PSY 2501 Lecture Notes - Lecture 5: Sex Steroid, Posterior Pituitary, Uterine Contraction
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Chapter 14 - biological rhythms, sleep & dreaming. Biological rhythms: biological rhythms have different durations (periods) In the absence of cues, humans have a free-running period of approximately 25 hours a. i. 1. Length of free-running period varies with age: endogenous circadian clock, suprachiasmatic nucleus (scn) a. i. a. ii. Located in the hypothalamus above the optic chiasm (ox) Do not show circadian rhythm when free-running: removal of scn disrupts circadian rhythm, when scn cells are transplanted into scn-lesioned animals c. i. Circadian rhythm was restored in those animals: how light entrains circadian rhythms, the retinohypothalamic pathway a. i. a. ii. a. iii. Consists of retinal ganglion cells that project to the scn. These ganglion cells do not receive input from rods and cones. The period in free running hamsters is shorter than normal a. ii. Hamsters with mutations in both copies of genes have normal circadian rhythms with light cues but becomes severely arrhythmic in constant dim light a. iii.
