Arterial baroreflex loops: (1) carotid sinus baroreceptors, nIX, medullary centres, sympathetic and parasympathetic fibres to heart and blood vessels; (2) aortic baroreceptors, nX, medullary centres, sympathetic and parasympathetic fibres to heart and blood vessels. Peripheral chemoreflex loops: (1) carotid body chemoreceptors, nIX, medullary respiratory centres, motor nerves to respiratory muscles; (2) aortic body chemoreceptors, nX, medullary respiratory centres, motor nerves to respiratory muscles. nIX = ninth cranial nerve (glossopharyngeal nerve), nX = tenth cranial nerve (vagus nerve); the arrows coming from the cortex signify the modulation of brainstem nuclei by higher, cortical centres. Adapted with permission from Timmers et al. 2001b.