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The Heart

Chapter 20
STUDY
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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
tetany
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 ________.
diastole
________ is when the heart can't maintain adequate cardiac output.
Heart failure
As the heart rate slows, ________ gets longer.
diastole
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 ________.
systole
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 ________.
regurgitation
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.
80-100
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.
left
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.
pacemaker
The cardiac ________ is the difference between the resting and maximal cardiac output.
reserve