CARDIOVASCULAR SYSTEM THE HEART Chapter 18. Overview of Cardiovascular System.
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Transcript of CARDIOVASCULAR SYSTEM THE HEART Chapter 18. Overview of Cardiovascular System.
CARDIOVASCULAR SYSTEMTHE HEART
Chapter 18
Overview of Cardiovascular
System
Location of the Heart
Pericarium
Coronary Circulation
Anastomoses
Cardiac Muscle
• Autorhythmic cells initiate depolarization
• Na+ influx (depolarization) goes down T-tubules
• depolarization opens slow Ca channels
• Ca2+ influx release of Ca2+ from sarcoplasmic reticulum
• Ca2+ binds troponin cross bridging of sliding myofilaments
• Ca2+ surge across membrane prolongs depolarization (plateau) increases duration of contraction
• K+ channels open and repolarize sarcolemma
Excitation Contraction Coupling
Cardiac Muscle: Energy Requirements
• More mitochondria than skeletal muscle;
– Higher dependence on O2
• Cardiac muscle readily adapts to available fuel sources
• O2 deficit is the cause of system failure with decreased blood flow
Heart Physiology: Electrical
• Intrinsic conduction system – Specialized cells that initiate & distribute impulses
– Autorhythmic cells of nodes & conducting pathway have unstable resting potential & have the capability of spontaneous depolarization