Endocrine Functions of Brain Dopamine
Nira Ben-Jonathan in Dopamine, 2020
Living organisms have an internal clock that helps the body adapt to the external environment. Throughout the 24-h day, the clock regulates many physiological, endocrine, and mental processes, including sleep, body temperature, metabolism, blood pressure, hormone release and alertness. Circadian rhythms are endogenously generated ~24-h biological rhythms that are organized in two levels: a molecular level represented by the clock genes, and a systemic regulatory level represented by the neuroendocrine networks. The circadian oscillation is synchronized by external environmental cycles, primarily the light/dark cycle of the geophysical day and night. External rhythmic events that can synchronize biological rhythms are called zeitgebers or synchronizers. “Entrainment” is defined as a synchronization between oscillators with different but similar periods that occurs when one of the oscillators imposes its period on the other.
Nathaniel Kleitman (1895–1999)
Andrew P. Wickens in Key Thinkers in Neuroscience, 2018
The results showed that Kleitman, who was then 43 years old, was unable to fully adjust to the 28-hour day – his sleep being intermittent and shallow, especially when it coincided with noon in the real Kentucky time outside. His body temperature also stubbornly followed the rhythms of the world that existed outside the cave, which led it to run in and out of synchronisation with his sleep patterns. Richardson, on the other hand, began to adapt to his temperature cycle and sleep pattern after 1 week. Although the study was not conclusive, the Mammoth Cave experiment lent support to the idea that human bodies contain a “clock” that maintains a roughly 24-hour temperature cycle, even in the absence of external cues. Later in the 1970s, experimenters would show that animals, including humans, do indeed have an internal clock, called the “suprachiasmatic nucleus”, located in the hypothalamus, which controls the release of the sleep-promoting hormone melatonin and is recalibrated on a daily basis by the occurrence of light.
ENTRIES A–Z
Philip Winn in Dictionary of Biological Psychology, 2003
Sleep is regulated by neuronal mechanisms located in both the BRAINSTEM and FOREBRAIN. REM sleep is thought to be induced by the activation of CHOLINERGIC neurons in the MESOPONTINE TEGMENTUM and ACETYLCHOLINE release in the PONTINE RETICULAR FORMATION, which in turn triggers ATONIA and the phasic components of REM sleep. MONOAMINERGIC neurons in the LOCUS COERULEUS and DORSAL RAPHE NUCLEUS are thought to have a permissive role in REM sleep induction, by disinhibiting the cholinergic neurons. At the same time, ascending pathways from the reticular formation activate the THALAMUS and forebrain structures to induce AROUSAL of the CEREBRAL CORTEX. The mechanisms for non-REM sleep are less well understood than for REM sleep. However, the PREOPTIC AREA in the HYPOTHALAMUS and the dorsal reticular formation of the MEDULLA including the NUCLEUSOF THE SOLITARY TRACT are thought to have a role in non-REM sleep. Humoural factors such as HORMONES, CYTOKINES and ADENOSINE have also been implicated in promotion of sleep. Sleep and wakefulness also show daily rhythms, and are controlled by the circadian clock (see BIOLOGICAL CLOCK;
Exploring the role of circadian clock gene and association with cancer pathophysiology
Published in Chronobiology International, 2020
Mahtab Keshvari, Mahdieh Nejadtaghi, Farnaz Hosseini-Beheshti, Ali Rastqar, Niraj Patel
In an evolutionary response to the 24-h period of Earth’s rotation, varied species from cyanobacteria to humans possess a molecular oscillator termed the biological clock. In mammals, the circadian clock is involved in the daily rhythms of numerous aspects of physiology, including sleep (Keijzer et al. 2017), metabolism (Sato et al. 2017), molecular and cellular responses (Dakup and Gaddameedhi 2017) and homeostatic balance of different organs. Human health and behaviors are affected mainly by the unique individual circadian timing system. The shift of the circadian rhythm occurs when children become adolescents when their chronotypes change from morning-preferred types to preferred evening ones. Many chronobiological studies have shown the internal clock is a determinant factor for physiological and pathological states. Myriad cellular, molecular, and biochemical processes including sleep/wakefulness, hormonal secretions, metabolism, mood, ion channels, and DNA repair are scheduled and control by these internal biological clocks. Several medications and treatments in the context of processing and metabolizing are affected by biological rhythms, for example, cancer, arthritis, allergic rhinitis and peptic ulcers are some disease where chronotherapy can be used to improve their treatment outcomes and helps to a better quality of care to patients (Antypa et al. 2017; Ko et al. 2009; Sen and Sellix 2016).
The daily, weekly, and seasonal cycles of body temperature analyzed at large scale
Published in Chronobiology International, 2019
Charles Harding, Francesco Pompei, Samantha F Bordonaro, Daniel C McGillicuddy, Dmitriy Burmistrov, Leon D Sanchez
In humans, body temperature usually follows a daily cycle that is lowest in the morning and highest in the afternoon and evening (Mackowiak et al. 1992; Ogle 1866; Wunderlich 1871). This is an aspect of the circadian rhythm and is tied to many body functions and states, such as sleep, hormone secretion, metabolic disorders, mood disorders, and the internal clock (Dunlap et al. 2009; Panda 2016). The first large studies of the cycles in human body temperature were performed by the pioneering physician Carl Reinhold August Wunderlich in the mid-1800s (Wunderlich 1871). Though Wunderlich’s research used large sample sizes, sometimes involving tens of thousands of individuals, only a few large studies of the cycles of human body temperature have been conducted since (Cross and Anderson 2018; Obermeyer et al. 2017).
Time of Day Influence on Postural Balance of Young and Older Men
Published in Experimental Aging Research, 2023
Vasileios Mylonas, Thomas Nikodelis, Iraklis Kollias
Many of the human physiologic mechanisms, however, are not consistent around the clock, but they display variance throughout the day (Widmaier, Raff, & Strang, 2014). The biological clock that regulates such variations is called the Circadian clock or Circadian Rhythm. Some of the primary functions of that clock are regulating the sleep-wake cycle, glucose homeostasis, body temperature, and more. Light is the main stimulus of the circadian clock, although more factors may be regulators such as temperature, hormones, and diet (Serin & Acar Tek, 2019). The circadian clock through the melatonin level, an indicator of the environmental light-dark circle, recognizes the time of day and then synchronizes various systems to optimize the body’s physiologic function (Nava Zisapel & Zisapel, 2018). The function of the circadian rhythm is noticed in the sleep-wake cycle. Sleepiness results from two factors summing up. First, the sleepiness adds up during the waking state, and second the circadian regulation sustains a 24-hour rhythm that determines the sleep schedule, mainly influenced by environmental temperature. Sleep is prohibited during the day and enhanced during the night for an organism with a smooth-running circadian clock. (Lack & Wright, 2007). These fluctuations are not fixed for everyone. The individual response to circadian rhythmicity is a characteristic called Chronotype and it is what defines a person as a morning-type (M-type), evening-type (E-type) or neither-type (N-type) (Adan et al., 2012).
Related Knowledge Centers
- Archaea
- Circadian Rhythm
- Drosophila Melanogaster
- Entrainment
- Suprachiasmatic Nucleus
- Bacterial Circadian Rhythm
- Hypothalamus
- Optic Chiasm
- Intrinsically Photosensitive Retinal Ganglion Cell
- Retinohypothalamic Tract