Regulation of respiration

Respiratory center

There are thee groups of neurons which are bilaterally represented in the medulla and the pons and they constitute the respiratory center

  1. Dorsal respiratory group which is found in the dorsal portion of the upper medulla. Most of its neurons are in the nucleus of the tractus solitarius but some may be found in the close by medullary reticular formation. Impulses arrive at this center through peripheral chemoreceptors, baroreceptors and miscellaneous lung receptors.  It is for inspiration
  2. Ventral respiratory group placed at the ventrolateral part of the medulla that causes mainly expiration, but can also be effective in inspiration.
  3. Pneumotaxic center which is found in the dorsal aspect of the superior part of the pons that control rate of breathing and its depth. Two main processes are involved in pulmonary ventilation or breathing.

The above centers discharge via the vagus and glossopharyngeal neurons to the periphery such as the intercostal muscles, lungs,   diaphragm, which are the peripheral apparatus that perform respiration.

Inspiratory ramp signal

This is responsible for initiating inspiration through the excitation of the diaphragm. The signal begins initially very weak and then increases in a ramp manner for about 2 seconds and then ceases abruptly for another 3 seconds . At its cessation the diaphragm is allowed to perform its elastic recoil in order to initiate expiration. The control of ramp also controls the depth of respiration so that in heavy respiration ramp increases rapidly to fill the lungs rapidly. Also the point at which ramp ceases suddenly determines the length of respiration. If it ceases after a longtime, that reduces the frquency of breathing and vice versa.

Hering-Breuer inflation reflex

Sensory signals from the lungs control respiration in addition to the control in higher neural centers. Stretch receptors are placed in the lungs which determine when the lung is overstretched. The stretch receptors cause a feedback loop which switches off the inspiratory ramp and causes inspiration to cease. This is the Hering-Breuer reflex.

Chemical control of respiration



















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