It receives the oxygenated, nutrient rich blood that it needs from the coronary arteries which branch off the aorta. The deoxygenated blood is then returned to the right atrium through the cardiac veins. The ventricles of the heart have thicker muscular walls than the atria. This is because blood is pumped out of the heart at greater pressure from these chambers compared to the atria. The left ventricle also has a thicker muscular wall than the right ventricle, as seen in the adjacent image.
This is due to the higher forces needed to pump blood through the systemic circuit around the body compared to the pulmonary circuit. There are four valves within the heart which serve to prevent backflow of blood as it passes through the various chambers of the heart and out through the associated arteries. The tricuspid valve is positioned between the right atrium and ventricle, and the mitral valve sits between the left atrium and ventricle, as seen in the adjacent image. As blood is pumped out of the ventricles through the aorta and the pulmonary arteries, these valves close to ensure the blood does not get pumped back into the respective atria it came from.
The pulmonary valve sits between the right ventricle and the pulmonary artery. Its role is to prevent the backflow of blood into the right ventricle after it contracts.
The aortic valve sits between the left ventricle and the aorta and prevents backflow of blood into the left ventricle after it contracts. These phases can be seen in the following image. The heart beat is controlled by the sympathetic and parasympathetic branches of the autonomic nervous system. The sympathetic system stimulates the heart to beat faster while the parasympathetic system returns the heart rate to its normal resting level.
Electrical impulses action potentials from both systems are sent to the sino-atrial SA node. This is shown on the below image. The AV node then further distributes the impulse from the SA node to both ventricles which contract a fraction of a second after the contraction of the atria.
The rate at which the SA node sends out impulses determines the rate at which the heart beats. As well as receiving impulses from the autonomic nervous system, the rate at which the SA node sends impulses can also be influenced by hormones such as adrenaline.
When released into the system adrenaline stimulates the SA node to send impulses at a faster rate, thus increasing the rate at which the heart beats. Make writing personal training programs easy with these custom designed exercise templates, and keep your clients focused and progressing. Pain-free clients are happy clients. More Human body Questions Q1. Hapatitis-B is also called. Which of the following is a female sex hormone?
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