Lecture 7: Sleep Physiology PDF

Lecture 7 ========= PYB 102 Common measures used to detect physiological changes during sleep Figure 2 Electroencephalography (EEG) - Electroencephalography uses electrodes placed on the scalp to detect and measure patterns of electrical activity emanating from the brain. - An EEG...

Lecture 7 ========= PYB 102 Common measures used to detect physiological changes during sleep Figure 2 Electroencephalography (EEG) - Electroencephalography uses electrodes placed on the scalp to detect and measure patterns of electrical activity emanating from the brain. - An EEG electrode amplifies electric potentials occurring in many thousands of brain cells trace\_eeg EEG signal - The image shows one second of EEG signal from a single electrode placed on the scalp  EEG during wakefulness and NREM sleep EEG during different sleep stages (including REM sleep) werve wakefulness -- alpha activity and beta activity, Stage 1 sleep -- theta activity, Stage 2 sleep -- spindle and k complex, Stage 3 sleep -- delta activity, Stage 4 sleep -- both delta activity, REM sleep -- theta and beta activity, Stage 3 and 4 together are slow wave sleep Sleep stage variations in EEG, EOG and EMG Notice...... - Lack of muscle activity in REM sleep - EEG in REM sleep is similar to EEG while awake (accordingly, REM sleep is often known as 'paradoxical sleep')  Sequence of sleep stages on a typical night image6  Age-related changes in total amount of daily sleep and percentage of REM sleep  Comparison of *generalised* physiological changes between REM (rapid eye movement) and NREM (non-rapid eye movement) --------------------------- -------------------------------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------- **Physiological Process** **During NREM** **During REM** Brain activity decreases from wakefulness increases in motor and sensory areas, while other areas similar to NREM Heart rate slows from wakefulness increases and varies from NREM Blood pressure decreases from wakefulness increases (up to 30%) and varies from NREM Blood flow to brain does not change from wakefulness in most regions increases from 50- 200% from NREM, depending on brain region Respiration decreases from wakefulness increases and varies from NREM, coughing suppressed Body temperature is regulated at a lower set point than wakefulness (i.e. shivering will not start until a *lower*-than-normal temp is reached) is not regulated; no shivering or sweating; temperature drifts toward that of the local environment --------------------------- -------------------------------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------- Average Total Sleep Requirements for Various Species (hours/day) A table of numbers with black text Description automatically generated Brain regions important for circadian rhythm and REM sleep Circadian Sleep Cycles - Sleep-wake cycle is intrinsically linked to the circadian rhythm - Circadian rhythm is predominantly entrained by light-dark transitions - At the neuronal level the circadian rhythm is controlled by the suprachiasmatic nucleus (SCN) - SCN, a small structure in the hypothalamus - Entrainment by light-dark cycle via retinohypothalamic tract - Sectioning optic nerves prevents light-dark regulation of circadian rhythms but not sectioning of the optic tract  The retinohypothalamic pathway BioPsych4e-Fig-14-05-0 Some neural systems involved in sleep (i) - The basal forebrain region in the ventral frontal lobe may be responsible for inducing SWS - The reticular formation in the brain stem may be responsible for activating/waking the brain from sleep Some neural systems involved in sleep (ii) - Regions of the pons are important for triggering REM sleep and the muscle atonia associated with the REM sleep stage. Some neural systems involved in sleep (iii) - A hypothalamic system may be important in regulating the transitions between the activation of the other neural sleep systems. Functions of sleep.... why do we do it??? - Restoration and recovery of bodily systems? - Energy conservation? - Memory consolidation? - Protection from predation? - Brain development? Sleep disorders - Insomnia - Sleep Apnoea - Somnabulism - Night terrors - REM sleep behaviour disorder - Narcolepsy Theories of Dreaming - Freud (early 1900's): *dreams as wish fulfilment* - Cartwright (early 1990's): *problem- solving view* - Hobson and McCarley (1970's to late 1990's): *activation- synthesis model*