How does a dog's heart beat? - briefly
A dog's heart beats at a rate that can vary depending on its age and size. On average, a healthy adult dog's heart beats between 60 to 100 times per minute.
How does a dog's heart beat? - in detail
A dog's heart, like that of many other mammals, functions as a vital pump responsible for circulating blood throughout the body. The canine heart is divided into four chambers: two atria (upper chambers) and two ventricles (lower chambers). The right side of the heart deals with deoxygenated blood, while the left side handles oxygenated blood.
The heartbeat in dogs begins with a signal from the sinoatrial node (SA node), often referred to as the heart's natural pacemaker. This node is located in the right atrium and initiates an electrical impulse that spreads across both atria, causing them to contract simultaneously. This coordinated contraction forces blood into the ventricles through the atrioventricular valves (tricuspid on the right side and mitral on the left).
Once the ventricles are filled with blood, another electrical signal, this time from the atrioventricular node (AV node), prompts the ventricles to contract. The AV node is situated near the interatrial septum and acts as a relay point, slightly delaying the impulse to ensure proper filling of the ventricles before they pump blood out of the heart. The contraction of the ventricles propels blood through the aortic valve (on the left side) and pulmonary valve (on the right side) into the systemic circulation.
The average resting heart rate for dogs ranges between 60 to 120 beats per minute, depending on factors such as age, breed, and overall health condition. Larger dog breeds tend to have slower heart rates compared to smaller ones. For instance, a Great Dane might have a normal resting heart rate of around 60-80 beats per minute, while a Chihuahua could have a heart rate closer to 120-140 beats per minute.
In addition to the regular heartbeat, dogs also possess a unique physiological response known as the "Bainbridge reflex." This reflex occurs when the heart's atria stretch due to an increase in blood volume, triggering an acceleration of the heart rate. Conversely, if the atria are not adequately filled with blood, the heart rate can slow down.
Overall, the intricate process of a dog's heartbeat is regulated by a complex interplay of electrical signals and mechanical contractions, ensuring efficient circulation of oxygenated and deoxygenated blood throughout the body.