Ch. 14.1 Many Animals Show Daily Rhythms in Activity Flashcards
What are circadian rhythms?
A pattern of behavioral, biochemical or physiological fluctuation that has a 24 hour period.
What is diurnal?
Active during the light periods of the daily cycle.
What is nocturnal?
Active during the dark periods of the daily cycle.
What does endogenous mean?
Having an internal cause or origin.
Explain how circadian rhythms are generated by an endogenous clock using the hamster and wheel example.
Hamsters are active a little before dark and remain active for most of the dark time. When dark times were changed, the hamster adjusted the active times to follow the routine.
What happened with the hamster in continual dim light?
In constant dim light, the hamster became active a few minutes later each day. This free-running activity rhythm indicates that the hamster has an endogenous clock that has a period slightly greater than 24 hours.
What is free-running?
Refers to a rhythm of behavior shown by an animal deprived of external cues about time of day.
What is a period?
The interval of time between two similar points of successive cycles, such as sunset to sunset.
What is a phase shift?
A shift in the activity of a biological rhythm, typically provided by a synchronizing environmental stimulus. ex: regular light/dark periods caused the hamster to shift from free-running to following the light/dark cycles.
What is entrainment?
The process of synchronizing a biological rhythm to an environmental stimulus. ex: the process of free-running to following the environment stimulus.
What is a zeitgerber?
The stimulus (usually the light-dark cycle) that entrains circadian rhythms. Ex: light is a zeitgerber. Food can also serve a cue.
What is the major value of circadian rhythms?
They synchronize behavior and body states to daily rhythms in the environment. Day and night have great significance for survival and the endogenous (internal) clock enables animals to anticipate an event, such as darkness and prepare for it.
