The Heart

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Chapter 20

If the connection between the SA node and AV node becomes blocked,

the ventricles will beat more slowly

The long plateau phase of the cardiac muscle action potential is due to

calcium channels remaining open

An increase in the rate of action potentials from baroreceptors will reflexly lead to

both decrease in heart rate and decrease in blood pressure.

During the T wave of the electrocardiogram, the ventricles are

both repolarizing and relaxing

Depolarization of the atria corresponds to the EKG's

P wave

As a result of the long refractory period in the cardiac action potential, cardiac muscle cannot exhibit


Cardiac cells damaged by infarction will show which of the following?

release of troponin T and I into the circulation.
switch to anaerobic metabolism.
release of enzymes into the circulation.
release of MB-CK into the circulation.

Analysis of the electrocardiogram can reveal all of the following, except the

stroke volume

A heart murmur might be caused by

aortic valve stenosis or mitral valve insufficiency or pulmonic valve insufficiency.

The relaxation phase of the cardiac cycle is called ________.


________ is when the heart can't maintain adequate cardiac output.

Heart failure

As the heart rate slows, ________ gets longer.


If the connection between the vagus nerve and the heart is cut, which of these changes will occur?

None of the above

During the isovolumetric phase of ventricular systole, the

atrioventricular valves and semilunar valves are closed.

The closing of the left AV valve occurs near the beginning of __________.

ventricular systole

The majority of ventricular filling occurs while the ventricles and atria are in what state(s)?

ventricular and atrial diastole

Which of the following most correctly describes end-diastolic volume?

\the volume of the ventricle when it is most full

Left ventricular filling occurs __________.

while the AV valve is open

Heart valves are in what state during isovolumetric contraction?

AV valves and semilunar valves are closed

The decrease in left ventricular pressure at the end of ventricular systole causes __________.

the semilunar valves to close

Ventricular diastole begins with the closing of the semilunar valves. What phase of the cardiac cycle happens between this event and the later opening of the AV valves?

isovolumetric relaxation

The contraction phase of the cardiac cycle is called ________.


Compared to the right ventricle, which of these statements about the left ventricle is false?

it ejects more blood

During the cardiac cycle, the

both QRS complex of the ECG precedes the increase in ventricular pressure and first heart sound coincides with the QRS complex of the ECG.

Isovolumetric relaxation and ventricular filling (two phases of the cardiac cycle) take place during __________.

ventricular diastole

Isovolumetric relaxation and ventricular filling (two phases of the cardiac cycle) take place during __________.

Most blood flows passively into the ventricles through open AV valves

Describe the pressures in the atria and ventricles that would cause the opening of the AV valves.

Pressure in the atria would be greater than the pressure in the ventricles.

What causes the aortic semilunar valve to close?

greater pressure in the aorta than in the left ventricle

Put the phases of the cardiac cycle in the correct order, starting after ventricular filling.

isovolumetric contraction, ventricular ejection, isovolumetric relaxation

Increased pressure in the ventricles would close what valve(s)?

AV valves only

The backward flow of blood from a ventricle to its atrium or from a outflow vessel to its ventricle is called ________.


Which of the following would increase heart rate?

decreased parasympathetic stimulation of nodal fibers
increased levels of epinephrine
increased sympathetic stimulation of SA node
faster depolarization of the pacemaker potential

Each of the following factors will increase cardiac output, except

increased parasympathetic stimulation

Cardiac output is increased by

more sympathetic stimulation and increased stroke volume.

Drugs that block the beta-one adrenergic receptors will

decrease the heart rate

If a patient's tricuspid valve was leaking during systole, what would happen?

regurgitation into the right atrium

The amount of blood returning to the heart is the ________.

venous return

The ________ is the volume of blood in a ventricle at the beginning of systole.

end-diastolic volume

The phase in the cardiac cycle when the mitral valve is closed and the aortic valve is open is the

systolic ejection phase

The first heart sound ("lub")

is associated with the closing of the mitral valve

Pacemaker cells isolated from the SA node generate action potentials at ________ beats per minute.


During ventricular systole,

AV valves are closed

Which of the following would increase cardiac output to the greatest extent?

increased heart rate and increased stroke volume

Which of the following would increase heart rate?

norepinephrine and epinephrine

How would an increase in the sympathetic nervous system increase stroke volume?

increased contractility

By what mechanism would an increase in venous return increase stroke volume?

increased end-diastolic volume

How would a decrease in blood volume affect both stroke volume and cardiac output?

decreased stroke volume and no change in cardiac output

The heart is innervated by ________ nerves.

both parasympathetic and sympathetic

The volume of blood ejected from each ventricle during a contraction is called the

stroke volume

Drugs known as calcium channel blockers such as nifedipine can be used to

decrease blood pressure.
decrease the force of cardiac contraction.
produce a negative inotropic effect.
dilate the coronary arteries.

Stroke volume depends on

end diastolic volume, the contractility of the ventricle, and the pressure required to pump blood into the aorta.

Heart rate is controlled by neurons of the cardiovascular center located in the

medulla oblongata

Which of these would cause stroke volume to increase?

both when venous return is increased and when diastolic blood pressure is decreased

In mitral valve prolapse, the cusps of the mitral valve are pushed into the ________ atrium.


Cardiac output can be increased by all of the following except one. Choose the exception.

decreasing ejection fraction

"An increase in end-diastolic volume increases the stroke volume" is a way of stating

Starling's law of the heart

Which of these is not needed to determine cardiac output?

blood pressure

Acetylcholine slows the heart because it

opens potassium ion channels in SA node cells and causes the pacemaker potential to depolarize more slowly.

Which of these is true about the atrial reflex?

depends on sympathetic innervation
triggered by atrial mechanoreceptors
also called Bainbridge reflex
triggered by increasing venous return

Pacemaker cells in the SA node

both show a slow spontaneous depolarization and are connected by gap junctions to atrial myocytes.

Which of the following would be greater?

the end-diastolic volume when the heart rate is 60 beats/minute (as opposed to 150 bpm)

Activation of which kind of receptor causes heart rate to increase?

beta-one receptor

The cardioacceleratory center activates sympathetic neurons and the cardioinhibitory center controls parasympathetic neurons.

Both parts of the statement are true and relate to brainstem control of heart rate.

David suffers from a prolapsed mitral valve. This condition would cause

both increased effort by the left ventricle and systolic murmur.

The ________ is the amount of blood in a ventricle after it has contracted and before it begins to refill.

end-systolic volume

The principle that increasing the end-diastolic volume results in a corresponding increase in the stroke volume is known as ________.

Starling's law of the heart

Cells that spontaneously make action potentials make up ________ tissue.


The cardiac ________ is the difference between the resting and maximal cardiac output.


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