PSY290H1 Lecture Notes - Lecture 29: Lightdark, Freerunning, Superior Colliculus
Document Summary
Biological rhythms are repetitive cycles of biological processes with a certain frequency. Circadian rhythms refer to changes that follows a almost 24 hour cycle, responding to light and darkness in environment. Circatidal (~ 1 year) (~ 1 month) (~ 12. 4 hours) The earth rotates once in 24 hours with respect to the sun. Significant events tend to repeat themselves every ~24 hours. Sunrise & sunset able to anticipate the recurrence of these events. All land animals coordinate their behaviour according to this daily rhythm. Examples ! sleep-awake, hormone levels, body temperature, etc. They run on a wheel during awake cycle (dark phase) Measuring circadian rhythms in laboratory animals (e. g. hamsters) A typical running activity log (actogram) looks like this. Hamsters circadian rhythm eventually follow the light-dark cycle. This is called the natural activity rhythms or free-running period (not exactly 24 hours, but slightly longer) Light is the cue that an animal uses to synchronize with the environment.
