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
The cardiac chambers consist of two atria. two ventricles. and four valves The cardiac valves consist of thin flaps of tough, flexible, endothelium-covered fibrous art tissue firmly attached at the Pul base to the fibrous valve rings Movements of the valve leaflets are essentially passive, and the orientation of the cardiac valves is responsible for the unidirectional flow of blood through the heart
The cardiac chambers consist of two atria, two ventricles, and four valves The cardiac valves consist of thin flaps of tough, flexible, endothelium-covered fibrous tissue firmly attached at the base to the fibrous valve rings. Movements of the valve leaflets are essentially passive, and the orientation of the cardiac valves is responsible for the unidirectional flow of blood through the heart
Cardiac valves are interposed between atria and ventricle Atrioventricular valves The tricuspid valve lies between the right atrium and right ventricle and is se made up of three cusps, The mitral valve lies between the left atrium and left ventricular and has two cusps
The tricuspid valve lies between the right atrium and right ventricle and is made up of three cusps, Cardiac valves are interposed between atria and ventricle • Atrioventricular valves . The mitral valve lies between the left atrium and left ventricular and has two cusps
Semilunar valves The valves between the right and between the left ventricle ventricle and pulmonary arter and aorta consist of three cuplike ly cusps attached to the valve rings. PU At the end of the reduced ejection phase of ventricular systole, blood flow reverses briefly toward the ventricles. This flow reversal snaps the cusps together and prevents regurgitation of blood into the ventricles
The valves between the right ventricle and pulmonary artery and between the left ventricle and aorta consist of three cuplike cusps attached to the valve rings. • Semilunar valves At the end of the reduced ejection phase of ventricular systole, blood flow reverses briefly toward the ventricles. This flow reversal snaps the cusps together and prevents regurgitation of blood into the ventricles
The pericardium is an epithelialized fibrous sac that invests the heart The pericardium consists of a visceral laver that is adherent to the epicardium and a parietal layer separated from the visceral layer by a thin layer of fluid. The fluid layer provides lubrication for the continuous movement of the enclosed heart. The pericardium is nor very distensible and thus strongly resists a large, rapid increase in cardiac size. Therefore the pericardium helps prevent sudden over distention of the heart chambers
The pericardium consists of a visceral layer that is adherent to the epicardium and a parietal layer separated from the visceral layer by a thin layer of fluid. The fluid layer provides lubrication for the continuous movement of the enclosed heart. The pericardium is nor very distensible and thus strongly resists a large, rapid increase in cardiac size. Therefore the pericardium helps prevent sudden over distention of the heart chambers. The pericardium is an epithelialized fibrous sac that invests the heart
The Cardiac Cycle is the Sequential Contraction and Relaxation of atria and ventricles Ventricular systole is initiated by 13 Ventricular excitation ontic valve closes Aortic (1)Isovolumic contraction pressure The interval between the start of Mitral ventricular systole and the opening of the semilunar valves is called isovolumic eft atrial pressu contraction because ventricular volume isi,A constant during this brief period. Ventricular pressure rises abruptly 220
The Cardiac Cycle is the Sequential Contraction and Relaxation of Atria and Ventricles (1) lsovolumic contraction Ventricular systole is initiated by Ventricular excitation • The interval between the start of ventricular systole and the opening of the semilunar valves is called isovolumic contraction because ventricular volume is constant during this brief period. • Ventricular pressure rises abruptly
