2. Medicinal Applications of the Circulatory System

3. Observing the Heartbeat Since the heartbeat is electrically stimulated, it can be observed by measuring the strength and length of its electrical signals Use an electrocardiograph that records them as an electrocardiogram referred to an ECG (sometimes EKG) Person is hooked up to several electrodes that measure variations in voltage.

4. Regulation of Heart Rhythm Heartbeat initiated in the sinoatrial node, which is a mass of nerve and muscle cells. There is another node called the atrioventricular node (AV) that have special conducting fibres called the Purkinje Fibres that run down the septum and throughout the muscle cells of the ventricles.

5. Analyzing the Heartbeat Heartbeat starts with an electrical stimulus from the SA node Spreads and causes the contraction of the atria, creating the P wave Travels to the AV node (with brief delay in transmission) QRS complex follows when the electical stimulus travels down the Purkinje fibres Slight delay as ventricles recover (T wave)

6. Arteriosclerosis Hardening of the arteries One way arteries harden is due to plaque (fatty deposits on walls of arteries). Can occur in any artery in the body, but when it occurs in the heart arteries, it is called coronary artery disease (second leading cause of death in Canada)

7. Risk factors are high blood pressure, high cholesterol, diabetes, overweight, smoking, physical inactivity, gender, genetics, age. Symptoms of CAD is angina (pain in chest area, pain in left shoulder, tightness in chest) that can be treated with nitroglycerin drug. A consequence of CAD is a heart attack or myocardial infarction which is when there is a death to the cardiac muscle due to oxygen deprivation.

8. Sometimes a heart attack can interfere with the rhythm of the heart, and the heart stops beating, this is called cardiac arrest. Treatments are: –Lifestyle changes (regular exercise, healthier diet, quit smoking) –Angioplasty (opening up a blocked artery by inflating a balloon or inserting an expandable mesh tube called a stent –Bypass surgery (surgery that reroutes blood around clogged artery)