Download 11.2 Regulation of the Heart

Chapter 11: The Cardiovascular System
Lesson 11.2
Regulation of the Heart
Regulation of the Heart
Section Overview
1. internal control of the heart
2. external control
3. the conduction system
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Internal Control of the Heart
• Sinoatrial node
– pacemaker
– sends electrical impulse
– tells heart to beat 60–100 bpm
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External Control of the Heart
• The cardiac center
– sympathetic nerve system speeds up
– parasympathetic nerve system slows down
• The endocrine system
– some hormones speed up
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Permission granted to reproduce for educational use only.
The Conduction System
•
•
•
•
SA node
AV node
bundle of His
bundle
branches–
right and left
• Purkinje
fibers
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Permission granted to reproduce for educational use only.
Electrocardiogram
• ECG or EKG
– electrical activity of the heart
– depolarize–contract
– repolarize–relax
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Permission granted to reproduce for educational use only.
Cardiac Arrhythmias
• normal contractility condition
– sinus rhythm – normal beating of
the heart = SA node is contracting
normally and bpm is between 60 100
• abnormal contractility condition
– arrhythmia
• abnormal beating of the heart, too
fast or too slow
• ventricle or atria contraction is not
normal
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Permission granted to reproduce for educational use only.
Cardiac Arrhythmias
• bradycardia
– slow heart beat – rate
below 60 bpm (athletes)
• tachycardia
– fast heart beat – rate
above 100 bpm
• premature atrial
contraction (PACs)
– Irritable piece of atria
contracts before SA
node (caffeine, stress,
stimulants – red bull)
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Permission granted to reproduce for educational use only.
Cardiac Arrhythmias
• atrial fibrillation (Afib)
– atria contract faster than 350 bpm
– atria are not coordinated, they
“quiver”
– If severe, may need a pacemaker
• premature ventricular
contractions (PVCs)
– ventricles contract too soon
– Purkinje fibers fire before SA node
• ventricular tachycardia (VT)
– ventricles, rather than SA node,
cause beat = lifethreating
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Permission granted to reproduce for educational use only.
Cardiac Arrhythmias
• ventricular fibrillation (VF)
– ventricles “quiver”, contract
faster than 350 bpm
– No cardiac output
• heart block
– impulse from SA node to AV
node
• first–impulse delayed
• second–intermittently
blocked
• third–completely blocked
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Permission granted to reproduce for educational use only.
Defibrillators and Life-Threatening
Arrhythmias
• automatic external defibrillator (AED)
–
–
–
–
electric shock
stops heart
allows heart to start normal rhythm
anyone can use one
© Goodheart-Willcox Co., Inc.
Permission granted to reproduce for educational use only.