The effect of Exercise on Pulse rate

In this experiment I am going to be looking at how exercise affects the pulse rate of the body. By the end of the experiment I hope to have found a connection between exercise and how it affects the pulse rate (for example, does the pulse rated increase or decrease?). I will study this by taking a group of students and asking them to exercise for a short amount of time, taking their pulse before and after this exercise to find out if there is any change in the rate of it.

Hypothesis and Biological knowledge

The heart is a huge muscle found in the chest. The main use of the heart is to pump blood, which delivers oxygen, glucose and much-needed chemicals to other parts of the body.

The muscle making up the heart is called Cardiac muscle; this special muscle does not wear down as other muscle does in the body. This is because it has to constantly beat to keep us alive, so cannot die out and be replaced by new muscle. The cardiac muscle also has another difference to any other muscle that we find in places like our legs or arms, this is that it has it’s own beat, moving to make the whole heart pump, this type of muscle is called myogenic muscle, which means (moves on it’s own).

There are three sections to how the heart pumps. As the heart never stops pumping these three stages carry on in a circle.

Diastole is when the muscles of the heart relax. This allows oxygenated blood to rush in to the left atria and de-oxygenated blood in to the right atria. As the blood enters the atrium they swell and the pressure inside them increase.

Atria Systole – This process means the contraction of the atria. As the pressure in the atrium increases and more blood rushes in to it there is more and more pressure placed on the valves between the atria and the ventricles. Once the atrium are full the valves leading from the blood vessels delivering the oxygen close, not allowing anymore blood in to the heart. Once this happens the valves from the atrium to the ventricles open and the atria contract, pushing the blood through in to the ventricles. (The valve between the atria and ventricle on the left hand side of the heart is called the bicuspid valve, and on the right hand side it is called the tricuspid valve).

Ventricular Systole is the contraction of the ventricles. This happens once all the blood from the atrium have entered the ventricles and the bicuspid and tricuspid valves have closed, stopping the blood flowing backwards in to the atria again. Just as in the atrium the pressure inside the ventricles increases until the blood pushes open the semi-lunar valves and rushing out of the heart. Once the blood has been successfully pumped out of the heart the semi-lunar valves close very quickly, stopping the blood from flowing backwards in to the heart.

As the blood is pushed out of the heart it travels along arteries, towards the different parts of the body where it will be needed.

Arteries and veins are known as blood vessels, they carry blood around the body, centring around the heart and lungs. They are different in the way that they are made up, because they have different jobs.

(Reference: http://www.sci.sdsu.edu/class/bio590/pictures/lect5/artery-vein.jpeg)

Veins have thin walls; this is because the pressure in the veins is less than the arteries. Veins carry blood towards the heart and lungs; this means that it is coming from places in our bodies where the blood has been exchanging foods and energy.

As it reaches these places the blood has to be forced through tiny blood vessels called capillaries, as this happens the pressure in the vessels builds up and energy is released, after the blood comes out of these capillaries the pressure is quite low as the energy has been used to push them through. As the pressure is so low the walls do not need to be very thick to withstand it, but they do have valves in them to stop the blood from flowing backwards on it’s way back to the heart.

Arteries have much thicker wall than veins. This is because the pressure in them is much greater as they come straight from the heart, and the blood is being pumped very fast. Arteries come from the heart; they collect oxygenated blood from the lungs and deliver it to other parts of the body. The pressure in the arteries is so high because the blood has to be pumped all over the body, going down to our toes is easy as it follows the laws of gravity and falls, but it takes enormous effort for the blood to go uphill to out heads, so the pressure has to be high to pump it there.

Arteries are the blood vessels that we can feel our pulse by. Everywhere an artery crosses a bone we can feel our pulse, this is because the bone acts as a surface for the artery to press against. As this happens the shockwaves that are sent down the walls of the arteries from the heart can be felt, this is what we are feeling when we are looking for our pulse. The pulse rate is the amount of ripples along the artery walls; this shows how fast the heart is beating and pumping the blood around the body.

Inside the heart there are receptors, which are part of the nervous system these are connected to small systems called the cardio-acceleratory system and cardio-inhibitory centre. The cardio-acceleratory system responds to things picked up by the SA node in the heart, it is linked with the sympathetic nervous system and increases the working of the heart, causing it to beat faster.

The cardio-inhibitory system also responds to the SA node in the heart, this time it’s connected to the parasympathetic nervous system and decreases the work of the heart, thus decreasing the pulse and heart rate of the person. In my experiment I will be looking at how exercise affects the pulse rate of the individual. Whilst doing exercise there is an increase in respiration, this means that the amount of carbon dioxide in the blood will also increase as the oxygen is used up. This will mean that the PH of the blood will also increase; a swelling in the carotid artery called the carotid body will pick this up and send instructions to the cardio-acceleratory or inhibitory systems depending on which is needed to be used.

My hypothesis is that the pulse rates of the pupils will increase during and for a small while after exercise because of the need for more oxygen in the body. I then predict that the rate will lower after exercise as less respiration in the muscles is occurring and the blood is not needed to be pumped as fast.

In my experiment the cardiovascular system will provide the most important system. As the body uses up oxygen and sugars when it is working during exercise they will need to be replaced. The blood delivers the oxygen an other things needed in the respiration and working of the muscles to them, and as more of the oxygen and sugars will be used up during exercise this will mean that there should be an increase in the blood flow to these parts in the body.

For this blood flow to take place the heart has to beat faster and pump harder to get the blood to the areas it’s needed, this increase in heart activity will mean that the heart pumps the blood faster around the body. This blood will then pass faster through the arteries coming from the heart, therefore causing more ripples along their surfaces and an increase in the pulse rate as it is these ripples that we count to measure the pulse rate and how fast the heart is working.

From the biological knowledge and information that I have collected I predict that the pulse rates of the people I am using in my experiment will increase as they exercise. This will be because the heart has to pump quicker and more often to deliver sufficient oxygen to the areas that are working in the body, and keep them going.

As the heart pumps faster the blood is pumped around the body quicker, collecting oxygen from the lungs and taking it to where it’s needed more often. So, as the heart pumps quicker the blood is pushed through the arteries faster, making more ripples from the heart and a faster pulse rate.

After the five minutes rest I expect the pulse rate to drop again, either back to what it was before if they are fit, if not then to drop to a lower rate that it was straight after exercise. This is because the heart will be slowing down again as the oxygen and energy isn’t needed as much in the places that had been working so hard before.