Behavioral Neuroscience, lecture on Sensory input for Rhythmicity
USD Department of Biology
Behavioral Neuroscience
Rhythmicity & Behavior
Sensory input for Rhythmicity
Afferent path to the SCN
Figures of Rhythmicity
Eyes to molecular rhythms Circadian Rhythms
Efferent SCN output
Integration of Rhythms into Behavior
Molecular SCN
end  Acronyms/Abbreviations   Syllabus
II. Sensory input for Rhythmicity 			

	A. Sensory input is necessary for Entrainment of Rhythms

		1. zeitgeibers reset biological clocks through a
		   variety of sensory systems
			a. phase shift free running period

				i. move circadian rhythms from 23 or 28 h to 24 h
				ii. match variable onset

		2. photoreceptive organs

			a. retina, retinal ganglia

				i. light, greeness, social cues
					(1) night sensitivity greatest
			b. parietal eye (sharks, frogs, lizards)
				i. light, temperature (IR light)

			c. photosensitive nuclei - photoreceptive pineal (birds)
			   i. blinded house sparrows still show circadian
				  	(1) require brighter lights
					(2) light passes through skull 
					    and brain tissue
							(a) even in humans

		3. chemoreceptive organs
			a. olfactory - food availability, social cues
			b. vomeronasal - social cues
			c. gustatory

		4. Auditory - sound

		5. Tactile

			a. temperature, moisture, water pressure, gravity

			b. activity (proprioception?)

				i. path from Intergeniculate leaflet (IGL) to
				   SCN entrains rhythms

				ii. activates "clock" genes in IGL
				iii. IGL neuropeptide Y (NPY) phase shifts SCN

			c. food-eating (distention - stretch receptors?)

		6. Magnetic

			a. Ampullae of Lorenzini - sharks
			b. Magnetite/ferrite in brain
				i. nucleus of the basal optic root 

	B. Eyes
		1. Retina
			a. neural lining of the eye
				i. contains rods and cones
				ii. with rhodopsin - photosensitive pigment

		2. Retinal Ganglia
			a. Rods and Cones are NOT sufficient for entrainment

				i. retinal ganglia cells receive signals from 
				   rods and cones
					(1) some RGCs innervate the SCN

			b. Melanopsin
				i. circadian photoreceptor
				ii. other photoreceptors: cryptochromes

			c. Rods + Cones + Melanopsin together necessary
				i. cascade from Glu and PACAP
					(1) activate genetic (mPer1+2)
					    cirdadian mechanism
				ii. directly to SCN and via IGL

III. Glutamate

IV. Afferent path to SCN