Circadian Rhythms
Experiment 1 - cut the optic tracts
Did not eliminate the ability of light-dark cycles to entrain circadian rhythms
Suprachiasmatic Nucleus (SCN)
Prime candidate for circadian control (cutting optic tracts doesnt eliminate circadian rhythms)
Can be grown in cultures
If replaced, cannot entrain themselves (nerve fibers such as optic tracts are severed)
Definition
A circadian rhythm is any biological process that displays an endogenous, entrainable oscillation of about 24 hours
SNC controls this across all vertebrates
Shifts in work, time zones, etc.
Could throw it off
The Biological Clock
Controlling rhythms
1) Fibers project from SCN to PVN
These relay the signals to the sympathetic system adjacent to the spinal cord
Sympathetic system signals the pineal gland
The pineal gland secretes melatonin which is a global regulator for sleep/wake
Measured by
Over time-width and without an external signal source.
Live at different latidudes (can be entrained)
in SCN