ECG New

Question 1

Electrical charge normally seen in cardiac cells and what happens in depolarization?

Answer 1

Negative inside and positive outside, Cardiac cells can lose their internal negativity in a process called
depolarization

Question 2

What are the types of cells found in the heart?

Answer 2

Pacemaker cells—under normal circumstances, the electrical power source
of the heart
Electrical conducting cells—the hard wiring of the heart
Myocardial cells—the contractile machinery of the heart

Question 3

Features of pacemaker cells

Answer 3

• These cells are able to depolarize spontaneously over and over again
• The rate of depolarization is
  determined by the innate electrical characteristics of the cell and by external
  neurohormonal input.
• Each spontaneous depolarization serves as the source of a wave of depolarization that initiates one complete cycle of cardiac contraction
  and relaxation

Question 4

Dominant pacemaker cells of the heart

Answer 4

Sinoatrial node or sinus node

Question 5

What happens to myocardial cells when an electrical potential reaches them?

Answer 5

• Calcium is released within the cell, causing the cell to contract.
• This process, in which calcium plays
  the key intermediary role, is called excitation–contraction coupling.

Question 6

What groups can be formed from the different limb leads and what do they allow us to do?

Answer 6

Leads II (+60degrees), III (+120 degrees), and aVF (+90 degrees) are called the inferior leads because they most
effectively view the inferior surface of the heart. The inferior surface, or wall, of
the heart is an anatomic term for the bottom of the heart, the portion that rests on the diaphragm.
Leads I (0 degress) and aVL (-30 degrees) are often called the left lateral leads because they have the
best view of the left lateral wall of the heart.
aVR is a loner among the limb leads. It is the only true right-sided limb lead (-150 degrees).

Question 7

Precordial vs limb lead plane of measurments

Answer 7

• Vertical plane for limb leads
• Horizontal plane (anterior posterior) for precordial leads

Question 8

What groups can be formed from the different pericordial and limb leads and what do they allow us to do?

Answer 8

Lead V1 lies directly
over the right ventricle, V2 and V3 over the interventricular septum, V4 over the
apex of the left ventricle, and V5 and V6 over the lateral left ventricle.
Leads V2 through V4 are often referred to as the anterior leads, V5 and V6
join I and aVL as left lateral leads, and leads aVR and V1 are the right
ventricular leads.

Question 9

What position should a person be in when measuring an ECG?

Answer 9

Lying as flat as possible

Question 10

Normal QRS interval duration

Answer 10

0.06 to
0.1 seconds in duration