Diaphragmatic contraction

Other skeletal muscle contributions include the contraction of the muscles of the pelvic floor. The sling of the puborectalis and other levator ani muscles are responsible for maintaining fecal continence along with a trained sympathetic reflex. Relaxation of these muscles and the rectal sphincter is under voluntary control and is facilitated by diaphragmatic contraction when necessary. The diaphragm is also involved in a type... 

Pharmacology The methyixanthines (theophylline, its soluble salts and derivatives) directly relax the smooth muscle of the bronchi and pulmonary blood vessels, stimulate the CNS, induce diuresis, increase gastric acid secretion, reduce lower esophageal sphincter pressure, and inhibit uterine contractions. Theophylline is also a central respiratory stimulant. Aminophylline has a potent effect on diaphragmatic contractility in healthy people and may then be capable of reducing fatigability and thereby improve contractility in patients with chronic obstructive airways disease. Pharmacokinetics ... 

The respiratory actions of the methylxanthines may not be confined to the airways, for they also strengthen the contractions of isolated skeletal muscle in vitro and improve contractility and reverse fatigue of the diaphragm in patients with COPD. This effect on diaphragmatic performance—rather than an effect on the respiratory center—may account for theophylline s ability to improve the ventilatory response to hypoxia and to diminish dyspnea even in patients with irreversible airflow obstruction. 

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