Are the external and internal intercostal muscles synergist or antagonist in the cat?
The electrical activity of the external and internal intercostal muscles was recorded in decerebrated cats during eupnea and in the course of dyspnoea artificially induced to reinforce the inspiratory or expiratory central drive. In the cephalic part of the thorax (1st-5th ribs) the lateral part of the external and internal intercostal muscles are synergist and inspiratory. In the caudal part of the thorax (9th-13th ribs) these muscles are also synergist but expiratory. In the intermediate part (5th-9th ribs) the intercostal muscles are antagonist, the external ones are inspiratory and the internal ones are expiratory.
