Cardiac Pump OBJECTIVES Describe how the heart enable it to pump blood through the systemic and pulmonary circulations. Discuss the pressure changes in the heart chambers and great vessels during a complete cardiac cycle. List the factors that determine cardiac contractile force Explain how electrical excitation of the heart is coupled to its contractions
• Discuss the pressure changes in the heart chambers and great vessels during a complete cardiac cycle. Cardiac Pump OBJECTIVES • Describe how the heart enable it to pump blood through the systemic and pulmonary circulations. • Explain how electrical excitation of the heart is coupled to its contractions. • List the factors that determine cardiac contractile force
The Structures of the Heart is Designed for Optimal Function Several important morphological and functional differences exist between myocardial and skeletal muscle cells A striking difference is that cardiac muscle appears to be a syncytium(a functional syncytium, not a true anatomical skeletal Muscle (t/m) Cardiac Musde R 300x syncytium Nucleus with branching and interconnecting fibers whereas skeletal muscle cells Nucleus do not interconnect nternal diac muscle in longitudinal section (x700) cr口“ section (x
The Structures of the Heart is Designed for Optimal Function Several important morphological and functional differences exist between myocardial and skeletal muscle cells • A striking difference is that cardiac muscle appears to be a syncytium (a functional syncytium, not a true anatomical syncytium ) • with branching and interconnecting fibers, whereas skeletal muscle cells do not interconnect
Cardiac muscle functions as a syncytium because a wave of depolarization, followed by contractions of the atria and ventricles(an all-or-none response), occurs when a uprathreshold stimulus is applied potentials, first depolarizing then re 十++++十++十 Autorhythmic cell ne(ms 十++++++十 升++++ 闺 十+++++十+ Autorhythmic cell Contractile cell
Cardiac muscle functions as a syncytium because a wave of depolarization, followed by contractions of the atria and ventricles (an all-or-none response), occurs when a uprathreshold stimulus is applied
As the wave of excitation Capilla approaches the end of a cardiac endotbelium cell, the spread of excitation to agination of transerse tubule the next cell depends on the electrical conductance of the Mitochondria boundary between the two cells. Mline Gap junctions(nexuses) with 性 Sarcomere high conductance are present in the intercalated disks between adjacent cells. MAGNIFIED VIEW OF CARDIAC MUSCLE CELLS Desmosome sarcoplasmic cardiac impulse from one cell to the next, are made up Gap junction intercalated of connexons, T-tubule Cardiac moonbi
As the wave of excitation approaches the end of a cardiac cell, the spread of excitation to the next cell depends on the electrical conductance of the boundary between the two cells. Gap junctions (nexuses) with high conductance are present in the intercalated disks between adjacent cells. cardiac impulse from one cell to the next, are made up of connexons
Red cell in cardiac muscle is richly Connective endowed with mitochondria transverse bule Gap junction (sarcosomes)which contain the Manduria respiratory enzymes necessary H zone for oxidative phosphorylation. To provide adequate o2 and substrate for its metabolic machinery, the myocardium is also endowed with a rich capillary supply, about one capillary per fiber
• cardiac muscle is richly endowed with mitochondria (sarcosomes) which contain the respiratory enzymes necessary for oxidative phosphorylation. • To provide adequate O2 and substrate for its metabolic machinery, the myocardium is also endowed with a rich capillary supply, about one capillary per fiber