• Question: how do people heart work?

    Asked by 478sprg52 to Andrew, Dan, Emilia, Helen, Katy, LauraAnne, Stephanie on 7 Nov 2016.
    • Photo: Helen Hanstock

      Helen Hanstock answered on 7 Nov 2016:

      Aha, the heart! A very important organ!

      The heart basically acts like a pump. Its a powerful muscle that pumps blood around our body so that it gets to all the tissues such as your muscles, skin, brain etc. These tissues need blood because it carries important nutrients such as oxygen and sugar, as well as messengers such as hormones that carry signals around the body. Our blood also helps to get rid of waste products and provides immune defence against harmful bacteria and viruses!

      The heart works by generating electrical signals in a rhythmic pattern to maintain a regular heart beat. These signals make sure that the heart keeps pumping blood around the body so that oxygen gets to all the tissues (which keeps us alive!). The part of the heart that controls the heart beat is called the pacemaker. If someone’s heart is beating too slowly (and therefore not pumping enough blood) or there is a problem generating these electrical signals then they might be given an artificial pacemaker to control their heart rate for them. But, most peoples’ hearts are very good adapting the rhythm and strength of the heart beat to pump exactly the right amount of blood to the tissues that we need at a given moment in time.

      At rest your heart rate might be about 60 beats per minute (1 time per second) – but this varies between people! When we start to exercise and our muscles need more oxygen then our heart rates can go as high as 200 beats per minute!

      Hope this answers your question! Perhaps some of the other scientists might have something more to add?

    • Photo: Dan Gordon

      Dan Gordon answered on 8 Nov 2016:

      Lovely question. The heart is a muscle which is constructed of four chambers, two atria and two ventricles. Blood comes into the heart from the atria, where a valve opens allowing the blood to flow into the ventricle. As the blood flows into the ventricle the pressure starts to increase. Once the pressure reaches a cut-off point the valve between the atria and the ventricles closes, at this point the ventricle is closed to both incoming and outgoing blood. Now with the raised pressure this triggers the opening of the valve from the ventricle into the circulation. With the ventricle under high pressure this cause the ejection of the blood, of course the pressure will now start to fall as the blood leaves the heart. At some point the pressure in the artery connecting to the heart is higher than in the ventricle. This causes the valve between the ventricle and the artery to close. The process now starts again.
      As Helen as explained so well the heart is controlled through electrical signals which ‘cascade’ down the heart in a formation termed a wave of excitation. The heart is essence pumps blood out which can be expressed in a couple of ways. There is the number of beats (heart rate HR), there is the volume of blood per beat of the heart (stroke volume SV) and there is the cardiac output which the volume of blood over a minute (Q). So we can express the function of the heart as follows:
      Q = HR x SV

    • Photo: LauraAnne Furlong

      LauraAnne Furlong answered on 9 Nov 2016:

      One of the clever and interesting things about the heart (and probably the bit I remember the best) is that when we start exercising the place in the body that the most blood gets sent to changes, this is called the vascular shunt mechanism. When we start exercising, the working muscles get priority and so the majority of the blood flow goes to them – the blood flow to other organs like the kidneys or your digestive system (that don’t really need it at that time) gets reduced, to ensure that the most amount of oxygen gets sent to where it is needed most at the working muscle. I think that’s a very interesting thing that the vascular (heart) system is involved in.

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