Biological Rhythms Flashcards
What are the four types of biological rhythm based on the duration of each cycle?
Ultradian, circadian, infradial, circannual
What is a free running rhythm? Why do humans and animals express a free running rhythm?
What is the difference between free running and entrained circadian rhythm?
An entrained circadian rhythm adapts to environmental cues while a free running rhythm exists despite environmental cues (changes in sunlight).
What is the function of the suprachiasmatic nucleus (SCN) in biological rhythm? What is the evidence that supports SCN’s critical function?
What is the importance of the retinohypothalamic tract?
Where can we find the intrinsically photosensitive retinal ganglion cells? How are they sensitive to light? Why is their function related to the type of circadian blind people express?
ipRGCs detect brightness and are receptive to light because they express melanopsin, a light-sensitive protein. When ipRGCs are still intact in blind people, they are able to express an entrained biological rhythm because the SCN still receives visual information of light.
How is the SCN involved in circannual rhythm?
Where is melatonin produced? What is the role of melatonin in the circannual breeding rhythm of hamsters?
Melatonin is produced in the pineal gland. In hamsters, testosterone secretion is inhibited by the larger amount of melatonin produced in the winter, leading to less breeding in the winter season and more when daylight lengthens.
In what conditions will we express free running circadian rhythm?
How can we become arrhythmic?
Lesions in SCN, leading to irregular locomotor activity patterns.