Control of Respiration - Ventilatory Pattern

Ventilatory Pattern

The pattern of motor stimuli during breathing can be divided into inspiratory and expiratory phases. Inspiration shows a sudden, ramped increase in motor discharge to the inspiratory muscles (including pharyngeal dilator muscles). Before the end of inspiration, there is a decline in motor discharge. Exhalation is usually silent, except at high minute ventilation rates.

The mechanism of generation of the ventilatory pattern is not completely understood, but involves the integration of neural signals by respiratory control centers in the medulla and pons. The nuclei known to be involved are divided into regions known as the following:

• medulla (reticular formation)
  • ventral respiratory group (nucleus retroambigualis, nucleus ambigus, nucleus parambigualis and the pre-Bötzinger complex). The ventral respiratory group controls voluntary forced exhalation and acts to increase the force of inspiration.
  • dorsal respiratory group (nucleus tractus solitarius). The dorsal respiratory group controls mostly inspiratory movements and their timing.
• pons
  • pneumotaxic center.
    • Coordinates transition between inhalation and exhalation
    • Sends inhibitory impulses to the inspiratory area
    • The pneumotaxic center is involved in fine tuning of respiration rate.
  • apneustic center
    • Coordinates transition between inhalation and exhalation
    • Sends stimulatory impulses to the inspiratory area – activates and prolongs inhalate (long deep breaths)
    • overridden by pneumotaxic control from the apneustic area to end inspiration

There is further integration in the anterior horn cells of the spinal cord.