The medulla and the pons are involved in the regulation of the ventilatory pattern of respiration. Involuntary respiration is any form of respiratory control that is not under direct, conscious control. Breathing is required to sustain life, so involuntary respiration allows it to happen when voluntary respiration is not possible, such as during sleep.
Involuntary respiration also has metabolic functions that work even when a person is conscious. Involuntary respiration is controlled by the respiratory centers of the upper brainstem sometimes termed the lower brain, along with the cerebellum. This region of the brain controls many involuntary and metabolic functions besides the respiratory system, including certain aspects of cardiovascular function and involuntary muscle movements in the cerebellum.
Anatomy of the brainstem : The brainstem, which includes the pons and medulla. The respiratory centers contain chemoreceptors that detect pH levels in the blood and send signals to the respiratory centers of the brain to adjust the ventilation rate to change acidity by increasing or decreasing the removal of carbon dioxide since carbon dioxide is linked to higher levels of hydrogen ions in blood. There are also peripheral chemoreceptors in other blood vessels that perform this function as well, which include the aortic and carotid bodies.
The medulla oblongata is the primary respiratory control center. Its main function is to send signals to the muscles that control respiration to cause breathing to occur.
There are two regions in the medulla that control respiration:. Neural Mechanisms Respiratory Center The medulla and the pons are involved in the regulation of the ventilatory pattern of respiration.
Learning Objectives Describe the neural mechanism of the respiratory center in respiration control. Key Takeaways Key Points The ventral respiratory group controls voluntary forced exhalation and acts to increase the force of inspiration.
The dorsal respiratory group nucleus tractus solitarius controls mostly inspiratory movements and their timing. Ventilatory rate minute volume is tightly controlled and determined primarily by blood levels of carbon dioxide as determined by metabolic rate. Chemoreceptors can detect changes in blood pH that require changes in involuntary respiration to correct. The apneustic stimulating and pnuemotaxic limiting centers of the pons work together to control rate of breathing.
The medulla sends signals to the muscles that initiate inspiration and expiration and controls nonrespiratory air movement reflexes, like coughing and sneezing. Key Terms respiratory control centers : The medulla which sends signals to the muscles involved in breathing, and the pons which controls the rate of breathing. The Medulla The medulla oblongata is the primary respiratory control center.
There are two regions in the medulla that control respiration: The ventral respiratory group stimulates expiratory movements. The dorsal respiratory group stimulates inspiratory movements. The Pons The pons is the other respiratory center and is located underneath the medulla. It has two main functional regions that perform this role: The apneustic center sends signals for inspiration for long and deep breaths.
It controls the intensity of breathing and is inhibited by the stretch receptors of the pulmonary muscles at maximum depth of inspiration, or by signals from the pnuemotaxic center. It increases tidal volume. The pnuemotaxic center sends signals to inhibit inspiration that allows it to finely control the respiratory rate. Its signals limit the activity of the phrenic nerve and inhibits the signals of the apneustic center.
It decreases tidal volume. Neural Mechanisms Cortex The cerebral cortex of the brain controls voluntary respiration. Learning Objectives Describe the mechanism of the neural cortex in respiration control. Key Takeaways Key Points The motor cortex within the cerebral cortex of the brain controls voluntary respiration the ascending respiratory pathway. Voluntary respiration may be overridden by aspects of involuntary respiration, such as chemoreceptor stimulus, and hypothalamus stress response.
The phrenic nerves, vagus nerves, and posterior thoracic nerves are the major nerves involved in respiration. Voluntary respiration is needed to perform higher functions, such as voice control. Key Terms The Phrenic Nerves : A set of two nerves that brings nerve impulses from the spinal cord to the diaphragm.
Chemoreceptor Regulation of Breathing Chemoreceptors detect the levels of carbon dioxide in the blood by monitoring the concentrations of hydrogen ions in the blood. Learning Objectives Describe the role of chemoreceptors in the regulation of breathing. In response to a decrease in blood pH, the respiratory center in the medulla sends nervous impulses to the external intercostal muscles and the diaphragm, to increase the breathing rate and the volume of the lungs during inhalation.
Hyperventilation causes alakalosis, which causes a feedback response of decreased ventilation to increase carbon dioxide , while hypoventilation causes acidosis, which causes a feedback response of increased ventilation to remove carbon dioxide.
Any situation with hypoxia too low oxygen levels will cause a feedback response that increases ventilation to increase oxygen intake. Vomiting causes alkalosis and diarrhea causes acidosis, which will cause an appropriate respiratory feedback response. Key Terms hypoxia : A system-wide deficiency in the levels of oxygen that reach the tissues.
Proprioceptor Regulation of Breathing The Hering—Breuer inflation reflex prevents overinflation of the lungs. Learning Objectives Evaluate the effect of proprioception the sense of the relative position of the body and effort being employed in movement on breathing. Key Takeaways Key Points Pulmonary stretch receptors present in the smooth muscle of the airways and the pleura respond to excessive stretching of the lung during large inspirations.
The Hering—Breuer inflation reflex is initiated by stimulation of stretch receptors. The deflation reflex is initiated by stimulation of the compression receptors called proprioceptors or deactivation of stretch receptors when the lungs deflate.
Activation of the pulmonary stretch receptors via the vagus nerve results in inhibition of the inspiratory stimlus in the medulla, and thus inhibition of inspiration and initiation of expiration. An increase in pulmonary stretch receptor activity leads to an elevation of heart rate tachycardia. A cyclical, elevated heart rate from inspiration is called sinus arrhythmia and is a normal response in youth.
Inhibition of inspiration is important to allow expiration to occur. Key Terms sinus arryhthmia : A normal cyclical heart rate change in which an increase in heart rate occurs during inspiration, but returns to normal during expiration. Licenses and Attributions. CC licensed content, Shared previously.
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