Circadian rhythms Flashcards
What is the suprachiasmatic nucleus (SCN)?
a small cluster of cells located in the hypothalamus, a region of the brain that controls a variety of physiological processes.
The SCN is often referred to as the “master clock” of the body, as it helps to regulate the timing of many circadian rhythms, including the sleep-wake cycle.
What inputs does the SCN receive?
The SCN receives input from a variety of sources, including light and other environmental cues known as “zeitgebers.”
Light is the most important zeitgeber for the SCN, as it helps to reset the body’s internal clock each day.
Specialized cells in the retina called ganglion cells are able to detect light and send signals to the SCN via the retinohypothalamic tract.
What does the SCN help regulate?
Once the SCN receives input from these zeitgebers, it uses this information to synchronize the body’s circadian rhythms.
For example, the SCN helps to regulate the timing of the release of hormones such as melatonin and cortisol, which play a key role in regulating the sleep-wake cycle and other physiological processes.
By coordinating these rhythms with environmental cues, the SCN helps to ensure that the body is able to function optimally in a 24-hour cycle.
What does it mean for a biological clock to be endogenous?
A biological clock is said to be endogenous if it operates independently of external cues.
This means that it can maintain its rhythm even in the absence of environmental cues like light, temperature, or social cues.
What is entrainment?
entrainment is when the biological clocks are able to adjust to external cues from the environment.
For example, the sleep-wake cycle is regulated by an endogenous biological clock that operates on a roughly 24-hour cycle. However, this cycle can be adjusted by external cues such as exposure to light, which can help to reset the clock and keep it in sync with the 24-hour day.
