Chapter 18 (heart) What causes normal heart sounds? Which ventricular wall is th

Question

Chapter 18 (heart) What causes normal heart sounds? Which ventricular wall is the thickest and why? Which vessels take blood to or from the four chambers? Describe the intracardiac blood flow What is the cardiac intrinsic conduction system? Sequence of depolarization Where do you place the stethoscope to listen (auscultate) different heart valves? What is angina pectoris and what causes it? What are the effects of the sympathetic and parasympathetic divisions of the ANS on the heart? What are the states of the valves and the blood flow during ventricular systole and diastole? What do P, QRS andT represent on the EKG?

Explanation / Answer

#1 Normal heart sounds are caused by the closing of valves and the collision of blood against them when they close. There are two normal heart sounds caused by closure of atrioventricular valves an semilunar valves respectively.

#2 The left ventricle has a much thicker wall than the right ventricle in order to pump blood around the whole body, hence it requires more muscle. The blood in the left ventricle is under higher pressure than the blood in the right ventricle.

#3 The right atrium receives deoxygenated blood from the superior vena cava, as well as from the inferior vena cava. In addition, the right atrium receives blood from the coronary sinus. The right ventricle pumps the blood through the pulmonary arteries. The left atrium receives the oxygen-rich blood from the lungs via the pulmonary veins. The left ventricle pumps out oxygenated blood through aorta, the major artery of the body, taking oxygenated blood to the organs and muscles of the body.

#4 The right atrium of the heart receives deoxygenated blood from the body (via the superior and inferior vena cava) and from cardiac muscles (coronary sinus). The deoxygenated blood moves through to the right ventricle which pumps it towards the lungs (via the pulmonary artery). The left atrium receives oxygenated blood from the lungs (via the pulmonary vein). The oxygenated blood then moves through to the left ventricle, which pumps it around the whole body (via the aorta).

#5 Implied by the name, this system remains within the heart. This conduction system is a network of noncontractile cells those initiate and distribute impulses to coordinate the depolarization and contraction of the heart. The 5 parts of the intrinsic conduction system are sa node, av node, av bundle, right and left bundle branches and purkinje fibers. Depolarization occurs first in both the atria and then both the ventricles depolarize.

# 6 Valves : Positions for placing stethoscope to auscultate

A. Pulmonary valve:  Over the second intercostal space (the space between the 2nd and 3rd rib) left side of the patient’s sternum.

B. Aortic valve: Over the 2nd intercostal space right side of the patient’s sternum.

C. Tricuspid valve: Over the 5th intercostal space left side of the patient’s chest.

D. Mitral valve: Over the 5th intercostals space inline with the middle of the collar bone.

#7. According to American Heart Association, Angina pectoris is the medical term for chest pain or discomfort due to coronary heart disease. It occurs when the heart muscle doesn't get as much blood as it requires to function properly. This usually happens because one or more of the heart's arteries is narrowed or blocked, also called ischemia.

#8. Autonomic nervous system comprises both sympathetic and parasympathetic nervous system. Parasympathetic stimulation of the heart slows the heart rate and reduces the strength of cardiac muscles contraction; however, sympathetic stimulation accelerates the heart rate and increases the strength of contraction.

#9. Early ventricular systole : Ventricles begin to contract. Bicuspid and tricuspid valves close with lubb sound or first heart sound. Semilunar valve still remain closed. Blood flow through aortic valve to aorta.

Late ventricular systole : Semilunar open up. Blood flows through semilunar valves to pulmonary pulmonary artery.

Early ventricular diastole : Semilunar closes with dubb or second heart sound, AV valve still remains closed. Blood fills in both atria.

Late ventricular diastole : AV valves open and semilunar remains closed. Blood flows from both atria to ventricles.

#10. These represent different parts of the EKG. The first little “hump” in EKG is known as the P-wave. The P-wave represents atrial depolarization. The next part immediately after a P-wave is a spiked part called the QRS complex. The QRS complex represent ventriclular depolarization. After this spike,a “bump” represents T-wave and is caused by the ventricles relaxing.

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