Download Chapter01_Detailed_Answers

Chapter 1
Detailed Answers to Assess Your Understanding
1.
d:
The electrocardiogram measures the heart’s electrical activity. The pulse strength is
measured by taking the patient’s pulse while the blood pressure is measured with a
sphygmomanometer.
2.
b:
The electrocardiograph cannot determine the perfusion status of the patient. You must
perform an assessment that includes, but is not limited to, such things as checking for a pulse,
taking the patient’s blood pressure and assessing the patient’s the SPO2 (pulse oximetry). It can,
however, be used to identify irregularities in the heart rhythm, reveal the presence of, injury of,
death of, or other physical changes in the heart muscle and diagnose noncardiac diseases such
as pulmonary embolism or hypothermia.
3.
False: When an electrical impulse in the heart moves toward a positive electrode, the ECG
waveform takes positive deflection.
4.
b:
The heart is the pump of the circulatory system. Each time it contracts, it pushes blood
throughout the body. The typical adult heart beats an average of 75 times a minute, 24 hours a
day, 365 days a year, never stopping to take a rest. In an average day it pumps between 7000
and 9000 liters (L) of blood. This circulates enough blood to deliver needed oxygen and nutrients
to the tissues and to remove waste products.
5.
c:
The heart lies on the diaphragm in front of the trachea, esophagus, and thoracic
vertebrae and between the two lungs. About two-thirds of the heart is situated in the left side
of the chest cavity.
6.
d:
The pericardial cavity holds a small amount of clear lubricating fluid.
7.
a:
The myocardium is the thickest of the three layers of the heart.
8.
b:
The upper chambers of the heart are called the atria. The ventricles are the lower
chambers of the heart.
9.
a:
Functions of the skeleton of the heart include allowing the top and bottom parts of the
heart to act as separate pumps.
10.
False: It is the specialized cells of the electrical conduction system that initiate and carry
impulses throughout the heart. The working cells contract to pump blood out of the heart’s
chambers.
11.
d:
Automaticity, a property of the heart, is the ability to produce an electrical impulse
without the need for outside nerve stimulation.
12.
b:
Depolarization occurs when there is a rapid influx of positively charged ions from
outside to inside the cell. During depolarization sodium enters the cells through the fast
channels followed by calcium entering through the slow channels.
13.
b:
Nerve impulses stimulate muscle cells to contract. Without this nerve stimulation, the
muscles will not contract. For this reason you can see that nerve impulse stimulation is
extremely important.
14.
a:
While electrical impulses can arise from other locations in the heart, the electrical
impulse that arises from the SA node normally initiates the heartbeat.
15.
c:
The impulse traveling through the His-Purkinje fibers generates a flat line following the P
wave on the ECG.
16.
b:
17.
a:
Depolarization of the myocardium progresses from the atria to the ventricles in an
orderly fashion. This is necessary to produce the coordinated contraction of the atria and then
the ventricles.
18.
c:
The T wave represents ventricular repolarization.
19.
b:
An alternate pacemaker site can initiate the heartbeat if the SA node fails to do so.
20.
b:
The AV junction pacemaker cells have an intrinsic rate of 40 to 60 beats per minute. The
ventricles including the His-Purkinje system have an intrinsic rate of 20 to 40 beats per minute.
21.
d:
22.
b:
The myocardium receives its blood supply via the coronary arteries. Blood flow through
the coronary arteries occurs during diastole. The coronary veins return the blood to the right
atrium.
23.
d:
Cardiac output is equal to the stroke volume (amount ejected from the ventricles with
contraction) multiplied by the heart rate. A decrease in either the stroke volume or the heart
rate can decrease cardiac output.
24.
c:
The sympathetic branch of the autonomic nervous system, also referred to as the
adrenergic system, produces the “fight or flight” response. It works the opposite of the
parasympathetic nervous system.
25.
c:
The parasympathetic nervous system is not referred to as the “adrenergic nervous
system.” Instead it is referred to as the “cholinergic nervous system.”
26.
a:
The QRS complex represents ventricular depolarization.
The circulatory system includes roughly 4.7 to 5.7 L of blood.
Myocardial ischemia will occur if the flow of blood in the coronary arteries is diminished.
27.
b:
Pain causes a release of epinephrine which acts through the sympathetic nervous
system to increase heart rate and blood pressure. The pain originates in the heart muscle which
is starving for oxygen. Hypertension alone will not cause the heart rate to increase. Nicotine in
large doses will cause the heart rate to increase but not to the level seen in this case.
Parasympathetic nervous system stimulation would decrease, not increase, the heart rate.
28.
d:
The affected myocardial tissue becomes necrotic.