![]() The responsible motor neurons are located in the anterior horn of the spinal column. The collective output of the respiratory control center to the motor neurons controls the muscles of respiration (the effectors), and it is this output that results in automatic, rhythmic respiration. Finally, the ventilatory pattern can be modulated by pulmonary mechanoreceptors and irritant receptors in the lung in response to the degree of lung inflation or the presence of an irritant in the airways. These chemoreceptors respond to changes in their local environment associated with decreases in P o 2, increases in P co 2, and decreases in the pH of arterial blood and give afferent information to the central respiratory control center through the vagus nerve (aortic bodies) and the carotid sinus nerve, a branch of the glossopharyngeal nerve (carotid bodies), to make adjustments in alveolar ventilation that change whole body P co 2, pH, and P o 2. Chemosensitive peripheral chemoreceptors are located on specialized cells in the aortic arch ( aortic bodies ) and at the bifurcation of the internal and external carotid arteries in the neck ( carotid bodies ). Peripheral structures also provide input to the integrator and control ventilatory drive. These chemoreceptors detect changes in the P co 2 /pH of brainstem interstitial fluid and modulate ventilation. Within the central nervous system, central chemoreceptors are located just below the ventrolateral surface of the medulla. Input to the integrator arises from higher brain centers including the cerebral cortex, hypothalamus, amygdala, limbic system, and cerebellum. The integrator controls the pattern generator and determines the appropriate ventilatory drive. It consists of two main parts: a ventilatory pattern generator, where the rhythmic pattern is generated and an integrator, which processes inputs from higher brain centers and chemoreceptors and controls the rate and amplitude of the ventilatory pattern. This center is not a discrete nucleus, but rather a poorly defined collection of different nuclei that generate and modify the basic rhythmic ventilatory pattern. The respiratory control center is located in the reticular formation of the medulla oblongata beneath the floor of the fourth ventricle. Respiratory rate is determined by the signal frequency from the central controller to the effectors, whereas tidal volume is determined by the activity of the individual nerve fibers in the effectors to their motor units, including the frequency and duration of discharges and the number of units activated. Stimulation of the effectors subsequently reduces sensor activity through negative feedback.Īs described in Chapter 5, alveolar ventilation is a function of respiratory rate and tidal volume. ![]() In turn, the respiratory control center sends signals to the effectors such as the respiratory muscles and the diaphragm. Sensors, including central and peripheral chemoreceptors and pulmonary mechanoreceptors, feed information to the respiratory control center. The three major elements of the respiratory control system. ![]() A third goal of breathing is to maintain the acid–base environment of the brain through the effects of ventilation on arterial P co 2. From a mechanical perspective, the goal of breathing is to minimize work from a physiologic perspective, the goal is to maintain blood gas levels and specifically to regulate arterial P co 2. Ventilatory control refers to the generation and regulation of rhythmic breathing by the respiratory center in the brainstem and its modification by the input of information from higher brain centers and systemic receptors. At the same time, however, voluntary hyperventilation is easy, breath-holding is possible within limits, and the breathing pattern is modulated by the need for speech and singing. Inspiration and exhalation occur automatically under the control of neurons located in the brainstem. Although intermittent respiratory movements have been observed in utero, regular, automatic respiration begins at birth. Respiration demonstrates automaticity as well as self-modulation (voluntary). List three diseases associated with abnormal respiratory control. Provide an overview of the three basic elements of the ventilatory control system.Įxplain the structure and function of central chemoreceptors and peripheral chemoreceptors and their interrelationship.ĭescribe five chest wall and lung reflexes important in the control of respiration.ĭescribe the anatomy of the central respiratory control center and the relationship between the ventral and dorsal respiratory groups.ĭescribe the role of cerebrospinal fluid hydrogen ion and HCO 3 – in the regulation of respiration.Įxplain the effects of hypoxemia, increased work of breathing, sleep, and acidosis on the ventilatory response to CO 2.
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