DR. ZAHOOR ALI SHAIKH

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CARDIOVASCULAR SYSTEMLECTURE - V

• DR. ZAHOOR ALI SHAIKH

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PROPERTIES OF CARDIAC MUSCLE

• EXCITABILITY
• RHYTHMICITY
• CONDUCTIVITY

• CONTRACTILITY

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CONTRACTILITY
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We will study the contractility of cardiac muscle
but before that lets see the contractility of
skeletal muscle.
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• Steps in Cardiac muscle contraction

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Source of ca for cardiac muscle contraction
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Effect of Sympathetic Parasympathetic ANS on

• Contractility
• (you should know effect on Heart rate
  Conduction also)

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FACTORS AFFECTING CONTRACTILITY

• Positive ionotropic effect.
• Sympathetic stimulation
• Adrenaline Noradrenaline
• Calcium ion
• Caffine
• Drugs eg. Digitalis (Digoxin)
• Negative ionotropic effect
• Parasympathetic stimulation
• Acetyl choline
• Potassium ion
• Hypoxia (Decrease oxygen)
• Acidosis
• Bacterial toxin
• Drugs eg. Calcium channel blockers, ß- Blockers

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Frank Starlings Law

• Within physiological limits, if there is increase
  in initial length of cardiac muscle fiber ( due
  to increase venous return) there will be
  increased strength of contraction.
• Reason
• Because Actin Myosin filaments are brought to
  more optimal degree of sliding therefore increase
  force of contraction
• Note starlings law affects cardiac
  contractility but details you will learn with
  Cardiac out put .

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WHAT YOU SHOULD KNOW FROM THIS LECTURE?

1. Characteristics of cardiac muscle.
2. Comparison between cardiac skeletal muscle.
3. Effect of sympathetic parasympathetic
   stimulation on cardiac contractility.
4. Positive negative ionotropic factors.
5. Frank Starlings law of heart effect on
   contractility.