BIOL 1080 Lecture Notes - Lecture 4: Bone Density, Bone Fracture, Chronobiology
18 Nov 2017
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Chronobiology: the study of timescales and cycles in biology. Ultradian: less than 24 hours ex. appetite, meals (ghrelin), cortisol (pulsatile) Circadian: 24 hour cycle ex. cortisol: nadir, midnight (sleep initiation), peak, 8 am (after awakening. Infradian: more than 24 hours ex. menstrual cycle. Height is charted over years by physicians to alert them to possible osteoporosis development and increased risk of bone fracture. Criteria: loss of more than 2 cm (3/4 inch) in one year. There is approx. a 1. 5 cm diurnal daily variation in height. Due to compression/expansion of intervertebral disks of the spinal column. Most of the effect of compression occurs in the first hour of getting out of bed, don"t measure height after waking up. Should be measured at the same time every day. Must be careful when measuring, everyday 2 hours after waking up. Duel energy x-ray absorptiometry (dexa) to determine bone mineral density (bmd) Scanner machine with two x-ray beams, low dose radiation.
