The Non-chemical stimuli usually results in feedback from stretch receptors which are located in the lungs, as the lungs inflate, inhibitory impulses are sent to the inspiratory centre, to stop breathing in anymore air. Sensory nerves endings are found in the joints and tendons of the body, the impulses sent to these sensory nerves by the lungs al helps to control breathing in the body.
The Chemical stimuli usually have different chemical changes that occur in the body, these affect the rate of respiration. However, A decrease in the concentration of oxygen results in stimulation in the inspiratory centre, on the other hand, this increase in oxygen has been found to have a small or in some cases no result on respiration.
The Increased levels of the concentration of the carbon dioxide are detected by chemoreceptors which live in the medulla oblongata. Once the change in the concentration is detected,Once the change has been detected, the medullary rhythmicity centre is stimulated to increase respiration rate. This means that a greater volume of air is moving in and out of the lungs at a faster rate, which removes more carbon dioxide from the blood and causes the concentration of carbon dioxide to reduce back to a safer level. Decreased levels of carbon dioxide are also detected by the chemoreceptor. When a decrease is detected, then the medullary rhythmicity centre is inhibited so respiration rate decreases as breathing is slower.
A decrease in pH of the blood makes it more acidic. This can be harmful for the tissues and cells in the body and therefore needs to be increased. This happens by increasing the rate of breathing, which helps remove more carbon dioxide from the body via the lungs.
With these feedback mechanisms, both chemical and neuronal, respiration is controlled.
Experiments on Respiration
Component 3
B
Describe the processes of inspiration and expiration involved in respiration.
Movement of air into and out of the respiratory system is known as pulmonary ventilation. Movement of air into the body is called inspiration, whereas movement of air out of the body is called expiration.
For inspiration to occur, pressure gradient needs to be established where the pressure is greater in the atmosphere than in the lungs. Pressure in the lungs is known as intrapulmonary pressure. This allows air to be drawn into the lungs. In order for the pressure gradient to be established correctly, the volume of the lungs needs to be increased. This is achieved by increasing the volume of the thorax. By contracting the diaphragm and the external intercostals muscles (i.e. ribs move up and out), the thorax length and diameter are both increased respectively.
Expiration is a passive process, where air rushes out of the lungs into the atmosphere. Here, the pressure gradient is established where it is higher in the lungs than the pressure found in the atmosphere. For expiration to occur, the thorax needs to reduce its size. This occurs when the diaphragm and internal intercostals muscles relax. Therefore, the thorax will be reduced in length and have a smaller diameter. This results in a decreased size of the lungs, causing the intrapulmonary pressure to rise above atmospheric pressure and results in expelling air from the lungs.
