Pacemaker generating the rhythm for breathing is
Pro-Botzinger complex generates the rhythm for automated breathing. These are also known as pacemaker cells located in the medulla. These are the first set of neurons which initiate inspiration. These neurons discharge rhythmically, and they produce rhythmic discharges in the phrenic motor neurons. Breathing is under the control of both the following: Voluntary control: Located in the cerebral coex ( coicospinal tract) Automatic Control: Driven by pacemaker cells in the medulla (Pre-Botzinger complex). These activate motor neurons cervical (Phrenic nerve innervating diaphragm) and thoracic spinal cord (external intercostal muscle). There is a reciprocal innervation to expiratory and inspiratory muscles in that motor neurons supplying expiratory muscles are inactive when motor neurons supplying inspiratory muscles are active, and vice versa. Inspiration Initiation Pre-Botzinger complex (pacemaker cells) in Medulla Maintenance Apneustic center in lower pons stimulates Dorsal group of neurons in the medulla Termination Apneustic center initiated by vagus and Pneumotaxic center Regulation of expiration: During quiet breathing, expiration is a passive process; there is no firing of neurons. Ventral respiratory group of neurons are involved in forceful expiration like during excercise. Ref: Ganong&;s Review of Medical Physiology 26th edition Pgno: 646
Pneumotaxic centre
Dorsal group of neurons in the medulla
Pre-Botzinger complex
Apneustic centre
G.I.T