Circulatory System The Heart 1 What is the difference in thickness between the right and left ventricle The right ventricle is less thick than the left the left has much more muscle The right ventricle only pumps blood to the lungs pulmonary circulation while the left ventricle pumps blood to the entire body systemic circulation 2 How does blood flow from the atria to the ventricles Blood flows from the atriums to the ventricles through atrioventricular valves AV valves The right AV valve is also called Tricuspid valve The left AV valve is also called the Bicuspid valve or the Mitral valve 4 Does the All or None law apply to the heart Yes it does If an electrical impulse does not hit the threshold no conduction occurs There will be no spread of an impulse through gap junctions therefore none of the heart will be stimulated and there will not be a heartbeat 5 To what structure are the chordae tendinae attached What is the purpose of these attachments The chordae tendinae connect the valve cusps to papillary muscles on the floor of the ventricles These muscles prevent the AV valves from flipping inside out or bulging into the atria when the ventricles contract 6 What is functional syncytium In a functional syncytium electrical impulses propagate freely between communicating cells via gap junctions so that the myocardium functions as a single contractile unit This property allows rapid synchronous depolarization of the myocardium 7 What is responsible for the plateau phase of the cardiac action potential After Na has a peaked voltage of 30 mV Calcium slowly enters into Ca2 channels This prolongs the depolarization of the cardiocyte creating a plateau As long as the action potential is in plateau the cardiocytes contract 8 Where does the intrinsic rhythm of the heart begin The intrinsic rhythm of the heart begins at the SV node in the right ventricle The SV node is also known as the pacemaker and it initiates the heartbeat 10 What happens during the quiescent period The quiescent period of the heart occurs after isovolumetric relaxation or ventricle systole the ventricles are relaxed and filling with blood The heart spends most of its time in the quiescent period 11 What is the term of volume in the heart after filling The volume in the heart after filling is called the end diastolic volume preload 12 What is the term of the volume after ejecting emptying End systolic volume 13 What happens during the isovolumetric period of heart muscle contraction During isovolumetric contraction the atria completely repolarize and the ventricles completely depolarize causing the QRS complex Pressure increases changing the pressure gradient between the atria and ventricles Ventricular contraction begins The AV valves close causing the first heart sound Turbulence occurs in the blood as it surges against closed AV valves and heart wall No blood is ejected pressure rises and blood volume stays the same 14 What valves are opened and closed at points A B C D A AV valves Mitral Valve open B AV Valve Closes Isovolumetric Contraction C Aortic Valve Semi Lunars opens D 15 What are the electrocardiographic events during the cardiac cycle a P wave produced when the signal from the SA node spreads throughout the atria and depolarizes them b QRS complex small downward deflection Q a tall sharp peak R and a final downward deflection S It is produced when the signals from the AV node spread through the ventricular myocardium and depolarize the muscle c T wave generated by repolarization immediately before diastole