Ch 21 - Control of Respiratory Function Flashcards
What is the structural organization of the respiratory system? Lungs and Respiratory airways?
Conducting airways - nasal passages - it passes through it is filtered, warmed and humidified with coarse hairs, mouth, pharynx. larynx - connects the oropharynx with the trachea, are supported by rigid cartilaginous structures to prevent collapse during inspiration. , bronchi, and bronchioles - is viewed as system of branching tubes, has four distinct layers
Lungs - in addition to their gas exchange function, they inactivate vasoactive substances such as bradykinin, convert angiotensin I to II, and serve as a reservoir for blood storage.
Pleura - the lungs are encased in a thin double-layered closed sac. Outer parietal layer of the pleural sac lines the pulmonary cavities and adheres to the thoracic wall, the mediastinum and diaphragm. The inner visceral pleura closely covers the lung and is adherent to all its surfaces. The thin film of serous fluid separates the two layers, allowing them to glide over each other, yet hold together so there is no separation between the lungs and the chest wall.
Respiratory Lobules - The gas exchange function of the lung takes place here. Consists of bronchiole, alveoli, and pulmonary blood vessels. Has two types of alveolar cells I and II. I are not capable of regeneration. II are interspersed between type I are secretory cells and release surfactant. There are 4 type of surfactant. B is important to the surface reducing film the other to innate immune system.
Pulmonary and bronchial circulation? Innervation?
Has a dual blood supply; the pulmonary and bronchial circulations. Pulmonary comes from the pulmonary artery and provides for the gas exchange function of the lungs. It returns oxygenated blood by way for pulmonary veins. Bronchial blood vessels are the only ones that can undergo angiogenesis and develop collateral circulation when vessels in the pulmonary circulation are obstructed.
Innervation - the lung is innervated by both the sympathetic and parasympathetic divisions of the autonomic nervous system. They are derived from vagal nerves and the sympathetic fibers, which originate in the upper thoracic and cervical ganglia, form the pulmonary plexuses that enter the lung in the region of the hilus. Parasympathetic fibers are excitatory neurons that respond to acetylcholine. Is responsible for airway constriction, blood vessel dilation and inc glandular secretion. The sympathetic nervous, which responds to catecholamines norepinephrine and epinephrine, produces bronchodilation, blood vessel constriction and inhibition of glandular secretion
Basic properties of Gases? Pulmonary Ventilation? Respiratory Pressures?
Made up of a mixture of gases, mainly nitrogen and oxygen. Combined pressure exerted is atmospheric pressure. Are always relative to respiratory to atmospheric. Pressure exerted by a single gas in a mixture is partial pressure.
Ventilation refers to exchange of gases within the respiratory system. Two types; pulmonary and alveolar. Pulmonary refers to the total exchange of gases between the atmosphere and the lungs. It relies on a system of open airways and a change in pressure that is created as the respiratory muscles change the size of the chest cage. Alveolar to the transfer of gases within the gas exchange portion of the lungs.
Intrapulmonary pressure or alveolar - the pressure inside the airways and alveoli of the lungs. the gases in the lungs are in communication with atmospheric air pressure. When the mouth is open and air is not moving into or out of the lungs pressure is zero or equal to atmospheric.
Intrapleural pressure - is always negative in relation to alveolar pressure in the normally inflated lung. during inspiration, expansion of the chest cage pulls outward on the lungs to increase the negative pressure so air can move into the lungs; and during expiration, the pressures are reversed causing air to move out of the lung.
Intrathoracic pressure - is the pressure in the thoracic cavity. is essentially equal to intrapleural pressure and is the pressure to which the lungs, heart, and great vessels are exposed
Chest cage and respiratory muscles? Lung compliance? Elastic properties
Chest cage is a closed compartment bounded on the top by the neck muscles and at the bottom by the diaphragm. Outer walls are formed by 12 pairs of ribs, the sternum, the thoracic vertebrae, and the intercostal muscles that lie between the ribs. Air moves between the atmosphere and the lungs because of a pressure difference or gradient.
The diaphragm is the principal muscle of inspiration. When it contracts, the abd contents are forced downward and the chest expands from top to bottom. Innervated mainly from the C4 but also the C3 and C5. Spinal cord injuries above this require ventilation.
Lung compliance refers to the ease with which the lungs can be inflated. It can be appreciated by comparing the ease of blowing up a balloon that has been previously inflated with a new balloon that is stiff and noncompliant. It is determined by elastic properties of the lung and alveolar surface tension.
Elastic properties - 3 components; distensibility, stiffness and elastic recoil.
Surface tension? Airway resistance?
The alveoli are lined with a thin film of liquid, it is at the interface between this liquid film and the alveolar air that surface tension develops. Surfactants also stabilize alveolar inflation by changing their density in relation to alveolar size, with the surfactant molecules becoming more tightly compressed in the small alveoli with their alveoli with their lower surface tension.
Resistance - during breathing, the flow or volume of air that moves into and out of the lungs is directly related to the pressure difference between the lungs and the atmosphere and inversely related to the resistance that the air and inversely related to the resistance that the air encounters as it moves through the conducting airways.
- Airway radius - the primary determinant of airway resistance to airflow is the radius of the conducting airway.
- Lung volume - being less during inspiration than during expiration.
- neural and local control of airway diameter - The smooth muscles in the airways are under ANS control. Stimulation of the parasympathetic nervous system produces bronchial constriction as well as inc mucus secretion. sympathetic is the opposite.
- Laminar and turbulent airflow - depending on the velocity and pattern of flow.
- airway compression during forced expiration - It is significantly inc during forced expiration, such as occurs during forced expiration
Lung volumes and pulmonary function studies?
Lung volumes or the amount of air exchanged during ventilation, can be subdivided into three components 1. tidal volume - is about 500 mL, is the amount of air that moves into and out of the lungs during normal breath. 2. inspiratory reserve volume - the maximum amount of air that can be inspired in excess of the normal TV, 3 expiratory reserve volume.- is the maximum amount that can be exhaled in excess of the normal tv. Approx 1200 mL of air remains after forced expiration; this air is residual volume RV. Measured with a spirometer.
Exchange of gases within the lungs? Alveolar ventilation?
Gas exchange is divided into 3 processes;
1. Alveolar ventilation - is to continually renew the air in the gas exchange areas of the lungs where the air is in close proximity to the blood.
distribution of alveolar ventilation - the distribution of ventilation between the base and apex of the lung varies with body position and reflects the effects of gravity on intrapleural pressure and lung compliance
dead air space - refers to the air that must be moved with each breath but doesn’t participate in gas exchange.
- perfusion - is used to describe the flow of blood through the gas exchange portion of the lungs. The pulmonary blood vessels are thinner, more compliant, and offer less resistance to flow than those in the systemic circulation, and the pressures in the pulmonary system are much lower. So accommodates the delivery of varying amounts of blood from the systemic circulation without producing signs and symptoms of congestion. It is approx. 500 mL
distribution of pulmonary blood flow - is affected by body position and gravity. Shunt - refers to blood that moves from the right to the left side of the circulation without being oxygenated. usually results from destructive lung diseases that impairs ventilation or from heat failure that interferes. - Diffusion - takes place in the respiratory portions of the lung and refers to the movement of gases across the alveolar - capillary membrane. Is affected by 1. difference in the pressure of the gas on the either side of the membrane. 2. the surface area that is available for diffusion 3. the thickness of the alveolar-capillary membrane through which the gas must pass 4. diffusion characteristics of the gas.
Oxygen and carbon dioxide transport?
Oxygen transport - it is transported in the dissolved state and in chemical combination with hemoglobin. It carries about 97% of oxygen in the blood and is the main transporter. It is influenced by pH, carbon dioxide concentration, and body temperature.
Plasma transport - PO2 the partial pressure of oxygen represents the level of dissolved oxygen in plasma.
Oxygen hemoglobin dissociation curve - the relationship between the oxygen carried in combination with hemoglobin and the PO2 of the blood is described by the oxygen hemoglobin dissociation curve,
Carbon dioxide transport - CO2 is transported in the blood in three forms: dissolved in plasma, attached to hemoglobin and as bicarbonate. Acid base balance is influenced by the amount of dissolved carbon dioxide and the bicarbonate level in the blood. As it is formed during metabolism, it diffuses out of cells into the tissue spaces and then into the capillaries.
Control of breathing? Respiratory center?
The muscles that control respiration require continuous input from the nervous system. It is this ventilation is integrated by neurons located in the pons and medullar. The respiratory center consists of two dense, bilateral aggregates of respiratory neurons involved in initiating inspiration and expiration and incorporating afferent impulses into motor responses of the respiratory muscles. The first (dorsal) group of neurons is concerned primarily with inspiration. They control the activity of the phrenic nerves that innervate the diaphragm and drive the second, group of respiratory neurons. The second group contains inspiratory and expiratory neurons, controls the spinal motor neurons of the intercostal and adb muscles
Two groups of neurons; pneumotaxic center in the upper pons - switches inspiration off, assisting in the control of respiratory rate and inspiratory volume and apneustic center in the lower pons - has an excitatory effect on inspiration, tending to prolong inspiration.
Regulation of breathing? Cough reflex? Dyspnea?
Has both automatic and voluntary components.
1. chemoreceptors - monitor blood levels of oxygen, carbon dioxide, and the pH and adjust ventilation to meet the changing metabolic needs of the body. Two types central located in the brain stem - are sensitive to PCO2, peripheral located in the carotid arteries and aorta - monitor PO2 levels.
- lung and chest wall receptors - monitor the status of breathing in terms of airway resistance and lung expansion. 3 types of lung receptors; stretch, irritant, and juxtacapillary receptors - close to the pulmonary capillaries.
Voluntary regulation of ventilation - integrates breathing with voluntary acts such as speaking, blowing and singing. Are initiated by the motor and premotor cortex, cause a temporary suspension of automatic breathing.
Coughing is a neutrally mediated reflex that protects the lungs from the accumulation of secretions and from entry of irritating and destructive substances. It is initiated by receptors located in the tracheobronchial wall, receptors that are extremely sensitive to irritating substances and the presence of excess secretions. Afferent impulses from these receptors are transmitted through the vagus to the medullary center, which integrates the cough response. Is difficult to quantify because it relies on a person’s perception of the problem.
Dyspnea - is the perceived shortness of breath or difficulty breathing.
