Cardiovascular Factors and Exercise

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Cardiovascular Factors and Exercise
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The Cardiovascular System An Overview

• Hollow 4-chambers.LA,LV,RA,RV
• Size of your fist
• Cardiac muscle is involuntary and highly aerobic.
• Cells are joined together by intercalated disks
  which facilitates the all or none principle of
  cardiac tissue
• All muscle cells have an intrinsic rhythm,
  highest rate tissue sets the paceSA Node

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Cardiac Cycle

• Consists of an active Phase (systole) and
  relaxation phase (diastole)
• Cycle
• Low oxygenated blood returns to the heart via the
  SVC and IVC and empties into the RA.
• RA -to- RV
• RV to- lungs via the pulmonary arteries to pick
  up O2
• Pulmonary veins carry oxygenated blood back to
  the LA
• LA -to- LV
• LV to the Aorta to be pumped to the system

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Terms Review

• Stroke Volume (SV)
• Amount of blood ejected from each ventricle
  during systole
• Determined by the difference between ventricular
  filling and ventricular emptying.
• End Diastolic Volume (EDV)
• Volume at the peak of ventricular filling
• End Systolic Volume (ESV)
• Volume of blood remaining in the heart after
  systole

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Terms Review

• Ejection Fraction (EF)
• Percentage of the blood EDV pumped from the
  ventricles
• Cardiac Output (Q)
• Amount of blood pumped by the heart per unit of
  time

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Factors Determining Cardiac Performance

• Cardiac performance is determined by preload,
  afterload, contractility and heart rate.
• Preload-the extent to which the heart chambers
  are stretched when they fill with blood
• Afterload-resistance the heart meets while it
  tries to pump blood into the circulation
• Contractility-strength of cardiac contraction
• Heart Rate-speed of heart beats

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Pre-Load

• Frank-Starling Mechanism
• Relationship between myocardial stretch and
  stroke volume.
• Increased myocardial stretch increases pressure
  in the ventricles which leads to an increase in
  stroke volume and stroke work.
• Rate Pressure Product (RPP)
• HR X SBP
• Measure of myocardial oxygen consumption

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The LV Pressure-Volume Relation
Stroke Volume Stroke Work Ejection Fraction
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Ventricular Preload

• Preload is the blood volume in the ventricle at
  the end of diastole immediately before
  contraction begins.
• The Ventricular End-Diastolic Pressure
• Atrial Pressure

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How Preload Affects Ventricular Performance
STROKE VOLUME OR STROKE WORK
LV PRESSURE
LEFT VENTRICULAR END-DIASTOLIC VOLUME
LEFT VENTRICULAR END-DIASTOLIC VOLUME

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Increased Preload Increased Stroke Volume
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WHAT IS THE ROLE THAT STARLINGS LAW OF THE HEART
PLAYS IN HEART FUNCTION??
STARLINGS LAW OF THE HEART ALLOWS THE OUTPUT OF
THE LEFT AND RIGHT VENTRICLES TO EQUALIZE!!!!
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Factors affecting preload during exercise

• Cardiac Output-increased preload will lead to an
  increase in Q
• Blood Volume Increased blood volume will lead
  to an increase in preload
• Muscle and Thoracic Pump- increase venous return
• Posture supine position leads to a lower EDV
• Venous Tone- veins are sympathetically stimulated
  to vasoconstrict which in turn leads to increased
  venous return

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Afterload

• Impedance or resistance to ventricular emptying
• Increased afterload has a negative effect on
  cardiac performance
• Males tend to have a higher afterload than
  females when performing identical high tension
  exercise
• Valsalva maneuver can lead to a higher afterload

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HOW THE CV SYSTEM COMPENSATES FOR INCREASED
AFTERLOAD
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Contractility

• Strength of cardiac contractility is determined
  by the rate of reaction
• Higher contraction strength increases stroke
  volume
• Cardiac contractility depends upon the amount of
  intracellular calcium available
• Sympathetic stimulation, catecholamines and
  inotropic agents can increase contractility
• Coronary blood flow plays a role as well.

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HOW THE CV SYSTEM COMPENSATES FOR INCREASED
AFTERLOAD
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Contractility and Starling Curves
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Heart Rate

• Major determinant of cardiac output
• MHR fairly constantonly changes with age, not
  training
• Training will help to decrease resting heart rate

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Cardiovascular Responses to Exercise

• Increased Q
• Increased skin blood flow
• Decreased blood flow to the kidneys
• Decreased visceral flow
• Vasoconstriction of the spleen
• Maintenance or slight increase in brain blood
  flow
• Increased blood flow to the coronary arteries
• Increased muscle blood flow.