The+heart

(1) In which direction does the heart tilt? left (2) What is the approximate size of the heart? make a fist then clasp the fist with your oppsoite hand this is the approximate side (3) Describe the mycoardium. the major portion of the heart consists largely of cardiac muscle tissue (4) Why do you think a heart attack is sometimes called a mycocardial infarction p. 97? occurs when a portion of the heart muscle dies due to a lack of oxygen (5) Describe the pericardium. thick embranous sac that supports and protects the heart (6) Describe the septum. a wall that seperates the heart into a right and left side (7) Where are the atria? Describe their walls. two upperthin walled atrium (8) Where are the ventricles? Describe their walls. two lower chambers, thick walled (9) Where are the atroventricular valves? Describe their shape (number of flaps) and various names. the valves that lie between the atria and the ventricles. 3 flaps (10) What are the chordae tendinae? strong fibrous strings that are valves that support the atrioventricular valves (11) Where are the semilunar valves? Why do they have that name? they are shaped like half moons giving them a name they lie between the ventricles and their attached vessels (12) List the path of blood through the heart. The superior vena cava and the inferior vena cava, which carry O2 poor blood enter the right atrium the right atrium sends blood though an atrioventricular valve to the right ventricle the right ventricle sends blood through the pulmonary semilunar valve into the pulonary trunk. The pulmonary trunk which carries O2 poor blood divides into two pulmonary arteries which go to the lungs four pilmonary veins which carry O2 rich blood enter the left atrium the left atrium sends blood though an atrionetricular valve to th left ventricle the left ventricle sends blood through semilunar valve into the aorta to the body proper (13) Where does blood go when it leaves the right side of the heart? through the lungs (14) Where does blood go when it leaves the left side of the heart? the entire body (15) Which side of the heart is stronger? Why? left side it has to do more work (16) Why is the heart a double pump? because it pumps blood to two different places simultaneously (17) Define systole. contraction of the chambers of the heart (18) Define diastole the resting phase of the chambers of the heart (19) How many times does the heart normally contract in a minute? 70 times (20) What causes the "lub" and "dup" of the heart sounds? lub occurs when increasing pressure of blood inside a ventricle forces the cusps of the AV valve to slam shut the dup sound comes when the ventricles relax and the blood in the arteries pushes back causing the semilunar valves to close (21) What is the sinoatrial node? What does it do? Why is called the pacemaker? initiates the heartbeat and automatically sends out an excitation impulse every .85 of a second the causes the atria to contract its called the pacemaker because it usually keeps the heartbeat regular (22) What is the atrioventricular bundle? Why is the delay important between the SA node and AV bundle? its a bundle of atrioventricular nodes. there important because gap junctions at intercalated disks allow electrical current to flow from cell to cell. (23) What does in ECG measure? recording of the electrical cahnges that occur in the myocardium during a cardiac cycle (24) What triggers the P wave? the Sa node triggers an impulse, the atrial fibers produce an electrical change called the P wave (25) What triggers the QRS wave? The electrical changes that occur as the ventriculur muscle fibers revocer produce the T wave