ELM 20 Rhythms + sleep Flashcards
Question: Why are biological clocks important for organisms?
Answer: Biological clocks are crucial for regulating various physiological and cellular processes, including sleep/wake cycles, body temperature, cardiac output, memory, energy metabolism, immune response, and detoxification. They help organisms adapt to the 24-hour changes in their environment.
Question: What is the impact of clock genes on organisms?
Answer: Clock genes and their components have a widespread impact on physiology, cellular processes, and disease association. They regulate sleep/wake patterns, energy metabolism, cell cycle progression, DNA repair, immune response, and neuron excitability. Dysfunction of clock genes is associated with various disorders such as affective disorders, sleep disorders, neurodegenerative diseases, obesity, inflammation, and cancer.
Question: How do modern lifestyles challenge natural biological rhythms?
Answer: Modern lifestyles often disrupt natural biological rhythms through factors like chronic shift work, sleep deprivation, altered eating habits, and jet lag. These disruptions can lead to health problems, industrial accidents, road accidents, and long-term effects associated with shift work.
Question: What are the different types of biological rhythms?
Answer: Biological rhythms can be categorized into circadian rhythms (daily rhythms), ultradian rhythms (several times in one day, with a period of less than 20 hours), and infradian rhythms (lasting longer than one day). Examples of infradian rhythms include menstrual cycles and seasonal breeding patterns.
Question: What are the mechanisms of circadian rhythms?
Answer: Circadian rhythms are driven by a self-sustained oscillator with a period of approximately 24 hours. They are entrained by environmental cues, with light being the principal factor. The suprachiasmatic nucleus (SCN) in the hypothalamus acts as the central clock and generates rhythmical outputs. Melanopsin-expressing retinal ganglion cells are involved in the entrainment process.
Question: What is the molecular basis of circadian rhythms?
Answer: Circadian rhythms are regulated by a set of clock genes expressed in a rhythmic fashion. The circadian expression of these genes within SCN neurons generates circadian rhythms in neuronal function. Clock genes are also expressed throughout the body, and the circadian timing system synchronizes these clocks to optimize physiology in response to environmental changes.
Question: How does melatonin regulate circadian rhythms?
Answer: Melatonin is secreted by the pineal gland, which is connected to the SCN. It is primarily secreted during the night and inhibited during the day. Melatonin is often used as a drug to help regulate sleep patterns and is involved in the synchronization of the body’s circadian rhythms.
Question: What does chronopharmacology study?
Answer: Chronopharmacology investigates how the kinetics and dynamics of medications are affected by endogenous biological rhythms, as well as how the timing of medication dosing influences the biological clock.
Question: How does the time of day affect drug activity?
Answer: Studies in cancer chronotherapy have shown that the time of day can significantly impact the efficacy and tolerability of drugs. Conventional chemotherapy often assumes that greater toxicity leads to better overall survival, but chronotherapy challenges this notion by demonstrating that better survival rates are associated with less toxicity. For example, oxaliplatin, the first cancer chronodrug, showed improved efficacy and tolerability when administered according to circadian rhythms.
Question: Give an example of a drug that affects the biological clock and its implications.
Answer: Lithium, commonly used in the treatment of bipolar disorder, affects the expression of circadian genes and can alter sleep-wake and body temperature rhythms by causing period lengthening and phase delay. This illustrates how medications can influence the biological clock. Additionally, light therapy, which affects the biological clock by influencing light-sensitive pathways, has been beneficial in mood disorders, Alzheimer’s disease, jet lag, and insomnia, leading to improved mood and sleep efficiency.
Question: Why is sleep necessary?
Answer: Sleep is a basic homeostatic need essential for functions such as learning, memory consolidation, growth, and repair. Sleep deprivation can lead to cognitive impairment, decreased performance, and immune system dysfunction.
Question: What are the stages of sleep?
Answer: Sleep consists of five stages, including REM (Rapid Eye Movement) and non-REM stages. Non-REM stages 3 and 4 represent slow-wave sleep, while REM sleep is the dreaming stage. On average, a night of sleep comprises five cycles, each containing these stages.
Question: How is sleep regulated in the brain?
Answer: Sleep regulation involves complex interactions between brain regions. The brainstem arousal system and the hypothalamic sleep center play crucial roles. Circadian control involves the suprachiasmatic nucleus (SCN), while the homeostatic sleep drive is governed by the ventrolateral preoptic area (VLPO). External factors such as light, jet lag, caffeine, and medications also influence sleep patterns.
Question: What is narcolepsy?
Answer: Narcolepsy is a chronic sleep disorder characterized by profound daytime sleepiness and a tendency to fall asleep at inappropriate times.
Question: What causes narcolepsy?
Answer: Narcolepsy is caused by a disruption to the brain’s orexin pathways. Orexin is a neuropeptide produced by a few neurons in the hypothalamus and acts on the G protein-coupled receptor Hcrtr2. In most cases, narcolepsy results from an autoimmune attack on orexinergic neurons, leading to their destruction.
