Cardiovascular Physiology Review

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Cardiovascular Physiology Review

• Jennifer LaPointe MS IV
• December 7, 2006
• The University of North Dakota School of Medicine
  and Health Sciences

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Cardiovascular Physiology

• Hemodynamics
• Electrophysiology
• Muscle Physiology
• Cardiac cycle
• Regulation
• Microcirculation

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Some definitions

• Preload the initial stretching of the cardiac
  myocytes prior to contraction.
• End diastolic volume the volume of blood in a
  ventricle at the end of filling
• Determining factor
• Venous return

Preload Pumps up the heart.
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Some definitions

• Afterload the force the sarcomere must overcome
  in order to shorten during systole
• Determining factor
• Aortic pressure

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Frank Starling

• Intrinsic regulation of heart pumping
• Increased venous return leads to increased stroke
  volume
• COSV x HR

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Fick Principle

• Cardiac output
• A man has a resting O2 consumption of 250 ml
  O2/min, a femoral arterial O2 content of 0.20 ml
  O2/ml blood, and a pulmonary arterial O2 content
  of 0.15 ml O2/ml blood.
• CO 250 ml O2/min
  5000 ml/min

O2 Consumption
O2 pulmonary vein O2 pulmonary artery
0.20 ml O2/ml 0.15 ml O2/ml
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Variables that affect cardiac output

• Vasculature
• Venous tone
• Blood volume
• Total peripheral resistance (affects preload)
• Heart
• Contractility
• Total peripheral resistance (affects afterload)

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Cardiac and Vascular function curves

• Point of equilibrium ? predicts cardiac output
  and central venous pressure
• Steady state of this particular system

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Changes in contractility

• Digoxin
• inhibits Na-K ATPase
• Ca builds up

Ejection fraction is an indicator of
contractility EF SV/EDV
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Changes in volume mean systemic pressure

• Decreased blood volume
• Decreased venous compliance

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Changes in Total Peripheral Resistance

• Constrict arterioles
• Increased afterload
• Decreased venous return

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Pressure-Volume Loop

• ?Preload
• ?Afterload
• ?Contractility

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Pressure-Volume Loop

• ?Preload
• ?Afterload
• ?Contractility

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Pressure-Volume Loop

• ?Preload
• ?Afterload
• ?Contractility

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Pressure-Volume Loop

• ?Preload
• ?Afterload
• ?Contractility

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Sympathetic and parasympathetic control

• Sympathetic
• Stimulate increase HR and increase
  vasoconstriction
• Inhibit decrease HR and decrease
  vasoconstriction
• Parasympathetic (vagus)
• Stimulate decreases HR
• and causes vasodilation

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BaroreceptorsChanges during Valsalva maneuver

• Forced expiration against a closed glottis
• Intrathoracic pressure compresses vessels in chest

• Aortic compression
• Vena cava compression
• Breathe- sudden loss of compression
• Increased venous return

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Gravity

• Gravity acts on vascular volume
• Mostly venous due to high compliance
• Preload decreases
• CO and arterial pressure fall
• Baroreceptor reflex
• HR increases
• Vasoconstriction

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Questions
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• Preload
• Afterload
• Stroke Volume
• Heart Rate
• Venous return
• Total Peripheral Resistance

• Pregancy
• Exercise
• Heart Failure
• Transfusion
• B-blocker
• Diuretic
• Hemorrhage