in the Zone


An image taken with our Vein viewer

The beat goes on…

In the Zone takes you 'Under the Skin' to uncover the secrets of human circulation

Our team used the latest technology to take a closer look at the body’s transport system. Special infrared viewers highlighted the blood vessels filled with blood flowing back to the heart.

Red blood cells give blood its characteristic colour and are stuffed full of a protein called haemoglobin which carries oxygen molecules around your body. For our filming we use Vein viewers which shine infra-red light. The picture is produced because the skin, muscle and the haemoglobin in the arteries, which are carrying lots of oxygen, reflect this light, while the haemoglobin in the veins absorbs the Near Infra-red light.

The branching patterns of these vessels shows the veins joining together; eventually they will all connect before the blood enters the heart, ready to be pumped into the lungs for an oxygen top up.

The circulation system forms two loops with the heart at the centre. The right side of the heart takes in the blood coming from the body where most of the oxygen has been used and carrying the waste carbon dioxide. That blood is then pumped out to the lungs where the carbon dioxide is released and oxygen absorbed. The oxygen rich blood then enters back into the left hand side of the heart where it can be pumped out to the rest of the body.

It’s easy to forget about your heart because it gets on with its duties without you having to remind it. Sometimes though, you may have been aware of your heart beating. For instance, after exercise you can feel your heart racing. It has been working hard to pump blood along your arteries and veins as your working muscles demand more oxygen and create waste products for removal.

A heart beat is generated by small amounts of electricity flowing into the cells, causing them to squeeze. When they do this together the effect is for the heart to squeeze the blood like a pump. Our team took a closer look at a single heart beat.

The trace we record is a graph showing changes in the voltage across the heart over time. Peaks show the activity as firstly, the top chambers (the atria) contract, then the much larger chambers (the ventricles) at the bottom contract.

You may also have noticed your heart race watching a scary film, seeing your current crush or cheering on your favourite team. Here there is a chemical involved; adrenaline.

Adrenaline is a hormone released into the bloodstream in response to stress or excitement. Released from glands attached to your kidneys, it makes your heart beat faster, dilates your pupils and relaxes your airways - a set of effects called the ‘Fight or Flight’ response. It prepares you for physical action.

Big hearted athletes 

It’s not just bodybuilders who end up with big muscles.

When muscles are repeatedly exercised they adapt in response to the physical stresses. They get bigger and stronger and the heart is no different. 

As a general rule a normal adult’s heart is around the size of their fist and has a resting heart rate of around 70 beats per minute (bpm).

When athletes train, their heart is at the core of the adaptations in their body and can undergo remarkable changes. Continued training to build up an athlete’s stamina can result in ‘Athletic heart syndrome’.

The left hand side of their heart gets bigger so that each beat of the heart pumps more blood around their body. Their heart is more efficient and so doesn’t need to beat as often.

These changes are especially pronounced in endurance athletes like rowers or cyclists. At his peak Lance Armstrong reportedly had a resting heart rate of 32-34 bpm!