Sleep Flashcards

Question

K-complex

Answer 1

A K-complex is a waveform that may be seen on an electroencephalogram (EEG). It occurs during stage 2 of NREM sleep. It is the "largest event in healthy human EEG".[1] They are more frequent in the first sleep cycles. K-complexes have two proposed functions:[1] first, suppressing cortical arousal in response to stimuli that the sleeping brain evaluates not to signal danger, and second, aiding sleep-based memory consolidation.

Answer 2

is a non-invasive method[1] of monitoring human rest/activity cycles. A small actigraph unit, also called an actimetry sensor,[2] is worn for a week or more to measure gross motor activity. The unit is usually in a wristwatch-like package worn on the wrist. The movements the actigraph unit undergoes are continually recorded and some units also measure light exposure. The data can be later read to a computer and analysed offline; in some brands of sensors the data are transmitted and analysed in real time.

Answer 3

Two internal biological mechanisms–circadian rhythm and homeostasis–work together to regulate when you are awake and sleep. **Circadian rhythms** direct a wide variety of functions from daily fluctuations in wakefulness to body temperature, metabolism, and the release of hormones. They control your timing of sleep and cause you to be sleepy at night and your tendency to wake in the morning without an alarm. Your body’s biological clock, which is based on a roughly 24-hour day, controls most circadian rhythms. Circadian rhythms synchronize with environmental cues (light, temperature) about the actual time of day, but they continue even in the absence of cues. **Sleep-wake homeostasis** keeps track of your need for sleep. The homeostatic sleep drive reminds the body to sleep after a certain time and regulates sleep intensity. This sleep drive gets stronger every hour you are awake and causes you to sleep longer and more deeply after a period of sleep deprivation. Factors that influence your sleep-wake needs include medical conditions, medications, stress, sleep environment, and what you eat and drink. Perhaps the greatest influence is the exposure to light. Specialized cells in the retinas of your eyes process light and tell the brain whether it is day or night and can advance or delay our sleep-wake cycle. Exposure to light can make it difficult to fall asleep and return to sleep when awakened. Night shift workers often have trouble falling asleep when they go to bed, and also have trouble staying awake at work because their natural circadian rhythm and sleep-wake cycle is disrupted. In the case of jet lag, circadian rhythms become out of sync with the time of day when people fly to a different time zone, creating a mismatch between their internal clock and the actual clock.

Answer 4

Several structures within the brain are involved with sleep. The **hypothalamus**, a peanut-sized structure deep inside the brain, contains groups of nerve cells that act as control centers affecting sleep and arousal. Within the hypothalamus is the **suprachiasmatic nucleus (SCN)** – clusters of thousands of cells that receive information about light exposure directly from the eyes and control your behavioral rhythm. Some people with damage to the SCN sleep erratically throughout the day because they are not able to match their circadian rhythms with the light-dark cycle. Most blind people maintain some ability to sense light and are able to modify their sleep/wake cycle. **The brain stem**, at the base of the brain, communicates with the hypothalamus to control the transitions between wake and sleep. (The brain stem includes structures called the pons, medulla, and midbrain.) Sleep-promoting cells within the hypothalamus and the brain stem produce a brain chemical called **GABA**, which acts to reduce the activity of arousal centers in the hypothalamus and the brain stem. The brain stem (especially the pons and medulla) also plays a special role in REM sleep; it sends signals to relax muscles essential for body posture and limb movements, so that we don’t act out our dreams. **The thalamus** acts as a relay for information from the senses to the cerebral cortex (the covering of the brain that interprets and processes information from short- to long-term memory). During most stages of sleep, the thalamus becomes quiet, letting you tune out the external world. But during REM sleep, the thalamus is active, sending the cortex images, sounds, and other sensations that fill our dreams. **The pineal gland**, located within the brain’s two hemispheres, receives signals from the SCN and increases production of the hormone melatonin, which helps put you to sleep once the lights go down. People who have lost their sight and cannot coordinate their natural wake-sleep cycle using natural light can stabilize their sleep patterns by taking small amounts of melatonin at the same time each day. Scientists believe that peaks and valleys of melatonin over time are important for matching the body’s circadian rhythm to the external cycle of light and darkness. **The basal forebrain**, near the front and bottom of the brain, also promotes sleep and wakefulness, while part of the midbrain acts as an arousal system. Release of adenosine (a chemical by-product of cellular energy consumption) from cells in the basal forebrain and probably other regions supports your sleep drive. Caffeine counteracts sleepiness by blocking the actions of adenosine. **The amygdala**, an almond-shaped structure involved in processing emotions, becomes increasingly active during REM sleep.

Answer 5

Delayed sleep phase syndrome (DSPS) is a disorder in which a person’s sleep is delayed by two hours or more beyond what is considered an acceptable or conventional bedtime. The delayed sleep then causes difficulty in being able to wake up at the desired time. **The effects of DSPS** People with delayed sleep phase syndrome generally have difficulty: **Falling asleep,** unless they go to bed very late (usually some hours after midnight) because their internal clock is sending alerting signals until late into the night Waking up at a **"normal" time** in the morning, because their internal clock is not yet producing strong alerting signals. **Treatment:** **Bright light therapy:** We use light to gradually shift your sleeping pattern to a more conventional schedule. **Chronotherapy:** This technique aims to reset your circadian clock by slowly delaying your bedtime (and your sleep period) by about two hours every few days. The disadvantage is that it disrupts your normal schedule of activity during the shift, when day and night are reversed.

Sleep Flashcards

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