Translation 8: Metabolism 1. Metabolism 2. Cell Respiration 3. Photosynthesis 9: Plant Biology 1. Xylem Transport 2. Phloem Transport 3. Plant Growth 4.
Plant Reproduction Genetics 1. Meiosis 2. Inheritance 3. Speciation Animal Physiology 1. Antibody Production 2. Movement 3. A deep breath, called diaphragmatic breathing, requires the diaphragm to contract. As the diaphragm relaxes, air passively leaves the lungs. A shallow breath, called costal breathing, requires contraction of the intercostal muscles. As the intercostal muscles relax, air passively leaves the lungs.
In contrast, forced breathing , also known as hyperpnea, is a mode of breathing that can occur during exercise or actions that require the active manipulation of breathing, such as singing.
During forced breathing, inspiration and expiration both occur due to muscle contractions. In addition to the contraction of the diaphragm and intercostal muscles, other accessory muscles must also contract.
During forced inspiration, muscles of the neck, including the scalenes, contract and lift the thoracic wall, increasing lung volume. During forced expiration, accessory muscles of the abdomen, including the obliques, contract, forcing abdominal organs upward against the diaphragm.
This helps to push the diaphragm further into the thorax, pushing more air out. In addition, accessory muscles primarily the internal intercostals help to compress the rib cage, which also reduces the volume of the thoracic cavity.
Respiratory volume is the term used for various volumes of air moved by or associated with the lungs at a given point in the respiratory cycle. There are four major types of respiratory volumes: tidal, residual, inspiratory reserve, and expiratory reserve Figure 4.
Figure 4. These two graphs show a respiratory volumes and b the combination of volumes that results in respiratory capacity. Tidal volume TV is the amount of air that normally enters the lungs during quiet breathing, which is about milliliters. Expiratory reserve volume ERV is the amount of air you can forcefully exhale past a normal tidal expiration, up to milliliters for men.
Inspiratory reserve volume IRV is produced by a deep inhalation, past a tidal inspiration. This is the extra volume that can be brought into the lungs during a forced inspiration. Residual volume RV is the air left in the lungs if you exhale as much air as possible. The residual volume makes breathing easier by preventing the alveoli from collapsing.
Respiratory capacity is the combination of two or more selected volumes, which further describes the amount of air in the lungs during a given time. TLC is about mL air for men, and about mL for women. Vital capacity VC is the amount of air a person can move into or out of his or her lungs, and is the sum of all of the volumes except residual volume TV, ERV, and IRV , which is between and milliliters.
Inspiratory capacity IC is the maximum amount of air that can be inhaled past a normal tidal expiration, is the sum of the tidal volume and inspiratory reserve volume. On the other hand, the functional residual capacity FRC is the amount of air that remains in the lung after a normal tidal expiration; it is the sum of expiratory reserve volume and residual volume.
Watch this video to learn more about lung volumes and spirometers. Explain how spirometry test results can be used to diagnose respiratory diseases or determine the effectiveness of disease treatment. In addition to the air that creates respiratory volumes, the respiratory system also contains anatomical dead space, which is air that is present in the airway that never reaches the alveoli and therefore never participates in gas exchange. Alveolar dead space involves air found within alveoli that are unable to function, such as those affected by disease or abnormal blood flow.
Total dead space is the anatomical dead space and alveolar dead space together, and represents all of the air in the respiratory system that is not being used in the gas exchange process. Breathing usually occurs without thought, although at times you can consciously control it, such as when you swim under water, sing a song, or blow bubbles. The respiratory rate is the total number of breaths, or respiratory cycles, that occur each minute. Respiratory rate can be an important indicator of disease, as the rate may increase or decrease during an illness or in a disease condition.
The respiratory rate is controlled by the respiratory center located within the medulla oblongata in the brain, which responds primarily to changes in carbon dioxide, oxygen, and pH levels in the blood. The normal respiratory rate of a child decreases from birth to adolescence. A child under 1 year of age has a normal respiratory rate between 30 and 60 breaths per minute, but by the time a child is about 10 years old, the normal rate is closer to 18 to By adolescence, the normal respiratory rate is similar to that of adults, 12 to 18 breaths per minute.
The control of ventilation is a complex interplay of multiple regions in the brain that signal the muscles used in pulmonary ventilation to contract Table 2. The result is typically a rhythmic, consistent ventilation rate that provides the body with sufficient amounts of oxygen, while adequately removing carbon dioxide.
Neurons that innervate the muscles of the respiratory system are responsible for controlling and regulating pulmonary ventilation. The major brain centers involved in pulmonary ventilation are the medulla oblongata and the pontine respiratory group Figure 5. The DRG is involved in maintaining a constant breathing rhythm by stimulating the diaphragm and intercostal muscles to contract, resulting in inspiration.
When activity in the DRG ceases, it no longer stimulates the diaphragm and intercostals to contract, allowing them to relax, resulting in expiration. The VRG is involved in forced breathing, as the neurons in the VRG stimulate the accessory muscles involved in forced breathing to contract, resulting in forced inspiration. The VRG also stimulates the accessory muscles involved in forced expiration to contract.
The second respiratory center of the brain is located within the pons, called the pontine respiratory group, and consists of the apneustic and pneumotaxic centers. The apneustic center is a double cluster of neuronal cell bodies that stimulate neurons in the DRG, controlling the depth of inspiration, particularly for deep breathing. The pneumotaxic center is a network of neurons that inhibits the activity of neurons in the DRG, allowing relaxation after inspiration, and thus controlling the overall rate.
The respiratory rate and the depth of inspiration are regulated by the medulla oblongata and pons; however, these regions of the brain do so in response to systemic stimuli. It is a dose-response, positive-feedback relationship in which the greater the stimulus, the greater the response. Thus, increasing stimuli results in forced breathing. Multiple systemic factors are involved in stimulating the brain to produce pulmonary ventilation.
The major factor that stimulates the medulla oblongata and pons to produce respiration is surprisingly not oxygen concentration, but rather the concentration of carbon dioxide in the blood. As you recall, carbon dioxide is a waste product of cellular respiration and can be toxic.
Concentrations of chemicals are sensed by chemoreceptors. A central chemoreceptor is one of the specialized receptors that are located in the brain and brainstem, whereas a peripheral chemoreceptor is one of the specialized receptors located in the carotid arteries and aortic arch. Concentration changes in certain substances, such as carbon dioxide or hydrogen ions, stimulate these receptors, which in turn signal the respiration centers of the brain.
In the case of carbon dioxide, as the concentration of CO2 in the blood increases, it readily diffuses across the blood-brain barrier, where it collects in the extracellular fluid.
As will be explained in more detail later, increased carbon dioxide levels lead to increased levels of hydrogen ions, decreasing pH. The image above gives you a visual to go along with the model we will be discussing. The portions of the image which are blue represent where the ribs and sternum get to on an inhalation. The ribs at rest are in yellow. On the left of the image is the spine, which serves as the door frame.
The orangy strip represents an external intercostal muscle fiber connecting two ribs. The external intercostal muscles on the outside of the ribcase wrap around from the back of the rib almost to the end of the bony part of the rib in front. The image above is seen from the inside. The yellowish bones are the sternum in the centre and the ribs and clavicle at the very top. Between the ribs can be seen the internal intercostals.
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