The+Heart+Questions+SLS

October 1, 2008 Science-Human Bio**
 * Shelby Smith

Many questions, but your answers can be brief except for number 12.
 * The Heart pp.88-91**

Toward the left.
 * (1) In which direction does the heart tilt?**

The heart is about the size of your fist.
 * (2) What is the approximate size of the heart?**

This is the major part of the heart, which is made up of mostly cardiac tissue. It is serviced by the coronary artery and the cardiac vein.
 * (3) Describe the mycoardium**


 * (4) Why do you think a heart attack is sometimes called a mycocardial infarction p. 97?**

(**5) Describe the pericardium.** This is a thick, membraneous sac that supports and protects the heart.

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

The atria are in the heat which is divided into four chambers. The walls of the atria are thin.
 * (7) Where are the atria? Describe their walls.**

The ventricles are the two lower chambers which are thick-walled, and there is a right ventricle and a left.
 * (8) Where are the ventricles? Describe their walls.**

They lie between the atria and the ventricles. There are four flaps and two of them are called the AV valves and the semilunar valves.
 * (9) Where are the atroventricular valves? Describe their shape (number of flaps) and various names.**

The chordae tendinae are the strong fibrous strings that support the AV valves.
 * (10) What are the chordae tendinae?**

The semilunar valves are appropriately named because they are shaped like half-moons, and they lie between the ventricles and their attached vessels.
 * (11) Where are the semilunar valves? Why do they have that name?**

The blood travels to the right atrium, and then it sends the blood through and AV valve to the right ventricle. The right ventricle then sends the blood through the pulmonary semilunar valve into the pulmonary trunk. The pulmonary trunk then takes the 0xygen poor blood into two pulmonary arteries. Four pulmonary veins enter the left atrium and the left atrium sends blood through an AV valve to the left ventricle. The left ventricle sends blood through the aortic semilunar valve into the aorta to the body proper.
 * (12) List the path of blood through the heart.**

When blood leaves the right side of the heart it goes into the left side of the heart.
 * (13) Where does blood go when it leaves the right side of the heart?**

When the blood leaves the left side of the heart it goes into the body proper.
 * (14) Where does blood go when it leaves the left side of the heart?**

The left side of the heart is stronger because the right side pumps only to the lungs and the left side pumps throughout the whole body.
 * (15) Which side of the heart is stronger? Why?**

The heart is a double pump because the right ventricle of the heart sends blood through the lungs, and the left ventricle sends blood through out the body.
 * (16) Why is the heart a double pump?**

The working phase, referring to the concentration of the chambers.
 * (17) Define systole.**

The resting phase, referring to the relaxation of the chambers.
 * (18) Define diastole.**

The heart contracts 70 times a minute.
 * (19) How many times does the heart normally contract in a minute?**

The ‘lub’ occurs when the increasing pressure of the blood inside a ventricle forces the cusps of the AV valve to slam shut. In contrast, the pressure of blood inside a ventricle causes the semilunar valves to open. The ‘dub’ occurs when the ventricles relax, and the blood in the arteries pushes back, causing semilunar valves to close.
 * (20) What causes the "lub" and "dup" of the heart sounds?**

The sinoatrial node is located in the upper dorsal wall of the right atrium and it initiates the heartbeat and automatically sends out and excitation pulse every .85 seconds. It is called the pacemaker because it usually keeps the heartbeat regular.
 * (21) What is the sinoatrial node? What does it do? Why is called the pacemaker?**

The AV bundle is the two branches that lead to the Purkinje fibers. They allow the electric current to flow from cell to cell.
 * (22) What is the atrioventricular bundle? Why is the delay important between the SA node and AV bundle?**

This is a recording of the electrical changes that occur in myocardium during a cardiac cycle.
 * (23) What does in ECG measure?**

This is an electrical charge that is produced by the atrial fibers. This indicates that the atria are about to contract.
 * (24) What triggers the P wave?**

The QRS waves are triggered by the P wave and they are complex signals that the ventricles are about to contract.
 * (25) What triggers the QRS wave?**