01:146:295 Lecture Notes - Lecture 17: Retinohypothalamic Tract, Circadian Rhythm, Optic Chiasm
18 Apr 2017
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Document Summary
Coordinated by the suprachiasmatic nucleus (scn); involves melatonin: scn. Part of the hypothalamus, right above the optic chiasm. Neurons are active on a 24-hour cycle; keeps track of time. Negative feedback loop: protein is produced by a gene as protein level increases, it inhibits transcription of its own gene. Some axons from ganglion cells in retina go to the scn: A. 3. b) how scn gets information regarding the sunlight/can reset biological clock: melatonin. Scn gets input from retinohypothalamic tract (sunlight suppresses release of melatonin) Scn output pineal gland melatonin released. Goes to lgn primary visual cortex. Rods and cones are light sensitive, but so are some. Have their own photopigment - melanopsin (b. 4. b. 1) specifically sensitive within blue (480 nm) wavelength range; probably because system evolved in the ocean (b. 4. b. 2) blue light suppresses sleep at night. Regulation of other organs can also be controlled by temperature. Cortisol: low during the night, but increase later in the night.
