Lesson 30 Electrocardiogram (ECG) – Study Guide and Practice Questions 2026 (1) Page 1 Lesson 30 Electrocardiogram (ECG) – Study Guide and Practice Questions 2026 (1).pdf
Lesson 30 Electrocardiogram
(ECG) – Study Guide and
Practice Questions 2026
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INTRO
Many providers use an electrocardiogram as part of a complete physical exam or for patients who have experienced
chest pain or other cardiac symptoms. It is often the medical assistant who records the ECG in a medical office or
clinic. Therefore, special knowledge and skills are required to perform this vital clinical task.
Page 2 of 38 2 of 38 2026-03-17
,LESSON 30_ ELECTROCARDIOGRAM Page 3 LESSON 30_ ELECTROCARDIOGRAM.pdf
The Heart
The heart is the pump of the circulatory system and is located between the lungs behind the sternum. It is surrounded
by the pericardial sac, and it is made up of three layers:
>Epicardium (outermost layer)
>Myocardium (middle layer)
>Endocardium (innermost layer)
The heart has four chambers—two upper chambers known as atria, and two lower chambers known as ventricles. The
atria collect blood and deliver it to ventricles. The ventricles pump the blood to the systemic and pulmonary
circulations. The right and left halves of the heart are separated by a dividing wall called the septum. Heart valves
permit the blood to flow through the heart in only one direction.
On its external surface, the heart is surrounded by coronary arteries that supply the myocardium with its blood
supply, from which oxygen and nutrients are obtained.
Page 3 of 38 3 of 38 2026-03-17
, LESSON 30_ ELECTROCARDIOGRAM Page 4 LESSON 30_ ELECTROCARDIOGRAM.pdf
Heart Cells
There are two kinds of cardiac cells: myocardial cells and electrical conduction system cells.
>Myocardial cells- These cells work to propel blood out of the heart's chambers.
>Electrical conduction system cells- These cells are located in distinct pathways through the heart and are sensitive to
electrical impulses.
Depolarization
The heart's conduction system is a group of specialized tissues that carry a wave of depolarization throughout the
heart. When electrical impulses are sent along the conduction system of the heart via the electrical cells, the
myocardial cells contract, causing the heart muscle to pump the blood from chamber to chamber and through the
lungs. The contraction of the cardiac cells is called depolarization.
Page 4 of 38 4 of 38 2026-03-17
Lesson 30 Electrocardiogram
(ECG) – Study Guide and
Practice Questions 2026
Guidehttps://www.stuvia.com/dashboard!@_)#*)(@$)($@*($@)($@*_1 of 38
Page 1 of 38 2026-03-17
,LESSON 30_ ELECTROCARDIOGRAM Page 2 LESSON 30_ ELECTROCARDIOGRAM.pdf
INTRO
Many providers use an electrocardiogram as part of a complete physical exam or for patients who have experienced
chest pain or other cardiac symptoms. It is often the medical assistant who records the ECG in a medical office or
clinic. Therefore, special knowledge and skills are required to perform this vital clinical task.
Page 2 of 38 2 of 38 2026-03-17
,LESSON 30_ ELECTROCARDIOGRAM Page 3 LESSON 30_ ELECTROCARDIOGRAM.pdf
The Heart
The heart is the pump of the circulatory system and is located between the lungs behind the sternum. It is surrounded
by the pericardial sac, and it is made up of three layers:
>Epicardium (outermost layer)
>Myocardium (middle layer)
>Endocardium (innermost layer)
The heart has four chambers—two upper chambers known as atria, and two lower chambers known as ventricles. The
atria collect blood and deliver it to ventricles. The ventricles pump the blood to the systemic and pulmonary
circulations. The right and left halves of the heart are separated by a dividing wall called the septum. Heart valves
permit the blood to flow through the heart in only one direction.
On its external surface, the heart is surrounded by coronary arteries that supply the myocardium with its blood
supply, from which oxygen and nutrients are obtained.
Page 3 of 38 3 of 38 2026-03-17
, LESSON 30_ ELECTROCARDIOGRAM Page 4 LESSON 30_ ELECTROCARDIOGRAM.pdf
Heart Cells
There are two kinds of cardiac cells: myocardial cells and electrical conduction system cells.
>Myocardial cells- These cells work to propel blood out of the heart's chambers.
>Electrical conduction system cells- These cells are located in distinct pathways through the heart and are sensitive to
electrical impulses.
Depolarization
The heart's conduction system is a group of specialized tissues that carry a wave of depolarization throughout the
heart. When electrical impulses are sent along the conduction system of the heart via the electrical cells, the
myocardial cells contract, causing the heart muscle to pump the blood from chamber to chamber and through the
lungs. The contraction of the cardiac cells is called depolarization.
Page 4 of 38 4 of 38 2026-03-17
