Cross-talk Between Body Systems. Respiratory-Cardiovascular Coupling in Health and Disease.

This chapter focuses on the central neural interconnectivity between the brainstem respiratory pattern generator and neural networks governing sympathetic and parasympathetic activity. The respiratory-related alterations in venous return/cardiac output described above also contribute to the respiratory modulation of arterial pressure. However, the fluctuations persist in the working heart brainstem preparation indicating again there is an important central neural component to the coupling. Loss of vagal tone in cardiovascular diseases can be clearly demonstrated by the diminished change in heart rate on administration a vagolytic drug like atropine and also by the loss of respiratory sinus arrhythmia (RSA). The burst of cardiac vagal activity seems to originate centrally at the level of the preganglionic neurons in the nucleus ambiguus that are inhibited during inspiration but excited during postinspiration. There are some key studies that need to be performed. Given its protective role, the site(s) and mechanisms of blockade of cardiac vagal transmission must be identified in cardiovascular disease to allow novel, targeted therapy to be devised.