Chapter 13, Cardiovascular system

Describe and explain the normal ECG pattern. (p. 568)

A normal ECG pattern consists of a P wave, a QRS complex, and a T wave. The P wave is caused by a depolarization of the atrial fibers just before they contract. The QRS complex is caused by the depolarization of ventricular fibers just prior to contraction of the ventricular walls. The T wave is caused by the relatively slow repolarization of the ventricular muscle fibers. The QRS complex obscures atrial repolarization.

Distinguish between a venule and a vein. (p. 579)

A venule is a microscopic vessel that continues from the capillaries and merges with other venules to form veins. Veins are the counterpart to the arterial system that carries blood back to the heart.

. Distinguish between an artery and an arteriole. (p. 574)

Arteries are strong, elastic vessels that are adapted for carrying the blood away from the heart under high pressure. An arteriole is a smaller, finer branch of an artery.

Relate how diffusion functions in the exchange of substances between blood plasma and tissue fluid. (p. 578)

Blood entering the capillaries of the tissues has higher concentrations of molecules and ions than in the tissue fluid itself. Diffusion is the process of moving from areas of higher concentrations to lower concentrations. The nutrients and oxygen tend to move into the tissues because the concentrations of these substances are higher in the blood. The wastes, such as carbon dioxide, are in higher concentrations in the tissues so these diffuse into the blood plasma.

Blood flows through the vena cava and coronary sinus into the right atrium, through the _______tricuspid valve____ to the right ventricle, through the pulmonary valve to the pulmonary trunk into the right and left _____pulmonary ateries____ to the lungs, then leaves the lungs through the pulmonary veins and flows into the ______left atrium __, through the mitral valve to the _____left atrium_____, and through the ___aortic valve_______ to the aorta. (p. 561)

Blood flows through the vena cava and coronary sinus into the right atrium, through the _______tricuspid valve____ to the right ventricle, through the pulmonary valve to the pulmonary trunk into the right and left _____pulmonary ateries____ to the lungs, then leaves the lungs through the pulmonary veins and flows into the ______left atrium __, through the mitral valve to the _____left atrium_____, and through the ___aortic valve_______ to the aorta. (p. 561)

. Describe the structure and function of a capillary. (p. 576)

Capillaries are the smallest blood vessels and connect the smallest arterioles to the smallest venules. They consist of a single layer of squamous epithelial cells that are continuous with the endothelium of the larger vessels. A capillary provides the semipermeable membranes through which substances in the blood are exchanged for substances in the tissue fluid surrounding body cells

. Explain how the cardiac conduction system controls the cardiac cycle. (p. 566)

Once the impulse leaves the S-A node (sinoatrial node), it passes into the atrial syncytium and the atria contract almost simultaneously. From there, the impulse travels along a system continuous with the atrial muscle fibers and into the A-V node (atrioventricular node) which is the only normal route to the ventricular syncytia. Because of the small diameter of nerve fibers from here, the impulse is slowed enough for the atria to empty and the ventricles to fill with blood. From here, the impulse passes through the A-V node and into the A-V bundle (atrioventricular bundle or bundle of His), which is comprised of larger diameter nerves. The impulse speeds up and splits into two branches (right and left) on the way to the Purkinje fibers. These fibers are even larger, and cause the impulse to move even faster. The Purkinje fibers branch into the papillary muscles and downward to the apex of the heart. There, they curve upward and branch along the entire walls of the ventricles until they become continuous with the cardiac muscle fibers. The whorl design of the myocardium causes the ventricles to contract in a "wringing" fashion that squeezes the blood out and into the arteries.

Distinguish between the roles of the S-A node and A-V node.(349)

The SA (sinoatrial) node is a small mass of specialized muscle tissue just beneath the epicardium. The fibers are self-exciting so they initiate impulses that spread to the myocardium and stimulate the muscle fibers to contract. The S-A node initiates one impulse seventy to eighty times per minute. Because it generates the rhythmic contractions of the heart, it is often called the pacemaker. The AV (atrioventricular) node is located in the inferior portion of the septum and just beneath the endocardium, providing the only normal conduction pathway between the atrial and ventricular syncytia.

Explain why water and dissolved substances leave the arteriolar end of a capillary and enter the venular end. (p. 578)

The blood pressure at the arteriolar end is greater than in the capillary itself. This allows for filtration of substances to occur at this site. The blood pressure decreases as the blood moves through a capillary, making the outward filtration force less than the osmotic pressure at the venular end. Consequently, there is a net movement, of water and dissolved materials, into the venular end of the capillary by osmosis.

Compare the layers of the heart wall. (p. 555)

The epicardium (visceral pericardium) functions as a protective layer. This layer consists of connective tissue covered by epithelium. Its deeper portion often contains adipose tissue. The myocardium is relatively thick and consists largely of cardiac muscle tissue. The muscle fibers are arranged in planes, separated by connective tissues, which are richly supplied with blood capillaries, lymph capillaries, and nerve fibers. The endocardium consists of epithelium and connective tissue containing many elastic and collagenous fibers. The connective tissues house the Purkinje fibers, which function with the conduction system of the heart. This layer is continuous with the inner linings of the blood vessels attached to the heart.

The cardiovascular system consists of:

The heart, capillaries, arteries, and veins

Describe the pericardium. (p. 554)

The pericardium encloses the heart and the proximal ends of large blood vessels to which it attaches

Distinguish between the pulmonary and systemic circuits of the cardiovascular system. (p. 590)

The pulmonary circuit of the cardiovascular system consists of those vessels that carry the blood from the heart to the lungs and back to the heart. The systemic circuits of the cardiovascular system are responsible for carrying the blood from the heart to all other parts of the body and back again.

Describe the control of blood pressure. (p. 585)

Two important mechanisms for blood pressure control involve the regulation of cardiac output and the peripheral resistance. Starling's law of the heart ensures that the volume of blood discharged from the heart is equal to the volume entering its chambers. Pressoreceptors trigger the neural regulation of the heart rate. Chemicals, such as epinephrine, emotions, physical exercise, and increased body temperature can also play a role in regulation of heart rate, thereby influencing the cardiac output. Peripheral resistance is regulated primarily by the changes in the diameters of arterioles. The vasomotor center of the medulla oblongata has neural control of the smooth muscle in the arteriole wall. Chemical substances, including carbon dioxide, oxygen, and hydrogen ions, also influence peripheral resistance by affecting the smooth muscle in the walls of arterioles and the actions of precapillary sphincters

. Explain control of vasoconstriction and vasodilation. (p. 576)

Vasoconstriction occurs when the smooth muscle in the wall of the vessels is stimulated by the vasomotor fibers of the sympathetic branches of the autonomic nervous system. This causes contraction to occur, thereby decreasing the diameter of the vessel. If the vasomotor impulses are inhibited, the muscle relaxes and the diameter of the vessel increases. This is known as vasodilation

. List the vessels through which blood flows from the aorta to the myocardium and back to the right atrium. (p. 561)

When the atria are relaxed, the pressure begins to rise as they fill with blood. As the atria contract, the pressure raises suddenly, forcing the remaining blood into the ventricles. Pressure is low in the ventricles when they are filling but begins to rise as they fill with blood. It rises sharply as the ventricles contract forcing the blood out into the appropriate vessels.

Describe the pressure changes in the atria and ventricles during a cardiac cycle. (p. 564)

When the atria are relaxed, the pressure begins to rise as they fill with blood. As the atria contract, the pressure raises suddenly, forcing the remaining blood into the ventricles. Pressure is low in the ventricles when they are filling but begins to rise as they fill with blood. It rises sharply as the ventricles contract forcing the blood out into the appropriate vessels.

List the major factors that promote venous blood flow. (p. 589)

a. Skeletal muscle contractions b. Respiratory movements c. Venoconstriction

Name several factors that influence the blood pressure, and explain how each produces its effect. (p. 582)

a. The amount of blood that enters the arterial system with each ventricular contraction. This is known as heart action. b. The amount of blood cells and plasma volume in the cardiovascular system, which is known as blood volume. c. The amount of peripheral resistance within the walls of the blood vessels. d. The viscosity (the ease with which molecules in a fluid slide past one another).

Draw a heart and label the chambers and valves. (p. 555)

chambers: Right atrium, right ventricle, left atrium, and left ventricle Valves: aortic valve, mitral valve, pulmonary valve, and tricuspid valve

Arterial blood pressure peaks when the ventricles contract. This maximum pressure achieved is called the ____________. (p. 580)

systolic pressure.