The Role of Energy in the Body and the Physiology of Three Named Body Systems in Relation to Energy Metabolism.

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Gemma Garbutt.        P4/M1

The Role of Energy in the Body and the Physiology of Three Named Body Systems in Relation to Energy Metabolism.

I am going to describe the role of energy in the body and the physiology of three named body systems in relation to energy metabolism.  Also I am going to explain the physiology of three named body systems in relation to energy metabolism.  

Energy Metabolism.

Metabolism is the sum of all the chemical reactions occurring in human physiology and these will involve using or releasing energy from chemical substances.

Roles of Energy in the Body.

Energy is necessary for muscular activity and movement as you probably already know, however, energy is also necessary:

  • to circulate blood, lymph and tissue fluid throughout the body;
  • for breathing and taking in oxygen;
  • for making new cells for carrying out growth and repair;


  • it is used to transmit nerve impulses so that we can respond to changes in the environment and;
  • it is needed to build different complex molecules such as enzymes and hormones from the simple molecules produced after diagnosis of food.

Energy Supply to the Cells.

The activities involved in energy supply include the roles of the:

  • Cardiovascular;
  • Respiratory, and;
  • Digestive systems.

Further through I will be talking about the above in more detail but first, here is an overall view.

The digestive system is responsible for taking in food and water and, using enzymes, breaking up complex molecules into the simple soluble materials capable of passing into the adjacent capillaries of the cardiovascular system.  The cardiovascular system transports these simple materials to the liver and body cells via the bloodstream, driven by the pumping action of the heart.  At the same time, the respiratory system constantly refreshes lung oxygen and disposes of waste products such as carbon dioxide and water through the process of breathing.  Dissolved oxygen passes through the thin alveolar walls into the bloodstream and Is transported to cells.  Body cells thus have a constant delivery of raw materials such as glucose and other nutrients and dissolved oxygen so that the breakdown (catabolic) process of glucose oxidation can take place and release energy to do work.  This takes place initially in the cytoplasm and is completed in the mitochondria.

Cardiovascular System.

The heart is a muscular pump which forces blood around the body through a system of blood vessels, namely arteries, veins and capillaries.  Blood carries dissolved oxygen to the body cells and at the same time removes the waste products of respiration, carbon dioxide and water.  However, blood is also important in distributing heat around the body, along with hormones, nutrients, salts, enzymes and urea.

The Structure of the Heart.

The adult heart is the size of a closed fist located in the thoracic cavity between the lungs and protected by the rib cage.  It is surrounded by a tough membrane, the pericardium, which contains a thin film of fluid to prevent friction.

The heart is a double pump, each side consisting of an upper chamber (the atrium) and a lower chamber (the ventricle).  The right side the heart pumps deoxygenated blood from the veins to the lungs for oxygenation.  The left side pumps oxygenated blood from the lungs to the body and the two sides are completely separated by a septum.  The blood passes twice through the heart in any one circle and this is often termed a double circulation.  

Below is a schematic diagram showing the circulation of the blood.

Each of the four heart chambers has a major blood vessel entering or leaving it.  Veins enter the atria and arteries leave the ventricles.  

Below is a picture that is showing the front view of the chest and the location of the heart.


The circulation to and from the lungs is known as the pulmonary circulation and that around the body is the systemic circulation.  

Arteries are blood vessels that leave the heart while veins take blood towards the heart.

In the pulmonary circulation, the pulmonary artery carrying deoxygenated blood leaves the right ventricle to go to the lungs – you will realise that it must divide fairly soon after leaving the heart because there are two lungs to be supplied – hence the right and left pulmonary arteries.  The pulmonary veins (there are four of them), now carrying oxygenated blood, must enter the left atrium.

The main artery to the body leaving the left ventricle to the aorta and the main vein bringing blood back to the heart from the body enters the right atrium and is the vena cava.  The vena cava has two branches, the superior vena cava returning blood from the rest of the body.  In many diagrams of the heart these are treated as one vessel.

It is important that the blood flows in only one direction through the heart so it is supplied with special valves to ensure that this happens.  There are two sets of valves between the atria and the ventricles, one on each side.  Sometimes these are called the right and left atrio-ventricular valves but the older names are also used – the bicuspid, or mitral (left side), and tricuspid (right side) valves.  These names refer to the number of ‘flaps’ known as cusps that make up the valve, the bicuspid having two cusps and the tricuspid having three cusps.  Each cusp is fairly thin so, to prevent them turning inside out with the force of the blood flowing by, they have tendinous cords attached to their free ends and these are tethered to the heart muscles of the ventricles by small papillary muscles.  The papillary muscles tense just before the full force of the muscle in the ventricles contracts so the tendinous cords act like guy ropes holding the valves in place.

The two large arteries, the pulmonary and the aorta, also have exists guarded by valves called semi-lunar valves (so-called because the three cusps forming each valve are half-moon shaped); when the blood has been forced into the arteries by the ventricular muscle contractions, the blood must not be allowed to fall back into the ventricles when they relax.  The valves mare also called the pulmonary and aortic valves.  

Below is a diagram of a section through the heart.

The Cardiac Cycle.

The cardiac cycle comprises the events taking place in the heart during one heart beat.  Taking the average number of beats in a minute or 60 seconds at rest to be 70, then the time for one beat or one cardiac cycle is 60 divided by 70 seconds, which works out at 0.8 seconds.  You must remember that this is based on an average resting heart rate.  When the heart rate rises to say 120 beats during moderate activity, the cardiac cycle will reduce to 0.5 seconds.  As we can see, the higher the heart rate, the shorter the cardiac cycle. Until a limit is reached when the heart would not have time to fill between successful cycles.

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Below is a diagram of the timing of events in the cardiac cycle.

                               1 cycle



        1 square equals 0.1 second

Atrial Systole = 0.1 second                          Systole  

Atrial Diastole = 0.7 seconds

Ventricular Systole = 0.3 seconds              Diastole

Ventricular Diastole = 0.5 seconds                          


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