biology

Ventromedial nucleus of the hypothalamus

Ventromedial nucleus of the hypothalamus is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Ventromedial nucleus of the hypothalamus rather than just read about it. In short: The ventromedial nucleus of the hypothalamus (VMN, VMH or ventromedial hypothalamus) is a nucleus of the hypothalamus. In 2007, Kurrasch et al. found that the ventromedial hypothalamus is a distinct morphological nucleus involved in terminating hunger, fear, thermoregulation, and sexual activity.

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Reference excerpt

The ventromedial nucleus of the hypothalamus (VMN, VMH or ventromedial hypothalamus) is a nucleus of the hypothalamus. In 2007, Kurrasch et al. found that the ventromedial hypothalamus is a distinct morphological nucleus involved in terminating hunger, fear, thermoregulation, and sexual activity. This nuclear region is involved in the recognition of the feeling of fullness.

Structure It has four subdivisions:

Anterior (VMHa) Dorsomedial (VMHdm) Ventrolateral (VMHvl) Central (VMHc) These subdivisions differ anatomically, neurochemically, and behaviorally.

Function The ventromedial nucleus (VMN) is most commonly associated with satiety. Early studies showed that VMN lesions caused over-eating and obesity in rats. The interpretation of these experiments was questioned when Gold reported that precision-lesioning the VMN did not result in hyperphagia. Nevertheless, numerous studies have shown that the immediacy of hyperphagia and obesity syndrome are a consequence of VMN lesions or procaine injections, and point to the VMN's role in satiety. A major review of the subject in 2006 concluded that, "anatomical studies done both before and after Gold's study did not replicate his results with lesions, and in nearly every published direct comparison of VMH lesions vs. PVN or VNAB lesions, the group with VMH lesions ate substantially more food and gained twice as much weight." This strongly substantiates the classification of VMN as the primary satiety center in the hypothalamus. It has also been found that lesions to the VMH in rats caused increased plasma insulin levels. Rats with a VMH lesion overproduce a circulating satiety factor (leptin) compared to normal rats, to which the control rats can respond but rats with a VMH lesion cannot, causing them to overeat (leading to obesity). Researchers looked at a series of twenty-one animals of various degrees of adiposity, with respect to growth appearance, fat distribution, general physical condition, and the correlation between the level of adiposity attained and the correlation of the hypothalamic lesion. Lesions in the hypothalamic area, particularly the region of the ventromedial hypothalamus interrupts a large number of the descending fibers from the hypothalamic cell groups that were found to contribute to obesity in rats. Another study found that there seems to be a higher concentration of cannabinoid receptor mRNA within the VMH in comparison to other nuclei within the hypothalamus. The cannabinoid ingestion has been linked to rewarding processes, and also with the release of dopamine in the brain. VMH is also important in mammal play behaviour. Lesions to VMH along with the hippocampus, amygdala, the cerebellum, and the lateral hypothalamus are all linked to reduced play. The VMHdm has a role in the male vocalizations and scent marking behaviors. The VMHvl contains many distinct neuronal populations that contribute to varying, often distinct, functions. Notably, this region plays a role in sexual behaviors in females (lordosis), thus stimulating their sexual arousal. The VMHvl has also been found to play a role in estrogen-mediated movement and energy expenditure/thermogenesis. Bilateral FOS expression in the VMH after repeated seizures is associated with alteration in the severity of flurothyl induced seizures in C57BL/6J mice that are not present in DBA/2J mice. Moreover, bilateral lesions of the VMH are able to block the propagation of seizure discharge to enter the brainstem seizure system.

Surgery In West Germany, at least 70 men had their VMN operated on between 1962 and 1979. Most of these individuals had been involuntarily institutionalized or imprisoned for deviant sexual behavior, such as homosexuality, perceived hypersexuality among heterosexual men, and pedophilia. This surgery was not commonly performed elsewhere.

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Worked examples

Example 1 — a first encounter with Ventromedial nucleus of the hypothalamus

Start with the simplest possible case. Write down what Ventromedial nucleus of the hypothalamus claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Ventromedial nucleus of the hypothalamus before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Ventromedial nucleus of the hypothalamus ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Ventromedial nucleus of the hypothalamus

In research: Ventromedial nucleus of the hypothalamus appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Ventromedial nucleus of the hypothalamus in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Ventromedial nucleus of the hypothalamus is common in secondary-school and first-year university syllabi. It links to neighbouring topics Hypothalamus, Neuroendocrinology, so understanding it makes those chapters shorter.
In everyday life: Look for Ventromedial nucleus of the hypothalamus outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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Frequently asked questions

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