The+Heart+AG

(1) In which direction does the heart tilt? The heart is tilted so that the apex is oriented to the left.

(2) What is the approximate size of the heart? The size of your fist clasped by the opposite hand.

(3) Describe the mycoardium. It consists largely of cardiac muscle tissue. It is serviced by the coronary artery and cardiac vein and not by the blood it pumps.

(4) Why do you think a heart attack is sometimes called a mycocardial infarction p. 97? Because this occurs when a portion of the heart muscle dies due to a lack of oxygen. (5) Describe the pericardium. A thick, membranous sac the supports and protects the heart. Th inside of the pericardium secretes a lubrication fluid and the pericardium slides smoothly over the surface as the heart pumps.

(6) Describe the septum. The septum separates the heart into a right side and left side.

(7) Where are the atria? Describe their walls. Twho upper, thin walled atria are called the right atrium and the left atrium. Each atrium has a wrinkled, protruding appendage called an auricle.

(8) Where are the ventricles? Describe their walls. The thick walled ventricles are called the right ventricle and the left ventricle, located below the atria.

(9) Where are the atroventricular valves? Describe their shape (number of flaps) and various names. The atroventricular valves lie between the atria. These valves are supported by strong fibrous strings called chordae tenineae.

(10) What are the chordae tendinae? They are attached to muscular projections of the ventricular wals called papillary musecles and support the valves and prevent them from inverting when the heart contracts.

(11) Where are the semilunar valves? Why do they have that name? They have flaps shaped like half-moons that lie between the ventricles and their attached vessels. Thy are named for their attached vessels.

(12) List the path of blood through the heart. The superior vena cava and the inferior vena cava, which carry O2 enter the right atrium. The right atrium sends blood through an atrioventricular valve to the right ventricle. The right ventricle sends blood through the pulmonary semilunar valve into the pulmonary trunk. The pulmonary trunk, which carries O2, divides into two pulmonary artieries, which go to the lungs. Four pulmonary veins, which carry O2, enter the left atrium. The left atrium sends blood through an atrioventricular valve to the left ventricle. The left ventricle sends blood through the aortic semilunar valve into the aorta to the body proper.

(13) Where does blood go when it leaves the right side of the heart? The lungs.

(14) Where does blood go when it leaves the left side of the heart? Through the rest of the body.

(15) Which side of the heart is stronger? Why? The left because it pumps the blood through out the whole body, not just the lungs.

(16) Why is the heart a double pump? The double pump allows both deoxygenated and oxygenated blood to flow.

(17) Define systole. Systole refers to contraction of the chambers.

(18) Define diastole Diastole is the relaxation of the chambers.

(19) How many times does the heart normally contract in a minute? A rate of 60 to 80 beats per minute.

(20) What causes the "lub" and "dup" of the heart sounds? When increasing pressures of blood inside a ventricle forces the cusps of the AV valve to slam shut. Then the ventricles relax and the blood arteries pushes back causes the semiluminar valves to close.

(21) What is the sinoatrial node? What does it do? Why is called the pacemaker? Located in the upper dorsal wall of the right atrium. It initiates the heartbeat and automatically sends out an excitation impule every .85 seconds causing the atria to contract. It is called the peacemaker for keeping the heartbeat regular.

(22) What is the atrioventricular bundle? Why is the delay important between the SA node and AV bundle? The AV bundle, its branches, and the Purkinje fibers work efficiently because gap junctions at intercalated disks allow electrical current to flow from cell to cell. If the SA node fails to work properly, the heart still beats due to impulses generated by the AV node.

(23) What does in ECG measure? An ECG is a recording of the electrical changes that occur in myocardium during a cardiac cycle. When ECG is being taken, electrodes placed on the skin are connected by wires to an instrument that detects the myocardium’s electrical changes.

(24) What triggers the P wave? When the SA node triggers an impulse, the artial fibers produce an electrical change called the P wave.

(25) What triggers the QRS wave? The P wave indicates the atria are about to contract. The QRS complex signals that the ventricles are about to contract.