receptors estereoceptors and proprioceptors

The subfornical organ, at the foramen of Monro the organum vasculosum of the lamina terminalis, at the anteroventral tip of the third ventricle the median eminence, at the midline in the floor of the tuberal hypothalamus and the area postrema, at the caudal end of the fourth ventricle all have fenestrated capillaries. These circumventricular organs are specialized neuro-hemal contact zones, along the borders of the ventricular system of the brain ( Broadwell and Brightman, 1976 Oldfield and McKinley, 1990). To overcome this barrier, the brain maintains a set of small “windows” on the circulation. This arrangement prevents any hydrophilic compounds from entering the brain from the blood stream unless they are specifically transported in. Direct access for these molecules to the brain is prohibited by the blood–brain barrier, consisting of tight junctions between capillary endothelial cells that lack fenestrations. In addition, the brain must have access to information about the levels of various nutrients and hormones in the blood stream. These include neurons within the hypothalamus that are especially responsive to local temperature (Boulant and Bignall, 1973 Hori et al., 1986), glucose (Oomura, 1988 Lee et al., 1999 Shiraishi et al., 1999), osmolality (Bourque and Oliet, 1998), or sodium ( Voisin et al., 1999), as discussed below. Homeostatic drives require both access to sensory inputs from the body, as described above, as well as interoceptors, or neuronal receptors that are internal to the brain. Saper, in The Human Nervous System (Third Edition), 2012 Circuitry Supporting Hypothalamic Drives

Receptors estereoceptors and proprioceptors