Long description

On the left a drawing of the ribcage with the diaphragm within the base of the cage, and intercostal muscles between the ribs.

On the right a diagram of part of the hind-brain (pink) with the pons at the top and the medulla oblongata below, leading down to the spinal cord. Within the pons is a yellow dot, the pontine respiratory group; at the top of the medulla is a red dot, the dorsal respiratory group, and a blue dot, the ventral respiratory group; the dorsal and ventral respiratory groups form the medullary respiratory centre.

A black line (representing neuronal links) from the pontine respiratory group to the dorsal respiratory group and thence to a synapse at the base of the medulla oblongata links to a dark blue line to the diaphragm from the lower end of the medulla oblongata; this represents the phrenic nerve to the diaphragm.

A black line from the ventral respiratory group to synapse at the base of the medulla oblongata links to a light blue line (intercostal nerves) to internal intercostal muscles (involved in expiration), and to a green line (intercostal nerves) to external intercostal muscles (involved in inspiration).