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Control of Respiration

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Introduction

Introduction The process of gas exchange within the body is know as respiration and has three fundamental stages: * Pulmonary ventilation - also known as breathing, is the inhalation and exhalation of gas between the air outside and the alveoli of the lungs * External respiration - refers to the exchange of gases in the alveoli of the lungs and the blood in pulmonary capillaries, where the capillary blood gains O� and loses CO� * Internal respiration - is the gas exchange between blood in systemic capillaries and tissue cells. This process can also be referred to as cellular respiration. Pulmonary ventilation is a result of alternating pressure differences, between the atmosphere and the alveoli of the lungs, due to contraction and relaxation of respiratory muscles. To enable air to flow into the lungs, the pressure within the alveoli must be lower than that of the atmosphere outside. This can be achieved by increasing the volume of the lungs. The process of pulmonary ventilation is organized by the CNS via the spinal nerves. These spinal nerves innervate the intercostals muscles and the diaphragm by fibers of the phrenic nerves which appear from the spinal cord at cervical levels C3, C4 & C5. The output of these fibers, also known as motor neurons, is controlled by the medullary ryhthmicity area located at the respiratory center in the medulla oblongata in the brain. ...read more.

Middle

This in turn causes no response to any input and results in a decrease in the breathing rate, which further lowers the concentration in PO� levels causing it to fall lower creating a positive feedback mechanism to occur. When this happens this could have a fatal result. The purpose of this practical is to determine which arterial gas pressure O� or CO� is the primary drive for respiration in an inactive person of good health. Also the effects of each gas mixtures on the rate of tidal ventilation will be investigated. Materials & Method Materials The equipment and materials used within this practical were as follows: * Dry flow head spirometer with anti-rebreathe valve * 1000L Douglas bag * Nose clip * Mouthpiece * PowerLab digital recording and analysis package * Three gas mixtures: Room Air (79% N�, 20% O�, 0.04% CO� 100% O� 95% O�/ 5% CO� Method Before starting the experiment ensure that the dry spirometer and the computer have been calibrated and that there is enough gas in the Douglas bag each time a new gas mixture is being utilized. The gas selection switch should primarily be set so that the subject is breathing in room air. As soon as the subject is relaxed and seated a nose clip should be placed upon the nose and a mouthpiece in their mouth. ...read more.

Conclusion

With the presence of carbonic anhydrase in the blood CO� is combined with H�O to form carbonic acid (H�CO�). If an increase of H+ molecules occur this causes the breakdown of carbonic acid into H+ and HCO�. This results in an increased amount of H+ present in the blood. When a high concentration of both CO� and H+ is detected the peripheral chemoreceptors become stimulated and initiate responses to brain to restore the concentrations back to normal. As the chemoreceptors participate in a negative feedback mechanism, they cause the inspiratory area to become highly active and produce a change in the rate and depth of breathing. Increased ventilation will occur when high concentrations of CO� are detected as it can be dangerous to have high levels within the body therefore the CO� molecules need to be exhaled out. The frequency of ventilation for each gas had increased; this could have been as a result of the subject hyperventilating slightly due to the conditions in which they were under. Therefore it was essential that that subject was given time to acclimatize each time before they started to breathe in each of the gas mixtures. The highest BPM reading was recorded under the room air gas. The reason as to why this may have occurred is also due to the fact the subject may not have entirely acclimatized before breathing in this air which then caused them to hyperventilate slightly. ?? ?? ?? ?? ...read more.

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