chapter 13
The volume of blood ejected from the ventricle with each contraction can be described by the equation
(end - diastolic volume) - (end - systolic volume).
In an ECG recording, the RR interval is 0.5 seconds. What is the heart rate?
120 beats/ minute
Normal resting heart rate is around 70 beats per minute due to the SA node. If the SA node fails, what would you expect the heart beats per minute to be?
50 beats per minute
Conduction through which of the following is slow to allow atria to contract before the ventricles?
A V node
Which of the following is an effect of parasympathetic activity to the heart?
A) The rate of spontaneous depolarization in SA nodal cells decreases.
An increase in venous return would result in a(n)
A) increased end- diastolic volume.
Which of the following describes the effect of end- diastolic volume on stroke volume?
An increase in end - diastolic volume stretches ventricular muscle cells to lengths closer to optimum, increasing the strength of contraction and thereby increasing stroke volume.
Why do A V nodal cells N OT determine the heart rate under normal circumstances?
As depolarization initiated in the SA node reaches the A V node, it leaves the A V node in a refractory state.
Which of the following is a F A LSE statement about sympathetic activity to the SA node?
B) Potassium channel closing is enhanced
Which of the following statements best describes a portal system?
Blood flows from one capillary bed to another, bypassing general circulation.
Which chamber of the heart has the thickest musculature?
Both ventricles have equal thickness and are thicker than the atria.
The volume of blood that is pumped by the heart every minute is determined by the equation
CO= HR x SV
In what phase is the cardiac cycle when all four valves are closed and pressure in the ventricle is decreasing?
D) isovolumetric relaxation
The second heart sound coincides with the beginning of which period in the cardiac cycle?
D) isovolumetric relaxation
Which statement best describes why atrial depolarization is usually not detected on a normal ECG?
It occurs at the same time as the QRS complex.
Which channel type is responsible for ion movement during the depolarization phase of the autorhythmic cell action potential?
L-type calcium channel
What channels open during the plateau phase of the cardiac contractile cell action potential?
L-type calcium channels
Which of the following describes second- degree heart block?
Not every atrial contraction is followed by a ventricular contraction.
Which component of an ECG represents atrial depolarization?
P wave
Which of the following components of an ECG represents atrial depolarization?
P wave
Which component of an ECG represents the A V nodal conduction time?
P-R interval
Which component of an ECG represents ventricular systole?
Q-T interval
Which component of an ECG represents ventricular depolarization?
QRS complex
Which of the following components of an ECG represents ventricular depolarization?
QRS complex
What is the pacemaker of the heart?
SA node
Which of the following is the correct conduction pathway through the heart?
SA node, A V node, bundle of His, bundle branches, Purkinje fibers
Given end - diastolic volume = 130 mL and end- systolic volume = 50 mL, what is the stroke volume and ejection fraction?
SV = 80 mL, EF = 0.61
What is the equation relating stroke volume (SV), end - diastolic volume (EDV), and end- stroke volume (ESV)?
SV = EDV - ESV
The repolarization of the ventricle is reflected in the ________ of the electrocardiogram.
T wave
Which component of an ECG represents ventricular repolarization?
T wave
Which of the following components of an ECG represents ventricular repolarization?
T wave
Which component of an ECG represents ventricular diastole?
T-Q segment
Which channel type allows calcium movement into the cell during the late spontaneous depolarization in autorhythmic cells?
T-type calcium channels
What is occurring during ventricular ejection?
The A V valves are closed and the semilunar valves are open as blood is leaving the ventricles.
Which statement best describes why clinicians use a defibrillator?
The applied current depolarizes all the muscle cells at the same time, returning synchronous electrical activity to the heart.
Which statement best describes parallel flow in the circulatory system?
The organs of the body are arranged in a parallel circuit to allow adequate flow and pressure to all body systems and maintain homeostasis of blood pressure.
If both the SA node and the A V node fail, what would be the expected outcome of impulse rate within the heart?
The rate would be 30-40 beats per minute due to the concentration of pacemaker cells in the Purkinje fibers.
Which of the following best describes the effect of sympathetic activity on ventricular contractile cells?
The rates of contraction and relaxation and the force of contraction all increase.
Which of the following statements best describes the function of the chordae tendineae?
They pull downward on the valve cusps, thereby preventing the A V valves from being pushed into the atria (prolapsing).
Which of the following is TRUE of the ventricular filling phase of the cardiac cycle?
Ventricular pressure is less than aortic pressure.
An increase in heart rate can be mediated through which of the following?
a decrease in parasympathetic activity and an increase in sympathetic activity
If damage to the A V node slowed down conduction through this tissue, what would be observed on an ECG?
a longer PR interval
Which of the following variables is N OT involved in determining ventricular preload?
afterload
Which of the following is responsible for the rapid depolarization phase of an action potential within the pacemaker cells?
an increase in Pca
When blood moves through the body it travels in a circular pattern. The general pattern of blood flow follows which sequence of vessels as it leaves the heart?
arteries, arterioles, capillaries, venules, veins
The small increase in ventricular pressure observed late in diastole is caused by
atrial contraction
The P wave of the electrocardiogram is created by
atrial depolarization
Which of the following is N OT a part of the excitation- contraction coupling in cardiac muscle?
calcium binds to calmodulin in the cytosol
The rapid depolarization phase of a pacemaker cell action potential is caused by movement of
calcium through L-type channels
The depolarization of the action potential in the pacemaker cells is driven by the rapid influx of ________ ions through ________ channels.
calcium: L-type calcium
The primary site of exchange between blood and interstitial fluid occurs across what type of blood vessel?
capillaries
Blood supply to the heart comes from
coronary arteries
Which of the following would N OT result from an increase in ventricular contractility?
decreased end - diastolic volume
What structure separates the thoracic cavity from the abdominal cavity?
diaphragm
The opening and closure of the atrioventricular and semilunar valves is driven by
differences in pressure across the valve
The preload is approximately the same as the ________ pressure.
end-diastolic
What are the three layers of the heart, from inside to outside?
endothelium, myocardium, and epicardium
Although blood is a fluid, nearly half its volume is composed of cells. The most numerous cells are ________. The remainder of the cells are ________, which help the body defend itself against foreign particles and microorganisms.
erythrocytes : leukocytes
Regulation of the heart (or any organ or tissue) by neural input, circulating hormones, or any other factor originating from outside the organ is referred to as ________ control.
extrinsic
Which channel type allows sodium movement into the cell during the early spontaneous depolarization in autorhythmic cells?
funny channels
What structure provides the pathway for the movement of electrical current between the cells of the conduction pathway and the ventricular muscle fibers?
gap junctions
The term autorhythmicity refers to the heart's ability to
generate its own contractile cycle
Cardiac output is determined by what two variables?
heart rate and stroke volume
Which of the following factors determines preload?
heart rate and venous return
Which of the following variables is N OT an intrinsic factor that alters cardiac function?
hormonal stimulation
Which of the following is responsible for the repolarization of pacemaker cells?
increase in pK
Which of the following decreases heart rate?
increase in parasympathetic activity
A decrease in afterload will lead to which of the following?
increased stroke volume
The increased aortic pressure that occurs during systole reflects a(n)
increased volume of blood in the aorta
What phase of the cardiac cycle is the heart in when all four valves of the heart are closed and ventricular pressure is building, but is not yet great enough to open a valve?
isovolumetric contraction
The mitral valve separates what chamber from its associated ventricle?
left atrium
Which heart structure receives blood from the pulmonary veins?
left atrium
During isovolumetric contraction, which chamber has the greatest pressure?
left ventricle
What chamber empties into the aorta?
left ventricle
What chamber has the thickest myocardium?
left ventricle
Whereas the contractile activity of skeletal muscle is called ________, that of cardiac muscle is ________ because the contraction originates within the musculature itself.
neurogenic: myogenic
During which phase of the cardiac cycle are all four heart valves open?
none
The T- Q segment is the time from the end of the T wave to the beginning of the QRS complex which measures the time
of ventricular diastole
During repolarization (phase 3) of a contractile cell action potential,
only potassium permeability is increased
The increase in ventricular volume early in diastole reflects the
passive movement of blood through the atrium and into the ventricle.
Which channel type allows ion movement out of the cell during repolarization of the autorhythmic cells?
potassium channels
The initial depolarization that occurs in pacemaker cells is caused by closing of ________ channels and opening of ________ channels.
potassium: funny
Ejection of blood from the right ventricle will continue until
pressure in the pulmonary artery is greater than pressure in the right ventricle.
Closure of the atrioventricular valve occurs when
pressure inside the ventricle is greater than pressure inside the atrium
The circulatory system consists of two divisions and is supplied with blood by different sides of the heart. The right heart supplies blood to the ________ circuit, whereas the left heart supplies blood to the ________ circuit.
pulmonary : systemic
Blood returns to the left atrium via what blood vessels?
pulmonary veins
What component of the conduction pathway transmits the action potential to the ventricular contractile cells?
purkinje fibers
What is the function of the sodium- calcium exchanger in cardiac muscle?
remove calcium from the cytosol by transporting it to the extracellular fluid thereby relaxing the muscle
Where is the SA node located?
right atrium
Which heart structure receives deoxygenated blood from veins?
right atrium
Blood is moved through the pulmonary vasculature by pressure generated within the
right ventricle
Which chamber is connected to the pulmonary arteries?
right ventricle
Keeping blood on the left side of the heart from mixing with the blood on the right side is a function of what structure(s)?
septum
What two major regions of the heart contain a concentration of pacemaker cells?
sinoatrial node and atrioventricular node
What causes the rapid depolarization phase of a contractile cell action potential?
sodium movement into the cell
The end- diastolic volume minus the end- systolic volume is the
stroke volume
Starling curves plot ________ against ________.
stroke volume : end - diastolic volume
The SA node is innervated by the
sympathetic and parasympathetic nervous systems
The period of ventricular contraction is called ________, whereas the period of ventricular relaxation is called ________.
systole:diastole
During isovolumetric relaxation,
the A V and semilunar valves are closed and ventricular pressure is decreasing.
The R-R interval is the time between the peaks of two successive QRS complexes and represents
the amount of time between heartbeats
Under resting conditions, heart rate is primarily under the control of what control system?
the parasympathetic nervous system
The Q - T interval is the time from the onset of the QRS complex to the end of the T wave which measures
the time of ventricular systole
What causes the sounds that one hears as the heart beats?
the turbulence created as the valves close
What is the primary function of the A V and semilunar valves?
to permit blood to flow forward while preventing it from flowing backward
Which of the following ion channels does N OT participate in the contractile cell action potential?
type T calcium channels
Blood is ejected from the left ventricle once pressure within the
ventricle is greater than pressure within the aorta
Which of the following structures is poorly innervated by the parasympathetic nervous system and, therefore, an increase in parasympathetic activity has little effect on this structure?
ventricles
In what phase is the cardiac cycle when the semilunar valves are open and A V valves are closed?
ventricular ejection
In what phase of the cardiac cycle does ventricular pressure exceed aortic pressure?
ventricular ejection
In what phase is the cardiac cycle when the A V valves are open and semilunar valves are closed?
ventricular filling
Opening of what channels is responsible for the depolarization phase of the cardiac contractile cell action potential?
voltage- gated sodium channels
