Humans and other many animals rely on blood flowing through their bodies to keep them alive. The blood travels through a system that consists of the heart and many of blood vessels. This system is called the cardiovascular system. This essay will explore the role and control of the cardiovascular system, and will highlight the cardiac cycle and cardiac output method which calculates the volume of blood pumped by each ventricle per minute.

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The main functions of the cardiovascular system: (CVS) is that it ensures all the organs and cells are supplied with nutrients and that waste products are removed. It also picks up carbon dioxide and other waste products that the body produces so that they can eventually be disposed of. The CVS works together with the other systems in the body such as the urinary system and the role of kidneys in the body to create an internal homeostasis. By transporting and distribution the blood throughout the body a healthy homeostasis is achieved.
For thousands of years, people have been star struck by the cardiovascular system. This was due to the fact that for humans and other animals, life is associated with a beating heart. During the ancient times, people had general understanding about the cardiovascular system. Yet it was not until the 17th century that William Harvey showed that the cardiovascular system was more than just a beating heart. He found that it formed a closed loop in which blood is pumped by the heart. The purpose of the cardiovascular system was then later discovered to ensure that all organs and cells are supplied with nutrients and that carbon dioxide and other waste products are removed from the body.
Also this then lead to the discovery of three important components of the cardiovascular system;
Heart
Blood vessels
Blood
The heart is a hollow, muscular organ about the size of a fist. Its purpose is to pump blood through a network of blood vessels. These vessels form a loop, which starts at the heart, goes out through your body, and then ends back at the heart again.
The cardiovascular system, also known as the circulatory system, consists of your heart, blood and blood vessels. The cardiac cycle is the series of events that occurs every time the heart beats. There are two phases of the cardiac cycle.
The diastole phase
The systole phase
In a healthy heart, the atria contract simultaneously. Then, they start to relax, contraction of the ventricles begins. The diastole phase are relaxed, this then allows the heart to fill up with blood. In the systole phase, the ventricles contract and pump blood along to the arteries. One cardiac cycle is finished when the heart fills with blood and the blood is then pumped to the heart. The cardiac cycle is basically the blood that enters the heart, is pumped to the lungs, and then travels back to the heart and is pumped out to the rest of the body. The term cardiac cycle refers to the proceedings of one entire heartbeat, during which both atria and ventricles contract and then relax.
(Cardiac cycle (2011). Regina Bailey).
http://bp0.blogger.com/_bq1X-Rc5e5E/R9J4z6YJEeI/AAAAAAAAAUE/VfFwIWnHle0/s320/HD002+cardiac+cycle+2007r1.gif
(Figure 1 taken from: Image of cardiac events occurring in the cardiac cycle. http://www.google.co.uk/imgres?imgurl=http://bp0.blogger.com).
This shows Cardiac events occurring in the cardiac cycle. Two complete cycles are illustrated.
Cardiac output is the volume of blood pumped by the heart per minute (ml blood/minute). Cardiac output is a function of heart rate and stroke volume. The heat rate is simply the number of heart beats per minute times the stroke volume of blood. This, in a simpler form is:
Cardiac output = heart rate X stroke volume = ml/minute
An average person has a resting heart rate of 75 beats per minute and a resting stroke volume of 70 mls per beat. Therefore the cardiac output for an average person at rest is:
Cardiac Output = CO
Heart Rate = HR
Stroke Volume = SV
CO = HR (75 beats/min) X SV (70 ml/beat) = 5250 (ml/beat)
(Cardiac output (2009). Cardiac sensor system.)
The standard adult blood volume is about 5000ml, the complete blood supply passes through the body just the once each minute. Cardiac output varies with the strain of the body. It rises when the stroke volume is increased or the heart beats quicker or both; it drops when either or both of these factors decrease.
(Essentials of human anatomy & physiology. Seventh edition. Elaine N. Marieb. (2003)).
The cardiac output method plays a very important factor in the determination of the effectiveness of the heart to deliver blood to the rest of the body. It can show indication of heart failure and an inadequate circulation.
The main components of the cardiovascular system are the heart, blood vessels, and blood. When a problem arises within the system, it is known as a cardiovascular disease. In practice these can be treated by cardiologists, vascular surgeons and interventional radiologists, it all depends on the organ system that needs treated. Most countries face high and increasing rate of cardiovascular disease. Every year the death rate of heart disease rises. In recent years, cardiovascular risk in woman has been increasing and has now killed more women than breast cancer. Vascular illness starts from adolescence, making it necessary for childhood prevention to be focused on. By the time that heart problems are detected, the underlying cause is usually quite advanced, therefore healthy eating, exercise and avoidance of smoking is emphasised so much these days to help the prevention of many diseases, but one main one being cardiovascular disease.
Blood pressure is the pressure the blood exerts against the inner walls of the blood vessels, it is forced to keep blood circulating continuously even between heartbeats.
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(Figure 2 taken from: Image of measuring a blood pressure.
http://www.google.co.uk/imgres?imgurl=http://bp0.blogger.com)
The importance of the elasticity of the arteries is best appreciated when it is lost, as happens in arteriosclerosis, which is a thickening of the vessel walls and accumulation of calcium with consequent loss of elasticity and lessened blood flow. Measuring a blood pressure is important the higher your blood pressure is, the high the risk you may have in the future.
If your blood pressure is high, it puts an extra strain on your arteries and on your heart. Eventually this strain could cause the arteries to become thicker and less flexible, it could also lead your arteries becoming weaker. If your arteries become less flexible of thicker, then they will become more narrow making them easier to be clogged up, and if an artery becomes fully clogged up (formally known as a blood clot) then this can lead to a heart attack, stroke dementia or even a kidney disease. Less likely, if an artery has become weaker, the extra strain may sooner or later lead to the artery bursting. This could also cause a heart attack or stroke. However there are many ways to lower your blood pressure and put less strain on your arteries and heart such as:
Are you over weight? Lose weight!
Eat les salt and sodium
Drink less alcohol
Increase physical activity
Do you smoke? Stop smoking!
Try relaxing techniques
(Blood pressure association (2008). The facts about blood pressure).
There for in conclusion this essay has examined the function of the cardiovascular system, its impotency to the human homeostasis, the three components to the cardiovascular system, the cardiac system, the cardiac output and blood pressure. These topics covered, are the main operations and control of the cardiovascular system. I personally found the cardiac output an interesting and enjoyable topic to examine. It fascinates me how a simple calculation can lead to such findings that allow one individual to be aware of their cardiac output, allowing them to assess their likeliness of developing diseases related to the cardiovascular system, and allowing them to take action to prevent any cardiovascular disease. Overall, in conclusion it is made clear that the cardiovascular system is of key importance, and its contribution to the human and animal body should not be underestimated.