Ch 20

Two key factors determine EDV (end-diastolic volume)

(1) the duration of ventricular diastole and (2) venous return, the volume of blood returning to the right ventricle. When heart rate increases, the duration of diastole is shorter. Less filling time means a smaller EDV, and the ventricles may contract before they are adequately filled. By contrast, when venous return increases, a greater volume of blood flows into the ventricles, and the EDV is increased.

cardiac output

(CO) is the product of the heart rate (HR), i.e. the number of heartbeats per minute (bpm), and the stroke volume (SV), which is the volume of blood pumped from the ventricle per beat

Role of Bundle Branches in cardiac action potential spreads through the conduction system.

- After propagating through the AV bundle, the action potential enters both the right and left bundle branches. The bundle branches extend through the interventricular septum toward the apex of the heart.

Describe an action potential in terms of depolarization, plateau, and repolarization.

- Depolarization. Unlike autorhythmic fibers, contractile fibers have a stable resting membrane potential that is close to −90 mV. When a contractile fiber is brought to threshold by an action potential from neighboring fibers, its voltage-gated fast Na+ channels open. These sodium ion channels are referred to as "fast" because they open very rapidly in response to a threshold-level depolarization. Opening of these channels allows Na+ inflow because the cytosol of contractile fibers is electrically more negative than interstitial fluid and Na+ concentration is higher in interstitial fluid. Inflow of Na+ down the electrochemical gradient produces a rapid depolarization. Within a few milliseconds, the fast Na+ channels automatically inactivate and Na+ inflow decreases. - The next phase of an action potential in a contractile fiber is the plateau, a period of maintained depolarization. It is due in part to opening of voltage-gated slow Ca2+ channels in the sarcolemma. When these channels open, calcium ions move from the interstitial fluid (which has a higher Ca2+ concentration) into the cytosol. This inflow of Ca2+ causes even more Ca2+ to pour out of the sarcoplasmic reticulum into the cytosol through additional Ca2+ channels in the sarcoplasmic reticulum membrane. The increased Ca2+ concentration in the cytosol ultimately triggers contraction. Several different types of voltage-gated K+ channels are also found in the sarcolemma of a contractile fiber. Just before the plateau phase begins, some of these K+ channels open, allowing potassium ions to leave the contractile fiber. Therefore, depolarization is sustained during the plateau phase because Ca2+ inflow just balances K+ outflow. The plateau phase lasts for about 0.2 sec, and the membrane potential of the contractile fiber is close to 0 mV. By comparison, depolarization in a neuron or skeletal muscle fiber is much briefer, about 1 msec (0.001 sec), because it lacks a plateau phase. - The recovery of the resting membrane potential during the repolarization phase of a cardiac action potential resembles that in other excitable cells. After a delay (which is particularly prolonged in cardiac muscle), additional voltage-gated K+ channels open. Outflow of K+ restores the negative resting membrane potential (−90 mV). At the same time, the calcium channels in the sarcolemma and the sarcoplasmic reticulum are closing, which also contributes to repolarization.

Role of atrioventricular (AV) bundle in cardiac action potential spreads through the conduction system.

- From the AV node, the action potential enters the __ ___(also known as the bundle of His, pronounced HIZ). This bundle is the only site where action potentials can conduct from the atria to the ventricles. (Elsewhere, the fibrous skeleton of the heart electrically insulates the atria from the ventricles.)

Examine the possible effects of an artificial pacemaker.

- Infection where the pacemaker was implanted. - Allergic reaction to the dye or anesthesia used during your procedure. - Swelling, bruising or bleeding at the generator site, especially if you take blood thinners. - Damage to your blood vessels or nerves near the pacemaker. - Collapsed lung.

Explain the structural and functional features of the cardiac conduction system of the heart.

- The main parts of the system are the SA node, AV node, bundle of HIS, bundle branches, and Purkinje fibers. - SA node starts the sequence by causing the atrial muscles to contract. (anatomical pacemaker). - the signal travels to the AV node, through the bundle of HIS, down the bundle branches, and through the Purkinje fibers, causing the ventricles to contract. - This signal creates an electrical current that can be seen on a graph called an electrocardiogram, or EKG.

Difference of semilunar valves compared with the atrioventricular valves.

- Tricuspid valve: mitral valve and tricuspid valve, which control blood flow from the atria to the ventricles. - Seminular valve: aortic valve and pulmonary valve , which control blood flow out of the ventricles.

Describe the difference in structure of the semilunar valves compared with the atrioventricular valves, and show how they operate under higher pressure conditions.

- aortic valve and the pulmonic valve, which control blood flow out of the ventricles. - are made up of three crescent moon-shaped cusps. Each cusp attaches to the arterial wall by its convex outer margin. The _____ valves allow ejection of blood from the heart into arteries but prevent backflow of blood into the ventricles. The free borders of the cusps project into the lumen of the artery. When the ventricles contract, pressure builds up within the chambers. The semilunar valves open when pressure in the ventricles exceeds the pressure in the arteries, permitting ejection of blood from the ventricles into the pulmonary trunk and aorta. As the ventricles relax, blood starts to flow back toward the heart. This backflowing blood fills the valve cusps, which causes the free edges of the semilunar valves to contact each other tightly and close the opening between the ventricle and artery

Describe the major coronary arterial vessels, their distribution, and interconnected nature.

- branch from the ascending aorta and supply oxygenated blood to the myocardium. - left coronary artery passes inferior to the left auricle and divides into the anterior interventricular and circumflex branches. 1. anterior interventricular branch or left anterior descending (LAD) artery is in the anterior interventricular sulcus and supplies oxygenated blood to the walls of both ventricles. 2. circumflex branch (SER-kum-fleks) lies in the coronary sulcus and distributes oxygenated blood to the walls of the left ventricle and left atrium. - right coronary artery supplies small branches (atrial branches) to the right atrium. It continues inferior to the right auricle and ultimately divides into the posterior interventricular and marginal branches. 1. posterior interventricular branch follows the posterior interventricular sulcus and supplies the walls of the two ventricles with oxygenated blood. 2. marginal branch beyond the coronary sulcus runs along the right margin of the heart and transports oxygenated blood to the wall of the right ventricle.

Describe the ways in which myocardial fibers produce energy.

- cardiac muscle produces little of the ATP it needs by anaerobic cellular respiration. Instead, it relies almost exclusively on aerobic cellular respiration in its numerous mitochondria. The needed oxygen diffuses from blood in the coronary circulation and is released from myoglobin inside cardiac muscle fibers. Cardiac muscle fibers use several fuels to power mitochondrial ATP production. In a person at rest, the heart's ATP comes mainly from oxidation of fatty acids (60%) and glucose (35%), with smaller contributions from lactic acid, amino acids, and ketone bodies. During exercise, the heart's use of lactic acid, produced by actively contracting skeletal muscles, rises. - cardiac muscle also produces some ATP from creatine phosphate

Role of sinoatrial (SA) node in cardiac action potential spreads through the conduction system.

- do not have a stable resting potential. Rather, they repeatedly depolarize to threshold spontaneously. The spontaneous depolarization is a pacemaker potential. When the pacemaker potential reaches threshold, it triggers an action potential. Each action potential from the ___ ____node propagates throughout both atria via gap junctions in the intercalated discs of atrial muscle fibers. Following the action potential, the two atria contract at the same time.

electrocardiogram- ECG or EKG

- is a composite record of action potentials produced by all of the heart muscle fibers during each heartbeat. The instrument used to record the changes is an electrocardiograph.

Describe the sequence in which the cardiac action potential spreads through the conduction system.

- sinoatrial (SA) node- do not have a stable resting potential. Rather, they repeatedly depolarize to threshold spontaneously. The spontaneous depolarization is a pacemaker potential. When the pacemaker potential reaches threshold, it triggers an action potential. Each action potential from the SA node propagates throughout both atria via gap junctions in the intercalated discs of atrial muscle fibers. Following the action potential, the two atria contract at the same time. - By conducting along atrial muscle fibers, the action potential reaches the atrioventricular (AV) node.At the AV node, the action potential slows considerably as a result of various differences in cell structure in the AV node. This delay provides time for the atria to empty their blood into the ventricles. - From the AV node, the action potential enters the atrioventricular (AV) bundle (also known as the bundle of His, pronounced HIZ). This bundle is the only site where action potentials can conduct from the atria to the ventricles. (Elsewhere, the fibrous skeleton of the heart electrically insulates the atria from the ventricles.) - After propagating through the AV bundle, the action potential enters both the right and left bundle branches. The bundle branches extend through the interventricular septum toward the apex of the heart. - Purkinje fibers, rapidly conduct the action potential beginning at the apex of the heart upward to the remainder of the ventricular myocardium. Then the ventricles contract, pushing the blood upward toward the semilunar valves.

Examine the events which occur during atrial systole.

- the atria are contracting. At the same time, the ventricles are relaxed. 1 Depolarization of the SA node causes atrial depolarization, marked by the P wave in the ECG. 2 Atrial depolarization causes atrial systole. As the atria contract, they exert pressure on the blood within, which forces blood through the open AV valves into the ventricles. 3 Atrial systole contributes a final 25 mL of blood to the volume already in each ventricle (about 105 mL). The end of atrial systole is also the end of ventricular diastole (relaxation). Thus, each ventricle contains about 130 mL at the end of its relaxation period (diastole). This blood volume is called the end-diastolic volume (EDV). 4 The QRS complex in the ECG marks the onset of ventricular depolarization.

Examine the events which occur during ventricular systole.

- the ventricles are contracting. At the same time, the atria are relaxed in atrial diastole. 5 Ventricular depolarization causes ventricular systole. As ventricular systole begins, pressure rises inside the ventricles and pushes blood up against the atrioventricular (AV) valves, forcing them shut. For about 0.05 seconds, both the SL (semilunar) and AV valves are closed. This is the period of isovolumetric contraction. During this interval, cardiac muscle fibers are contracting and exerting force but are not yet shortening. the muscle contraction is isometric (same length). Moreover, because all four valves are closed, ventricular volume remains the same (isovolumic). 6 Continued contraction of the ventricles causes pressure inside the chambers to rise sharply. When left ventricular pressure surpasses aortic pressure at about 80 millimeters of mercury (mmHg) and right ventricular pressure rises above the pressure in the pulmonary trunk (about 20 mmHg), both SL valves open. At this point, ejection of blood from the heart begins. The period when the SL valves are open is ventricular ejection and lasts for about 0.25 sec. The pressure in the left ventricle continues to rise to about 120 mmHg, and the pressure in the right ventricle climbs to about 25-30 mmHg. 7 The left ventricle ejects about 70 mL of blood into the aorta and the right ventricle ejects the same volume of blood into the pulmonary trunk. The volume remaining in each ventricle at the end of systole, about 60 mL, is the end-systolic volume (ESV). Stroke volume, the volume ejected per beat from each ventricle, equals end-diastolic volume minus end-systolic volume: SV = EDV − ESV. At rest, the stroke volume is about 130 mL − 60 mL = 70 mL (a little more than 2 oz). 8 The T wave in the ECG marks the onset of ventricular repolarization.

Describe the anatomically common and distinct features of the two atrioventricular valves, and then discuss how these valves work during a cycle of the heart.

- tricuspid and bicuspid valves are located between an atrium and a ventricle, which control blood flow from the atria to the ventricles. - When the ventricles are relaxed, the papillary muscles are relaxed, the chordae tendineae are slack, and blood moves from a higher pressure in the atria to a lower pressure in the ventricles through open AV valves When the ventricles contract, the pressure of the blood drives the cusps upward until their edges meet and close the opening. At the same time, the papillary muscles contract, which pulls on and tightens the chordae tendineae. This prevents the valve cusps from everting (opening into the atria) in response to the high ventricular pressure. If the AV valves or chordae tendineae are damaged, blood may regurgitate (flow back) into the atria when the ventricles contract.

Explain how the contraction and relaxation of the heart chambers creates a pressure gradient which enables the blood to flow from high pressure to low pressure.

1. Depolarization of the SA node causes atrial depolarization, marked by the P wave in the ECG. 2. Atrial depolarization causes atrial systole. As the atria contract, they exert pressure on the blood within, which forces blood through the open AV valves into the ventricles. 3. Atrial systole contributes a final 25 mL of blood to the volume already in each ventricle (about 105 mL). The end of atrial systole is also the end of ventricular diastole (relaxation). Thus, each ventricle contains about 130 mL at the end of its relaxation period (diastole). This blood volume is called the end-diastolic volume (EDV). 4. The QRS complex in the ECG marks the onset of ventricular depolarization. ***ventricular systole, which lasts about 0.3 sec, the ventricles are contracting. At the same time, the atria are relaxed in atrial diastole. 5. As ventricular systole begins, pressure rises inside the ventricles and pushes blood up against the atrioventricular (AV) valves, forcing them shut. SL (semilunar) and AV valves are closed. This is the period of isovolumetric contraction During this interval, cardiac muscle fibers are contracting and exerting force but are not yet shortening--the muscle contraction is isometric (same length). Since, because all four valves are closed, ventricular volume remains the same (isovolumic). 6. Continued contraction of the ventricles causes pressure inside the chambers to rise sharply. When left ventricular pressure surpasses aortic pressure and right ventricular pressure rises above the pressure in the pulmonary trunk, both SL valves open. At this point, ejection of blood from the heart begins. The period when the SL valves are open is ventricular ejection. The pressure in the both ventricle continues to rise 7. The left ventricle ejects blood into the aorta and the right ventricle ejects the same volume of blood into the pulmonary trunk. The volume remaining in each ventricle at the end of systole- end-systolic volume (ESV). Stroke volume, the volume ejected per beat from each ventricle, equals end-diastolic volume minus end-systolic volume: 8. The T wave in the ECG marks the onset of ventricular repolarization. *** Relaxation Period the atria and the ventricles are both relaxed. As the heart beats faster and faster, the relaxation period becomes shorter and shorter, whereas the durations of atrial systole and ventricular systole shorten only slightly. 9. Ventricular repolarization causes ventricular diastole. As the ventricles relax, pressure within the chambers falls, and blood in the aorta and pulmonary trunk begins to flow backward toward the regions of lower pressure in the ventricles. Backflowing blood catches in the valve cusps and closes the SL valves. Rebound of blood off the closed cusps of the aortic valve produces the dicrotic wave on the aortic pressure curve. After the SL valves close, there is a brief interval when ventricular blood volume does not change because all four valves are closed. This is the period of isovolumetric relaxation. 10. As the ventricles continue to relax, the pressure falls quickly. When ventricular pressure drops below atrial pressure, the AV valves open, and ventricular filling begins. The major part of ventricular filling occurs just after the AV valves open. Blood that has been flowing into and building up in the atria during ventricular systole then rushes rapidly into the ventricles. At the end of the relaxation period, the ventricles are about three-quarters full. The P wave appears in the ECG, signaling the start of another cardiac cycle.

stenosis

A narrowing of a heart valve opening that restricts blood flow

Describe the chamber volumes that affect the calculation of stroke volume, and state the physical conditions that modify these volumes.

At rest, the stroke volume is 50-60% of the end-diastolic volume because 40-50% of the blood remains in the ventricles after each contraction (end-systolic volume). Three factors regulate stroke volume and ensure that the left and right ventricles pump equal volumes of blood: (1) preload, the degree of stretch on the heart before it contracts; (2) contractility, the forcefulness of contraction of individual ventricular muscle fibers; and (3) afterload, the pressure that must be exceeded before ejection of blood from the ventricles can occur.

describe the factors that affect Cardiac Output and note changes with exercise in relation to cardiac reserve.

Blood volume affect Cardiac Output. actors that increase stroke volume or heart rate normally increase CO. During mild exercise, for example, stroke volume may increase to 100 mL/beat, and heart rate to 100 beats/min. Cardiac output then would be 10 L/min. During intense (but still not maximal) exercise, the heart rate may accelerate to 150 beats/min, and stroke volume may rise to 130 mL/beat, resulting in a cardiac output of 19.5 L/min. Cardiac reserve is the difference between a person's maximum cardiac output and cardiac output at rest. The average person has a cardiac reserve of four or five times the resting value. Top endurance athletes may have a cardiac reserve seven or eight times their resting CO. People with severe heart disease may have little or no cardiac reserve, which limits their ability to carry out even the simple tasks of daily living.

Role of atrioventricular (AV) node in cardiac action potential spreads through the conduction system.

By conducting along atrial muscle fibers, the action potential reaches the ____ ____.At the ____ ____, the action potential slows considerably as a result of various differences in cell structure in the ___ ____. This delay provides time for the atria to empty their blood into the ventricles.

Discuss the chemical, hormonal, and ionic conditions that directly impact function of cardiac muscle tissue and thus influence their rate of contraction.

Chemicals influence both the physiology of cardiac muscle and heart rate Hypoxia, acidosis and alkalosis all depress cardiac activity Hormones - epinephrine and norepinephrine (from the adrenal medulla) enhance heart rate and contractility Thyroid hormone - causes enhanced cardiac contractility and increased heart rate Cations - ionic imbalances compromise effectiveness of heart K+ and Na+ decrease contractility and heart rate Na+ blocks Ca2+ inflow during AP decreasing force of contraction Moderate increase of Ca2+ increases heart rate and strengthens heart beat.

Afterload

Ejection of blood from the heart begins when pressure in the right ventricle exceeds the pressure in the pulmonary trunk (about 20 mmHg), and when the pressure in the left ventricle exceeds the pressure in the aorta (about 80 mmHg). At that point, the higher pressure in the ventricles causes blood to push the semilunar valves open. The pressure that must be overcome before a semilunar valve can open is termed the afterload. An increase in afterload causes stroke volume to decrease, so that more blood remains in the ventricles at the end of systole. Conditions that can increase afterload include hypertension (elevated blood pressure) and narrowing of arteries by atherosclerosis (see the entry on coronary artery disease in the Disorders: Homoeostatic Imbalances section at the end of this chapter).

Describe how the primary coronary veins converge in the coronary sinus.

Most of the deoxygenated blood from the myocardium drains into a large vascular sinus in the coronary sulcus on the posterior surface of the heart, called the ____ _____. (A vascular sinus is a thin-walled vein that has no smooth muscle to alter its diameter.) The deoxygenated blood in the ____ _____ empties into the right atrium. The principal tributaries carrying blood into the ___ ____are: Great cardiac vein in the anterior interventricular sulcus, which drains the areas of the heart supplied by the left coronary artery (left and right ventricles and left atrium) Middle cardiac vein in the posterior interventricular sulcus, which drains the areas supplied by the posterior interventricular branch of the right coronary artery (left and right ventricles) Small cardiac vein in the coronary sulcus, which drains the right atrium and right ventricle Anterior cardiac veins, which drain the right ventricle and open directly into the right atrium

Describe how the autonomic nervous system interacts with the cardiovascular center, receptors, and higher ANS centers to modulate heart rate.

Nervous system regulation of the heart originates in the cardiovascular (CV) center in the medulla oblongata. This region of the brain stem receives input from a variety of sensory receptors and from higher brain centers, such as the limbic system and cerebral cortex. The cardiovascular center then directs appropriate output by increasing or decreasing the frequency of nerve impulses in both the sympathetic and parasympathetic branches of the ANS

Describe the potential effects of regenerating heart cells.

Our inability to repair damage from a heart attack has been attributed to a lack of stem cells in cardiac muscle and to the absence of mitosis in mature cardiac muscle fibers. A recent study of heart transplant recipients by American and Italian scientists, however, provides evidence for significant replacement of heart cells. The researchers studied men who had received a heart from a female, and then looked for the presence of a Y chromosome in heart cells. (All female cells except gametes have two X chromosomes and lack the Y chromosome.) Several years after the transplant surgery, between 7% and 16% of the heart cells in the transplanted tissue, including cardiac muscle fibers and endothelial cells in coronary arterioles and capillaries, had been replaced by the recipient's own cells, as evidenced by the presence of a Y chromosome. The study also revealed cells with some of the characteristics of stem cells in both transplanted hearts and control hearts. Evidently, stem cells can migrate from the blood into the heart and differentiate into functional muscle and endothelial cells. The hope is that researchers can learn how to "turn on" such regeneration of heart cells to treat people with heart failure or cardiomyopathy (diseased heart).

major deflections and intervals in a normal ECG include:

P wave - atrial depolarization P-Q interval - time it takes for the atrial kick to fill the ventricles QRS wave - ventricular depolarization and atrial repolarization S-T segment - time it takes to empty the ventricles before they repolarize (the T wave)

Define and describe myocardial infraction and ischemia.

Partial obstruction of blood flow in the coronary arteries may cause ____ ___- ( to obstruct; in the blood), a condition of reduced blood flow to the myocardium. Usually, _____ causes hypoxia (reduced oxygen supply), which may weaken cells without killing them. Angina pectoris which literally means "strangled chest," is a severe pain that usually accompanies ___ ____. Typically, sufferers describe it as a tightness or squeezing sensation, as though the chest were in a vise. The pain associated with angina pectoris is often referred to the neck, chin, or down the left arm to the elbow.

What is the membrane that surrounds and protects the heart?

Pericardium

Regulation of HR - Sympathetic

The cardioacceleratory center is found in the medulla. Sensory information from baroreceptors in the carotid body and in the arch of the aorta relay information about blood pressure and blood flow to the cardioacceleratory center. - Sympathetic nerves are present throughout the atria (especially in the SA node) and ventricles. Sympathetic activity increases the heart rate and the strength of myocardiac contraction to increase blood flow

Cardiac circulation

The circulation of blood around the heart only

systemic circulation

The left side of the heart is the pump for ______ ________; it receives bright red oxygenated (oxygen-rich) blood from the lungs. The left ventricle ejects blood into the aorta. From the aorta, the blood divides into separate streams, entering progressively smaller systemic arteries that carry it to all organs throughout the body—except for the air sacs (alveoli) of the lungs, which are supplied by the pulmonary circulation. In systemic tissues, arteries give rise to smaller-diameter arterioles, which finally lead into extensive beds of systemic capillaries. Exchange of nutrients and gases occurs across the thin capillary walls. Blood unloads O2 (oxygen) and picks up CO2 (carbon dioxide). In most cases, blood flows through only one capillary and then enters a systemic venule. Venules carry deoxygenated (oxygen-poor) blood away from tissues and merge to form larger systemic veins. Ultimately the blood flows back to the right atrium.

Regulation of HR - Parasympathetic

The medulla also contains the cell bodies of the neurons that make up the cardioinhibitory center: The same sensory information coming in from peripheral baroreceptors goes to this area as well. However, the parasympathetic nerves decrease heart rate (but not contractility)

pulmonary circulation

The right side of the heart is the pump for ______ ______; it receives all of the dark-red deoxygenated blood returning from the systemic circulation. Blood ejected from the right ventricle flows into the pulmonary trunk, which branches into pulmonary arteries that carry blood to the right and left lungs. In pulmonary capillaries, blood unloads CO2, which is exhaled, and picks up O2 from inhaled air. The freshly oxygenated blood then flows into pulmonary veins and returns to the left atrium.

Contractility

The second factor that influences stroke volume is myocardial contractility, the strength of contraction at any given preload. Substances that increase contractility are positive inotropic agents (īn′-ō-TRŌ-pik); those that decrease contractility are negative inotropic agents. Thus, for a constant preload, the stroke volume increases when a positive inotropic substance is present. Positive inotropic agents often promote Ca2+ inflow during cardiac action potentials, which strengthens the force of the next contraction. Stimulation of the sympathetic division of the autonomic nervous system (ANS), hormones such as epinephrine and norepinephrine, increased Ca2+ level in the interstitial fluid, and the drug digitalis all have positive inotropic effects.

Explain the basic function of the heart valves

The valves prevent the backward flow of blood.

Explain why the heart muscle requires its own blood supply even though the body's entire blood volume passes through the chambers very minute.

Your heart muscle needs its own supply of blood because, like the rest of your body, it needs oxygen and other nutrients to stay healthy. For this reason, your heart pumps oxygen-rich blood to its own muscle through your coronary arteries.

Describe the histology of the cardiac muscle and the role of the intercalated discs.

____ ______ _____ are shorter in length and less circular in transverse section. They also exhibit branching, which gives individual _______ muscle fibers a "stair-step" appearance. Usually one centrally located nucleus is present, although an occasional cell may have two nuclei. The ends of ------- muscle fibers connect to neighboring fibers by irregular transverse thickenings of the sarcolemma called intercalated discs. The discs contain desmosomes, which hold the fibers together, and gap junctions, which allow muscle action potentials to conduct from one muscle fiber to its neighbors. Gap junctions allow the entire myocardium of the atria or the ventricles to contract as a single, coordinated unit.

rheumatic fever

acute systemic inflammatory disease that usually occurs after a streptococcal infection of the throat. The bacteria trigger an immune response in which antibodies produced to destroy the bacteria instead attack and inflame the connective tissues in joints, heart valves, and other organs. Even though rheumatic fever may weaken the entire heart wall, most often it damages the mitral and aortic valves.

aortic stenosis

aortic valve is narrowed

aortic insufficiency

backflow of blood from the aorta into the left ventricle

Preload: Effect of Stretching

can be compared to the stretching of a rubber band. The more the rubber band is stretched, the more forcefully it will snap back. Within limits, the more the heart fills with blood during diastole, the greater the force of contraction during systole. This relationship is known as the Frank-Starling law of the heart. The preload is proportional to the end-diastolic volume (EDV) (the volume of blood that fills the ventricles at the end of diastole). Normally, the greater the EDV, the more forceful the next contraction.

coronary circulation

circulation of blood through the coronary blood vessels to deliver oxygen and nutrients to the heart muscle tissue

myocardial infarction (MI)

commonly called a heart attack. Infarction means the death of an area of tissue because of interrupted blood supply. Because the heart tissue distal to the obstruction dies and is replaced by noncontractile scar tissue, the heart muscle loses some of its strength. Depending on the size and location of the infarcted (dead) area, an infarction may disrupt the conduction system of the heart and cause sudden death by triggering ventricular fibrillation. Treatment for a _____ ______ may involve injection of a thrombolytic (clot-dissolving) agent such as streptokinase or tPA, plus heparin (an anticoagulant), or performing coronary angioplasty or coronary artery bypass grafting. Fortunately, heart muscle can remain alive in a resting person if it receives as little as 10-15% of its normal blood supply.

Describe the role of the dense connective tissue that forms the fibrous skeleton of the heart.

consists of four dense connective tissue rings that surround the valves of the heart, fuse with one another, and merge with the interventricular septum. In addition to forming a structural foundation for the heart valves, the _________ __________ prevents overstretching of the valves as blood passes through them. It also serves as a point of insertion for bundles of cardiac muscle fibers and acts as an electrical insulator between the atria and ventricles.

Discuss what various alterations in the usual heart sound, like murmurs, indicate.

heart murmur is an abnormal sound consisting of a clicking, rushing, or gurgling noise that either is heard before, between, or after the normal heart sounds, or may mask the normal heart sounds. They often subside or disappear with growth. Although some heart murmurs in adults are innocent, most often an adult murmur indicates a valve disorder. When a heart valve exhibits stenosis, the heart murmur is heard while the valve should be fully open but is not. For example, mitral stenosis produces a murmur during the relaxation period, between S2 and the next S1. An incompetent heart valve, by contrast, causes a murmur to appear when the valve should be fully closed but is not. So, a murmur due to mitral incompetence occurs during ventricular systole, between S1 and S2.

Great cardiac vein

in the anterior interventricular sulcus, which drains the areas of the heart supplied by the left coronary artery (left and right ventricles and left atrium)

Small cardiac vein

in the coronary sulcus, which drains the right atrium and right ventricle

Middle cardiac vein

in the posterior interventricular sulcus, which drains the areas supplied by the posterior interventricular branch of the right coronary artery (left and right ventricles)

failure of a valve to close completely is called

insufficiency

Systolic BP

is the higher pressure measured during left ventricular ------ when the aortic valve is open.

Diastolic BP

is the lower pressure measured during left ventricular ----- when the valve is closed.

Define cardiac output (CO)

is the volume of blood ejected from the left ventricle (or the right ventricle) into the aorta (or pulmonary trunk) each minute. Cardiac output equals the stroke volume (SV), the volume of blood ejected by the ventricle during each contraction, multiplied by the heart rate (HR), the number of heartbeats per minute:

Silent myocardial ischemia

ischemic episodes without pain, is particularly dangerous because the person has no forewarning of an impending heart attack.

State why the sounds of atrioventricular and semilunar valves closing occur at exact times in the cardiac cycle, and why they have different characteristics.

lubb sound, is louder and a bit longer than the second sound. S1 is caused by blood turbulence associated with closure of the AV valves soon after ventricular systole begins. The second sound (S2), which is shorter and not as loud as the first, can be described as a dupp sound. S2 is caused by blood turbulence associated with closure of the SL valves at the beginning of ventricular diastole. Although S1 and S2 are due to blood turbulence associated with the closure of valves, they are best heard at the surface of the chest in locations that are slightly different from the locations of the valves

Role of Purkinje fibers in cardiac action potential spreads through the conduction system.

rapidly conduct the action potential beginning at the apex of the heart upward to the remainder of the ventricular myocardium. Then the ventricles contract, pushing the blood upward toward the semilunar valves.

mitral stenosis

scar formation or a congenital defect causes narrowing of the mitral valve.

Compare and contrast the systemic and pulmonary circulations.

systemic circulation- circulation that supplies blood to all the body except to the lungs pulmonary circulation- flow of blood from the heart to the lungs and back to the heart

ventricle systole

the atria are relaxed.

atrial systole

ventricles are relaxed.

Anterior cardiac veins,

which drain the right ventricle and open directly into the right atrium

Examine the events which occur during the relaxation period.

which lasts about 0.4 sec, the atria and the ventricles are both relaxed. As the heart beats faster and faster, the relaxation period becomes shorter and shorter, whereas the durations of atrial systole and ventricular systole shorten only slightly.