CARDIOVASCULAR SYSTEM THE HEART Chapter 18
Jan 11, 2016
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