Download Electrical System Of The Heart

DATE:
NAME:
CHAPTER 8
HANDOUT
Electrical System of the
Heart
CLASS:
BLM 8.1.5
Part A Electrical System of the Heart
1. Label the electrical system of the heart
2. Describe what happens when the electrical stimulus travels through the heart.
Part B An electrocardiogram (ECG) records the electrical activity of the heart
3. Label the PQRST complex on the ECG reading below.
Copyright © 2007, McGraw-Hill Ryerson Limited, a subsidiary of the McGraw-Hill Companies. All rights reserved.
This page may be reproduced for classroom use by the purchaser of this book without the written permission of the publisher.
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DATE:
NAME:
CHAPTER 8
HANDOUT
Electrical System of the
Heart
CLASS:
BLM 8.1.5
4. The PQRST complex represents a complete cardiac cycle. Identify what part of the cardiac cycle
is occurring at each part of the complex.
ECG Wave Part
P
Corresponding Cardiac Cycle
QRS
T
Copyright © 2007, McGraw-Hill Ryerson Limited, a subsidiary of the McGraw-Hill Companies. All rights reserved.
This page may be reproduced for classroom use by the purchaser of this book without the written permission of the publisher.
2
DATE:
NAME:
CHAPTER 8
HANDOUT
Electrical System of the
Heart
CLASS:
BLM 8.1.5
Part A Electrical System of the Heart
1.
2. The SA node sends out an electrical stimulus that causes the atria to contract. When this stimulus
reaches the AV node, it is passed through the bundle of His and the Purkinje fibres. The stimulus
causes the ventricles to contract, starting from the apex and then upward, which forces blood
toward the pulmonary artery and aorta. The chordae tendinae are strong, fibrous strings that
prevent the valves in the heart from inverting when the heart contracts.
Copyright © 2007, McGraw-Hill Ryerson Limited, a subsidiary of the McGraw-Hill Companies. All rights reserved.
This page may be reproduced for classroom use by the purchaser of this book without the written permission of the publisher.
3
DATE:
NAME:
CHAPTER 8
HANDOUT
Electrical System of the
Heart
CLASS:
BLM 8.1.5
Part B
3.
4.
ECG Wave Part
P
QRS
T
Corresponding Cardiac Cycle
Atrial excitation begins and atria contract, AV valves open, semilunar valves
closed.
Ventricular excitation and ventricles contract, AV valves (bicuspid and
tricuspid) close. Semilunar valves forced open by ventricular contraction.
Ventricles relax –AV valves open, semilunar valves closed.
5. There may be more than one explanation as to why PQRST is used on the ECG wave. One idea
is that Einthoven, the scientist who identified the parts of the ECG wave, chose letters from the
middle of the alphabet to allow for letters before and after in case more parts of the wave were
discovered (for example “U” was later identified).
Copyright © 2007, McGraw-Hill Ryerson Limited, a subsidiary of the McGraw-Hill Companies. All rights reserved.
This page may be reproduced for classroom use by the purchaser of this book without the written permission of the publisher.
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