Systole~ Contraction of the heart muscles. Diastole~ Relaxation of the heart muscles
Contract & generate tension on chordae tendineae
Difference between resting and maximal cardiac output
Pain due to deficient blood supply to the myocardium. Caused by transient stress-induced spasms of coronary arteries, increased physical demands on the heart or arteriosclerosis. Cells are weakened.
Hear Attack. Prolonged coronary blockage= prolonged lack of oxygen to the heart muscles= cardiac muscle cell death. These cells are AMITOTIC; replaced with non-contractile scar tissue. May be repairable depending on the extent of the damage and time
Layers of the Heart
Epicardium aka visceral pericardium- visceral layer of the serous pericardium. Myocardium- Spiral bundles of cardiac muscle cells held together by elastic & collagen fibers that form a dense network called the Fibrous Skeleton of the heart. Endocardium innermost- Endothelial layer of the inner myocardial surface that is continuous with blood vessel linings. Creates a smooth surface for easy blood flow.
Contraction of the Heart
Sinoatrial node (SA Node-Pacemaker) 60-100 beats/min. Atrioventricular node (AV Node) 40-60 beats/min. Atrioventricular (AV) bundles (Bundle of His) 0-40 beats/min Right and Left bundle branches 0-40 beats/min Ventricular Purkinje Fibers 0-40 beats/min
Caused by the closing of heart valves. First Sound~ occurs as AV valves close and signifies beginning of systole (contraction). Second Sound~ occurs when SL valves close at the beginning of ventricular diastole (relaxed)
Pathway of blood through Heart (Pulmonary circuit)
Right atrium-tricuspid valve-right ventricle-pulmonary semilunar valve-pulmonary arteries-Lungs-pulmonary veins-left atrium
Pathway of blood through Heart (Systemic circuit)
Left atrium-bicuspid (mitral) valve-Left ventricle-aortic semilunar valve-aorta-to the body-vena cavas-right atrium
isovolumetric Contraction~ All 4 valves are closed. Atria relax; ventricles contract (0.3 seconds) Isovolumetric Relaxation~ All 4 valves are closed. Occurs in early diastole. Ventricles relax. Backflow of blood in aorta and pulmonary trunk closes semilunar valves. Quiescent period (0.4 seconds)
Takes places mid-to-late diastole. Atrial contraction (0.1 seconds). AV valves are open. 80% of blood passively flows into ventricles. Remaining 20% delivered with atrial systole. Heart blood pressure is low as blood enters atria and flows into ventricles.
Development aspects of the heart
Fetal heart structures that bypass pulmonary circulation. Forman Ovale~ connects the two atria. After birth this closes and becomes the Fossa Ovalis. Ductus Arteriosus~ connects pulmonary trunk and the aorta. After birth this closes and becomes the Ligamentum Ateriosum
Cardiac Output Equation
CO= SV (Stroke Volume) X HR (Heart Rate) If HR or SV goes up so does CO; same is true for going down
Stroke Volume Equation
SV= EDV (End Diastolic Volume) - ESV (End Systolic Volume) EDV~ amount of blood collected in a ventricle during diastole (120ml) ESV~ amount of blood remaining in a ventricle after contraction (50ml) Average Stroke Volume~ 70ml
Sympathetic neuron activation releases Norepinephrine
Parasympathetic fibers in the vagus nerves release Acetylcholine. If vagus nerves are cut= inc HR by ~ 25 bpm (THIS IS CALLED VAGAL TONE)
Congestive Heart Failure (CHF)
The heart is a "double pump" and each side can initially fail independently of the other. LEFT SIDE~ Pulmonary congestion~ blood backing up into the lungs > pulmonary edema. Can lead to suffocation. RIGHT SIDE~ Peripheral Congestion~ blood backs up at the tissue level > edema in the extremities. Can lead to tissue hypoxia.
Often lethal disruption of heart rhythm that occurs as a result of a blow to the area directly over the heart, at a critical time during the cycle of a heart beat causing cardiac arrest. It is a form a ventricular fibrillation, not mechanical damage to the heart muscle or surrounding organs, and not the result of heart disease.
Normal blood pressure in Pulmonary Trunk