Formal Lab Report -Human Respiratory Physiology

Formal Lab Report -Human Respiratory Physiology - Abstract...

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Abstract The negative feedback loop limits the duration of one’s breath hold by setting a threshold limit and when this level is reached, one is forced to breathe once again. And so we hypothesized that increasing the initial CO 2 level shortens the duration of one’s apnea because initial CO 2 levels start closer to the threshold level of CO 2 . Since the lung can take on different volumes at different times of the respiratory cycle, the negative feedback regulation of these volumes were indirectly observed by performing a breath-hold experiment by changing the initial CO2 level of our subject. This was carried out by utilizing different breathing techniques- normal, hyperventilating room air and breathing in a bag. In addition, gender specific differences in lung volume parameter were explored using forced vital capacity (FVC) and relative FVC as our factors. Past studies by Baig and Qureshi among non-smoking staff and students at The Aga Khan University (2007) found that FVC was higher in males compared to females due to height (2007). Therefore, I expect the values of FVC and relative FVC to be higher for males then females due to males being heavier on average. Lung volume parameters were measured using a computerized spirometer, which involved a computer program Labscribe 2 (1). Results of the experiment suggest that the duration of one’s breath-hold depends on the initial CO2 level. Lowering the initial CO2 level (hyperventilation) increases ones duration by furthering ones initial CO2 level from the threshold placed by the negative feedback loop. Increasing ones initial CO2 levels by breathing in a plastic bag decreases the duration of one’s breath hold by bringing one closer to the CO2 threshold. In addition, the study suggests that there are differences in male and female forced vital capacity and relative-FVC due to males being genetically bigger in size (weight and height). Introduction In mammals, the single site for gas exchange is the lungs. Ventilation is an active process that involves inhaling air through the actions of the diaphragm and the external intercostals muscles and exhaling CO 2 by relaxing these inspiratory muscles. A change in ventilation occurs when there is a change in the level of O 2 and CO 2 . Ventilation is only regulated by oxygen when its’ in short supply. This is due to hemoglobin being well saturated at moderate O 2 levels. Therefore, ventilation is regulated by changes in arterial blood CO 2 levels because even small changes in its levels are detected as changes in pH. This occurs because as CO 2 dissolves in water a spontaneous reaction occurs between these two molecules to form carbonic acid ( CO2 + H2O <-> H2CO3 <-> HCO3- + H+), which accounts for the lowered pH value. In other words the more CO 2 in the blood the more acidic it becomes and thus acquires a lower pH. This deviation is detected by the chemoreceptors of the aortic bodies, carotid bodies, and medulla. A negative feedback loop is used by the Respiratory center which compares this information to a set point CO 2 /pH value. Variations from the set point are dealt by the respiratory and
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