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Explore how our biological rhythms influence daily functioning and the stages of sleep. Learn about the brain waves and characteristics of different sleep stages. Discover the factors that affect sleep patterns and the functions of sleep.
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23.1 – Describe how our biological rhythms influence our daily functioning. • Circadian Rhythms: repeating fluctuations, such as sleeping and waking, that occur over a period of twenty-four hours. An “internal clock” located in the hypothalamus, the suprachiasmatic nucleus, monitors circadian rhythms. The suprachiasmatic nucleus receives information from ganglion cells located in the retina that send information based on whether it is light or dark out. In response, neurons in the suprchiasmatic nucleus trigger the release of a hormone called melatonin, which is produced in the pineal gland. When the ganglion cells detect darkness and melatonin is released, the individual experiences tiredness. When it starts to become light outside, melatonin decreases, helping the individual wake up. This “internal clock” makes it possible to maintain circadian rhythms regardless of external cues. Environmental factors can disrupt circadian rhythms (“jet lag”). Taking melatonin supplements can lessen the symptoms of jet lag; such supplements are also common treatment for insomnia.
23.1 – Describe how our biological rhythms influence our daily functioning. • Sleep: periodic, natural loss of consciousness – as distinct from unconsciousness resulting from a coma, general anesthesia, or hibernation.
23.2 – Describe the biological rhythm of our sleeping and dreaming stages. • Brain Waves: A person who is awake and attentive shows brain activity through beta waves. A person who is awake but inattentive would show alpha waves. Theta waves follow alpha waves and indicated even slower brain waves. Delta wavesshow low brain activity and are associated with deep sleep. About every 90 minutes we pass through a cycle of four distinct sleep stages.
23.2 – Describe the biological rhythm of our sleeping and dreaming stages. • Stages of Sleep NREM Stage 1: Brain waves: -Alpha and Theta waves Characteristics: -Lasts only a few minutes -Person can quickly gain consciousness. -Experiences hypnagogic hallucinations – vivid sensory experiences. The most common hypnagogic hallucination is the sensation of falling, which is accompanied by myoclonic jerk – an involuntary muscle spasm throughout the body that often awakes the person.
23.2 – Describe the biological rhythm of our sleeping and dreaming stages. • Stages of Sleep NREM Stage 2: Brain waves: -Theta and the start of Delta waves Characteristics: -Start of true sleep -Sleep spindlesin EEG patterns – sudden bursts of brain activity.
23.2 – Describe the biological rhythm of our sleeping and dreaming stages. • Stages of Sleep NREM Stage 3: Brain waves: -Delta brain waves Characteristics: -Considered NREM Stage 4 when delta waves exceed 50 percent of brain activity. Person does not experience sensory stimulation – hard to wake up. -Referred to as slow-wave sleep (or S-sleep).
23.2 – Describe the biological rhythm of our sleeping and dreaming stages. • Stages of Sleep REM Sleep Brain waves: -Beta brain waves Characteristics: -Brain activity becomes more active, resembling that of an awakened state; approximately 85 percent of dreams occur during this stage. -Muscle activity is suppressed (referred to as “muscle atonia”). -Physiological arousal is high – heart rate, blood pressure. -Eyes move rapidly back and forth beneath eyelids – Rapid Eye Movement (also called paradoxical sleep).
23.2 – Describe the biological rhythm of our sleeping and dreaming stages. • With each 90-minute cycle, NREM Stage 3 sleep decreases and the duration of NREM Stage 2 and REM sleep increases. • Over the course of a person’s lifetime, NREM Stages 3 and 4 gradually decrease. In fact by late adulthood, most individuals average only about 20 minutes in these stages as compared to the young child, who spends two or more hours in NREM Stages 3 and 4.
23.3 – Explain how biology and environment interact in our sleep patterns. • What affects our sleep patterns? • Suprachiasmatic Nucleus – light triggers the suprachiasmatic nucleus in the hypothalamus to decrease the hormone melatonin. Nightfall triggers an increase of melatonin. 2) Environmental Impacts on Sleep: -Artificial light delays sleep -Irregular sleep schedules (weekends vs. School/work days) -Shift work, social media, and other modern diversions cause us to stay up later than past generations. Research shows that genetics also impacts the amount of sleep each individual needs.
23.4 – Describe sleep’s functions. • Why do we sleep? -Researchers know that sleep is important. -We spend 1/3 of our lives sleeping. -If an individual remains awake for several days, immune function and concentration deteriorates and the risk of accidents increases.
23.4 – Describe sleep’s functions. • Sleep Theories 1) Sleep protects: sleeping in the darkness when predators loomed about kept our ancestors out of harm’s way. 2) Sleep helps us recuperate: sleep helps restore and repair brain tissue. 3) Sleep helps us remember: sleep restores and rebuilds our fading. 4) Sleep feeds creative thinking: a complete night’s sleep boosts our thinking and learning. Sometimes dreams inspire noteworthy achievements. 5) Sleep supports growth: during sleep, the pituitary gland releases growth hormone. Older people release less of this hormone and also spend less time in deep sleep.
