The suprachiasmatic nucleus or nuclei (SCN) is a small region of the brain in the hypothalamus, situated directly above the optic chiasm. It is the principal circadian pacemaker in mammals and is necessary for generating circadian rhythms. Reception of light inputs from photosensitive retinal ganglion cells allow the SCN to coordinate the subordinate cellular clocks of the body and entrain to the environment. The neuronal and hormonal activities it generates regulate many different body functions in an approximately 24-hour cycle.
The idea that the SCN is the main circadian pacemaker in mammals was proposed by Robert Moore, who conducted experiments using radioactive amino acids to find where the termination of the retinohypothalamic projection occurs in rodents. Early lesioning experiments in mouse, guinea pig, cat, and opossum established how removal of the SCN results in ablation of circadian rhythm in mammals.
Moreover, the SCN interacts with many other regions of the brain. It contains several cell types and several different peptides (including vasopressin and vasoactive intestinal peptide) and neurotransmitters.
Disruptions or damage to the SCN has been associated with different mood disorders and sleep disorders, suggesting the significance of the SCN in regulating circadian timing
The SCN is situated in the anterior part of the hypothalamus immediately dorsal, or superior (hence supra) to the optic chiasm bilateral to (on either side of) the third ventricle. It consists of two nuclei composed of approximately 10,000 neurons.
The morphology of the SCN is species dependent. Distribution of different cell phenotypes across specific SCN regions, such as the concentration of VP-IR neurons, can cause the shape of the SCN to change.
The nucleus can be divided into ventrolateral and dorsolateral portions, also known as the core and shell, respectively. These regions differ in their expression of the clock genes, the core expresses them in response to stimuli whereas the shell expresses them constitutively.
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This course introduces the student to the fudamentals of pharmacology, pharmacokinetics and drug-receptor interactions. It discusses also pharmacogenetics and chronopharmacology, to exemplify the chal
The suprachiasmatic nucleus or nuclei (SCN) is a small region of the brain in the hypothalamus, situated directly above the optic chiasm. It is the principal circadian pacemaker in mammals and is necessary for generating circadian rhythms. Reception of light inputs from photosensitive retinal ganglion cells allow the SCN to coordinate the subordinate cellular clocks of the body and entrain to the environment. The neuronal and hormonal activities it generates regulate many different body functions in an approximately 24-hour cycle.
A circadian rhythm (sərˈkeɪdiən), or circadian cycle, is a natural oscillation that repeats roughly every 24 hours. Circadian rhythms can refer to any process that originates within an organism (i.e., endogenous) and responds to the environment (is entrained by the environment). Circadian rhythms are regulated by a circadian clock whose primary function is to rhythmically co-ordinate biological processes so they occur at the correct time to maximise the fitness of an individual.
Chronobiology is a field of biology that examines timing processes, including periodic (cyclic) phenomena in living organisms, such as their adaptation to solar- and lunar-related rhythms. These cycles are known as biological rhythms. Chronobiology comes from the ancient Greek χρόνος (chrónos, meaning "time"), and biology, which pertains to the study, or science, of life.
Explores the health effects of artificial light on living organisms and the principles of fluorescence guided surgery, along with the mechanisms and history of bright light therapy for psychiatric disorders.
Mammals have evolved an internal timing system, the circadian clock, which synchronizes physiology and behavior to the daily light and dark cycles of the Earth. The master clock, located in the suprac
Cold Spring Harbor Lab Press, Publications Dept2017
In mammals the circadian clock drives daily behavioural and physiological changes that resonate with environmental cues, which can be observed, for example, in the intricate timing of rest during the
Mammals have evolved an internal timing system, the circadian clock, which synchronizes physiology and behavior to the daily light and dark cycles of the Earth. The master clock, located in the suprac
Cold Spring Harbor Lab Press, Publications Dept2017