Lecture 20- Sleep and Arousal PDF

• In humans, lack of sleep leads to impaired memory and reduced cognitive abilities and, if the deprivation persists, mood swings and often hallucinations • Genetic disease “fatal familial insomnia” appears in middle age, is characterized by hallucinations, seizures, loss of motor control, and the i...

• In humans, lack of sleep leads to impaired memory and reduced cognitive abilities and, if the deprivation persists, mood swings and often hallucinations • Genetic disease “fatal familial insomnia” appears in middle age, is characterized by hallucinations, seizures, loss of motor control, and the inability to enter a state of deep sleep—patients die within several years of onset *Clinical Correlation • The receptors that sense the light changes are located within the ganglion cell layer of retina • these photoreceptors contain melanopsin, and are depolarized by light (rods and cones) • the axons runs the retinohypothalamic tract, which projects to the suprachiasmatic nucleus (SCN) of the anterior hypothalamus • Abnormalities in delta sleep, or deep sleep, are common in individuals with depression. • Delta sleep begins in sleep stage 3, and by sleep stage 4 delta waves make up more than 50% of the EEG recording. • This disturbance in delta sleep may not allow a depressed individual ample opportunity to physically restore the body • In depression, multiple awakenings are common. • Patients with depression shows a shortened period of REM latency. • REM latency is the elapsed time between onset of sleep and the first REM sleep. *Clinical Correlation In Summary… • The control of sleep and wakefulness depends on brainstem and hypothalamic modulation of the thalamus and cortex • It is the thalamocortical loop that generates the EEG signature of mental function along the continuum of deep sleep to high alert Purves, Neuroscience 4th ed. Sleep disorders • Insomnia, is the inability to sleep for a sufficient length of time • Stress, jet lag, too much caffeine • Depression: impaired balance between modulatory systems that control the sleep cycles • Sleep apnea, is a pattern of interrupted breathing during sleep • The airway collapses during breathing, and blocks the airway *Clinical Correlation Sleep apnea • Patients awake frequently and never descend into stages III or IV sleep Purves, Neuroscience 4th ed. Sleep disorders • Restless Leg syndrome, represents with unpleasant prickling, or tingling sensations in one or both legs and feet, and an urge to move them about to obtain relief • In severe cases, benzodiazepins may help • Narcolepsy, represents with frequent “REM sleep attacks” (lasting 30 sec to 30 min) during the day • They enter REM sleep from wakefulness without going through non-REM sleep *Clinical Correlation