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Heart Essay

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Submitted By harrypink
Words 1980
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Heart Essay
When a performer starts to exercise, they inevitably increase rate of respiration, meaning they require more glucose and oxygen (if aerobic) and need to primarily remove more carbon dioxide as well as lactic acid (if anaerobic).
The first way this is done is by secretion of the hormone adrenaline into the bloodstream. Adrenaline in blood is picked up by chemoreceptors in the aortic arch, impulses are then sent to cardiac control centre (in the medulla oblongata) via sympathic nerve which increases heart rate. Adrenaline (epinephrine) facilitates greater cardiac output, meaning a greater volume of blood pumped into the systemic circuit, carrying more oxyhaemoglobin. Adrenal gland also secrets norepinephrine (a different hormone), which causes the blood vessels to constrict (narrowing of lumens) the increases blood pressure.
When the cardiac control centre in the medulla oblongata receives nerve impulses it sends a nerve impulse to the SA (Sino-Atrial) Node, which sends the wave excitation across both atria causing atrial muscles to contract (atrial systole) forcing blood through bicuspid and tricuspid valves. The wave of excitation (electrical impulse) hits the AV (atrio-ventricular) Node. This sends the wave down the septum through the bundle of his and purkinje fibers, which then hits apex of the heart and spreads round ventricle muscular walls causing them contract. This is called ventricular systole, causing bottom to top contraction forcing blood into arteries (pulmonary artery & aorta) through aortic and pulmonary valves.
This wave of exciting regulates heart rate and controls the cardiac cycle; this is the flow of blood around the chambers of the heart. Deoxygenated blood returns to the right atria, it then flows through the tricuspid valves into the right ventricle. It leaves this chamber via the pulmonary valve (and starts the…...

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