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The circulatory system is called the cardiovascular system. It contains around 5 litres

or 8 pints of blood, which our heart is continuously recirculating. Each day our heart

beats around 100,000 times and pumps about 23,000 litres (5,000 gallons) of blood. It

is the size of a clenched fist and weighs approximately 10.5 ounces and it contracts

and releases around 70 times a minute. www.bhf.org.uk/

For your heart to beat regularly it needs an electrical supply this provided by a specialgroup of heart cells called the sinus node which is known as your hearts natural pace

maker. www.bhf.org.uk/The circulatory system consists of two circuits that blood travels through, the

pulmonary and the systemic. Exercise effects these systems, when we exercise it

causes the heart to pump faster around the body so that we can exercise for longer

periods.

The heart is made up of four chambers the atria, which are the two upper chambers of

the heart and the ventricles the lower two chambers of the heart.

The heart wall consists of the epicardium which makes up the outer layer of the wall

of the heart. The myocardium makes up the middle layer of the wall of the heart and

the endocardium which makes up the inner layer of the heart.

Oxygenated blood travels into the heart via the pulmonary artery and enters the left

atrium which is one of four chambers in the heart .

There are two stages of the cardiac cycle, the diastole phase and the systole phase.

During the diastole phase the muscles of the atria and the ventricles are relaxed.

Blood then flows into the right and left atria, the valves located between the atria and

the ventricles open allowing the blood to flow through to the ventricles

Atrioventricular valves open

The sinoatrial node which starts cardiac conductionopens causing atrial contraction

The atria empty blood into the ventricles

Semilunar valves close preventing flow back

During systole phase the ventricles contract pumping blood into the arteries. The right

ventricle sends blood to the lungs through the pulmonary artery. The left ventricle

pumps blood to the aorta.

The ventricles contract

Atroventricular valves close and semilunar valves open

Blood flows to either pulmonary artery or the aorta

The sound that we can hear and know as the heart beat is the sound of the closing of

the heart valves.

The main function of the heart is to pump blood around the body. Your heart never

rests, it starts to beat before we are born and continues to beat throughout our lives.

The function of the blood is to provide a fluid environment for cells. It is also wheremany materials are carried to and from the cells. Blood also has a number of functions


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such as regulation, distribution and protection. Blood can help the bodys temperature

by absorbing and distributing heat, transport nutrients from the intestines to the liver

and also the body cells, waste products are also taken from tissues to the kidneys.

(Adams, Barker, Gledhill, Lydon, Mulligan, Phillippo, Sutton (2010).)Oxygenated blood from the lungs travels through large vessels called the pulmonary

veins and enters the left side of the heart emptying blood directly into the left atrium.The pulmonary vein is unusual in that it carries oxygenated blood all other veins carry

deoxygenated blood.

Blood flows from the left atrium through a one-way valve called the bicuspid valve

into the left ventricle. Most of this flow occurs when the heart is relaxed, the atrium

then contracts filling the ventricle with blood.

The ventricle then contracts forcing the blood to exit through the large artery called

the aorta, the artrioventricular valve closes and prevents the back flow of blood back

to the atrium. ( Parker 1996)

The aorta is closed off from the left ventricle by a one-way valve, the aorti7yc semi

lunar valve, it allows the flow of blood out from the ventricle but then it snaps shut to

prevent back flow of blood.The heart is connected to an intricate network of blood vessels, these hollow tubes

transport blood throughout the whole of our body, the major ones relating to the heart

are the:

Arteries

the aorta is the largest artery in the body and most ofthe major arteries branch of from it

brachiocephalic artery carries oxygenated blood to thehead and neck from the aorta

carotid arteries supply oxygenated blood to the headand neck

common iliac arteries carry oxygenated blood from theabdominal aorta to the legs and feet

coronary aorta carries oxygenated and nutrient filledblood to the heart muscle

pulmonary artery carries de-oxygenated blood from theright ventricle to the lungs

subclavian arteries carry oxygenated blood to the arms

Veins

brachiocephalic veins join to form the superior venacava

common iliac veins join to form the inferior vena cava

pulmonary veins transport oxygenated blood from thelungs to the heart

venae cavae transport de-oxygenated blood around thebody from the heart


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Blood passes from the right atrium into the right ventricle through a one-way valve

called the tricuspid valve.

Blood then passes out of the contracting right ventricle through a second valve called

the pulmonary semi lunar valve into a single pulmonary artery, which branches off

into the arteries that carry deoxygenated blood to the lungs. The blood then returnsfrom the lungs to the left side of the heart replenished with oxygen.

The pumping of the heart is a repeated cardiac cycle of relaxation and contraction of

the atria and the ventricles. ( Parker 1996)

When the body undertakes exercise the cardiovascular system will experience

changes in the way it functions these include thermoregulation, vasodilation and

vasoconstriction.

Thermoregulation occurs when the body requires an increase of energy being used

during exercise. Adjustments in the blood flow are made and as a result thecardiovascular system is affected due to it being the distribution and redistribution of

heat within the human body.

(Adams, Barker, Gledhill, Lydon, Mulligan, Phillippo, Sutton (2010)).

Vasodilation occurs during exercise the vascular portion of active muscles willincrease when the arterioles dilate. As a result an increase of the diameter ofblood vessels will occur to decrease the amount of resistance to the flow ofthe blood in the specific area supplied via the vessels(Adams, Barker, Gledhill, Lydon, Mulligan, Phillippo, Sutton (2010)).

Vasoconstriction is a function that can temporarily shut down the blood flow tothe body tissues. This function decreases the diameter of the blood vesselsand the resistance of the blood vessel is increased.(Adams, Barker, Gledhill, Lydon, Mulligan, Phillippo, Sutton (2010)).The heart valves are flap like structures that allow blood to flow in one direction only,

the heart has four main valves, they are the:

Aortic valve which prevents the back flow of blood as itis pumped from the left ventricle to the aorta

Mitral valve which stops the flow of blood back from theleft atrium to the left ventricle

Pulmonary valve which stops the flow of blood back as itis pumped from the right ventricle to the pulmonaryartery

Tricuspid valve which prevents the back flow of blood asit is pumped from the right atrium to the right ventricle


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