The hypothalamus and other regions associated with the limbic system are involved in regulating respiration in response to emotions, pain, and temperature. For example, an increase in body temperature causes an increase in respiratory rate.
Feeling excited or the fight-or-flight response will also result in an increase in respiratory rate. Sleep apnea is a chronic disorder that can occur in children or adults, and is characterized by the cessation of breathing during sleep. These episodes may last for several seconds or several minutes, and may differ in the frequency with which they are experienced. Sleep apnea leads to poor sleep, which is reflected in the symptoms of fatigue, evening napping, irritability, memory problems, and morning headaches.
In addition, many individuals with sleep apnea experience a dry throat in the morning after waking from sleep, which may be due to excessive snoring. There are two types of sleep apnea: obstructive sleep apnea and central sleep apnea.
Obstructive sleep apnea is caused by an obstruction of the airway during sleep, which can occur at different points in the airway, depending on the underlying cause of the obstruction. For example, the tongue and throat muscles of some individuals with obstructive sleep apnea may relax excessively, causing the muscles to push into the airway.
Another example is obesity, which is a known risk factor for sleep apnea, as excess adipose tissue in the neck region can push the soft tissues towards the lumen of the airway, causing the trachea to narrow. In central sleep apnea, the respiratory centers of the brain do not respond properly to rising carbon dioxide levels and therefore do not stimulate the contraction of the diaphragm and intercostal muscles regularly.
As a result, inspiration does not occur and breathing stops for a short period. In some cases, the cause of central sleep apnea is unknown. However, some medical conditions, such as stroke and congestive heart failure, may cause damage to the pons or medulla oblongata.
In addition, some pharmacologic agents, such as morphine, can affect the respiratory centers, causing a decrease in the respiratory rate. The symptoms of central sleep apnea are similar to those of obstructive sleep apnea. A diagnosis of sleep apnea is usually done during a sleep study, where the patient is monitored in a sleep laboratory for several nights.
Treatment of sleep apnea commonly includes the use of a device called a continuous positive airway pressure CPAP machine during sleep. The CPAP machine has a mask that covers the nose, or the nose and mouth, and forces air into the airway at regular intervals.
This pressurized air can help to gently force the airway to remain open, allowing more normal ventilation to occur. Other treatments include lifestyle changes to decrease weight, eliminate alcohol and other sleep apnea—promoting drugs, and changes in sleep position.
In addition to these treatments, patients with central sleep apnea may need supplemental oxygen during sleep. Pulmonary ventilation is the process of breathing, which is driven by pressure differences between the lungs and the atmosphere.
Atmospheric pressure is the force exerted by gases present in the atmosphere. The force exerted by gases within the alveoli is called intra-alveolar intrapulmonary pressure, whereas the force exerted by gases in the pleural cavity is called intrapleural pressure. Typically, intrapleural pressure is lower, or negative to, intra-alveolar pressure. The difference in pressure between intrapleural and intra-alveolar pressures is called transpulmonary pressure.
In addition, intra-alveolar pressure will equalize with the atmospheric pressure. Pressure is determined by the volume of the space occupied by a gas and is influenced by resistance. Air flows when a pressure gradient is created, from a space of higher pressure to a space of lower pressure. A gas is at lower pressure in a larger volume because the gas molecules have more space to in which to move. The same quantity of gas in a smaller volume results in gas molecules crowding together, producing increased pressure.
Resistance is created by inelastic surfaces, as well as the diameter of the airways. Resistance reduces the flow of gases. The surface tension of the alveoli also influences pressure, as it opposes the expansion of the alveoli. However, pulmonary surfactant helps to reduce the surface tension so that the alveoli do not collapse during expiration.
The ability of the lungs to stretch, called lung compliance, also plays a role in gas flow. The more the lungs can stretch, the greater the potential volume of the lungs. The greater the volume of the lungs, the lower the air pressure within the lungs. Pulmonary ventilation consists of the process of inspiration or inhalation , where air enters the lungs, and expiration or exhalation , where air leaves the lungs.
During inspiration, the diaphragm and external intercostal muscles contract, causing the rib cage to expand and move outward, and expanding the thoracic cavity and lung volume. This creates a lower pressure within the lung than that of the atmosphere, causing air to be drawn into the lungs. During expiration, the diaphragm and intercostals relax, causing the thorax and lungs to recoil.
The air pressure within the lungs increases to above the pressure of the atmosphere, causing air to be forced out of the lungs.
However, during forced exhalation, the internal intercostals and abdominal muscles may be involved in forcing air out of the lungs. Respiratory volume describes the amount of air in a given space within the lungs, or which can be moved by the lung, and is dependent on a variety of factors. Tidal volume refers to the amount of air that enters the lungs during quiet breathing, whereas inspiratory reserve volume is the amount of air that enters the lungs when a person inhales past the tidal volume.
Expiratory reserve volume is the extra amount of air that can leave with forceful expiration, following tidal expiration. Residual volume is the amount of air that is left in the lungs after expelling the expiratory reserve volume. Respiratory capacity is the combination of two or more volumes. Anatomical dead space refers to the air within the respiratory structures that never participates in gas exchange, because it does not reach functional alveoli.
Respiratory rate is the number of breaths taken per minute, which may change during certain diseases or conditions. Both respiratory rate and depth are controlled by the respiratory centers of the brain, which are stimulated by factors such as chemical and pH changes in the blood. These changes are sensed by central chemoreceptors, which are located in the brain, and peripheral chemoreceptors, which are located in the aortic arch and carotid arteries.
A rise in carbon dioxide or a decline in oxygen levels in the blood stimulates an increase in respiratory rate and depth. Answer the question s below to see how well you understand the topics covered in the previous section. Skip to main content. Module 6: The Respiratory System. Search for:. The LabScribe 3 software which was pre-installed on the personal computer was used to operate the IXTA data acquisition unit.
Subjects were instructed to sit still and quietly and were given time to get accustomed to breathing normally through the flow-head before experimental trials were performed. Before starting each experiment trials, the flow-head was calibrated to zero airflow by placing the flow-head with the mouthpiece attached laterally at the level of the mouth to prevent any air from the nose or mouth entering the flow-head.
This position was held for 15 seconds before the subject was asked to begin breathing normally through the flow-head for at least 8 — 10 breaths. After 8 — 10 breaths through the spirometer flow-head, the subject inspired deeply until inspiratory capacity IC was attained and held their breath for 10 seconds. After holding their breath for 15 seconds the subject expired the total IC volume and resumed breathing normally for another 8 — 10 breaths before stopping. This procedure was repeated 5 times on different days so that 5 trials were recorded for each subject on each day over the 5 days.
After 8 — 10 breaths through the spirometer flow-head, the subject expired maximally until only residual volume RV remained in the lungs and held their breath for 15 seconds. The values for the variables were taken from the Heart Rate channel. The experiment was performed on 4 subjects with 5 trials ran for each of the 5 replicates which were done on different days. Single factor ANOVA was used to perform a simple analysis of variance on data for the 4 subjects in this experiment.
The analysis provided a test of the hypothesis that each sample is drawn from the same underlying probability distribution against the alternative hypothesis that underlying probability distributions are not the same for all samples. A total of 8 data points for each trial multiplied by 5 trials a day equals 40 data points multiplied by 5 replicates equals data points per subject per treatment group compared statistically. The grand total of data points compared statistically for this experiment is data points per subject per treatment group multiplied by 4 subjects equals data points multiplied by 4 experimental groups 1 normal breathing vs.
Figures 1,4,7,10,13,16,19 and 22 depict the pulse Electrocardiogram [ECG] tracing , air flow, lung volumes, and heart rate as displayed on the IXTA Main window during the Inspire-Hold treatments and during the Expire-Hold treatments for all 4 subjects who participated in this study.
Each of the 4 channels i. This is important in order to obtain data that are consistent among the 4 subjects. It minimizes variability between subjects that is due to differences among subjects in performing the activities within the treatments in the study thereby isolating the true effects of the treatments being measured. During normal inspiration and expiration HR does indeed increase and decrease respectively, a phenomenon known as Respiratory Sinus Arrhythmia RSA , which has been amply demonstrated by many articles [].
It cannot be overstated how critical it is to understand the phenomenon that is RSA. In this study we wanted to accentuate the conditions under which heart rate increases and decreases during RSA by having subjects maximally expire and inspire then hold breath for 15 seconds. What is the true meaning of inspiration? Why inspiration is active process? Inspiration is an active process whereas expiration is a passive process. Inspiration occurs when the muscles of the diaphragm contract to increase the overall volume of the thoracic cavity.
As the muscles use energy for contraction, inspiration is called active process. What is the mechanism of inspiration? During inspiration, the external intercostal muscles contract and the internal one relax. The muscle of diaphragm contract which lowers the diaphragm.
As a result the size of thoracic cavity increases as well as the lungs expand simultaneously. As the lungs expand, the air pressure inside the lungs decreases.
Why can't you hold your breath long after exercising? When you exercise and your muscles work harder, your body uses more oxygen and produces more carbon dioxide. You may feel 'out of breath' after exercise, but you will not be 'short of breath'. When you have reduced lung function, you may use a large part of your breathing reserve. Why can you hold your breath longer after hyperventilation? In the case of controlled hyperventilation, every bit of air that can be exhaled is released from the lungs.
This lowers the carbon dioxide CO2 in the blood stream. This raises the oxygen in the blood. Physiological Principles Normal Tidal Breathing Diaphragm and intercostal muscles contract to increase the size of the thorax. This results in increase in negative pressure in pleura. The gradient between atmosphere and alveoli causes air to enter lung - inspiration. During this process elastic recoil forces increase.
Once the inspiration is stopped the elastic recoil forces in the lung causes expiration. Expiration is passive and no muscles contract to produce expiration. Accessory Inspiratory Muscles When one takes a deep breath, accessory muscles of respiration are brought into action Scalene, sternomastoid and trapezium. Scalene is the first muscle to start contracting and gradually other two muscles are brought into action. When these muscles contract for tidal breathing - it is abnormal.
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