Chapter 10 Visual Summary

Animals show circadian rhythms of activity that can be entrained by light. These rhythms synchronize behavior to changes in the environment. In constant dim light, animals free-run, displaying a period of about 24 hours. Review Figure 10.2 and Figure 10.6, Animation 10.2 and Animation 10.3

Lesions of the suprachiasmatic nucleus (SCN) abolish activity rhythms in constant conditions. Transplanting the SCN from one animal into another results in a free-running rhythm of the donor, demonstrating that the SCN contains a clock that can drive circadian activity. Several proteins (including Clock and Cycle) interact, increasing and decreasing in a cyclic fashion that takes about 24 hours. This molecular clock, pooled from many SCN neurons, drives circadian rhythms. Review Figure 10.3, Figure 10.4, Figure 10.5, Figure 10.6, Figure 10.7, Figure 10.8, Animation 10.4

Almost all mammals show two sleep states: rapid-eye-movement (REM) sleep and non-REM sleep. Human non-REM sleep has three distinct stages (stages 1, 2, 3) defined by electroencephalography (EEG) criteria, including sleep spindles and large, slow delta waves in stage 3. Review Figure 10.10, Table 10.1, Activity 10.1

REM sleep is characterized by rapid, low-amplitude EEG waves (almost like an EEG while awake), but also by profound muscle relaxation because motoneurons are inhibited. People awakened from REM frequently report vivid dreams, while people awakened from SWS report ideas or thinking. Review Table 10.1

Sleep stages cycle through the night, with stage 3 SWS prominent early, while REM predominates later. Infants sleep a lot, with lots of REM, but as we grow up we sleep less, with less REM. Elderly people sleep even less, and stage 3 sleep eventually disappears. Review Figure 10.11, Figure 10.12, Figure 10.13, Figure 10.14, Figure 10.15

Four proposed functions of sleep are energy conservation, ecological niche adaptation, body and brain restoration, and memory consolidation. A few people sleep only an hour per night, suggesting that they accomplish the function(s) of sleep very efficiently, but all healthy people sleep.

Sleep deprivation leads to impairments in vigilance and reaction times. It also incurs sleep debt, although the lost SWS and REM may be partially restored in subsequent nights. Prolonged sleep deprivation compromises the immune system and leads to death. Review Figure 10.16

Four brain systems control sleep and waking. The basal forebrain promotes SWS, the brainstem reticular formation promotes arousal, a pontine system triggers REM sleep, and hypothalamic neurons releasing orexin regulate these three centers. Review Figure 10.18, Figure 10.19 and Figure 10.20, Activity 10.2, Video 10.5

Narcolepsy is characterized by sudden, uncontrollable periods of sleep, which may be accompanied by cataplexy, paralysis while remaining conscious. Disruption of orexin signaling causes narcolepsy. Review Figure 10.21 and Figure 10.22, Video 10.6

Sleep disorders fall into four categories: sleep-onset and sleep-maintenance insomnia; excessive drowsiness (e.g., narcolepsy); disruption of the sleep-waking schedule; and dysfunctions associated with sleep, sleep stages, or partial arousals (e.g., somnambulism, RBD). No pill guarantees a normal night's sleep. Review Figure 10.23, Table 10.2, Video 10.7

    Previous 1 of 10 Next