PHRM 123 Test 3 Exam Latest Update
What is an ECG/EKG? - ANSWER provides a visual representation of the spread of
electrical excitation through the heart as detected on the surface of the body
What do ECG electrodes record? - ANSWER the overall direction and magnitude of the
electrical events
What does an ECG tracing display? - ANSWER the electrical events as positive and
negative deflections over time
What are ECGs important in diagnosing? - ANSWER heart problems
What is an idealized ECG shape useful for understanding? - ANSWER differences
between the different types of ECGs and differences within a single patient in different
circumstances
What can the components of an ECG be correlated with? - ANSWER the electrical
activity of the atrial and ventricular muscle
What is the P wave produced by? - ANSWER atrial depolarization
What is the PR interval? - ANSWER onset of atrial depolarization to the onset of
ventricular depolarization
If a Q wave is present, what is the PR interval called? - ANSWER PQ interval
What is the PR segment? - ANSWER end of the P wave to the beginning of the QRS
complex
If a Q wave is present, what is the PR segment called? - ANSWER PQ segment
What is the QRS complex produced by? - ANSWER ventricular depolarization; atrial
repolarization also occurs but its contribution is small and hidden by the dominant
ventricular depolarization
What is the ST segment? - ANSWER isoelectric line from the end of the QRS complex to
the beginning of the T wave; it is the time when the ventricles are depolarized
What is the T wave produced by? - ANSWER ventricular repolarization
What is the approximate duration while at rest with a heart rate of 60BPM of a P wave? -
ANSWER 0.10s
What is the approximate duration while at rest with a heart rate of 60BPM of a PR
interval? - ANSWER 0.20s
What is the approximate duration while at rest with a heart rate of 60BPM of a QRS
, complex? - ANSWER 0.08s
What is the approximate duration while at rest with a heart rate of 60BPM of a ST
segment? - ANSWER 0.08s
What is the approximate duration while at rest with a heart rate of 60BPM of a T wave? -
ANSWER 0.16s
What is the approximate duration while at rest with a heart rate of 60BPM of a QT
interval? - ANSWER 0.40s
During exercise, an increase in heart rate corresponds to a shortening of the cardiac
cycle in which intervals? - ANSWER the time between two successive R waves
decreases; most of the shortening occurs in the TP interval; QT interval also shortens,
slightly
What is the important factor to consider on the ECG for segments? - ANSWER change
from the isoelectric line (elevation or depression)
What is the important factor to consider on the ECG for intervals? - ANSWER duration
What generates an electrical signal which travels along a set conduction pathway? -
ANSWER autorhythmic cells of the heart
What do the autorhythmic cells of the heart ensure? - ANSWER coordinated contraction
of the heart
In a healthy heart, what generates cardiac action potentials at a greater frequency than
other cardiac muscle cells? - ANSWER Sinoatrial node
Where is the sinoatrial node located? - ANSWER medial to the opening of the superior
vena cava
Excitation at the SA node leads to excitation along? - ANSWER internodal tracts towards
the left atrium and the AV node
Where is the Atrioventricular node and Bundle of His located? - ANSWER medial to the
right atrioventricular valve
Where are action potentials propagated slowly compared to the rest of the heart's
conducting system? - ANSWER AV node, bundle of His
What happens from the time when action potentials arrive at the AV node until they pass
through to the most distal portion of the node, the Bundle of His? - ANSWER significant
delay (0.12s)
Why is there a significant delay from the time the action potentials arrive at the AV node
until they pass through to the Bundle of His? - ANSWER allows atrial contraction to be
completed before ventricular contraction can begin
What is an ECG/EKG? - ANSWER provides a visual representation of the spread of
electrical excitation through the heart as detected on the surface of the body
What do ECG electrodes record? - ANSWER the overall direction and magnitude of the
electrical events
What does an ECG tracing display? - ANSWER the electrical events as positive and
negative deflections over time
What are ECGs important in diagnosing? - ANSWER heart problems
What is an idealized ECG shape useful for understanding? - ANSWER differences
between the different types of ECGs and differences within a single patient in different
circumstances
What can the components of an ECG be correlated with? - ANSWER the electrical
activity of the atrial and ventricular muscle
What is the P wave produced by? - ANSWER atrial depolarization
What is the PR interval? - ANSWER onset of atrial depolarization to the onset of
ventricular depolarization
If a Q wave is present, what is the PR interval called? - ANSWER PQ interval
What is the PR segment? - ANSWER end of the P wave to the beginning of the QRS
complex
If a Q wave is present, what is the PR segment called? - ANSWER PQ segment
What is the QRS complex produced by? - ANSWER ventricular depolarization; atrial
repolarization also occurs but its contribution is small and hidden by the dominant
ventricular depolarization
What is the ST segment? - ANSWER isoelectric line from the end of the QRS complex to
the beginning of the T wave; it is the time when the ventricles are depolarized
What is the T wave produced by? - ANSWER ventricular repolarization
What is the approximate duration while at rest with a heart rate of 60BPM of a P wave? -
ANSWER 0.10s
What is the approximate duration while at rest with a heart rate of 60BPM of a PR
interval? - ANSWER 0.20s
What is the approximate duration while at rest with a heart rate of 60BPM of a QRS
, complex? - ANSWER 0.08s
What is the approximate duration while at rest with a heart rate of 60BPM of a ST
segment? - ANSWER 0.08s
What is the approximate duration while at rest with a heart rate of 60BPM of a T wave? -
ANSWER 0.16s
What is the approximate duration while at rest with a heart rate of 60BPM of a QT
interval? - ANSWER 0.40s
During exercise, an increase in heart rate corresponds to a shortening of the cardiac
cycle in which intervals? - ANSWER the time between two successive R waves
decreases; most of the shortening occurs in the TP interval; QT interval also shortens,
slightly
What is the important factor to consider on the ECG for segments? - ANSWER change
from the isoelectric line (elevation or depression)
What is the important factor to consider on the ECG for intervals? - ANSWER duration
What generates an electrical signal which travels along a set conduction pathway? -
ANSWER autorhythmic cells of the heart
What do the autorhythmic cells of the heart ensure? - ANSWER coordinated contraction
of the heart
In a healthy heart, what generates cardiac action potentials at a greater frequency than
other cardiac muscle cells? - ANSWER Sinoatrial node
Where is the sinoatrial node located? - ANSWER medial to the opening of the superior
vena cava
Excitation at the SA node leads to excitation along? - ANSWER internodal tracts towards
the left atrium and the AV node
Where is the Atrioventricular node and Bundle of His located? - ANSWER medial to the
right atrioventricular valve
Where are action potentials propagated slowly compared to the rest of the heart's
conducting system? - ANSWER AV node, bundle of His
What happens from the time when action potentials arrive at the AV node until they pass
through to the most distal portion of the node, the Bundle of His? - ANSWER significant
delay (0.12s)
Why is there a significant delay from the time the action potentials arrive at the AV node
until they pass through to the Bundle of His? - ANSWER allows atrial contraction to be
completed before ventricular contraction can begin
