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Blood and the Circulation - Blood pressure and carbon dioxides effect on the heart.

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Blood and the Circulation Blood pressure and carbon dioxides effect on the heart The heart responds to both changes in blood pressure and changes in carbon dioxide levels in the blood. The pumping of the heart, combines with the narrowness of the smaller blood vessels, produces considerable pressure in the arteries. This is what we mean by blood pressure. It is important that our blood pressure should be reasonably high because it keeps the blood on the move. The heart rate responds to changes in blood pressure and the blood pressure goes up and down as the heart beats. It is highest when the heart contracts, systolic pressure, and lowest when the heart relaxes, diastolic pressure. This happens as there are pressure receptors in the walls of some of the main arteries. If the blood pressure rises then these receptors send impulses to the medulla. The medulla then sends impulses to the heart to decrease the heart rate and bring the blood pressure back to normal. If blood pressure falls below normal, impulses are sent to the heart from the medulla to increase the heart rate and blood pressure. The blood pressure is also affected by sodium chloride intake, as high intake of salt (sodium chloride) ...read more.


If blood pressure in the arteries is high, the stretch receptors are stimulated, and impulses are sent along the vagus nerve, which slows the rate of heart beat. On the other hand, if blood pressure is low, impulses are sent along the accelerator nerve speeding the rate of heart beat. The main hormone that helps to change the heart rate is adrenaline. Adrenaline is secreted from the adrenal glands in times of stress or need for action, and is carried in the blood to all areas of the body. It stimulates the heart to increase, and so increasing the heart rate. Importance of maintaining a constant blood pressure It is vital for the blood pressure to be as constant as possible. If a person's blood pressure is too high, they may suffer from hypertension, which is a condition commonly associated with narrowing of the arteries. This causes blood to be pumped with excessive force against the artery walls, pushing them out, often bursting them. The risk of this happening is greatest in old people whose arteries have become fragile. It is a sign that the heart and blood vessels are being overworked. Untreated, hypertension will cause the heart to eventually overwork itself to the point where serious damage can occur. ...read more.


It is an automatic reflex and so you are not aware of it. The heart beating faster means that more blood is sent to the muscles. The arteries serving the muscles widen, and those serving less needful organs get narrower. The result is extra blood is sent to the muscles. This would mean that whilst doing exercise, the blood pressure would increase, as the heart works harder to supply the muscles with more blood and so the pressure on the artery walls is larger. Therefore the blood pressure would rise and also the pulse rate. The blood carries the glucose and sugar which the muscles need to carry out their work and this is why more blood is needed to be pumped there. Immediately after exercise, the pulse will still be higher than normal, because the muscle may have used more energy than the blood could supply in the form of oxygen and glucose. The muscle will have to repay this "oxygen debt" by taking in more blood than normal for a time. A short while after exercise, the pulse rate would be closer to the resting pulse rate than immediately after exercise, as the muscles will have had some time to recover. The time it takes to regain the resting pulse rate after exercise is a useful way of telling a person's fitness. ...read more.

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