Category Archives: Hypothalamus

The paraventricular nucleus (PVN, PVA, or PVH) is a nucleus in the hypothalamus.[1] It is a group of neurons that can be activated by physiological changes including stress. Many PVN neurons project directly to the posterior pituitary where they release oxytocin into the general circulation. While the supraoptic nucleus releases vasopressin. Both the PVN and the supraoptic nucleus do produce small amounts of the other hormone, ADH and Oxytocin respectively. Other PVN neurons control various anterior pituitary functions, while still others directly regulate appetite and autonomic functions in the brainstem and spinal cord. The paraventricular nucleus lies adjacent to the third ventricle. It lies within the periventricular zone and is not to be confused with the periventricular nucleus, which occupies a more medial position, beneath the third ventricle. The PVN is highly vascularised and is protected by the bloodbrain barrier, although its neuroendocrine cells extend to sites (in the median eminence and in the posterior pituitary) beyond the bloodbrain barrier. The PVN contains magnocellular neurosecretory cells whose axons extend into the posterior pituitary, parvocellular neurosecretory (neuroendocrine) cells that project to the median eminence, and several populations of peptide-containing cells that project to many different brain regions including parvocellular preautonomic cells … Continue reading →

The lateral hypothalamus, also called the lateral hypothalamic area,[1] contains the primary orexinergic nucleus within the hypothalamus that widely projects throughout the nervous system;[2] this system of neurons mediates an array of cognitive and physical processes, such as promoting feeding behavior and arousal, reducing pain perception, and regulating body temperature, digestive functions, and blood pressure, among many others.[2][3][4] Clinically significant disorders that involve dysfunctions of the orexinergic projection system include narcolepsy, motility disorders or functional gastrointestinal disorders involving visceral hypersensitivity (e.g., irritable bowel syndrome),[3][5] and eating disorders.[6] The neurotransmitter glutamate and the endocannabinoids (e.g., anandamide) and the orexin neuropeptides orexin-A and orexin-B are the primary signaling neurochemicals in orexin neurons;[3][4][7] pathway-specific neurochemicals include GABA, melanin-concentrating hormone, nociceptin, glucose, the dynorphin peptides, and the appetite-regulating peptide hormones leptin and ghrelin, among others.[3][8] Notably, cannabinoid receptor 1 (CB1) is colocalized on orexinergic projection neurons in the lateral hypothalamus and many output structures,[4][7] where the CB1 and orexin receptor 1 (OX1) receptors form the CB1OX1 receptor heterodimer.[4][9][10] The orexinergic projections from the lateral hypothalamus innervate the entirety of the remainder of the hypothalamus, with robust projections to the posterior hypothalamus, tuberomammillary nucleus (the histamine projection nucleus), the arcuate nucleus, and the paraventricular hypothalamic … Continue reading →

The ventromedial nucleus of the hypothalamus (VMN, also sometimes referred to as the ventromedial hypothalamus, VMH) is a nucleus of the hypothalamus. "The ventromedial hypothalamus (VMH) is a distinct morphological nucleus involved in terminating hunger, fear, thermoregulation, and sexual activity."[1] This nuclear region is involved with the recognition of the feeling of fullness. It has four subdivisions: These subdivisions differ anatomically, neurochemically, and behaviorally. The ventromedial nucleus (VMN) is most commonly associated with satiety. Early studies showed that VMN lesions caused over-eating and obesity in rats. However, the interpretation of these experiments was summarily discredited when Gold's research demonstrated that precision lesioning of the VMN did not result in hyperphagia.[2] 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.[3][4][5][6][7][8][9] 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."[10] This strongly substantiates the … Continue reading →

The arcuate nucleus of the hypothalamus (also known as ARH,[1] ARC,[2] or infundibular nucleus[2][3]) is an aggregation of neurons in the mediobasal hypothalamus, adjacent to the third ventricle and the median eminence. The arcuate nucleus includes several important and diverse populations of neurons that help mediate different neuroendocrine and physiological functions, including: neuroendocrine neurons, centrally projecting neurons, and astrocytes. The populations of neurons found in the arcuate nucleus are based on the hormones they secrete or interact with and are responsible for hypothalamic function, such as regulating hormones released from the pituitary gland or secreting their own hormones. Neurons in this region are also responsible for integrating information and providing inputs to other nuclei in the hypothalamus or inputs to areas outside this region of the brain. These neurons, generated from the ventral part of the periventricular epithelium during embryonic development, locate dorsally in the hypothalamus, becoming part of the ventromedial hypothalamic region.[1][2][4] The function of the arcuate nucleus relies on its diversity of neurons, but its central role is involved in homeostasis. The arcuate nucleus provides many physiological roles involved in feeding, metabolism, fertility, and cardiovascular regulation.[1][2][4][5] Different groups of arcuate nucleus neuroendocrine neurons secrete various types or combinations … Continue reading →

What is Hypothalamus - Brief Introduction: As you can see in the hypothalamus pictures, it measures about the size of an almond or pearl. It is an extremely important part of brain in human beings and other higher animals. Hypothalamus constitutes one of the four major components of diencephalon, while the other three are: thalamus, epithalamus and subthalamus. It is intimately associated with the function of autonomic & endocrine systems, formation of behavioral patterns, temperature control, reproduction, and so on. With the help of hypophysis (or pituitary gland), the hypothalamus develops a connection between endocrine system and nervous system in the body. A number of medical conditions have been found associated with this part of the interbrain that may arise out of various factors, and include nutritious, infectious, neoplastic and inflammatory disorders that are manifested by severe symptoms in the victim. As these problem areas are located inside the human brain, the diagnosis and treatment is not easy. However, if identified at an early stage, the symptoms can be relieved through medication. Hypothalamus can be distinguished into three structurally distinct parts, namely, anterior, middle and posterior regions. These regions are alternately known as the supraoptic, tuberal and mammillary, respectively. Some … Continue reading →

More About Location of the Hypothalamus A 3-D animation that shows the location of the hypothalamus in a mouse's brain. Location of the Hypothalamus Background The hypothalamus is located in a very specific location of a mouse's brain, just above the optic chiasm. This area controls much of a mouse's basic behavior, including feeding. The hypothalamus is one of the areas of the brain that responds to the leptin hormonal signal from fat tissue. From Lecture Four of the 2004 Holiday Lectures Series "The Science of Fat." Location of the Hypothalamus Teaching Tips The animations in this section have a wide variety of classroom applications. Use the tips below to get started but look for more specific teaching tips in the near future. Please tell us how you are using the animations in your classroom by sending e-mail to biointeractive@hhmi.org. Resources The 2004 Holiday Lectures Series "The Science of Fat" Location of the Hypothalamus Credits Director: Dennis Liu, Ph.D. Scientific Direction: Jeffrey Friedman, M.D., Ph. D. Scientific Content: Satoshi Amagai, Ph.D. Animators: Eric Keller, Chris Vargas More: Location of the Hypothalamus | HHMI BioInteractive … Continue reading →

If youve ever noticed that you tend to feel energized and drowsy around the same times every day, you have your circadian rhythm to thank. What is it, exactly? Your circadian rhythm is basically a 24-hour internal clock that is running in the background of your brain and cycles between sleepiness and alertness at regular intervals. It's also known as your sleep/wake cycle. For most adults, the biggest dip in energy happens in the middle of the night (somewhere between 2:00am and 4:00am, when they're usually fast asleep) and just after lunchtime (around 1:00pm to 3:00pm, when they tend to crave a post-lunch nap). Those times can be different if youre naturally a night owl or a morning person. You also wont feel the dips and rises of your circadian rhythm as strongly if youre all caught up on sleep. Its when youre sleep-deprived that youll notice bigger swings of sleepiness and alertness. A part of your hypothalamus (a portion of your brain) controls your circadian rhythm. That said, outside factors like lightness and darkness can also impact it. When its dark at night, your eyes send a signal to the hypothalamus that its time to feel tired. Your brain, … Continue reading →

What is the hypothalamus? The hypothalamus is a small region of the brain. Its located at the base of the brain, near the pituitary gland. While its very small, the hypothalamus plays a crucial role in many important functions, including: The hypothalamus has three main regions. Each one contains different nuclei. These are clusters of neurons that perform vital functions, such as releasing hormones. This area is also called the supraoptic region. Its major nuclei include the supraoptic and paraventricular nuclei. There are several other smaller nuclei in the anterior region as well. The nuclei in the anterior region are largely involved in the secretion of various hormones. Many of these hormones interact with the nearby pituitary gland to produce additional hormones. Some of the most important hormones produced in the anterior region include: The anterior region of the hypothalamus also helps regulate body temperature through sweat. It also maintains circadian rhythms. These are physical and behavioral changes that occur on a daily cycle. For example, being awake during the day and sleeping at nighttime is a circadian rhythm related to the presence or absence of light. This area is also called the tuberal region. Its major nuclei are the … Continue reading →

The Hypothalamus Gland The hypothalamus is part of the brain lying under the thalamus. The stalk of the pituitary gland is attached to the hypothalamus. The main function of the hypothalamus is homeostasis, or maintaining the body's status quo. Factors such as blood pressure, body temperature, fluid and electrolyte balance, and body weight are held to a precise value called the set-point. Although this set-point can migrate over time, from day to day it is remarkably fixed. The general functions of the hypothalamus are of extreme importance for the body The hypothalamus controls and integrates the overlapping functions of the endocrine system and the autonomic nervous system. The hypothalamus links the brain to the hormonal system and plays a vital role in powerful basic drives for survival such as hunger, thirst, sex and the strong emotions such as rage or ecstatic joy, that may accompany them. The hypothalamus sends out nerve signals to various muscles, often through the autonomic nervous system. For example, in response to a sudden scare, the hypothalamus takes control and tells the adrenal glands to release adrenaline which tells the heart to beat faster, and the skeletal muscles to tense in readiness for sudden action: the … Continue reading →

Hunger Motivation Most of us love food. In fact, I can truthfully say that I think about food probably more than I have thought about anything in my whole life. Everyday, even when teaching, I think about what I am going to eat for my next meal (or snack). If I am in a Vegan phase, I think about nuts, pasta and fruits. If not I think about big juicy cheeseburgers, fresh warm Krispy Crme donuts and a thick chemical enhanced Micky Ds chocolate shake. Damn, I LOVE FOOD. Our bodies need food!!! However, we sometimes eat even when we do not need food. Thus, the motivation for hunger goes beyond simple nourishment. There are both biological and psychological factors around the motivation of hunger. Biological Basis of Hunger When your stomach feels stuffed you probably do not feel hungry and when your stomach is empty you probably get that take me to Taco Bell feeling. Researchers used to believe that the feeling of hunger comes from our stomach. To test the theory out, they made some dude swallow a balloon and inflated the balloon inside his stomach. The dude felt full for awhile. But after a few hours he … Continue reading →