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BIOL 204 – Week 4 Lab. Electrocardiography Human Arteries and Veins Blood Vessel Histology. Objective 1ECG An electrocardiogram is a graphical recording of the hearts electrical changes during a cardiac cycle (heart beat) - PowerPoint PPT Presentation
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BIOL 204 – Week 4 Lab
ElectrocardiographyHuman Arteries and Veins
Blood Vessel Histology
Objective 1 ECG An electrocardiogram is a graphical recording of the hearts electrical changes during a cardiac cycle (heart beat)
- Electrical changes initiated and propagated through themyocardium by specialized cells of the heart’s intrinsic conduction system
Structures of the Intrinsic Conduction Voltage changes seen System
The voltage changes are recorded by leads which can be placed in different locations on the body
We will use limb leads, placed on the appendages to record ECGs in this lab
Lead 1: RA -, LA + most sensitive
to electrical activity spreading horizontally across the heart
Lead 2
RA -, LL + most sensitive to electrical activity spreading vertically (from the base to the apex)
Lead 3LA - . LL + also records electrical
activity spreading from the base to the apex, but from a different orientation
When an ECG tracing is recorded using these lead combinations, a series of wave forms are generated which respond to the spread of electricity through the heart after it originates at the SA node
A typical ECG tracing
Y (vertical) axis measure voltage:
- typically, 10 squares = 1 mV
X axis measures time:
- At a chart speed of 25 mm/sec:
each small block = 0.04 sec
and
each large block (5 small blocks)
= 5 X 0.04 sec.
= 0.20 sec.
What is the duration of the :
P wave?
P-R interval?
QRS complex?
Q-T interval?
T wave?
To determine the heart rate from an ECG tracing:
Method #1: count the number of small squares from one R wave to thenext R wave and divide that number into 1500
Heart Rate (bpm) = 1500/#small squares
Method #2 locate an R wave on a bold line and identify the next R wave:
HR = 72 bpm HR = 37 bpm
In this exercise you will evaluate a baseline ECG, and then identify and discuss changes in the ECG after a period of exercise and after a period of breath holding
Objective 2 Blood Vessel Histology
Arteries and Veins have three tunics, or tissue layers:
Tunica intima (interna)Inner layer of endothelium and subendothelial areolar CT
Tunica media smooth muscle and elastic tissue
Tunica adventitia (externa)Dense irregular connective tissue
Comparison of arteries and veins:
Small artery: thick tunica media, thin Small vein: thin tunica media tunica externa thick tunica
externa
maintains its shape collapsible
Objective 3 Some Human Arteries:
Major Veins of the Body