Transcript heart beats, blood pressure, heart rate

HEART BEATS, BLOOD PRESSURE,
HEART RATE
SB1 3C: DECEMBER 2012
ELECTRICITY AND THE HEART:
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WHY DO YOU SHOCK A PERSON TO GET THEIR
HEART BEATING AGAIN?
The heart generates its own electrical impulse
The cardiac electrical signal controls:
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the number of electrical impulses (heart rate)
It triggers the heart muscle to contract in the correct
sequence as it spreads across the heart
MEASURING HEART BEATS:
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Electrical activity of the heart is measured using an
electrocardiograph:
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Instrument that detects electrical activity of the heart
Electrocardiograph produces electrocardiogram (ECG or
EKG)
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Graphical record of heart rate and rhythm
AED
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AED (automated external defibrillator)
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Machine that delivers electric shock to the heart to restart the
heart
Used when:
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heart contractions are not coordinated and muscles are quivering
not contracting (ventricular fibrillation)
Heart rate is abnormal (cardiac arrhythmia)
Heart rate is too fast (ventricular tachycardia)
Improves survival rates by up to 30% if delivered in the first
few minutes.
With each passing minute, the probability of survival declines
by 7 to 10%
HEART RATE:
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Number of heart beats per unit time
Expressed as beats per minute (bpm)
Changes during rest, activity, exercise
Detected by taking pulse:
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Radial artery (wrist)
Carotid artery (neck)
What is your pulse?
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Average healthy adult – 60-80bpm at rest
Lance Armstrong – 32bpm at rest
HEART SOUNDS:
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Lubb-dubb heart sounds are caused by closing of heart
valves
Valves of the heart close when heart contracts to prevent
blood from flowing back into the ventricles
Steps:
http://www.youtube.com/watch?v=qYBtchCqPao
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Atria relax, fill with blood – diastole
Atria pushes blood into ventricle
Ventricles contract, pushing blood into arteries – systole
Increased pressure during systole causes AV valves to
close – lubb sound
Ventricles relax, pressure decreases, causes Semilunar
valves to close – dubb sound
BLOOD PRESSURE:
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The force of the blood on the walls of the arteries
Measured using a sphygmomanmeter
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Cuff with air pocket is wrapped around arm
Air pocket is inflated
Cuts off blood flow to the arteries in the arm
Stethoscope listens to blood entering the arm as the air is
gradually released
The pressure that you first hear the sound at is called the
systolic blood pressure
The cuff is deflated until you can’t hear the sound
anymore, at this pressure it is diastolic pressure
BLOOD PRESSURE:
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Normal systolic blood pressure for young people:
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Normal diastolic BP for young people:
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80mm Hg
Therefore, BP would be recorded as:
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120mm Hg
120/80 or 120 over 80
Now you try:
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Lab: measuring heart rate and blood pressure