1. Regulation of the Heartbeat  Pacemaker  A specific region of your heart muscle  sets the rate at which your heart contracts.

2. The pacemaker located in the wall of the right atrium. (SA Node) generates electrical impulses that spread rapidly over the walls of both atria, making them contract. impulses spread to a region of the heart called the AV node (atrioventricular node).

3. From there, the electrical impulses spread to the ventricles, causing them to contract. The contracting ventricles propel blood to the rest of the body.

4. Pacemaker ensures that the heart beats in a rhythmic cycle. The relaxation phase, called diastole, the atria and ventricles are relaxed, allowing blood from veins to enter the heart. The contraction phase is called systole.

5. The pacemaker is controlled by the nervous system and the endocrine system. two sets of opposing nerves by speeding it up and by slowing it down. Hormones secreted into the blood.

6. EX: The hormone epinephrine, also called adrenaline, increases heart rate when the body is under stress

7. Measuring Blood Pressure  When the ventricles contract, they increase pressure on the blood.  The resulting force that blood exerts against the artery walls is called blood pressure.  This force drives blood through the arteries and into the capillaries.  Artery walls are elastic, which enables them to stretch in response to this force.

8. Blood pressure represented by two numbers separated by a slash, such as 120/80. measured in millimeters of mercury (mm Hg), a standard unit of liquid pressure. The first number is referred to as systolic pressure, the highest recorded pressure in an artery when the ventricles contract (systole). Diastolic pressure, the second number, is the lowest recorded pressure in an artery during the relaxation phase of the heartbeat (diastole).

9. A blood pressure of about 120/80 is the average for a healthy young adult. As a person ages, blood pressure may increase. Smoking or a fatty diet can contribute to this increase by causing arteries to become less elastic. A blood pressure above 140/90 is considered high and may lead to other cardiovascular diseases.