To investigate how the heart rate and breathing rate increase with exercise.Scientific KnowledgeAerobic respiration needs an input of oxygen, and outputs carbon dioxide

Part of the brain known as the medulla oblongata is responsible for the control and co-ordination of important automatic reflex functions such as heart rate and breathing.

Inside the medulla are groups of neurones (nerve cells) which make up the respiratory centre for rhythmic breathing. This centre is in turn controlled to a certain extent by "higher voluntary centres in the brain. This means that you can consciously over-ride normal breathing, for example by holding your breath, whereas the medulla usually allows you to breathe normally without thinking.

As soon as we begin to exercise, the rate of respiration in our muscles increases and more carbon dioxide is released into the blood. This increase in toxic carbon dioxide concentration is detected by chemoreceptors in two areas of the body- in arteries in the neck, and in the aorta (near the heart). Central chemoreceptors in the medulla itself are also stimulated by the increased carbon dioxide concentration in the blood.

* Body exercises

* Muscles respire more

* Carbon dioxide level in blood increases

* Chemoreceptors in aorta (near heart) and carotid body (in neck) monitor carbon dioxide level

* Nerve fibres

* Medulla oblongata (responds to changes in carbon dioxide level)

* Nerve fibres

* Diaphragm and intercostal muscles

* Breathing rate increases

* Carbon dioxide level in blood decreases

These receptors send nerve impulses to the respiratory centre (the medulla) which brings about the appropriate response. The medulla stimulates the nerves to the diaphragm muscle across the base of the thorax (chest) and the intercostal muscles between the ribs. These bring about faster and deeper inspirations (breathing in) which get rid of the carbon dioxide but also help to breathe in the extra oxygen needed during exercise.

You have seen that if the body is to work efficiently it is important to keep steady levels of oxygen and carbon dioxide. These are not the only factors that need to be controlled. Body temperature and water are also crucial to your health and well being. The maintenance of all these factors at constant levels is called homeostasis. Good control requires the action of either the nervous or endocrine (hormonal) system.

Control of carbon dioxide involves the nervous system. A rise in carbon dioxide levels in the blood, as caused by exercise, will cause an increase in breathing rate so that the carbon dioxide will be breathed out. Alternatively if the carbon dioxide levels falls, less needs to be breathed out and the breathing rate will decrease.

This system involves negative feedback. Feedback happens when a change in a system can somehow act to affect whatever it was that caused the change. Negative feedback helps to keep things the same. In this case the carbon dioxide rise causes an increase in breathing rate which leads to the carbon dioxide level being reduced and eventually corrected. The breathing rate then also returns to normal.

When we exercise we also need to control our body temperature. We must keep the temperature inside us, our "core body" temperature, at a constant level (about 37oC at all times. If our core body temperature rises above 40oC we are very close to death. If it gets below about 35oC, we die of hypothermia. The temperature range over which all our bodily functions work properly is very narrow, and so the control of body temperature must be efficient and precise. It is important that:

Heat gained by body = Heat lost by body

Much of the energy resulting from respiration is transferred away from cells (lost) in the form of heat. This heat is then carried away around the body by the blood. If the loss of this heat from the body is controlled it is possible to keep body temperature at 37oC.

When we get hot during exercise or on a sunny day, the body will need to transfer (lose) more energy away from the body to maintain the correct temperature. In humans there are two main ways of doing this.

* Sweating- Sweat glands in your skin produce sweat which contains water, salts and a waste product called urea. Heat from the body is transferred to the water, causing the water to evaporate into the air. As a result this cools down the body.

* Vasodilation-Our skin contains many blood vessels. When we get hot some of these get wider (vasodilation). This means that more blood can be brought to the skin surface and we will look redder. This then makes it easier to transfer energy from the blood to the air by radiation.

Humans have a sensitive and well-developed centre to control body temperature: the hypothalamus. This organ is part of the brain and it continually monitors the temperature of the blood flowing through it. In addition it receives information from about 160000 temperature receptors found in the skin. The hypothalamus uses this information on blood and skin temperature to alter the levels of sweating, blood flow in the skin and shivering.

This control of the body temperature clearly shows the role of negative feedback in homeostasis. This means that any change in temperature will eventually lead to the temperature getting back to normal and as a result the correcting changes will no longer be needed.

When we sweat we need to control the amount of water we transfer to the skin. The human body is two-thirds water. We gain water from the food we eat as well as the liquids that we drink. In addition, the body gains some water from certain chemical reactions- such as respiration- where water is one of the main waste products.

There are a number of ways the body loses water. The average person, under normal conditions, loses about three litres of water a day in various ways:

* In liquid waste (urine) from the kidney

* In solid waste (faeces) from the gut

* By breathing out water vapour from the lungs

* By sweating from the skin

Water balance is important because cells of the body only work properly if there is the right amount of water present. If we lost just about a tenth of our body water, we would die from dehydration. If you didn't take in any water at all, this would happen in about ten days but a lot faster in hot dry conditions. Long before that time you would be very uncomfortable. The feeling of thirst would become unbearable.

Keeping the amount of water constant in the blood, and therefore in the whole body, is another important example of homeostasis:

Water gain = Water loss

Just as body temperature is controlled by the hypothalamus, so is the water content of the blood. The hypothalamus contains receptors that monitor the level of water in the blood. If the body is suffering from a lack of water, the receptors are stimulated and pass nerve impulses to the pituitary gland which is right next to the hypothalamus. This releases a hormone called antidiuretic hormone (ADH). This passes through the bloodstream to the kidney where it causes more water to be reabsorbed from the tubes back into the blood. As a result of this, the urine will contain less water, it will be more concentrated, darker yellow and smaller in amount.

On the other hand if there is a lot of water in the blood, for example after having a drink, the receptors in the blood will not be stimulated as much, less ADH will be produced, less water will be reabsorbed into the blood and more will pass into the urine. This will produce lots of weak pale urine.

Prediction

Using the knowledge above that I have learnt on the subject of homeostasis and how the body works, I will predict that the breathing rate and heart rate will increase with exercise. The more intense/longer the exercise the more they will increase. However there will a stage when the breathing rate and heart rate will reach a peak and this will be dependent on the intensity and type of activity. I believe this because exercise involves more CO2 being respired and more oxygen being needed in the muscles, so gaseous exchange will take place more often and quicker. This means that the breathing rate will increase and the heart rate will also increase due to the blood transferring the CO2 out of the body and taking in oxygen to where it is needed. The breathing and heart rate will reach a peak stage where they will stay almost constant. This is because a person's maximum heart rate is 220-age = max HR (BPM). Breathing rate would increase to a certain point and then the amount of gaseous exchange wouldn't be able to increase any further. The point at where the heart rate gets to its peak area probably will not show up on our experiment because we are only exercising for a minute at a time. It would show up if we did length of exercise period as our variable.

Fair test/Variables/Preliminary work

* Length of exercise period

* Type of exercise

* Intensity of exercise

* Frequency of exercise

* Health/fitness/age/size

* Weather conditions

I will choose one variable only and this will be:

* Intensity of exercise

In my preliminary work I tried different types of exercises. I tried:

* Sit ups

* Press ups

* Step ups

* Star jumps

I found that step-ups were the best because I am planning to do the exercises for 1 minute and press-ups for one minute is quite hard. Sit-ups make you very fatigued quickly too. I chose step ups because they are not too tiring but they increase your heart rate and breathing rate as shown in the table on the next page. I also used my preliminary work to choose the amount of step-ups per minute for my practical. The ones with * next to them are the ones I chose to use for my plan.

Step ups per min

BR

HR

*

6

8

66

*

8

20

68

0

24

72

*

2

26

78

6

29

82

*

20

30

86

25

33

90

*

30

35

98

*

60

40

30

When I did my preliminary work I watched other people doing the same sort of experiment as me and they were not allowing rest time. They were doing the exercise and then measuring their heart rate but then instead of allowing the body to recover they would go onto the next exercise. This is not a fair test because the heart and breathing rate are not the same for each of their exercises. Therefore when I did mine I did 1 minute of exercise and then recorded my breathing rate and heart rate. I then allowed time for my breathing rate and heart rate to go back to normal (resting rate) before starting the next exercise.

To keep it a fair test I will need to have recovery periods between each exercise so that I give my body time to recover from the previous exercise. In this time I will allow my pulse to go down to its resting heart rate before continuing to the next level of intensity and the same with my breathing rate.

The intensity will be

* 6 steps a minute

* 8 steps a minute

* 12 steps a minute

* 20 steps a minute

* 30 steps a minute

* 60 steps a minute

I will be doing intensity of exercise, the exercise being step-ups and I will do this indoors using the first step on a set of school stairs.

Method

I will measure my resting heart rate and my resting breathing rate. I will record this down in a table of results. I will then start the step ups at 6 steps every minute (1 step every 10 seconds) for 1 minute using a stopwatch. I will then take my heart rate immediately. At the same time my partner will be taking my breathing rate. I will then record my results down in the table of results and keep checking to see when my breathing rate and heart rate has gone back to what it was at the start of the exercise (resting HR + BR).

I will repeat this again but doing 8 steps a minute for 1 minute and then 12 steps per minute for 1 minute etc.

I will repeat the whole experiment again to get repeats so I can compare and get averages.

Equipment needed

* stopwatch

* table of results

* a partner

Results

Step ups per min

BR

HR

Step ups per min

BR

HR

6

24

72

6

8

66

8

30

72

8

24

66

2

30

78

2

24

78

20

30

90

20

24

90

30

36

02

30

24

96

60

42

32

60

30

38

Resting HR

70

Resting HR

60

Resting BR

24

Resting BR

2

Step ups per min

BR

HR

Step ups per min

BR

HR

6

2

60

6

24

70

8

2

60

8

30

72

2

8

66

2

30

84

20

24

78

20

30

90

30

30

90

30

36

96

60

36

32

60

42

26

Resting HR

60

Resting HR

64

Resting BR

2

Resting BR

24

Averages

Step ups per min

Av.

BR

Av.

HR

6

9.5

67

8

24

67.5

2

25.5

76.5

20

27

87

30

31.5

96

60

37.5

32

Av. Resting BR

(Breaths Per Min)

8

Av. Resting HR

(Beats Per Min)

63.5

Conclusion

From my results it is obvious that there is a strong positive relationship between breathing rate, heart rate and exercise. This is because as the number of steps per minute increases so does the breathing rate and heart rate. Increases in heart rate and breathing rate are important in removing carbon dioxide and water, and transferring heat energy away from the respiring muscles. They are proportional. When the heart rate increases so does the breathing rate.

The breathing rate is increasing because it is responding to the body doing exercise. This is due to homeostasis. Homeostasis is maintaining a constant internal environment. Medulla oblongata responds to changes in carbon dioxide level causing the increase in heart rate and breathing rate.

Negative feed causes us to breath faster to allow the increasing levels of carbon dioxide to be released out of the body and to increase the amount of oxygen in the body.

Glucose + Oxygen -> Carbon Dioxide + Water + Energy

Heart rate increases because the breathing rate has increased. It allows the increasing levels of carbon dioxide to be removed out of the muscles and to the lungs where gaseous exchange takes place as quickly as possible. The heart is told to increase by the part of the brain called the

When we exercise our muscles increase the amount of work they are doing causing us to breathe deeper and faster, which takes more oxygen into the lungs. To compensate for the increase in carbon dioxide levels the heart pumps faster, sending more blood, containing oxygen and glucose to the muscles and removing water and carbon dioxide. This allows the muscles to increase the amount of aerobic respiration, so that more energy can be provided for movement.

This supports my prediction as I predicted that as exercise increases so will heart rate and breathing rate.

Evaluation

I feel my results were quite accurate but I think I could have improved the accuracy of my results if I had been able to use a watch which have measured my pulse. This would have also allowed me to measure it quicker so that I could move on and perhaps try another exercise to see if it affects breathing rate and heart rate in the same way that step ups affect them.

I feel that doing the exercises like I did e.g. doing 20 step ups every minute and then waiting for my heart rate and breathing rate to back to normal before doing 30 steps per minute would have affected my glucose levels. This might have affected the levels at which my body would have worked. My results support my conclusion well. It shows a relationship and it matches my prediction.

If I could do the experiment again I would try different exercises to see if that would affect the heart rate and breathing rate as well as the step-ups did.