the pineal gland lies deep within the brain it's on the midline here is our pineal gland it sits
just below the corpus callosum and just above the midbrain the pineal gland is not controlled by the
hypothalamus and anterior pituitary gland like a lot of other endocrine glands are but it does
receive a lot of it its main input from it it's an endocrine loop it's a neuro endocrine loop
that begins with the retina light coming in to the retina going through the optic nerve goes to
a structure within the hypothalamus called the suprachiasmatic nucleus here is of course like
our eye so if we had retina here and then optic nerve which is remember is cranial nerve number
two goes to the hypothalamus which is this area and it goes to a specific area of the hypothalamus
called the suprachiasmatic nucleus or SCN the suprachiasmatic nucleus sends axons through the
midbrain are through the brainstem into the spinal cord and it goes to the intermedia lateral cell
column which if you remember from the neuro MOOC is where the preganglionic sympathetic neurons
live ok those neurons then send axons out into the civis the sympathetic chain and specifically
in this case to the superior cervical ganglion and as you recall from autonomics the superior
cervical ganglion is the sympathetic outflow for the entire head and neck the superior cervical
ganglion then innervates the pineal gland and stimulates it to secrete melatonin so
to draw this all one more time we go from retina through cranial nerve to the optic nerve to the
suprachiasmatic nucleus from the suprachiasmatic nucleus to the intermedia lateral cell column I
am now to the superior cervical ganglion and then up to the pineal gland okay so it's a loop retina
hypothalamus spinal cord sympathetic ganglia back up to the pineal gland melatonin then is
this secretory product of the pineal gland and it is what coordinates when it's secreted it
coordinates the rest of your body to control your circadian rhythms so you're sayin rhythms have to
do with when you bought how your body knows it's day or night out and it's not just that you can
see light or not see light your whole rest of your body that isn't photosensitive photosensitive has
to know that it's day or night and this is how it and this is how it knows by the secretion of
melatonin so the pineal gland not only helps in train the rest of your body today and night it
also is how you translate the length of day and night so the seasons into your body rhythms now
this is most important not so much for humans but for seasonal breeders so animals that breed
in the spring or breed in the fall they're the length of day and night is going to be you know
it's going to be recorded or translated to the body through this loop and then the the
secretion of melatonin has an influence on the secretion of gonadotropic and that is what in
trains the body for season seasonal changes so what do I do I want you to know about the pineal
gland which or what special sense regulates the pineal gland and what are the different
steps from that sensory input to the final innervation or stimulation of the pineal gland
to create melatonin oh and I just answered that one what hormone is secreted by the pineal gland
and then what is its function if you know all of these things you're ready for the assessment