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Cardiovascular System Heart Actions • • • • • • Cardiac cycle-heart beat Atria contract together Ventricles contract together Atrial systole-atria contract Diastole-relaxation of heart Ventricular systole-ventricles Cardiac Cycle Steps High pressure in atria High pressure in ventricles Pressure down in ventricles; build in atria CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display. Atrioventricular valves open and close HOW? • Contract – – – – Papillary muscles contract Pull on chordae tendinae Valves close! Papillary muscles contract due to stimulation from purkinje fibers • Relaxation-no muscle contraction/no pull on chordae tendinae – Valves Heart Sounds • Open and close of valves • Lubb-ventricular contraction, AV valves closing • Dupp-ventricles relax, pulmonary and aortic valves close • Heart murmur-cusps not close enough and cause blood leak Cardiac Conduction System • Impulse travels through myocardium (middle layer of heart) • SA node-pacemaker – Posterior right atrium – Creates impulse for heart beat – Sends impulse 70-80 times per minute • Impulse goes to atrial syncytium (mass of merging cells) – Left and right atrium contract Signal conduction continued • Impulse travels through junctional fibers – Slows signal down so atria can contract completely and empty of blood before the impulse goes down to the ventricles • Goes to AV (atrioventricular node) – Located in septum • Goes to AV bundle (bundle of His) • Branch into purkinje fibers – Make connection with papillary muscles – Action squeezes blood out of ventricles CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display. http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter22/ani mation__conducting_system_of_the_heart.html CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display. F. Electrocardiogram • a recording of the electrical changes that occur during a cardiac cycle. • P wave, – depolarization (contraction) of the atria. • QRS complex – depolarization of ventricles (contraction) and hides the repolarization (relaxation) of atria. CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display. • T waves – end the ECG pattern – ventricular repolarization (relaxation) http://www.nhlbi.nih.gov/health/dci/Diseases/h hw/hhw_electrical.html CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1. Atria begin depolarize 2. Atria depolarize. 3. Ventricles depolarize at apex; atria repolarize 4. Ventricles depolarize 5. Ventricles begin repolarization at apex. 6. Ventricles repolarize. How to read one? http://www6.district125.k12.il.us/science/secu re/wood/anatomy/ch13/ekgtutorial5criteria. mov Diagnostic Value of ECG • • • • • Abnormalities in conduction pathway Myocardial infarction (heart attack) Heart enlargement Electrolyte and hormone imbalance Ischemia-blood supply restriction Fast heart; chest pain, Shortness of breath, abnormal pacemaker Heart rate is less than 60 beats Blood pressure • Refers to pressure in arteries • Systolic (pressure in arteries when ventricles contract) over diastolic (pressure in arteries when ventricles are filling up with blood) pressure • 120/80 is normal • Pulse (normal is 60 to 100 beats)-expanding and recoiling of arteries • Many factors influence blood pressure Heart Action • This determines how much blood enters the arterial system when the ventricles contract • Stroke volume-volume of blood leaving LV – About 70 ml in average male • Cardiac output-volume per minute – Stroke volume x heart rate • Cardiac output, blood pressure, and stroke volume directly related Blood volume-Factor that influences this • Sum of formed elements and plasma volumes in the vascular system • Blood pressure is directly proportional to blood volume • Can change due to dehydration (bp drops), blood transfusion, hemorrhage (bp drops) Control of Blood Pressure • Autonomic nervous system responses • Peripheral resistance – Pressure between blood and vessel walls • Temperature change – Higher temp, higher blood pressure Baroreceptors • Located in aortic arch • Arterial blood increases, basoreceptors send nerve impulse to medulla oblongata • Sends impulse to SA node – Cause heart rate to decrease – Blood pressure return to normal • Arterial blood decreases, sends signal to SA node to increase heart work – Exercise, rise in temp, emotions Hypertension • Hypertension-high blood pressure in arteries – Caused by kidney disease, high sodium intake, obesity, stress, arteriosclerosis – Lead to enlarged heart due to increase pumping action of LV – Cause embolism, thrombosis, stroke Vein Control • Skeletal muscles-pushes blood to the heart • Breathing movements • Vasoconstriction-low pressure causes muscles to contract Sheep Heart Dissection http://www.youtube.com/watch?v=rI 23fdFVRvY