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The suprachiasmatic nucleus or nuclei (SCN) is a small region of the brain in the hypothalamus, situated directly above the optic chiasm. It is responsible for regulating sleep cycles in animals. [ 1 ] [ 2 ] Reception of light inputs from photosensitive retinal ganglion cells allow it to coordinate the subordinate cellular clocks of the body ...
The axons of the ipRGCs belonging to the retinohypothalamic tract project directly, monosynaptically, to the suprachiasmatic nuclei (SCN) via the optic nerve and the optic chiasm. [a] [2] The suprachiasmatic nuclei receive and interpret information on environmental light, dark and day length, important in the entrainment of the "body
The SCN is located in the hypothalamus and is associated with regulating sleep patterns by maintaining circadian rhythms, which are strongly associated with external light and dark cues. A disruption within the suprachiasmatic nucleus would seem to be an area that could cause the types of confusion that are seen in sundowning.
A circadian rhythm is an entrainable, endogenous, biological activity that has a period of roughly twenty-four hours. This internal time-keeping mechanism is centralized in the suprachiasmatic nucleus (SCN) of humans, and allows for the internal physiological mechanisms underlying sleep and alertness to become synchronized to external environmental cues, like the light-dark cycle. [3]
The suprachiasmatic nucleus in the hypothalamus is responsible for this cycle of secretion from the epithalamus, specifically from the pineal gland. [8] The Circadian timekeeping is driven in cells by the cyclical activity of core clock genes and proteins such as per2/PER2. [ 9 ]
Chief or pontine nucleus of the trigeminal nerve sensory nucleus (V) Motor nucleus for the trigeminal nerve (V) Abducens nucleus (VI) Facial nerve nucleus (VII) Vestibulocochlear nuclei (vestibular nuclei and cochlear nuclei) (VIII) Superior salivatory nucleus; Pontine tegmentum. Pontine micturition center (Barrington's nucleus) Locus coeruleus
One postsynaptic target of ipRGCs is the suprachiasmatic nucleus (SCN) of the hypothalamus, which serves as the circadian clock in an organism. ipRGCs release both pituitary adenylyl cyclase-activating protein (PACAP) and glutamate onto the SCN via a monosynaptic connection called the retinohypothalamic tract (RHT). [15]
The nucleus of a Type 2 pinealocyte contains many infoldings which contain large amounts of rough endoplasmic reticulum and ribosomes. [6] An abundance of cilia and centrioles has also been found in these Type 2 cells of the pineal gland. [7] Unique to the Type 2 is the presence of vacuoles containing 2 layers of membrane. [7]