Fibres leave the SCN to reach the ventrolateral preoptic area (VLPO) of the anterior hypothalamus multisynaptically. They initially relay in the sub-paraventricular zone before synapsing predominantly in the dorsomedial nucleus of the hypothalamus and then in the VLPO. At each of these locations integration of the circadian rhythms with other influences controlling not only sleep but temperature and endocrine function takes place.

Fibres also travel from the SCN to the hypothalamus, to control pituitary function, to the thalamus, the medial preoptic nucleus and multisynaptically to the pineal gland.

The latter take a tortuous course descending through the periventricular hypothalamus into the intermediolateral cell column of the thoracic spinal cord from which preganglionic sympathetic neurones project to the superior cervical ganglion and then postganglionic sympathetic fibres travel along the internal carotid artery to reach the pineal gland.

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