Behavioral Neuroscience, lecture on Sensory input for Rhythmicity
BIOLOGICAL RHYTHMS
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)
habenula
i. blinded house sparrows still show circadian
rhythms
(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