cardiovas

• Epinephrine takes a longer time to act on the heart than sympathetic stimulation does, but the effect lasts longer.
• The pericardium is a sac that surrounds the heart and consists of the fibrous pericardium and the serous pericardium.
• The fibrous pericardium helps hold the heart in place.
• The serous pericardium reduces friction as the heart beats.
• The parietal pericardium lines the fibrous pericardium.
• The visceral pericardium lines the exterior surface of the heart.
• The pericardial cavity lies between the parietal and visceral pericardia and is filled with pericardial fluid, which reduces friction as the heart beats.
• The heart wall has three layers: the outer epicardium (visceral pericardium), the middle myocardium, and the inner endocardium.
• The inner surfaces of the atria are mainly smooth.
• The auricles have muscular ridges called pectinate muscles.
• The ventricles have ridges called trabeculae carneae.
• Each atrium has a flap called an auricle.
• The coronary sulcus separates the atria from the ventricles.
• The inter-ventricular grooves separate the right and left ventricles.
• The inferior and superior venae cavae and the coronary sinus enter the right atrium.
• The four pulmonary veins enter the left atrium.
• The pulmonary trunk exits the right ventricle, and the aorta exits the left ventricle.
• Coronary arteries branch off the aorta to supply the heart.
• Blood returns from the heart tissues to the right atrium through the coronary sinus and cardiac veins.
• The interatrial septum separates the atria from each other, and the interventricular septum separates the ventricles.
• The tricuspid valve separates the right atrium and ventricle.
• The bicuspid valve separates the left atrium and ventricle.
• The chordae tendineae attach the papillary muscles to the atrioventricular valves.
• The semilunar valves separate the aorta and pulmonary trunk from the ventricles.
• Cardiac muscle cells are branched and have a centrally located nucleus.
• Actin and myosin are organized to form sarcomeres in cardiac muscle cells.
• The sarcoplasmic reticulum and T tubules are not as organized as in skeletal muscle in cardiac muscle cells.
• Cardiac muscle cells are joined by intercalated disks, which allow action potentials to move from one cell to the next.
• Parasympathetic stimulation has an inhibitory influence on the heart, primarily by decreasing the heart rate.
• The heart's pumping effectiveness is greatly influenced by relatively small changes in the preload, but it is very insensitive to large changes in afterload.
• The Starling law of the heart describes the relationship between changes in the pumping effectiveness of the heart and changes in preload.
• During exercise, skeletal muscle activity greatly influences heart activity by altering venous return and preload.
• During exercise, blood vessels in exercising skeletal muscles dilate and allow more blood to flow through the vessels, increasing O, and nutrient delivery to the exercising muscles.
• Skeletal muscle contractions repeatedly compress veins and cause blood to flow more rapidly from the skeletal muscles toward the heart, increasing venous return to the heart and increasing the preload.
• If venous return remains constant while the heart is inhibited by parasympathetic stimulation, stroke volume can actually increase.
• Afterload is the pressure the contracting left ventricle must produce to overcome the pressure in the aorta and move blood into the aorta.
• The increase in stroke volume results in increased cardiac output, and the volume of blood flowing to the exercising muscles increases.
• The increased preload causes an increased force of cardiac muscle contraction, which increases stroke volume.
• Aortic blood pressure must increase to more than 170 mm Hg before it hampers the ventricles' ability to.
• Strong parasympathetic stimulation can decrease the heart rate below resting levels by at least 20-30 bpm, but it has little effect on stroke volume.