Cardiovascular System

What does the cardiovascular system do?

The cardiovascular system (CVS) moves vital nutrients, gases and hormones around the body. The CVS is made up of the heart, lungs and blood vessels, all working together.

  • The heart functions as a pump.
  • The blood vessels act as pipes, carrying blood through the body.
  • The lungs supply the blood with oxygen and remove its carbon dioxide.

A number of complex nerve and hormone systems keep the CVS in balance with the body’s changing needs for oxygen and nutrients.

The heart

The heart is a pear-shaped organ in the centre of the chest. It is divided into a right side and left side, and each side is made up of two chambers: the atrium (top) and the ventricle (bottom).

The movement of blood through the heart is controlled by the contraction of the heart muscle, and special valves inside the heart that open and close at the right moments.

The two sides of the heart work in partnership.

  • The right side of the heart receives de-oxygenated blood (blood that has been depleted of its oxygen) from the major veins of the body, and pumps this blood into the lungs.
  • The left side of the heart then receives this oxygenated blood (blood rich in oxygen) from the lungs, and pumps it into the body through the aorta.

The heart muscle needs its own blood supply to carry out its work, which it receives via the left and right coronary arteries.

How the heart beats

Each heartbeat starts with an electrical signal generated from the part of the heart called the pacemaker (the sinoatrial or SA node). This signal travels through nerves in the heart and stimulates the heart muscle to contract, which forces blood to move. The movement of blood through the arteries can be felt as a ‘pulse’ in the wrist and the neck.

A healthy person usually has a resting heart rate of between 60 and 100 beats per minute.

Problems with the cardiovascular system

There are several reasons why the CVS may not work properly.

  • The body may not have enough of a blood supply because of dehydration, bleeding or swelling.
  • The heart muscle may not have a good enough blood supply to do its work.
  • The lungs may not be working properly, or may not be getting a proper blood flow, which places a strain on the heart muscle.
  • There may be too many or too few electrolytes (essential chemicals such as potassium and magnesium), which can lead to an irregular heartbeat.
  • The blood vessel walls may be weakened.
  • The heart muscle may be too weak to work properly.


The information on this page is general in nature and cannot reflect individual patient variation. It reflects Australian intensive care practice, which may differ from that in other countries. It is intended as a supplement to the more specific information provided by the doctors and nurses caring for your loved one. ICNSW attests to the accuracy of the information contained here but takes no responsibility for how it may apply to an individual patient. Please refer to the full disclaimer.