Respiratory System and Its Regulation Notes PDF

Dianne Salvaleon The Respiratory System and Its Regulation What is the importance of the respiratory system in exercise, physical activity and activities of daily living? Cardiovascular and Respiratory System Provide e ective delivery system of O2 to and removing of CO2 from all the tissues of the b...

Dianne Salvaleon The Respiratory System and Its Regulation What is the importance of the respiratory system in exercise, physical activity and activities of daily living? Cardiovascular and Respiratory System Provide e ective delivery system of O2 to and removing of CO2 from all the tissues of the body The transportation involves four separate processes: Pulmonary ventilation (breathing) Pulmonary di usion (exchange of gases bet. lungs and the blood) Transport of oxygen and carbon dioxide via the blood Capillary di usion (exchange of gases bet. Capillary blood and metabolically active tissues Note: External respiration; internal respiration Pulmonary Ventilation (breathing): movement of air into and out of the lungs First two processes: external respiration : involve moving gases from the outside of the body into the lungs and blood. I Once the gases are in the blood they must be transported ff ff ff Then the last last occurs: gas exchange bet blood and tissues or also called internal respiration In this chapter we’ll look at: Anatomy of the Lungs Pulmonary Ventilation Inspiration Expiration Gas Exchange at the Muscles Lungs Gross Anatomy pyramid-shaped, paired organs that are connected to the trachea by the right and left bronchi; on the inferior surface, the lungs are bordered by the diaphragm. Each lung is composed of lobes separated by ssures The diaphragm is a dome-shaped muscle located at the base of the lungs and thoracic cavity. The right lung is shorter and wider than the left lung, and the left lung occupies a smaller volume than the right. The cardiac notch is an indentation on the surface of the left lung, and it allows space for the heart. Each lung is composed of smaller units called lobes. Fissures separate these lobes from each other. The right lung consists of three lobes: the superior, middle, and inferior lobes. fi The left lung consists of two lobes: the superior and inferior lobes. Lungs Not directly attached to the ribs Suspended by a double walled pleural sacs Parietal pleural: lines thoracic wall Visceral pleural: lines the other aspects of the lungs Pleural walls have uid in between to reduce friction during breathing Connected to the lungs and to the inner surface of the thoracic cage, causing lungs to take the shape and size of the ribs as the chest expands and contracts The lungs are enclosed by the pleurae, which are attached to the mediastinum. fl In addition, these sacs are connected to the lungs and to the inner surface of the thoracic cage, causing the lungs to take the shape and size of the rib or thoracic cage as the chest expands and contracts. Lungs Blood Supply Nervous Innervation Major function of the lungs is to perform gas exchange Autonomic Nervous system which requires blood from the pulmonary circulation. Pulmonary circulation contains deoxygenated blood. Blood travels to the lungs where RBCs pick up oxygen to be transported to all body tissues Pulmonary artery carries deoxygenated blood to the alveoli Pulmonary arteries become pulmonary capillary network Capillary wall meets alveolar wall, creating a respiratory membrane Once blood is oxygenated, it drains from the alveoli by controls dilation and constriction of the airway Parasympathetic: bronchoconstriction Sympathetic: bronchodilation Re exes such as coughing Regulation of O2 and CO2 level way of many pulmonary veins which exit the lungs The blood supply of the lungs plays an important role in gas exchange and serves as a transport system for gases throughout the body. In addition, innervation by the autonomic nervous systems provides an important level of control through dilation and constriction of the airway. Blood Supply The major function of the lungs is to perform gas exchange, which requires blood from the pulmonary circulation. This blood supply contains deoxygenated blood and travels to the lungs where erythrocytes, also known as red blood cells, pick up oxygen to be transported to tissues throughout the body. The pulmonary artery is an artery that arises from the pulmonary trunk and carries deoxygenated, arterial blood to the alveoli. The pulmonary artery branches multiple times as it follows the bronchi, and each branch becomes progressively smaller in diameter. As they near the alveoli, the pulmonary arteries become the pulmonary capillary network. The pulmonary capillary network consists of tiny vessels with very thin walls that lack smooth muscle bers. The capillaries branch and follow the bronchioles and the structure of the alveoli. It is at this point that the capillary wall meets the alveolar wall, creating the respiratory membrane. Once the blood is oxygenated, it drains from the alveoli by way of multiple pulmonary veins, which exit the lungs. fi fl Nervous Innervation Dilation and constriction of the airway are achieved through nervous control by the parasympathetic and sympathetic nervous systems. The parasympathetic system causes bronchoconstriction, whereas the sympathetic nervous system stimulates bronchodilation. fl Re exes such as coughing, and the ability of the lungs to regulate oxygen and carbon dioxide levels, also result from this autonomic nervous system control. Pulmonary Ventilation Breathing through the nose helps humidity and warm the air during inhalation and lters out foreign particles from the air (Breathing) Process by which we move air into and out of the lungs Transport/ conduction zone: Air is drawn in through nose (mouth); the air travels through the pharynx, larynx, trachea and bronchial tree Function: Filtering, warmth, humidi er Pulmonary Ventilation or breathing is the process by which we move air into and out of the lungs Air is typically drawn through the nose (mouth). Nasal breathing advantageous because air is warmed and humidi ed as it swirls through bony irregular sinus surfaces and lters tiniest particles minimizing irritation and threat of respiratory infections. From the nose and mouth, the air travels through the pharynx, larynx, trachea and bronchial tree (transport zone) : gas exchange does not occur in these structures! fi fi fi fi Transport tube: respiratory bronchioles Respiratory zone: site of gas exchange occurs at the clusters of alveoli (alveolus) Pulmonary Ventilation (Respiratory Zone) Respiratory bronchioles: smallest the of bronchiole Alveoli: responsible for gas exchange; stretches during air intake Function: gas exchange respiratory bronchiole, the smallest type of bronchiole which then leads to an alveolar duct, opening into a cluster of alveoli. Pulmonary Ventilation (Mechanism of Breathing) Process by which we move air into and out of the lungs Dependent on the air pressure of the atmosphere and the air pressure within the lungs. Inspiration and expiration are dependent on the di erences in pressure between the atmosphere and the lungs. In a gas, pressure is a force created by the movement of gas molecules that are con ned. Boyle’s law describes the relationship between volume and pressure in a gas at a constant temperature. Boyle discovered that the pressure of a gas is inversely proportional to its volume: volume increases, pressure decreases. volume decreases, pressure increases. The anatomy of the lungs, the pleural sacs, the diaphragm muscle, and the thoracic cage determines air ow into and out of the lungs, that is, inspiration and expiration. Inspiration (or inhalation) and expiration (or exhalation) are dependent on the di erences in pressure between the atmosphere and the lungs. In a gas, pressure is a force created by the movement of gas molecules that are con ned. For example, a certain number of gas molecules in a two-liter container has more room than the same number of gas molecules in a one-liter container (Figure 22.15). fl ff ff fi fi In this case, the force exerted by the movement of the gas molecules against the walls of the two-liter container is lower than the force exerted by the gas molecules in the one-liter container. Therefore, the pressure is lower in the two-liter container and higher in the one-liter container. Pulmonary Ventilation (Mechanism of Breathing) The di erence in pressures drives pulmonary ventilation because air ows down a pressure gradient Air ows from an area of higher pressure to an area of lower pressure. Air ows into the lungs largely due to a di erence in pressure; atmospheric pressure is greater than intraalveolar pressure, and intra-alveolar pressure is greater than intrapleural pressure. Air ows out of the lungs during expiration based on the same principle; pressure within the lungs becomes greater than the atmospheric pressure. ff fl ff fl fl fl Intraalveolar pressure is the pressure inside the alveoli of the lungs. Intrapleural pressure is the pressure within the pleural cavity. Inspiration and Expiration Inspiration: process that causes air into lungs Expiration: process that causes air to leave the lungs Respiratory cycle: 1 sequence of inspiration and exhalation fl Inspiration is the process that causes air to enter the lungs, and expiration is the process that causes air to leave the lungs (Figure 22.17). A respiratory cycle is one sequence of inspiration and expiration. In general, two muscle groups are used during normal inspiration: the diaphragm and the external intercostal muscles. Additional muscles can be used if a bigger breath is required. Figure 7.2a shows the resting positions of the diaphragm and the thoracic cage, or thorax. With inspiration, the ribs and sternum are moved by the external intercostal muscles. The ribs swing up and out and the sternum swings up and forward. At the same time, the diaphragm contracts, attening down toward the abdomen. Inspiration Active process involving the diaphragm ad the external intercostal muscles. With inspiration, the ribs, sternum are moved by the external intercostal muscles. The ribs swing up and out, sternum swing up and forward. Diaphragm contracts attening down toward the abdomen This movement creates a larger thoracic cavity, thus increasing the volume Increase in volume creates a decrease in intraalveolar pressure, creating a pressure lower than atmospehric pressure. The pressure gradient is created, driving the air into the lungs When the diaphragm contracts, it moves inferiorly toward the abdominal cavity, creating a larger thoracic cavity and more space for the lungs. Contraction of the external intercostal muscles moves the ribs upward and outward, causing the rib cage to expand, which increases the volume of the thoracic cavity. Due to the adhesive force of the pleural uid, the expansion of the thoracic cavity forces the lungs to stretch and expand as well. This increase in volume leads to a decrease in intra-alveolar pressure, creating a pressure lower than atmospheric pressure. As a result, a pressure gradient is created that drives air into the lungs. scaleni, sternocleidomastoid, pectorals: help raise the ribs even more then during regular breathing fl fl During forced or labored breathing, as during heavyexercise, inspiration is further assisted by the action of other muscles, such as the scaleni (anterior, middle, and posterior) and sternocleidomastoid in the neck and the pectorals in the chest. These muscles help raise the ribs even more than during regular breathing. Inspiration Note: other muscles will be engaged to raise the ribs even more during forced or labored breathing (such as in exercise) Scaleni, sternocleidomastoid, pectorals What do you think is the e ect of having a larger thoracic cavity than normal? scaleni, sternocleidomastoid, pectorals: help raise the ribs even more then during regular breathing ff During forced or labored breathing, as during heavy exercise, inspiration is further assisted by the action of other muscles, such as the scaleni (anterior, middle, and posterior) and sternocleidomastoid in the neck and the pectorals in the chest. These muscles help raise the ribs even more than during regular breathing. Expiration Passive process involving the relaxation of the inspiratory muscles and elastic recoil of the lung tissue With expiration, diaphragm relaxes, returns to its normal upward, arched position, external muscles relaxes, ribs and sternum move back into their resting position Thoracic cavity and lungs decrease in volume causing an increasing in intrapulmonary pressure. The intrapulmonary rises above the atmospheric pressure creating a pressure gradient, air ows out of the lungs The process of normal expiration is passive, meaning that energy is not required to push air out of the lungs. Instead, the elasticity of the lung tissue causes the lung to recoil, as the diaphragm and intercostal muscles relax following inspiration. In turn, the thoracic cavity and lungs decrease in volume, causing an increase in intrapulmonary pressure. The intrapulmonary pressure rises above atmospheric pressure, creating a pressure gradient that causes air to leave the lungs. Internal intercostal muscles pull the ribs down. fl This active process can be assisted by the latissimus dorsi and quadratus lumborum muscles. Expiration Passive process involving the relaxation of the inspiratory muscles and elastic recoil of the lung tissue During forced or labored breathing, expiration becomes a more active process Assisted by: intercostal muscles, abdominal muscles, latissimus dorsi and quadratus lumborum muscles Internal intercostal muscles pull the ribs down. This active process can be assisted by the latissimus dorsi and quadratus lumborum muscles. Basics of ventilation: Mechanics of breathing | BMJ Learning Basics of ventilation: Anatomy of normal breathing | BMJ Learning How do lungs work? - Emma Bryce | TED-Ed Videos for Mechanism of Breathing Respiratory Pump Changes in the intra abdominal and intrathoracic pressure that accompany forced breathing also help return venous blood back to the heart Respiratory pump: Essential in maintaining venous return Changing pressure with the abdomen and thorax squeeze blood in the veins, assisting its return to the heart through milking action Intra-abdominal and intrathoracic pressure increases, blood is transported to the great veins (pulmonary veins and the superior and anterior vena cavae) Pressure decreases, the veins return to their original size and ll with blood As intra-abdominal and intrathoracic pressure increases, it is transmitted to the great veins—the pulmonary veins and superior and inferior venae cavae—that transport blood back to the heart. fi When the pressure decreases, the veins return to their original size and ll with blood. The changing pressures within the abdomen and thorax squeeze the blood in the veins, assisting its return through a milking action. This phenomenon is known as the respiratory pump and is essential in maintaining adequate venous retur Respiratory Rate and Control of Ventilation Breathing occurs without thought, but at times you can consciously control it Respiratory rate is the total number of breaths that occur each minute Rate is controlled by the respiratory center located in the medulla oblongata Responds to changes in CO2, O2 and pH levels in the blood Respiratory rate: under 1 y.o.: 30-60 breaths/minute, 10 y.o. : 18-30 breaths/minute, adults: 12-18 breaths/minute 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 30. By adolescence, the normal respiratory rate is similar to that of adults, 12 to 18 breaths per minute. Respiratory Rate and Depth of Ventilation Regulated by medulla oblongata and pons Stimulated to produce respiration by the carbon dioxide concentration in the blood Concentrations of chemicals are sensed by chemoreceptors. increased carbon dioxide levels lead to increased levels of hydrogen ions, Increase in H+ in the brain triggers the central chemoreceptors to stimulate the respiratory centers to initiate the contraction of the diaphragm and intercostal muscle As a result, the rate and depth of respiration increase, expelling carbon dioxide In contact, low levels of CO2 cause low levels of H+ in the brain, leading to a decrease in the rate of respiration and depth of ventilation (shallow breathing) 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, negative-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. major factor that stimulates the medulla oblongata and pons to produce respiration The increase in hydrogen ions in the brain triggers the central chemoreceptors to stimulate the respiratory centers to initiate contraction of the diaphragm and intercostal muscles. As a result, the rate and depth of respiration increase, allowing more carbon dioxide to be expelled, which brings more air into and out of the lungs promoting a reduction in the blood levels of carbon dioxide, and therefore hydrogen ions, in the blood. In contrast, low levels of carbon dioxide in the blood cause low levels of hydrogen ions in the brain, leading to a decrease in the rate and depth of pulmonary ventilation, producing shallow, slow breathing. Respiratory Rate and Depth of Ventilation Regulated by medulla oblongata and pons Stimulated to produce respiration by the carbon dioxide concentration in the blood Concentrations of chemicals are sensed by chemoreceptors. increased carbon dioxide levels lead to increased levels of hydrogen ions A decreasing, more acidic, pH level stimulate an increase in ventilation to remove CO2 from blood at a quicker rate Removal of CO2 from blood helps reduce H+, increasing systemic pH Another factor involved in in uencing the respiratory activity of the brain is systemic arterial concentrations of hydrogen ions. Increasing carbon dioxide levels can lead to increased H+ levels, as mentioned above, as well as other metabolic activities, such as lactic acid accumulation after strenuous exercise. fl Peripheral chemoreceptors of the aortic arch and carotid arteries sense arterial levels of hydrogen ions. When peripheral chemoreceptors sense decreasing, or more acidic, pH levels, they stimulate an increase in ventilation to remove carbon dioxide from the blood at a quicker rate. Removal of carbon dioxide from the blood helps to reduce hydrogen ions, thus increasing systemic pH. Respiratory Rate and Depth of Ventilation Blood oxygen levels also in uence respiratory rate. Chemoreceptors sense large changes of blood oxygen levels Low blood oxygen levels: < 60 mmHg, peripheral chemoreceptor stimulate an increase in respiratory activity Hypothalamus and other regions involved with the limbic system are involved in regulating respiration in response to emotions, pain and temperature. e.g. increase in body temperature = increase in respiratory rate, excitement = ?, ight or ight response = ? Blood levels of oxygen are also important in in uencing respiratory rate. The peripheral chemoreceptors are responsible for sensing large changes in blood oxygen levels. If blood oxygen levels become quite low—about 60 mm Hg or less—then peripheral chemoreceptors stimulate an increase in respiratory activity. The chemoreceptors are only able to sense dissolved oxygen molecules, not the oxygen that is bound to hemoglobin. As you recall, the majority of oxygen is bound by hemoglobin; when dissolved levels of oxygen drop, hemoglobin releases oxygen. Therefore, a large drop in oxygen levels is required to stimulate the chemoreceptors of the aortic arch and carotid arteries. fl fi fl fl fl fl fl The hypothalamus and other brain regions associated with the limbic system also play roles in in uencing the regulation of breathing by interacting with the respiratory centers. 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 ght-or- ight response will also result in an increase in respiratory rate. Pulmonary Diffusion Gas exchange in the lungs between the alveoli and the capillary blood Major functions Replenishes the blood’s oxygen supply Removes Carbon Dioxide ff ff Oxygen from air di uses from the alveoli into the blood in the pulmonary capillaries, and carbon dioxide di uses from the blood into the alveoli in the lungs. Oxygen Transport in the Muscle Oxygen is transported in the muscle into the mitochondria By binding to Myoglobin (storage of O2) Used in ETC as acceptor of H+ ions When oxygenated blood reaches muscle cells, the bond between oxygen and hemoglobin molecules loosens. When the red blood cells pass single le through the tiny capillaries that surround muscle cells ( gure 3.2), oxygen molecules are released from hemoglobin and di use into the muscle cells. The carbon dioxide produced by the muscle cells di uses into the bloodstream not as CO2 but as bicarbonate ion (HCO3 −) that is converted back into CO2 in the lungs, where it is exhaled. fi ff fi ff Once inside muscle cells, the oxygen can either bind to myoglobin (a protein like hemoglobin that enables muscle cells to store a small amount of oxygen) or enter the mitochondria to be used in the electron transport chain to accept the H+ ions produced by the oxidation of carbohydrate and fat. Factors Influencing Oxygen Delivery and Uptake Oxygen content of blood Any reduction in the blood’s normal oxygen carrying capacity would hinder oxygen delivery and reduce cellular uptake of oxygen Blood Flow Exercise increases blood ow through the muscles. Local Conditions (e.g., pH, temperature) Changes increase oxygen unloading from the hemoglobin molecule, facilitating oxygen delivery and uptake by the muscles Exercise increases blood ow through the muscles. As more blood carries oxygen through the muscles, blood ow improves oxygen delivery. fl fl fl Local conditions: pH: muscular activity increases due to lactate production Muscle temp and CO2 conc.increase because of increased metabolism