How Does a Healthy Heart Work?
By John T. Russo
The Heart’s Circulatory SystemThe heart is a fist-sized organ that weighs approximately one pound. It is a pump that circulates blood through the body. In fact, the heart pumps about 5 quarts of blood every minute or 1,800 gallons of blood every day.Arteries are the blood vessels that carry blood enriched with oxygen and nutrients to all parts of the body. Veins are the blood vessels that carry blood depleted of oxygen and nutrients back to the heart and lungs. Blood brings oxygen and nutrients to the organs and tissues as well as waste from the body’s cells. Waste products are removed as they filter through the kidneys, liver and lungs.
The Heart’s Primary Function: Pumping BloodBlood is pumped through the four chambers of the heart. The upper chambers are the right and left atria. The lower chambers are the right and left ventricles. Four valves control the one-way flow of blood through the heart. Changes in pressure occur as the heart contracts; the valves open and close and cause blood to flow. Blood is pumped through the heart when electrical impulses cause the four chambers of the heart to contract. Each chamber of the heart contracts when an electrical impulse moves across it. The signal begins in the right atrium in the sinus node, which acts as the heart’s natural pacemaker. Pumping blood through the lungs removes carbon dioxide and refreshes the blood with oxygen. The oxygenated blood is pumped to the body to provide oxygen and nutrients, and to remove waste products. A healthy heart beats steadily and rhythmically at a rate of about 60 to 100 beats per minute when at rest (normal sinus rhythm). During strenuous exercise, the heart can increase the amount of blood it pumps up to four times the amount it pumps when at rest, within a matter of seconds.
The Heart’s Electrical System
- Signals the heart to beat.
- Regulates the heart rate (beats per minute).
- Has special pathways (conduction pathways) that carry the electrical signals throughout the heart chambers for each heartbeat.
When heart cells in the atria (upper heart chambers) receive an electrical signal, they are shocked and contract (pump) and then relax. The blood from the atria is pumped into the relaxed ventricles (lower heart chambers) and as the ventricles contract, pump blood to the body.
The Flow of Electricity within the HeartIn a healthy heart, each heartbeat begins in the sinus node (the heart's natural pacemaker), which is located in the right atrium. The electrical signal from the sinus node (sinoatrial or SA node) starts an electrical chain reaction that moves across both atria, much like ripples on the calm surface of a lake. This effect causes the atria to contract and pump blood into the ventricles. There is an ongoing electrical chain reaction from the atria through an area between the atria and ventricles called the atrioventricular node (AV node or AV junction). The AV node acts as an electrical gateway to the ventricles. The conduction pathways deliver the signals to the ventricles and the ventricles pump blood to the body.
©2009 cardio calls All rights reserved
|
|
|
|
