Email address: Your name:. Example Question 1 : Respiratory Physiology. Which of the following muscles does NOT assist in forced inhalation? Possible Answers: Rectus abdominis. Correct answer: Rectus abdominis. Explanation : Normal inspiration typically involves the flattening contraction of the diaphragm in order to increase the volume of the thoracic cavity, and can be done unconsciously. Report an Error. Which section of the brain controls unconscious breathing?
Possible Answers: The hypothalamus. Correct answer: The pons. Explanation : Unconscious breathing is controlled by the pons and the medulla oblongata, both of which are parts of the brain stem. Example Question 3 : Respiratory Physiology. Possible Answers: The abdominal muscles contract, creating a negative pressure in the thoracic cavity. Correct answer: The diaphragm contracts, the external intercostal muscles contract, and there is a negative intrapleural pressure.
Explanation : At rest the diaphragm is slightly curved superiorly such that it makes this sort of shape: When it contracts, it flattens out, with the middle of the muscle being pulled down until the muscle is roughly horizontal. Example Question 4 : Respiratory Physiology. Possible Answers: The maximum volume of air that can be expired after a maximal inspiration.
The volume of air still in the lungs after a maximal expiration. The maximum volume of air that can be inspired after a normal expiration. The volume of air inspired or expired during normal breathing. The maximum volume of air that can be inspired after a normal inspiration. Correct answer: The volume of air inspired or expired during normal breathing. Example Question 5 : Respiratory Physiology.
Possible Answers: inhalation. Correct answer: inhalation. Explanation : During a respiratory cycle, the diaphragm contracts and moves downward. Example Question 6 : Respiratory Physiology. Possible Answers: Zero pressure in the lungs. Correct answer: Increased pressure in the lungs. Explanation : When exhaling, the lungs elasticity compresses the walls increasing the pressure within so that it exceeds atmospheric pressure and forces air out.
Example Question 7 : Respiratory Physiology. Possible Answers: Positive-pressure. Correct answer: Negative-pressure. Explanation : During the normal inspiratory phase of breathing, in other words, when a human is "breathing in," the physiological mechanism used is called "negative-pressure" breathing.
Example Question 8 : Respiratory Physiology. Which nerve is responsible for innervating the diaphragm during respiration? Possible Answers: Vagus nerve.
Thus, air is driven out of the lungs by bulk flow, until the atmospheric pressure and pressure within the alveoli are equal. Normally, expiration is effortless but if the respiratory passageways are narrowed by spasm of the bronchioles for example, in asthma or clogged with mucus or fluid for example, in chronic bronchitis or pneumonia , expiration becomes an active process Law and Watson, In forced expiration, when it is necessary to empty the lungs of more air than normal, the abdominal muscles contract and force the diaphragm upwards and contraction of the internal intercostal muscles actively pulls the ribs downwards.
This generates higher air pressures within the lungs and forces the air out more rapidly. Although breathing is simple mechanically, its control is complex. The respiratory control centre is situated in the medulla oblongata of the brain.
This sets the rhythm of breathing and contains neurons that are self-excitatory rather like the cells in the sino-atrial node in the heart and which fire off in a cycle. This maintains the normal respiratory rate of breaths a minute. When the inspiratory neurons in the medulla fire, they excite the muscles of inspiration - the phrenic nerve to the diaphragm and the intercostal nerves to the intercostal muscles - causing them to shorten and enlarge the volume of the chest cavity.
When the medullary neurons stop firing, the muscles recoil and the chest cavity returns to its resting size. During exercise we need to deliver more oxygen than normal to the tissues. The brain centres send more impulses to the respiratory muscles and we breathe more deeply and quickly. During forced expiration, areas in the medulla fire off impulses that contract the muscles of forced expiration - abdominal muscles and the internal intercostals.
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 Process of Breathing Learning Objectives By the end of this section, you will be able to: Describe the mechanisms that drive breathing Discuss how pressure, volume, and resistance are related List the steps involved in pulmonary ventilation Discuss the physical factors related to breathing Discuss the meaning of respiratory volume and capacities Define respiratory rate Outline the mechanisms behind the control of breathing Describe the respiratory centers of the medulla oblongata Describe the respiratory centers of the pons Discuss factors that can influence the respiratory rate.
Figure 5. Respiratory centers of the brain. Disorders of the Respiratory System: Sleep Apnea Sleep apnea is a chronic disorder that can occur in children or adults, and is characterized by the cessation of breathing during sleep.
What is respiratory rate and how is it controlled? Show Answers Lung compliance refers to the ability of lung tissue to stretch under pressure, which is determined in part by the surface tension of the alveoli and the ability of the connective tissue to stretch. Lung compliance plays a role in determining how much the lungs can change in volume,which in turn helps to determine pressure and air movement.
Quiet breathing occurs at rest and without active thought. During quiet breathing, the diaphragm and external intercostal muscles work at different extents, depending on the situation. For inspiration, the diaphragm contracts, causing the diaphragm to flatten and drop towards the abdominal cavity, helping to expand the thoracic cavity.
The external intercostal muscles contract as well, causing the rib cage to expand, and the rib cage and sternum to move outward, also expanding the thoracic cavity.
Expansion of the thoracic cavity also causes the lungs to expand, due to the adhesiveness of the pleural fluid. As a result, the pressure within the lungs drops below that of the atmosphere, causing air to rush into the lungs.
In contrast, expiration is a passive process. As the diaphragm and intercostal muscles relax, the lungs and thoracic tissues recoil, and the volume of the lungs decreases. This causes the pressure within the lungs to increase above that of the atmosphere, causing air to leave the lungs. Respiratory rate is defined as the number of breaths taken per minute. Respiratory rate is controlled by the respiratory center, located in the medulla oblongata. Conscious thought can alter the normal respiratory rate through control by skeletal muscle, although one cannot consciously stop the rate altogether.
The process of breathing, or respiration, is divided into two distinct phases. The first phase is called inspiration, or inhaling. When the lungs inhale, the diaphragm contracts and pulls downward. At the same time, the muscles between the ribs contract and pull upward.
This increases the size of the thoracic cavity and decreases the pressure inside.
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