Bio 232 @ Oit - Chapter 18 - Heart

Front 1

Just what is the mediastinum?

Back 1

The medial cavity of the thorax within which the heart, great vessels, and trachea are found.

Front 2

Which heart chamber has the thickest walls? What is the significance of thise structural difference?

Back 2

Left ventricle. It's the systemic pump that has to pump blood through the entire systemic circulation against high resistance.

Front 3

What is the function of the papillary muscles and chordae tendineae?

Back 3

They keep the AV valve flaps from everting into the atria as the ventricles contract.

Front 4

What ionic event produces the plateau in the AP of the contractile muscle cells?

Back 4

Calcium entry.

Front 5

Knowing that ventricular contraction follows the pattern of ventricular excitation, describe the path you expect the contraction wave to follow across the ventricles.

Back 5

From the apex of the heart superiorly toward the atria.

Front 6

Are the ventricular cardiac cells in isotonic or isometric contraction during phase 2a of part (b)?

Back 6

They are contracting isometrically until ventricular pressure rises above the pressure in the aorta.

Front 7

What problem might ensue relative to cardiac output if the heart beats far too rapidly for an extended period, that is, if tachycardia occurs? Why?

Back 7

Pathological increase in heart rate results in too little time for ventricular filling. Therefore, CO declines and the heart beats feebly.

Front 8

When the semilunar valves are open, which of the following are occuring?
A) 2, 3, 5, 6
B) 1, 2, 3, 7
C) 1, 3, 5, 6
D) 2, 4, 5, 7
(1) coronary arteries fill
(2) AV valves are closed
(3) ventricles are in systole
(4) ventricles are in diastole
(5) blood enters aorta
(6) blood enters pulmonary arteries
(7) atria contract

Back 8

A) 2, 3, 5, 6

Front 9

The portion of the intrinsic conduction system located in the interventricular septum is the:
A) AV Node
B) SA Node
C) AV Bundle
D) Purkinje fibers

Back 9

C) AV Bundle

Front 10

An ECG provides information about:
A) Cardiac output
B) Movement of the excitation wave across the heart
C) Coronary circulation
D) Valve impairment

Back 10

B) Movement of the excitation wave across the heart

Front 11

The sequence of contraction of the heart chambers is:
A) Random
B) Left chambers followed by right chambers
C) Both atria followed by both ventricles
D) Right atrium, right ventricle, left atrium, left ventricle

Back 11

C) Both atria followed by both ventricles

Front 12

The fact that the left ventricular wall is thicker than the right reveals that it:
A) Pumps a greater volume of blood
B) Pumps blood against greater resistance
C) Expands the thoracic cage
D) Pumps blood through a smaller valve

Back 12

B) Pumps blood against greater resistance

Front 13

The chordae tendineae:
A) Close the atrioventricular valves
B) Prevent the AV valve flaps from everting
C) Contract the papillary muscles
D) Open the semilunar valves

Back 13

B) Prevent the AV valve flaps from everting

Front 14

In the heart, which of the following apply?
A) All are true
B) 1, 3, 4
C) 1, 2, 3
D) 2, 3
(1) Action potentials are conducted from cell to cell across the myocardium via gap junctions
(2) The SA Node sets the pace for the heart as a whole
(3) Spontaneous depolarization of cardiac cells can occur in the absence of nerve stimulation
(4) Cardiac muscle can continue to contract for long periods in the absence of oxygen.

Back 14

C) 1, 2, 3

Front 15

The activity of the heart depends on intrinsic properties of cardiac muscle and on neural factors. Thus,
A) Vagus nerve stimulation of the heart reduces heart rate
B) Sympathetic nerve stimulation of the heart decreases time available for ventricular filling
C) Sympathetic stimulation of the heart increases its force of contraction
D) All of the above

Back 15

D) All of the above

Front 16

Freshly oxygenated blood is first received by the:
A) Right atrium
B) Left atrium
C) Right ventricle
D) Left ventricle

Back 16

B) Left atrium

Front 17

Describe the location of the human heart

Back 17

The human heart, about the size of a clenched fist, is located obliquely within the mediastinum of the thorax.

Front 18

Describe the coverings surrounding the heart

Back 18

The heart is enclosed within a double sac made up of the outer fibrous pericardium and the inner serous pericardium (parietal and visceral layers). The pericardial cavity between the serous layers contains lubricating serous fluid.

Front 19

List the layers of the heart wall, in order.

Back 19

Layers of the heart wall, from the interior out, are the endocardium, the myocardium (reinforced by a fibrous skeleton), and the epicardium (visceral layer of the serous pericardium.)

Front 20

Describe the physical structure of the heart

Back 20

The heart has two superior atria and two inferior ventricles. Functionally, the heart is a double pump.
Entering the right atrium are the superior vena cava, the inferior vena cava, and the coronary sinus. Four pulmonary veins enter the left atrium.
The right ventricle discharges blood into the pulmonary trunk, the left ventricle pumps blood into the aorta.

Front 21

Describe the oxygen exchange process within the cardiac system

Back 21

The right heart is the pulmonary circuit pump. Oxygen-poor systemic blood enters the right atrium, passes into the right ventricle, through the pulmonary trunk into the lungs, and back to the left atrium via the pulmonary veins.
The left heart is the systemic circuit pump. Oxygen-laden blood entering the left atrium from the lungs flows into the left ventricle and then into the aorta, which provides the functional supply of all body organs. Systemic veins return the oxygen-depleted blood to the right atrium.

Front 22

Describe the process of coronary circulation

Back 22

The right and left coronary arteries branch from the aorta and via their main branches (Anterior and posterior interventricular, marginal, and circumflex arteries) supply the heart itself. Venous blood, collected by the cardiac veins (great, middle, and small) is emptied into the coronary sinus.
Blood delivery to the myocardium occurs during heart relaxation.

Front 23

How is backflow prevented by the various heart valves?

Back 23

The artioventricular valves (tricuspid and mitral) prevent backflow into the atria when the ventricles are contracting, the pulmonary and aortic valves (semilunar valves) prevent backflow into the ventricles when the ventricles are relaxing.

Front 24

Describe the microscopic anatomy of cardiac cells

Back 24

Cardiac muscle cells are branching, striated, generally uninucleate cells. They contain myofibrils consisting of typical sarcomeres.
Adjacent cardiac cells are connected by intercalated discs containing desmosomes and gap junctions. The myocardium behaves as a functional syncytium becuase of electical coupling provided by gap junctions.

Front 25

Describe the mechanism and events of contraction. What advantage does the prolonged refractory period of cardiac muscle confer?

Back 25

As in skeletal muscle, the membrane depolarization of contractile myoocytes causes opening of sodium channels and sodium entry, which is responsible for the rising phase of the action potential curve. Depolarization also opens slow Ca2+ channels, Ca2+ entry prolongs the period of depolarization (creates the plateau). The action potential is coupled to sliding of the myofilaments by Ca2+ released by the SR and entering from the extracellular space. Compared to skeletal muscle, cardiac muscle has a prolonged refractory period that prevents tetany.

Front 26

How is ATP generated, within the heart?

Back 26

Cardiac muscle has abundant mitochondria and depends almost entirely on aerobic respiration to form ATP.

Front 27

Describe the regular electrical events present in heart physiology. What are the characteristics of cardiac muscle cells? What does the conduction system of the heart consist of? What elements are illustrated by an electrocardiogram?

Back 27

Certain noncontractile cardiac muscle cells exhibit automaticity and rhythmicity and can independently initiate action potentials. Such cells have an unstable resting potential called a pacemaker potential that gradually depolarizes, drifting toward threshold for firing. These cells compose the intrinsic conduction system of the heart.
The conduction system of the heart consists of the SA and AV nodes, the AV bundle and bundle branches, and the Purkinje fibers. This system coordinates the depolarization of the heart and ensures that the heart beats as a unit. the SA nodes has the fastest rate of spontaneous depolarization and acts as the heart's pacemaker; it sets the sinus rhythm.
Defects in the intrinsic conduction system can cause arrhythmias, fibrillation, and heart block (damage to the AV node, interfering with the ability of the ventricles to receive pacing impulses.)
The heart is innervated by the autonomic nervous system. Cardiac centers in the medulla include the cardioacceleratory center, which projects to the T1-T5 region of the spinal cord, which in turn projects to the cervical and upper thoracic sympathetic trunk. Postganglionic fibers innervate the SA and AV nodes and the cardiac muscle fibers. The cardioinhibitory center exerts its influence via the parasympathetic vagus nerves (X), which project to the heart wall. Most parasympathetic fibers serve the SA and AV nodes.
An electrocardiogram is a graphic representation of the cardiac conduction cycle. The P wave reflects atrial depolarization. The QRS complex indicates ventricular depolarization, the T wave represents ventricular repolarization.

Front 28

What kinds of heart problems might be indicated by abnormal heart sounds?

Back 28

Normal heart sounds arise chiefly from turbulent blood flow during the closing of heart valves. Abnormal heart sounds, called murmurs, usually reflect valve problems.

Front 29

Describe the cardiac cycle - how does pressure figure into this?

Back 29

A cardiac cycle consists of the events occurring during one heartbeat. During mid-to-late diastole, the ventricles fill and the aria contract. Ventricular systole consists of the isovolumetric contraction phase and the ventricular ejection phase. During early diastole, the ventricles are relaxed and are closed chambers until increasing atrial pressure forces the AV valves open and the cycle begins again. At a normal heart rate of 75 beats/min, a cardiac cycle lasts 0.8 seconds.
Pressure changes promote blood flow and valve opening and closing.

Front 30

How is cardiac output described, and measured?

Back 30

Cardiac output, typically 5 L/min, is the amount of blood pumped out by each ventricle in 1 minute. Stroke volume is the amount of blood pumped out by a ventricle with each contraction. Cardiac output = heart rate X stroke volume.
Stroke volume depends to a large extend on the degree of stretch of cardiac muscle by venous return. Approximately 70 ml, it is the difference between end diastolic volume (EDV) and end systolic volume (ESV). Anything that influences heart rate or blood volume influences venous return, hence stroke volume.

Front 31

How is the heart affected by the activation of the sympathetic and parasympathetic systems? What chemicals and ions affect operation? What other factors can affect heart rate?

Back 31

Activation of the sympathetic nervous system increased heart rate and contractility; parasympathetic activation decreases heart rate but has little effect on contractility. Ordinarily, the heart exhibits vagal tone.
Chemical regulation of the heart is effected by hormones (epinephrine and thyroxine) and ions (particularly potassium and calcium). Imbalances in ions severely impair heart activity.
Other factors influencing heart rate are age, sex, exercise, and body temperature.
Congestive heart failure occurs when the pumping ability of the heart is inadequate to provide normal circulation to meet body needs. Right heart failure leads to systemic edema; left heart failure results in pulmonary edema.

Front 32

Describe the early development of the heart. What age-related risks and developments are relevant to this organ?

Back 32

The heart begins as a simple (mesodermal) tube that is pumping blood by the fourth week of gestation. The fetal heart has two lung bypasses: the foramen ovale and the ductus arteriosus.
Congenital heart defects are the most common of all birth defects. The most common of these disorders lead to inadequate oxygenation of blood or increase the workload of the heart.
Age-related changes include sclerosis and thickening of the valve flaps, declines in cardiac reserve, fibrosis of cardiac muscle, and artherosclerosis.
Risk factors for cardiac disease include dietary factors, excessive stress, cigarette smoking, and lack of exercise.

Front 33

Name the anatomical structures contained within the mediastinum?

Back 33

The mediastinum is the medial cavity of the thorax, and contains the heart and lungs

Front 34

Another name for the epicardium is the:

Back 34

The visceral layer

Front 35

The right subclavian artery is a branch of the:

Back 35

Right brachiocephalic artery

Front 36

Name the opening between the right and left atria present during fetal development.

Back 36

The foramen ovalis a remnant of the foramen ovale that exists in the fetal heart

Front 37

Trace the flow of blood through the heart beginning with the superior vena cava.

Back 37

Superior vena cava to right atrium to right ventricle to pulmonary arteries to lungs to pulmonary veins to left atrium to left ventricle to capillary beds back to venae cavae

Front 38

The papillary muscles are associated with the:

Back 38

They play a role in valve function and project into the ventricular cavity.

Front 39

What is the function of the fibrous skeleton?

Back 39

Reinforces the myocardium internally and anchors the cardiac muscle fibers

Front 40

Which valve is associated with the ascending aorta?

Back 40

Aortic semilunar valve

Front 41

Name the major branches of the left coronary artery?

Back 41

The anterior interventricular artery and the circumflex artery.

Front 42

Angina pectoralis results from:

Back 42

Thoracic pain caused by a fleeting deficiency in blood delivery to the myocardium

Front 43

Briefly describe cardiac muscle tissue

Back 43

It is striated, and it contracts by the sliding filament mechanism. However, in contrast to the long, cylindrical, multi-nucleate skeletal muscle fibers, cardiac cells are short, fat, branched, and interconnected.

Front 44

In cardiac muscle, following threshold an action potential results from the influx of

Back 44

Ca2+

Front 45

What is the function of the atrioventricular valve

Back 45

Prevent backflow into the atria when the ventricles are contracting

Front 46

The walls of the left ventricle are thicker because

Back 46

Because the systemic circuit, which is served by the left ventricle, takes a long pathway through the entire body and encounters about 5 times as much friction

Front 47

The closure of the atrioventricular valves is accomplished by

Back 47

The chordae tendineae and the papillary muscles