Psych 261 Chapter 9 Psych 261 Physiological Psychology Kalat: Biological Psychology 10th Edition Chapter 9

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Psych 261 Chapter 9
Wakefulness & Sleep
-we have daily rhythms of wakefulness and sleep
Module 9.1
Rhythms of waking and sleeping
-animals: have 24 hour cycle of waking and sleep, partly dependent on temperature and light
Endogenous cycles
-endogenous circannual rhythm: for preparing for seasonal change; inner mechanism
-endogenous circadian rhythm: daily wake-sleep rhythm;
-ex. fluctuating temperature: 36.7C at night, 37.2C in late afternoon
-child: early sleep time and early wake; later times gradually up to age 20 then decreasing
Setting and Resetting the Biological Clock
-circadian rhythm is reset with light (zeitgeiber); also partly with exercise, noise, medications
-blind people: usually use other zeitgeibers; if circadian rhythm is disrupted, takes days to fix
Jet lag
-sleepiness in the day and sleeplessness at night
-usually easier to go west (backwards in time) than east (forwards)
-especially with nightshift; leads to increased grogginess
-best if one sleeps in a very dark room and works in a very bright room
Mechanisms of the biological clock
-biological clock: developed by brain; strong against interference (ex. Food deprivation, alcohol, brain damage)
The suprachiasmatic nucleus
-aka SCN: controls circadian rhythm; damage leads to inconsistent body temperature; doesn’t follow light/dark
-produces circadian rhythm itself; ex. If detach d from brain, still produces C.R.-like action potentials
How light resets the SCN
-SCN: above ooptic chiasm; connects via retinohhypothalamic path (retina->SCN)
-via group of retinal ganglion cells with specific melanopsin (photopigment)
-located near nose; doesn’t respond to instant light change but overall average amount of light
The Biochemistry of the circadian rhythm
-Genes (period and Timeless) produce per & tim proteins;
-low levels of per & tim lead to awake state; high levels lead to sleep
-altering the period gene leads to a faster than 24 hour clock; also leads to depression
-SCN: regulate wake and sleep via controlling some brain areas
-ex. Pineal gland: releases melatonin (usually at night to induce sleepiness
-pineal gland tumors lead to insomnia
-melatonin secretion happens around 2-3 hours before bed;
-moderate use (0.5mg) in afternoon helps sleep earlier
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