How the Brain Controls Breathing Flashcards
Conditions that depress the respiratory components of the medulla oblongata
Reduced blood flow through the medulla as a result of excess pressure caused by cerebral edema or some kind of other intracerebral abnormality
Acute poliomyelitis (Acute means temporary and curable)
Ingestion of drugs that depress the central nervous system.
Monitoring systems that influences the respiratory components of the medulla
rom the moment the respiratory components of the medulla ( DRG & VRG ) activate ventilatory patterns based on the information received from the several different monitoring systems throughout the body. The major know monitoring systems are the.
-Central Chemoreceptors
-Peripheral Chemoreceptors
Central Chemoreceptors
Located bilaterally on ventrally in the substance of the medulla responsible for the monitoring the H+ ion concentration of the cerebrospinal fluid an exces concentration of H+ in the CSF is the most powerful stimulate know to influence the respiratory components (DRG & VRG) of the medulla
As Carbon dioxide levels increase in the arterial blood this causes the central chemoreceptors to transmit signals to the respiratory components in the medulla which in turn increases the alveolar ventilation. The increase in the ventilation reduces th PaCO2, this decreases the stimulation of th central chemoreceptors the neural signal the respiratory components in the medulla also diminishes cause the alveolar ventilation to decrease.
Peripheral Chemoreceptors
Located high in the neck at the bifurcation of the internal and external cartid arteries and aortic arch they are special oxygen sensitive cells that react to the reduction of oxygen levels in the arterial blood. They are sometimes referred to as the carotid and aortic bodies.
When activated by low PaO2 signals are transmitted to the respiratory components in the medulla by the way of the glossopharyngeal nerve ( Cranial nerve 9) from the carotid bodies or by the vagus nerve ( Cranial nerve 10) from the aortic bodies.
Peripheral Chemoreceptor funtion
This action causes signals to be transmitted to the respiratory muscles, causing ventilation to increase compared to the aortic bodies, the carotid bodies play a much greater role in initiating ventilatory rate in response to the reduced arterial oxygen levels. the peripheral chemoreceptors are not significantly activated until oxygen content of inspired air is low enough to reduce PaO2 to 60 mmHG or (SaO2 of about 90%)
-Normal saturation levels are around (98%-100%) -Beyond this point , any further reduction of the PaO2 causes a marked increase in ventilation however, suppression of the peripheral chemoreceptors is seen when PaO2 falls below 30mmHG in the patient with low PaO2 and chronically high PaCO2 level (end -Stage Emphysema) the peripheral chemoreceptors may be totally responsible for the control of ventilation. This is a compensatory response to a chronically high CO2 concentration in the blood.
-Hering Breuer Reflex
-Generated by stretch receptors , located in the walls of the bronchi and bronchioles
-They become excited when the lungs overinflate. Signals from these receptors travel through the vagus nerve to the respiratory components in the medulla, cousin inspiration to cease, in other words, the lungs themselves provide a feedback mechanism to terminate inspiration. This reflex appears to be a protective mechanism that prevents pulmonary damage caused by excessive lung inflation. Compared to adults, the Hering Breuer Reflex appears to have more significance in the control of ventilation in newborns.
-Deflation Reflex
-An increased rate of breathing results when the lungs are compressed or deflated. The precise mechanism responsible for this is not known
-Irritant Reflex
-Located in the trachea bronchi, and bronchioles. Its stimulated when the lungs are exposed to noxious gasses when activated, a reflex response causes the ventilatory rate to increase and may also produce a reflex cough and bronchoconstriction
-Juxtapulmonary capillary receptors
-An extensive network of free nerve endings
-located in the small conducting airways, blood vessels, and interstitial tissues between the pulmonary capillaries, and alveolar walls. These nerve endings are located near the alveolar capillaries are called Juxtapulmonary capillary receptors or J receptors. They react to alveolar inflammation, pulmonary capillary congestion, edema, and lung deflation, and emboli (Clout). When stimulated, a reflex triggers rapid shallow breathing.
-Peripheral Proprioceptor Reflex
-Located in the muscle, tendons, joints, and pain receptors. In the muscles and skin when stimulated impulses are sent to the medulla in turn, the medulla sends out an increased number of inspiratory signals. Moving an individual’s limbs or producing prolonged pain to the skin, stimulating ventilation.
-The receptors in the joints and tendons are also believed to play an important role in initiating and maintaining an increased respiratory rate during exercise . The more joints and tendons are involved the greater the respiration rate.
-Hypothalamic Controls
-Excitement causes the respiration rate to increase. Increased body temperature causes the respiration rate to increase. Decreased body temperature produces the opposite effect. Sudden cold stimulus (ex: plunging into very cold water) can cause cessation of breathing or a gasp.
-Reflexes from the Aortic and Carotid sinus Baroreceptors
-Located near the aortic and carotid peripheral receptors initial reflexis that cause:
1.)Decreased heart and ventilatory rate in response to an elevated heart and ventilatory rate in response to an elevated systemic blood pressure 2.)An increased heart and ventilatory rate in response to a reduced systemic blood pressure 3.) Based on metabolic needs of the body. Elicits neural impulses of the muscles or ventilation
