1. HEART BEATS, BLOOD PRESSURE, HEART RATE SB1 3C: DECEMBER 2012

2. ELECTRICITY AND THE HEART: WHY DO YOU SHOCK A PERSON TO GET THEIR HEART BEATING AGAIN?  The heart generates its own electrical impulse  The cardiac electrical signal controls:  the number of electrical impulses (heart rate)  It triggers the heart muscle to contract in the correct sequence as it spreads across the heart

3. MEASURING HEART BEATS:  Electrical activity of the heart is measured using an electrocardiograph:  Instrument that detects electrical activity of the heart  Electrocardiograph produces electrocardiogram (ECG or EKG)  Graphical record of heart rate and rhythm

4. AED  AED (automated external defibrillator)  Machine that delivers electric shock to the heart to restart the heart  Used when:  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%

5. HEART RATE:  Number of heart beats per unit time  Expressed as beats per minute (bpm)  Changes during rest, activity, exercise  Detected by taking pulse:  Radial artery (wrist)  Carotid artery (neck)  What is your pulse?  Average healthy adult – 60-80bpm at rest  Lance Armstrong – 32bpm at rest

6. HEART SOUNDS:  Lubb-dubb heart sounds are caused by closing of heart valves http://www.youtube.com/watch?v=qYBtchCqPao http://www.youtube.com/watch?v=qYBtchCqPao  Valves of the heart close when heart contracts to prevent blood from flowing back into the ventricles  Steps: 1. Atria relax, fill with blood – diastole 2. Atria pushes blood into ventricle 3. 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

7. BLOOD PRESSURE:  The force of the blood on the walls of the arteries  Measured using a sphygmomanmeter  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

8. BLOOD PRESSURE:  Normal systolic blood pressure for young people:  120mm Hg  Normal diastolic BP for young people:  80mm Hg  Therefore, BP would be recorded as:  120/80 or 120 over 80  Now you try:  Lab: measuring heart rate and blood pressure