Question 1

Within a physiologic range,what does an increase in left ventricular end-diastolic volume (preload)result in?

Accepted Answer

This concept is expressed in the Frank-Starling law; the cardiac muscle,like other muscles,increases its strength of contraction when it is stretched.This selection is the only option that accurately describes the result of an increase in preload.

Question 2

Where is the major cardiovascular center in the central nervous system?

Accepted Answer

The major cardiovascular control center is in the brainstem in the medulla with secondary areas in the hypothalamus,the cerebral cortex,the thalamus,and the complex networks of exciting or inhibiting interneurons (connecting neurons)throughout the brain.This selection is the only option that accurately identifies the cardiovascular control center.

Question 3

What is the most important negative inotropic agent?

Accepted Answer

Chemicals affecting contractility are called inotropic agents.The most important negative inotropic agent is acetylcholine released from the vagus nerve.The most important positive inotropic agents produced by the body are norepinephrine released from the sympathetic nerves that supply the heart and epinephrine released by the adrenal cortex.Other positive inotropes include thyroid hormone and dopamine.Many medications have positive or negative inotropic properties that can have profound effects on cardiac function.This selection is the only option that accurately identifies the regulation that is involved in the described process.

Question 4

What is the major determinant of the resistance that blood encounters as it flows through the systemic circulation?

Accepted Answer

Of the options available,only the thick,smooth muscle layer of the arterioles is a major determinant of the resistance blood encounters as it flows through the systemic circulation.

Question 5

If the sinoatrial (SA)node fails,then at what rate (depolarizations per minute)can the atrioventricular (AV)node depolarize?

Accepted Answer

If the SA node is damaged,then the AV node will become the heart's pacemaker at a rate of approximately 40 to 60 spontaneous depolarizations per minute.

Question 6

Pressure in the left ventricle must exceed pressure in which structure before the left ventricle can eject blood?

Accepted Answer

Pressure in the ventricle must exceed aortic pressure before blood can be pumped out during systole.The aorta is the only structure in which pressure must be less than the amount of blood in the left ventricle for ejection to occur.

Question 7

Where in the heart are the receptors for neurotransmitters located?

Accepted Answer

Sympathetic neural stimulation of the myocardium and coronary vessels depends on the presence of adrenergic receptors,which specifically bind with neurotransmitters of the sympathetic nervous system.The b₁ receptors are found mostly in the heart,specifically the conduction system (AV and SA nodes,Purkinje fibers)and the atrial and ventricular myocardium,whereas the b₂ receptors are found in the heart and also on vascular smooth muscle.b₃ receptors are also found in the myocardium and coronary vessels.This selection is the only option that accurately identifies the location of the receptors for neurotransmitters.

Question 8

Which complex (wave)represents the sum of all ventricular muscle cell depolarizations?

Accepted Answer

Only the QRS complex represents the sum of all ventricular muscle cell depolarizations.

Question 9

What is an expected change in the cardiovascular system that occurs with aging?

Accepted Answer

Arterial stiffening occurs with aging even in the absence of clinical hypertension.Aging is not responsible for the other conditions.

Question 10

What enables electrical impulses to travel in a continuous cell-to-cell fashion in myocardial cells?

Accepted Answer

Only intercalated disks,thickened portions of the sarcolemma,enable electrical impulses to spread quickly in a continuous cell-to-cell (syncytial)fashion.

Question 11

After the baroreceptor reflex is stimulated,the resulting impulse is transmitted from the carotid artery by which sequence of events?

Accepted Answer

Neural impulses are transmitted over the glossopharyngeal nerve (ninth cranial nerve)from the carotid artery and through the vagus nerve from the aorta to the cardiovascular control centers in the medulla.These centers initiate an increase in parasympathetic activity and a decrease in sympathetic activity,causing blood vessels to dilate and the heart rate to decrease.This selection is the only option that accurately describes the correct sequence of events asked for in the question.

Question 12

The Bainbridge reflex is thought to be initiated by sensory neurons in which cardiac location?

Accepted Answer

The Bainbridge reflex causes changes in the heart rate after intravenous infusions of blood or other fluid.The changes in heart rate are thought to be caused by a reflex mediated by volume receptors found only in the atria that are innervated by the vagus nerve.

Question 13

The right lymphatic duct drains into which structure?

Accepted Answer

The right lymphatic duct drains lymph only into the right subclavian vein.

Question 14

Reflex control of total cardiac output and total peripheral resistance is controlled by what mechanism?

Accepted Answer

Reflex control of total cardiac output and peripheral resistance includes (1)sympathetic stimulation of the heart,arterioles,and veins; and (2)parasympathetic stimulation of the heart only.Neither autonomic nor somatic controls are involved in this process.

Question 15

As stated in the Frank-Starling law,a direct relationship exists between the _____ of the blood in the heart at the end of diastole and the _____ of contraction during the next systole.

Accepted Answer

As stated in the Frank-Starling law,the volume of blood in the heart at the end of diastole (the length of its muscle fibers)is directly related to the force (strength)of contraction during the next systole.This selection is the only option that accurately describes the relationship associated with the Frank-Starling law.

Question 16

What can shorten the conduction time of action potential through the atrioventricular (AV)node?

Accepted Answer

Catecholamines speed the heart rate,shorten the conduction time through the AV node,and increase the rhythmicity of the AV pacemaker fibers.This selection is the only option that can perform that function.

Question 17

The resting heart rate in a healthy person is primarily under the control of which nervous system?

Accepted Answer

The resting heart rate in healthy individuals is primarily under the control of parasympathetic stimulation.This selection is the only option that accurately identifies the nervous system responsible for the healthy resting heart.

Question 18

What is the effect of epinephrine on b₃ receptors on the heart?

Accepted Answer

b₃ receptors are found in the myocardium and coronary vessels.In the heart,stimulation of these receptors opposes the effects of b₁- and b₂-receptor stimulation and negative inotropic effect.Thus b₃ receptors may provide a safety mechanism that decreases myocardial contractility to prevent overstimulation of the heart by the sympathetic nervous system.This selection is the only option that accurately describes the effect of epinephrine on b₂ receptors on the heart.

Question 19

Continuous increases in left ventricular filing pressures result in which disorder?

Accepted Answer

Pressure changes are important because increased left ventricular filling pressures back up into the pulmonary circulation,where they force plasma out through vessel walls,causing fluid to accumulate in lung tissues (pulmonary edema).This selection is the only option that accurately identifies the disorder described in the question.

Question 20

When the volume of blood in the ventricle at the end of diastole increases,the force of the myocardial contraction during the next systole will also increase,which is an example of which law or theory about the heart?

Accepted Answer

This concept is expressed only in the Frank-Starling law; the cardiac muscle,like other muscles,increases its strength of contraction when it is stretched.

Quiz 31: Structure and Function of the Cardiovascular and Lymphatic Systems

Within a physiologic range,what does an increase in left ventricular end-diastolic volume (preload) result in?