing blood flow to cease?

A

When Central Venous Pressure = Pmc

mean circulatory pressure

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10
Q

What 2 factors does Pmc rely on?

A
  1. Volume of blood

2. Venous tone of the smooth muscle

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11
Q

What is another way to describe functional capacity?

A

FULLNESS of the system

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12
Q

Pmc is the relationship between ______ in the circulation compared to the _____ of the system/

A
  1. Volume of blood

2. Functional Capacity (venous tone)

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13
Q

What is the normal value for Pmc?

A

7 mmHg (on cardiac output axis)

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14
Q

If you lower cardiac output, does CVP increase or decrease?

A

INCREASES

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15
Q

If you INCREASE Cardiac Output, is the central venous pressure increased or decreased?

A

DECREASED

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16
Q

The pmc is pressure when what stops? Does a pressure gradient still form when this occurs?

A

the heart

  • central = peripheral venous pressure
  • NO PRESSURE GRADIENT anymore = blood stands still
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17
Q

If the heart stopped, where would most blood end up?Why?

A
  1. VENOUS SYSTEM

2. HIGH COMPLIANCE

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18
Q

How can venous system change its “functional capacity”?

A

CHANGE THE SIZE (fullness)

  1. venocontrict
  2. Venodilate
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19
Q

When is fullness reduced? Increased?

A

Hemorrhage/ Venodilation

Venoconstriction

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20
Q

What is the the independent variable on the Vascular Function or Venous Return Curve?

A

CARDIAC OUTPUT

  • changes Central Venous Pressure
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21
Q

An increase in cardiac output, increases or decreases:

  1. Pressure gradient for venous return
  2. Central Venous Pressure
A
  1. Increases
  2. Decreases

= INCREASED VENOUS RETURN

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22
Q

What occurs at NEGATIVE CVP?

A

Pressure collapses the LARGE VEINS

Result: zero venous return

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23
Q

What 7 factors influence venous return? What do they compensate for?

A
  1. Venous Valves
  2. Skeletal Leg muscle Pump
  3. Cardiac Suction
  4. Sympathetic Venoconstriction
  5. Respiratory pump (decrease intathoracic pressure)
  6. Blood Volume
  7. Pressure on Blood due to cardiac contraction

important factors that compensate for the decrease in filling time due to INCREASED Heart Rate

24
Q

Increasing venous return, helps to increase cardiac output how?

A

by:
1. Increasing End-Diastolic Volume (preload)

THUS:

  1. Increasing STROKE VOLUME
25
Q

What does the respiratory pump do to increase Venous Return & ultimately Cardiac Output?

A
  • decreases intrathoracic pressure and pulls more blood into the heart (important in heavy exercise)
  • if your HR increased but you DIDN’T breath –> the decrease in filling time would not be compensated ( this occurs in Ventricular Tachycardia )
26
Q

What is an example of an increase in HR but no compensation due to the lack of filling time?

A

Ventricular Tachycardia

  • cardiac output is compromised
27
Q

What do VENOUS VALVES do to increase Venous Return & ultimately Cardiac Output?

A
  • valves only let blood flow one direction = TO THE HEART

- so when skeletal muscle squeezes deep veins –> blood is forced to move through the valves

28
Q

How does the Skeletal Leg Muscle Pump increase Venous Return & ultimately Cardiac Output?

A

deep veins in legs are squeezed when skeletal muscles activated, pushes blood up into the heart

  • constricts veins

(important for exercise)

29
Q

How does venoconstriction increase Venous Return & CO?

A

DECREASES THE COMPLIANCE of venous system

  • prevents it from expanding when blood volume increases
  • by doing this it makes it a stiffer pipe and shoots blood up to the heart

(smaller area = faster velocity)

30
Q

How does PRESSURE on Blood due to cardiac contraction increase Venous Return & CO

A

creates a PRESSURE GRADIENT for blood to flow down on

31
Q

How does wall motion contribute to End - Diastolic Volume?

A

Floor for heart during systole, moves up - become rounder

During diastole - apex of the heart moves down & the heart SUCKS the blood into the ventricle during diastole

32
Q

When is the Skeletal Leg pump most important?

A

ON A PLANE

  • can get DEEP VEIN THROMBOSIS
  • need to stay hydrated since at high altitude/pressure, you are losing fluid quickly
  • w/o moving around, blood can become stasis & a clot can form

= PULMONARY EMBOLISM

33
Q

All the factors that increase venous return ultimately contribute to what?

A

PRELOAD!

  • End Diastolic Volume
34
Q

What are 4 ways to increase PERIPHERAL venous pressure?

A
  1. Sympathetic Venoconstriction 2. increases blood volume
  2. Cardiac Contraction (generates peripheral venous pressure = pressure gradient)
  3. SKELETAL LEG MUSCLE PUMPING activity
35
Q

What are 2 ways to DECREASE central venous pressure

A
  1. Respiratory Pump Activity

2. Cardiac Suction

36
Q

How does one create a pressure gradient between peripheral & central venous pressure? What is a system that constantly maintains this gradient during GRAVITATIONAL FORCES?

A
  1. Increase Peripheral Pressure

OR

  1. Decrease Central Pressure
  2. VENOUS VALVES
37
Q

What is cardiac function determined primarily by?

A

CONTRACTILITY

38
Q

How does a transfusion shift the vascular function curve?

A

UP & to the RIGHT

  • Pmc increases
  • CO increases
  • CVP increases

= more blood forced into the heart

39
Q

Does a transfusion affect contractility?

A

NO!

40
Q

How does hemorrhage affect the Venous Function curve?

A

DOWN & LEFT

  • CVP lower
  • Pmc lower
  • CO lower
41
Q

Does a transfusion/hemorrhage affect the SYSTEMIC CIRCULATORY PRESSURE?

A

YES!

  • transfusion - increases
  • hemorrhage - decreases
42
Q

Increasing blood volume does what to venous return?

A

INCREASES IT

43
Q

How does increasing venous tone (sympathetic nerve activity/drugs) affect venous tone?

A

causes VENOCONSTRICTION

44
Q

What 3 factors change the Cardiac Function curve? How is it changed?

A
  1. Sympathetics
  2. Inotropic Drugs
  3. Heart Failure (depress cardiac function curve)

first 2 = UP AND LEFT (CVP decreases, CO increases
last 1 = DOWN & RIGHT

45
Q

Why does CVP decrease with sympathetic stimulation?

A

More blood is pulled out of the venous system (cardiac output increased)

  • CONTRACTILITY increased
46
Q

Moderate or severe heart failure shifts the cardiac function curve which direction?

A

DOWN & RIGHT

47
Q

before blood changes, what increases & decreases:

  1. CO
  2. CVP
A
  1. CO decreases

2. CVP increases

48
Q

AFTER blood changes, what increases & decreases:

  1. CO
  2. CVP
A
  1. CO increases with HYPERVOLEMIA (up & right)

2. CVP increases

49
Q

With MODERATE HF, how is CVP & CO affected?

A
  1. CVP is INCREASED

2. Cardiac Output not changed (no reduction)

50
Q

With SEVERE HF, how is CVP & CO affected?

A
  1. CVP is increased

2. CO decreased

51
Q

What occurs to contractility during HF? How is the decreased Cardiac Output seen?

A

DECREASES

  • JUGULAR VEIN PRESSURE increases (CVP elevated)
52
Q

WHn kidneys sense a decrease in Cardiac Output, what is the result? How can this be treated?

A

Think it is HEMORRHAGE

  • increase water absorption in kidneys by releasing renin/angiotensin

= HEART CONGESTED WITH BLOOD

  • treat with diuretics/ace inhibitors
53
Q

What occurs during Hemorrhage?

A
  1. No compensation initially: Venous return curve falls down & LEFT
    - pmc is low & CVP is low
  2. Baroreceptors kick in = sympathetics VENOCONSTRICT to reduce compliance of venous system (make container smaller increases fullness)
  3. Cardiac Sympathetics Cause an increase in contractility which increase CARDIAC OUTPUT
54
Q

What is administered during hemorrhage?

A

FLUIDS Administered

55
Q

Loss of blood volume shifts the curve where? Loss in contractility?

A
  1. DOWN

2. DOWN & RIGHT (cardiac output)

56
Q

What is venous return equivalent to?

A

PRELOAD

FHB Exam 1 - Cardiovascular Physiology (26 decks)

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