Brain: Hypothalamus
Location of the human hypothalamus
Dienchephalon
Latin	hypothalamus
Gray's	subject #189 812
NeuroNames	hier-358
MeSH	Hypothalamus

The hypothalamus links the nervous system to the endocrine system via the pituitary gland (hypophysis). Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome. This is a list of the subjects in Gray's Anatomy: IX Neurology NeuroNames is a system of nomenclature for the human and/or macaque Brain. Medical Subject Headings ( MeSH) is a huge Controlled vocabulary (or metadata system for the purpose of indexing journal articles and books The nervous system is a Network of specialized cells that communicate information about an animal's surroundings and itself The endocrine system is an integrated system of small organs that involve the release of extracellular signaling molecules known as Hormones The endocrine system is instrumental The pituitary gland, or hypophysis, is an Endocrine gland about the size of a Pea. The hypothalamus, (from Greek ὑποθαλαμος = under the thalamus) is located below the thalamus, just above the brain stem. The thalamus (from Greek θάλαμος = room chamber, IPA= /ˈθæləməs/ is a pair and symmetric part of the brain The brain stem (or brainstem) is the lower part of the Brain, adjoining and structurally continuous with the Spinal cord. This brain region occupies the major portion of the ventral diencephalon. The diencephalon (or interbrain is the region of the Brain that includes the Thalamus, Hypothalamus, Epithalamus, Prethalamus or It is found in all mammalian brains. Mammals ( class Mammalia) are a class of Vertebrate Animals characterized by the presence of Sweat glands, including sweat glands The brain is the center of the Nervous system in animals All Vertebrates and the majority of Invertebrates have a brain In humans, it is roughly the size of an almond.

The hypothalamus is responsible for certain metabolic processes and other activities of the Autonomic Nervous System. Metabolism is the set of Chemical reactions that occur in living Organisms in order to maintain Life. &trade The autonomic nervous system ( ANS) (or visceral nervous system) is the part of the Peripheral nervous system that acts as a Control It synthesizes and secretes neurohormones, often called hypothalamic-releasing hormones, and these in turn stimulate or inhibit the secretion of pituitary hormones. Hormones (from Greek ὁρμή - "impetus" are chemicals released by cells that affect cells in other parts of the body Hormones (from Greek ὁρμή - "impetus" are chemicals released by cells that affect cells in other parts of the body

The hypothalamus controls body temperature, hunger, thirst, ^[1] fatigue, anger, and circadian cycles. Core temperature, also called core body temperature, is the operating Temperature of an Organism, specifically in deep structures of the body such as the Hunger is a feeling experienced usually followed by a desire to Eat. Thirst is the craving for liquids resulting in the basic Instinct of humans or animals to Drink.

Contents 1 Inputs 1.1 Olfactory stimuli 1.2 Blood-borne stimuli 1.3 Steroids 1.4 Neural inputs 2 Nuclei 3 Outputs 3.1 Neural projections 3.2 Endocrine hormones 4 Control of food intake 5 Sexual dimorphism 5.1 Responses to ovarian steroids 5.2 Gonadal steroids in neonatal life of rats 5.3 Androgens in primates 5.4 Other influences upon hypothalamic development 6 Effects of aging on the hypothalamus 7 See also 8 Additional images 9 References 10 External links

Inputs

The hypothalamus is a complex region in the brain of humans, and even small nuclei within the hypothalamus are involved in many different functions. The paraventricular nucleus for instance contains oxytocin and vasopressin (also called antidiuretic hormone) neurons which project to the posterior pituitary, but also contains neurons that regulate ACTH and TSH secretion (which project to the anterior pituitary), gastric reflexes, maternal behavior, blood pressure, feeding, immune responses, and temperature. The paraventricular nucleus (PVN is an aggregation of neurons in the Hypothalamus which produces many Hormones. Oxytocin ( IPA: /ˌɔksɪˈtoʊsɪn/ (Greek "quick birth" is a Mammalian Hormone that also acts as a Neurotransmitter in the Arginine vasopressin ( AVP) also known as vasopressin, argipressin or antidiuretic hormone ( ADH) is a Hormone found in The posterior pituitary (or neurohypophysis) comprises the Posterior lobe of the Pituitary gland and is part of the Endocrine system. Adrenocorticotropic hormone ( ACTH or corticotropin) is a Polypeptide Hormone produced and secreted by the Pituitary gland Thyroid-stimulating hormone (also known as TSH or thyrotropin) is a Peptide hormone synthesized and secreted by Thyrotrope cells in the The anterior pituitary (also called the adenohypophysis, from Greek adeno, "gland" hypo, "under" physis, "growth" The maternal bond is typically the relationship between a Mother and her child Blood pressure is also the title of a short story by Damon Runyan in Guys and Dolls and Other Stories An immune system is a collection of mechanisms within an Organism that protects against Disease by identifying and killing Pathogens and Tumor Temperature is a physical property of a system that underlies the common notions of hot and cold something that is hotter generally has the greater temperature

The hypothalamus co-ordinates many hormonal and behavioural circadian rhythms, complexity patterns of neuroendocrine outputs, complex homeostatic mechanisms,^[2] and many important behaviours. The hypothalamus must therefore respond to many different signals, some of which are generated externally and some internally. It is thus richly connected with many parts of the CNS, including the brainstem reticular formation and autonomic zones, the limbic forebrain (particularly the amygdala, septum, diagonal band of Broca, and the olfactory bulbs, and the cerebral cortex). The reticular formation is a part of the Brain that is involved in actions such as awaking/ sleeping cycle, and lying down The la amygdalae ( Latin, also la corpus amygdaloideum, singular la amygdala, from Greek el αμυγδαλή grc-Latn amygdalē, 'almond' A septum ( Latin: something that encloses; plural Septa) is a partition separating two cavities or spaces The diagonal band of Broca consists of fibers that are said to arise in the Parolfactory area, the Gyrus subcallosus and the Anterior perforated substance The olfactory bulb is a structure of the Vertebrate Forebrain involved in Olfaction, the perception of Odors. The cerebral cortex is a structure within the Brain that plays a key role in Memory, Attention, perceptual Awareness, Thought,

The hypothalamus is responsive to:

• Light: daylength and photoperiod for regulating circadian and seasonal rhythms
• Olfactory stimuli, including pheromones
• Steroids, including gonadal steroids and corticosteroids
• Neurally transmitted information arising in particular from the heart, the stomach, and the reproductive tract
• Autonomic inputs
• Blood-borne stimuli, including leptin, ghrelin, angiotensin, insulin, pituitary hormones, cytokines, plasma concentrations of glucose and osmolarity etc
• Stress
• Invading microorganisms by increasing body temperature, resetting the body's thermostat upward. Photoperiodicity is the physiological reaction of organisms to the length of day or night &trade The autonomic nervous system ( ANS) (or visceral nervous system) is the part of the Peripheral nervous system that acts as a Control Leptin (Greek leptos meaning thin is a 16 kDa Ghrelin is a Hormone produced mainly by P/D1 cells lining the fundus of the human Stomach and epsilon cells of the Pancreas that stimulates Angiotensin causes blood vessels to constrict and drives blood pressure up Insulin is a Hormone with intensive effects on both metabolism and several other body systems (eg vascular compliance Cytokines are a category of signalling Proteins and Glycoproteins that like Hormones and Neurotransmitters, are used extensively in cellular

Olfactory stimuli

Olfactory stimuli are important for sex and neuroendocrine function in many species. For instance if a pregnant mouse is exposed to the urine of a 'strange' male during a critical period after coitus then the pregnancy fails (the Bruce effect). The Bruce effect is a form of Pregnancy disruption in Mammals in which exposure of a Female to an unknown Male results in pre- (Bruce 1959 or Thus during coitus, a female mouse forms a precise 'olfactory memory' of her partner which persists for several days. Pheromonal cues aid synchronisation of oestrus in many species; in women, synchronised menstruation may also arise from pheromonal cues, although the role of pheromones in humans is doubted by some. Oestrus is also the biological genus name of the gadfly. The estrous cycle (also oestrous cycle; derived from Latin See also "Mensuration" a term sometimes used to describe Measurement, particularly in the context of Forestry.

Blood-borne stimuli

Peptide hormones have important influences upon the hypothalamus, and to do so they must evade the blood-brain barrier. Peptides (from the Greek πεπτίδια, "small digestibles" are short Polymers formed from the linking in a defined order of α- Amino The blood-brain barrier (BBB is a metabolic or cellular structure in the Central nervous system (CNS that restricts the passage of various chemical substances and microscopic The hypothalamus is bounded in part by specialized brain regions that lack an effective blood-brain barrier; the capillary endothelium at these sites is fenestrated to allow free passage of even large proteins and other molecules. Some of these sites are the sites of neurosecretion - the neurohypophysis and the median eminence. The posterior pituitary (or neurohypophysis) comprises the Posterior lobe of the Pituitary gland and is part of the Endocrine system. The median eminence is part of the inferior boundary for the Hypothalamus part of the human Brain. However others are sites at which the brain samples the composition of the blood. Two of these sites, the subfornical organ and the OVLT (organum vasculosum of the lamina terminalis) are so-called circumventricular organs, where neurons are in intimate contact with both blood and CSF. The subfornical organ, situated on the ventral surface of the fornix, at the Foramen of Monro, is one of the Circumventricular organs of the Brain The organum vasculosum of the lamina terminalis (OVLT (or supraoptic crest) is one of the Circumventricular organs of the brain. Circumventricular organs (CVO are so named because they are positioned at distinct sites around the margin of the Ventricular system of the brain Cerebrospinal fluid ( CSF) Liquor cerebrospinalis, is a clear Bodily fluid that occupies the Subarachnoid space and the Ventricular system These structures are densely vascularized, and contain osmoreceptive and sodium-receptive neurons which control drinking, vasopressin release, sodium excretion, and sodium appetite. Drinking is the act of consuming a liquid through the mouth Water, for example is required for many of life's physiological processes and excess or decreased water intake Arginine vasopressin ( AVP) also known as vasopressin, argipressin or antidiuretic hormone ( ADH) is a Hormone found in They also contain neurons with receptors for angiotensin, atrial natriuretic factor, endothelin and relaxin, each of which is important in the regulation of fluid and electrolyte balance. Angiotensin causes blood vessels to constrict and drives blood pressure up Atrial natriuretic peptide ( ANP) atrial natriuretic factor ( ANF) or atriopeptin, is a protein ( Polypeptide) Hormone secreted Endothelins are proteins that constrict blood vessels and raise blood pressure For the Miles Davis album see Relaxin' with the Miles Davis Quintet. Neurons in the OVLT and SFO project to the supraoptic nucleus and paraventricular nucleus, and also to preoptic hypothalamic areas. The supraoptic nucleus ( SON) is a nucleus of Magnocellular neurosecretory cells in the Hypothalamus of the mammalian brain The paraventricular nucleus (PVN is an aggregation of neurons in the Hypothalamus which produces many Hormones. The circumventricular organs may also be the site of action of interleukins to elicit both fever and ACTH secretion, via effects on paraventricular neurons. Interleukins are a group of Cytokines (secreted Signaling molecules) that were first seen to be expressed by White blood cells ( Leukocytes hence

It is not clear how all peptides that influence hypothalamic activity gain the necessary access. In the case of prolactin and leptin, there is evidence of active uptake at the choroid plexus from blood into CSF. Prolactin ( PRL) or Luteotropic hormone ( LTH) is a Peptide hormone primarily associated with Lactation. Leptin (Greek leptos meaning thin is a 16 kDa The choroid plexus is the area on the ventricles of the brain where Cerebrospinal fluid (CSF is produced by modified Ependymal cells. Some pituitary hormones have a negative feedback influence upon hypothalamic secretion; for example, growth hormone feeds back on the hypothalamus, but how it enters the brain is not clear. Growth hormone ( GH) is a Peptide hormone that stimulates growth and cell reproduction in humans and other animals There is also evidence for central actions of prolactin and TSH. Prolactin ( PRL) or Luteotropic hormone ( LTH) is a Peptide hormone primarily associated with Lactation. Thyroid-stimulating hormone (also known as TSH or thyrotropin) is a Peptide hormone synthesized and secreted by Thyrotrope cells in the

Steroids

The hypothalamus contains neurons that are sensitive to gonadal steroids and glucocorticoids – (the steroid hormones of the adrenal gland, released in response to ACTH). Glucocorticoids (GC are a class of Steroid hormones characterised by an ability to bind with the glucocorticoid receptor ( GR) and trigger similar effects In Mammals the adrenal glands (also known as suprarenal glands) are the triangle-shaped Endocrine glands that sit on top of the Kidneys their Adrenocorticotropic hormone ( ACTH or corticotropin) is a Polypeptide Hormone produced and secreted by the Pituitary gland It also contains specialised glucose-sensitive neurons (in the arcuate nucleus and ventromedial hypothalamus), which are important for appetite. The arcuate nucleus (or infundibular nucleus is an aggregation of Neurons in the mediobasal Hypothalamus, adjacent to the Third ventricle and the Median The ventromedial nucleus (sometimes referred to as the ventromedial hypothalamus) is a nucleus of the Hypothalamus. The preoptic area contains thermosensitive neurons; these are important for TRH secretion. Thyrotropin-releasing hormone ( TRH) also called thyrotropin-releasing factor ( TRF) thyroliberin or protirelin, is a tropic

Neural inputs

The hypothalamus receives many inputs from the brainstem; notably from the nucleus of the solitary tract, the locus coeruleus, and the ventrolateral medulla. The brain stem (or brainstem) is the lower part of the Brain, adjoining and structurally continuous with the Spinal cord. The solitary nucleus and tract are structures in the Brainstem that carry and receive visceral sensation and Taste from the facial (VII The Locus ceruleus also spelled locus caeruleus or locus coeruleus (Latin for 'the blue spot' is a nucleus in the Brain stem involved with physiological Oxytocin secretion in response to suckling or vagino-cervical stimulation is mediated by some of these pathways; vasopressin secretion in response to cardiovascular stimuli arising from chemoreceptors in the carotid sinus and aortic arch, and from low-pressure atrial volume receptors, is mediated by others. Oxytocin ( IPA: /ˌɔksɪˈtoʊsɪn/ (Greek "quick birth" is a Mammalian Hormone that also acts as a Neurotransmitter in the Arginine vasopressin ( AVP) also known as vasopressin, argipressin or antidiuretic hormone ( ADH) is a Hormone found in In Human anatomy, the carotid sinus is a localized dilation of the Internal carotid artery at its origin the Common carotid artery Bifurcation In the rat, stimulation of the vagina also causes prolactin secretion, and this results in pseudo-pregnancy following an infertile mating. The vagina (from Latin, literally " Sheath " or " Scabbard " is a fibromuscular tubular tract leading from the Uterus Prolactin ( PRL) or Luteotropic hormone ( LTH) is a Peptide hormone primarily associated with Lactation. In the rabbit, coitus elicits reflex ovulation. Note This article deals primarily with Human ovulation nonhuman Animal ovulation is touched on briefly at the conclusion In the sheep, cervical stimulation in the presence of high levels of estrogen can induce maternal behavior in a virgin ewe. These effects are all mediated by the hypothalamus, and the information is carried mainly by spinal pathways that relay in the brainstem. Stimulation of the nipples stimulates release of oxytocin and prolactin and suppresses the release of LH and FSH. Luteinizing hormone ( LH, also known as lutropin) is a Hormone produced by the Anterior pituitary gland. Follicle-stimulating hormone ( FSH) is a Hormone synthesized and secreted by Gonadotropes in the Anterior pituitary gland.

Cardiovascular stimuli are carried by the vagus nerve, but the vagus also conveys a variety of visceral information, including for instance signals arising from gastric distension to suppress feeding. The vagus nerve (ˈveɪˌgəs (VĀ-gəs (also called pneumogastric nerve or cranial nerve X) is the tenth of twelve paired Cranial nerves, and is the Again this information reaches the hypothalamus via relays in the brainstem.

Nuclei

The hypothalamic nuclei include the following:^[3][4][5]

Region	Area	Nucleus	Function[6]
Anterior	Medial	Medial preoptic nucleus	urinary bladder contraction Decreased heart rate Decreased blood pressure
		Supraoptic nucleus (SO)	oxytocin release vasopressin release
		Paraventricular nucleus (PV)	oxytocin release vasopressin release[7]
		Anterior hypothalamic nucleus (AH)	thermoregulation panting sweating thyrotropin inhibition
		Suprachiasmatic nucleus (SC)	vasopressin release Circadian rhythms
	Lateral	Lateral preoptic nucleus
		Lateral nucleus (LT)	thirst and hunger
		Part of supraoptic nucleus (SO)	vasopressin release
Tuberal	Medial	Dorsomedial hypothalamic nucleus (DM)	GI stimulation
		Ventromedial nucleus (VM)	satiety neurendocrine control
		Arcuate nucleus (AR) neurendocrine control
	Lateral	Lateral nucleus (LT)	thirst and hunger
		Lateral tuberal nuclei
Posterior	Medial	Mammillary nuclei (part of mammillary bodies) (MB)	feeding reflexes
		Posterior nucleus (PN)	Increase blood pressure pupillary dilation shivering
	Lateral	Lateral nucleus (LT)

See also: ventrolateral preoptic nucleus

Outputs

The outputs of the hypothalamus can be divided into two categories: neural projections, and endocrine hormones. The preoptic area is a region of the Hypothalamus. According to the MeSH classification it is considered part of the anterior hypothalamus In Anatomy, the urinary bladder is a hollow muscular, and distensible (or elastic organ that sits on the Pelvic floor in Mammals It is the Measuring heart rate The Pulse rate (which in most people is identical to the heart rate can be measured at any point on the body where an Artery 's pulsation Blood pressure is also the title of a short story by Damon Runyan in Guys and Dolls and Other Stories The supraoptic nucleus ( SON) is a nucleus of Magnocellular neurosecretory cells in the Hypothalamus of the mammalian brain Oxytocin ( IPA: /ˌɔksɪˈtoʊsɪn/ (Greek "quick birth" is a Mammalian Hormone that also acts as a Neurotransmitter in the Arginine vasopressin ( AVP) also known as vasopressin, argipressin or antidiuretic hormone ( ADH) is a Hormone found in The paraventricular nucleus (PVN is an aggregation of neurons in the Hypothalamus which produces many Hormones. Oxytocin ( IPA: /ˌɔksɪˈtoʊsɪn/ (Greek "quick birth" is a Mammalian Hormone that also acts as a Neurotransmitter in the Arginine vasopressin ( AVP) also known as vasopressin, argipressin or antidiuretic hormone ( ADH) is a Hormone found in The Anterior hypothalamic nucleus is a nucleus of the Hypothalamus. Thermoregulation is the ability of an Organism to keep its body temperature within certain boundaries even when temperature surrounding is very different Thermoregulation is the ability of an Organism to keep its body temperature within certain boundaries even when temperature surrounding is very different Thyroid-stimulating hormone (also known as TSH or thyrotropin) is a Peptide hormone synthesized and secreted by Thyrotrope cells in the The suprachiasmatic nucleus ( SCN) is a bilateral region of the brain located in the Hypothalamus, that is responsible for controlling endogenous Circadian rhythms Arginine vasopressin ( AVP) also known as vasopressin, argipressin or antidiuretic hormone ( ADH) is a Hormone found in The preoptic area is a region of the Hypothalamus. According to the MeSH classification it is considered part of the anterior hypothalamus The Lateral hypothalamus or lateral hypothalamic area is a part of the Hypothalamus. Thirst is the craving for liquids resulting in the basic Instinct of humans or animals to Drink. Hunger is a feeling experienced usually followed by a desire to Eat. Arginine vasopressin ( AVP) also known as vasopressin, argipressin or antidiuretic hormone ( ADH) is a Hormone found in The Dorsomedial hypothalamic nucleus is a nucleus of the Hypothalamus. The ventromedial nucleus (sometimes referred to as the ventromedial hypothalamus) is a nucleus of the Hypothalamus. Cholecystokinin ( CCK; from Greek chole, "bile" cysto, "sac" kinin, "move" hence move the bile-sac The arcuate nucleus (or infundibular nucleus is an aggregation of Neurons in the mediobasal Hypothalamus, adjacent to the Third ventricle and the Median The Lateral hypothalamus or lateral hypothalamic area is a part of the Hypothalamus. Thirst is the craving for liquids resulting in the basic Instinct of humans or animals to Drink. Hunger is a feeling experienced usually followed by a desire to Eat. The mammillary bodies (mamillary bodies are a pair of small round bodies located on the undersurface of the Brain, that form part of the Limbic system. The posterior nucleus of the hypothalamus is one of the many nuclei that make up the hypothalamic region of the Brain. Blood pressure is also the title of a short story by Damon Runyan in Guys and Dolls and Other Stories The pupil is the hole that is located in the center of the iris of the eye and that controls the amount of light that enters the Eye. The Lateral hypothalamus or lateral hypothalamic area is a part of the Hypothalamus. The ventrolateral preoptic nucleus (VLPO is a group of Neurons in the Hypothalamus. ^[8]

Neural projections

Most fiber systems of the hypothalamus run in two ways (bidirectional).

• Projections to areas caudal to the hypothalamus go through the medial forebrain bundle, the mammillotegmental tract and the dorsal longitudinal fasciculus. In fields of Anatomy, anatomical terms of location are descriptive terms to help identify relative positions or directions within a species The Medial forebrain bundle (MFB is a complex bundle of axons coming from the basal olfactory regions the periamygdaloid region and the Septal nuclei, and passing to the The dorsal longitudinal fasciculus (DLF (not to be confused with the Medial longitudinal fasciculus) is a White matter fiber tract located within the Brain stem
• Projections to areas rostral to the hypothalamus are carried by the mammillothalamic tract, the fornix and terminal stria. The mammillothalamic fasciculus ( mammillothalamic tract, thalamomammillary fasciculus, bundle of Vicq d’Azyr) arises from cells in both the medial and The fornix (Latin "vault" or "arch" is a C-shaped bundle of fibres ( Axons in the Brain, and carries signals from the Hippocampus The stria terminalis ( terminal stria) is a structure in the Brain, being a band of fibers running along the lateral margin of the ventricular surface of the Thalamus

Endocrine hormones

The Hypothalamus affects the endocrine system and governs emotional behavior, such as, anger and sexual activity. Most of the hypothalamic hormones generated are distributed to the pituitary via the hypophyseal portal system. The hypophyseal portal system (or hypothalamo-hypophyseal portal system) is the system of Blood vessels that links the Hypothalamus and the Anterior ^[9] The hypothalamus maintains homeostasis this includes a regulation of blood pressure, heart rate, and temperature.

The primary hypothalamic hormones are:

Name	Other Names	Abbreviations	Location	Function
Corticotropin-releasing hormone	Corticotropin-releasing factor, Corticoliberin	CRH, CRF	parvocellular neuroendocrine neurons in the paraventricular nucleus	with vasopressin, stimulates anterior pituitary to secrete ACTH
Dopamine	Prolactin-inhibiting hormone	DA, PIH	neuroendocrine neurons of the arcuate nucleus	inhibits secretion of prolactin from the anterior pituitary
Gonadotropin-releasing hormone	Luteinising-hormone releasing hormone	GnRH, LHRH	neuroendocrine neurons in the medial preoptic and arcuate nuclei	stimulates anterior pituitary to secrete LH and FSH
Growth hormone-releasing hormone	Growth-hormone-releasing factor, somatocrinin	GHRH, GHRF, GRF	arcuate nucleus neuroendocrine neurons	stimulates anterior pituitary to secrete growth hormone
Melatonin			suprachiasmatic nucleus
Somatostatin	Growth hormone-inhibiting hormone, Somatotropin release-inhibiting factor	SS, GHIH, SRIF	neuroendocrine neurons of the periventricular nucleus	inhibits secretion of growth hormone from the anterior pituitary
Thyrotropin-releasing hormone	Thyrotropin-releasing factor, Thyroliberin, Protirelin	TRH, TRF	parvocellular neuroendocrine neurons in the paraventricular and anterior hypothalamic nuclei	stimulates anterior pituitary to secrete TSH

See also: Hypocretin

Control of food intake

The extreme lateral part of the ventromedial nucleus of the hypothalamus is responsible for the control of food intake. Corticotropin-releasing hormone ( CRH) originally named corticotropin-releasing factor ( CRF) and also called corticoliberin, is a Polypeptide The parvocellular ("small-celled" part of a nucleus in the Brain is one containing small-bodied punctate Neurons The term distinguishes it from The paraventricular nucleus (PVN is an aggregation of neurons in the Hypothalamus which produces many Hormones. Arginine vasopressin ( AVP) also known as vasopressin, argipressin or antidiuretic hormone ( ADH) is a Hormone found in The anterior pituitary (also called the adenohypophysis, from Greek adeno, "gland" hypo, "under" physis, "growth" Adrenocorticotropic hormone ( ACTH or corticotropin) is a Polypeptide Hormone produced and secreted by the Pituitary gland Dopamine is a Hormone and Neurotransmitter occurring in a wide variety of animals including both vertebrates and invertebrates The arcuate nucleus (or infundibular nucleus is an aggregation of Neurons in the mediobasal Hypothalamus, adjacent to the Third ventricle and the Median Prolactin ( PRL) or Luteotropic hormone ( LTH) is a Peptide hormone primarily associated with Lactation. The anterior pituitary (also called the adenohypophysis, from Greek adeno, "gland" hypo, "under" physis, "growth" Gonadotropin-releasing hormone ( GNRH) also known as Luteinizing-hormone releasing hormone ( LHRH) is a tropic Peptide Hormone The preoptic area is a region of the Hypothalamus. According to the MeSH classification it is considered part of the anterior hypothalamus The arcuate nucleus (or infundibular nucleus is an aggregation of Neurons in the mediobasal Hypothalamus, adjacent to the Third ventricle and the Median The anterior pituitary (also called the adenohypophysis, from Greek adeno, "gland" hypo, "under" physis, "growth" Luteinizing hormone ( LH, also known as lutropin) is a Hormone produced by the Anterior pituitary gland. Follicle-stimulating hormone ( FSH) is a Hormone synthesized and secreted by Gonadotropes in the Anterior pituitary gland. Growth-hormone-releasing hormone (GHRH also known as growth-hormone-releasing factor (GRF or GHRF or somatocrinin, is a 44- Amino acid Peptide hormone The arcuate nucleus (or infundibular nucleus is an aggregation of Neurons in the mediobasal Hypothalamus, adjacent to the Third ventricle and the Median Neuroendocrine nʊəroʊˈɛndəkrɪn cells are cells that release a hormone into the circulating blood in response to a neural stimulus The anterior pituitary (also called the adenohypophysis, from Greek adeno, "gland" hypo, "under" physis, "growth" Growth hormone ( GH) is a Peptide hormone that stimulates growth and cell reproduction in humans and other animals Melatonin is a naturally occurring Hormone found in most animals including humans and some other living organisms including Algae. The suprachiasmatic nucleus ( SCN) is a bilateral region of the brain located in the Hypothalamus, that is responsible for controlling endogenous Circadian rhythms Somatostatin (also known as growth hormone inhibiting hormone ( GHIH) or somatotropin release-inhibiting factor ( SRIF) is a Peptide hormone The Periventricular nucleus is a composite structure of the Hypothalamus. Growth hormone ( GH) is a Peptide hormone that stimulates growth and cell reproduction in humans and other animals The anterior pituitary (also called the adenohypophysis, from Greek adeno, "gland" hypo, "under" physis, "growth" Thyrotropin-releasing hormone ( TRH) also called thyrotropin-releasing factor ( TRF) thyroliberin or protirelin, is a tropic The parvocellular ("small-celled" part of a nucleus in the Brain is one containing small-bodied punctate Neurons The term distinguishes it from The paraventricular nucleus (PVN is an aggregation of neurons in the Hypothalamus which produces many Hormones. The Anterior hypothalamic nucleus is a nucleus of the Hypothalamus. The anterior pituitary (also called the adenohypophysis, from Greek adeno, "gland" hypo, "under" physis, "growth" Thyroid-stimulating hormone (also known as TSH or thyrotropin) is a Peptide hormone synthesized and secreted by Thyrotrope cells in the Orexins, also called hypocretins, are the common names given to a pair of highly excitatory Neuropeptide Hormones that were simultaneously discovered by In fields of Anatomy, anatomical terms of location are descriptive terms to help identify relative positions or directions within a species The ventromedial nucleus (sometimes referred to as the ventromedial hypothalamus) is a nucleus of the Hypothalamus. Stimulation of this area causes increased food intake. Bilateral lesion of this area causes complete cessation of food intake. A lesion is any abnormal tissue found on or in an organism usually damaged by disease or trauma Medial parts of the nucleus have a controlling effect on the lateral part. Bilateral lesion of the medial part of the ventromedial nucleus causes hyperphagia and obesity of the animal. Polyphagia is a compound word which literally means "eating too much Further lesion of the lateral part of the ventromedial nucleus in the same animal produces complete cessation of food intake.

There are different hypotheses related to this regulation:^[10]

1. Lipostatic hypothesis - this hypothesis holds that adipose tissue produces a humoral signal that is proportionate to the amount of fat and acts on the hypothalamus to decrease food intake and increase energy output. "Adipose" redirects here For the Doctor Who monster see " Partners in Crime " Tissue is a cellular organizational level intermediate between cells and a complete organism The Humoral Immune Response (HIR is the aspect of immunity that is mediated by secreted Antibodies (as opposed to Cell-mediated immunity which involves It has been evident that a hormone leptin acts on the hypothalamus to decrease food intake and increase energy output. Hormones (from Greek ὁρμή - "impetus" are chemicals released by cells that affect cells in other parts of the body Leptin (Greek leptos meaning thin is a 16 kDa
2. Gutpeptide hypothesis - gastrointestinal hormones like Grp, glucagons, CCK and others claimed to inhibit food intake. Glucagon is an important Hormone involved in Carbohydrate metabolism. Cholecystokinin ( CCK; from Greek chole, "bile" cysto, "sac" kinin, "move" hence move the bile-sac The food entering the gastrointestinal tract triggers the release of these hormones which acts on the brain to produce satiety. The brain contains both CCK-A and CCK-B receptors.
3. Glucostatic hypothesis - the activity of the satiety center in the ventromedial nuclei is probably governed by the glucose utilization in the neurons. Glucose (Glc a Monosaccharide (or simple Sugar) also known as grape sugar, is an important Carbohydrate in Biology. It has been postulated that when their glucose utilization is low and consequently when the arteriovenous blood glucose difference across them is low, the activity across the neurons decrease. Under these conditions, the activity of the feeding center is unchecked and the individual feels hungry. Food intake is rapidly increased by intraventricular administration of 2-deoxyglucose therefore decreasing glucose utilization in cells. 2-Deoxy-D-glucose is a Glucose Molecule which has the 2-hydroxyl group replaced by hydrogen so that it cannot undergo further Glycolysis.
4. Thermostatic hypothesis - according to this hypothesis, a decrease in body temperature below a given set point stimulates appetite, while an increase above the set point inhibits appetite.

Sexual dimorphism

Several hypothalamic nuclei are sexually dimorphic, i. Sexual dimorphism is the systematic difference in form between individuals of different Sex in the same Species. e. there are clear differences in both structure and function between males and females.

Some differences are apparent even in gross neuroanatomy: most notable is the sexually dimorphic nucleus within the preoptic area, which is present only in males. Sexually dimorphic nucleus (SDN is believed to be related to sexual behaviors by scientists The preoptic area is a region of the Hypothalamus. According to the MeSH classification it is considered part of the anterior hypothalamus However most of the differences are subtle changes in the connectivity and chemical sensitivity of particular sets of neurons.

The importance of these changes can be recognised by functional differences between males and females. For instance, the pattern of secretion of growth hormone is sexually dimorphic, and this is one reason why in many species, adult males are much larger than females. Growth hormone ( GH) is a Peptide hormone that stimulates growth and cell reproduction in humans and other animals

Responses to ovarian steroids

Other striking functional dimorphisms are in the behavioral responses to ovarian steroids of the adult. Sex steroids, also known as gonadal steroids, are Steroid hormones that interact with Vertebrate Androgen or Estrogen receptors Males and females respond differently to ovarian steroids, partly because the expression of estrogen-sensitive neurons in the hypothalamus is sexually dimorphic, i. e. estrogen receptors are expressed in different sets of neurons.

Estrogen and progesterone can influence gene expression in particular neurons or induce changes in cell membrane potential and kinase activation, leading to diverse non-genomic cellular functions. Estrogens (US otherwise oestrogens or œstrogens) are a group of Steroid compounds named for their importance in the Estrous cycle, Progesterone is a C-21 Steroid Hormone involved in the Female Menstrual cycle, Pregnancy (supports Gestation The cell membrane (also called the plasma membrane, plasmalemma, or "phospholipid bilayer" is a Selectively permeable Lipid bilayer In Chemistry and Biochemistry, a kinase, alternatively known as a phosphotransferase, is a type of Enzyme that transfers Phosphate Estrogen and progesterone bind to their cognate nuclear hormone receptors, which translocate to the cell nucleus and interact with regions of DNA known as Hormone response elements (HREs) or get tethered to another transcription factor's binding site. In the field of Molecular biology, nuclear receptors are a class of Proteins found within the interior of cells that are responsible for sensing the presence of A hormone response element (HRE is a Response element for Hormones, a short sequence of DNA within the Promoter of a gene that is able to bind In the field of Molecular biology, a transcription factor (sometimes called a sequence-specific DNA binding factor is a Protein that binds to specific sequences Estrogen receptor (ER) has been shown to transactivate other transcription factors in this manner, despite the absence of an estrogen response element (ERE) in the proximal promoter region of the gene. The estrogen receptor (ER is a member of the nuclear hormone family of Intracellular receptors which is activated by the Hormone 17β-estradiol A hormone response element (HRE is a Response element for Hormones, a short sequence of DNA within the Promoter of a gene that is able to bind ERs and Progesterone receptors (PRs) are generally gene activators, with increased mRNA and subsequent protein synthesis following hormone exposure. The progesterone receptor ( PR) also known as NR3C3 ( Nuclear receptor subfamily 3 group C member 3 is an intracellular Steroid receptor that

Male and female brains differ in the distribution of estrogen receptors, and this difference is an irreversible consequence of neonatal steroid exposure. Estrogen receptors (and progesterone receptors) are found mainly in neurons in the anterior and mediobasal hypothalamus, notably:

• the preoptic area (where LHRH neurons are located)
• the periventricular nucleus (where somatostatin neurons are located)
• the ventromedial hypothalamus (which is important for sexual behavior). Gonadotropin-releasing hormone ( GNRH) also known as Luteinizing-hormone releasing hormone ( LHRH) is a tropic Peptide Hormone Somatostatin (also known as growth hormone inhibiting hormone ( GHIH) or somatotropin release-inhibiting factor ( SRIF) is a Peptide hormone The ventromedial nucleus (sometimes referred to as the ventromedial hypothalamus) is a nucleus of the Hypothalamus.

Gonadal steroids in neonatal life of rats

In neonatal life, gonadal steroids influence the development of the neuroendocrine hypothalamus. For instance, they determine the ability of females to exhibit a normal reproductive cycle, and of males and females to display appropriate reproductive behaviors in adult life.

• If a female rat is injected once with testosterone in the first few days of postnatal life (during the "critical period" of sex-steroid influence), the hypothalamus is irreversibly masculinized; the adult rat will be incapable of generating an LH surge in response to estrogen (a characteristic of females), but will be capable of exhibiting male sexual behaviors (mounting a sexually receptive female).
• By contrast, a male rat castrated just after birth will be feminized, and the adult will show female sexual behavior in response to estrogen (sexual receptivity, lordosis}. Lordosis (commonly referred to as swayback, saddle back, or hyper-lordosis) is a medical term used to describe an inward curvature of a portion of the

Androgens in primates

In primates, the developmental influence of androgens is less clear, and the consequences are less complete. Androgen is the generic term for any natural or synthetic compound usually a Steroid Hormone, that stimulates or controls the development and maintenance of masculine 'Tomboyism' in girls might reflect the effects of androgens on the fetal brain, but the sex of rearing during the first 2-3 years is believed by many to be the most important determinant of gender identity, because during this phase either estrogen or testosterone will have permanent effects on either a female or male brain, influencing both heterosexuality and homosexuality. ^[11]

The paradox is that the masculinizing effects of testosterone are mediated by estrogen. Testosterone is a Steroid hormone from the Androgen group In mammals testosterone is primarily secreted in the testes of males and the Ovaries Within the brain, testosterone is aromatized to (estradiol), which is the principal active hormone for developmental influences. Estradiol (17β-estradiol (also oestradiol) is a Sex hormone. The human testis secretes high levels of testosterone from about week 8 of fetal life until 5-6 months after birth (a similar perinatal surge in testosterone is observed in many species), a process that appears to underlie the male phenotype. The testicle (from Latin testiculus, diminutive of testis, meaning "witness" virility plural testes) is the male Estrogen from the maternal circulation is relatively ineffective, partly because of the high circulating levels of steroid-binding proteins in pregnancy.

Other influences upon hypothalamic development

Sex steroids are not the only important influences upon hypothalamic development; in particular, pre-pubertal stress in early life determines the capacity of the adult hypothalamus to respond to an acute stressor. ^[12] Unlike gonadal steroid receptors, glucocorticoid receptors are very widespread throughout the brain; in the paraventricular nucleus, they mediate negative feedback control of CRF synthesis and secretion, but elsewhere their role is not well understood. Glucocorticoids (GC are a class of Steroid hormones characterised by an ability to bind with the glucocorticoid receptor ( GR) and trigger similar effects The paraventricular nucleus (PVN is an aggregation of neurons in the Hypothalamus which produces many Hormones. Corticotropin-releasing hormone ( CRH) originally named corticotropin-releasing factor ( CRF) and also called corticoliberin, is a Polypeptide

Effects of aging on the hypothalamus

Studies in female mice have shown that both Supraoptic nucleus (SON) and Paraventricular nucleus (PVN) lose approximately one-third of IGF-1R immunoreactive cells with normal aging. The supraoptic nucleus ( SON) is a nucleus of Magnocellular neurosecretory cells in the Hypothalamus of the mammalian brain The paraventricular nucleus (PVN is an aggregation of neurons in the Hypothalamus which produces many Hormones. Also, Old caloricly restricted (CR) mice lost higher numbers of IGF-1R non-immunoreactive cells while maintaining similar counts of IGF-1R immunoreactive cells in comparison to Old-Al mice. Consequently, Old-CR mice show a higher percentage of IGF-1R immunoreactive cells reflecting increased hypothalamic sensitivity to IGF-1 in comparison to normally aging mice. ^{[13] [14] [15]}

See also

• Hypothalamic-pituitary-adrenal axis (HPA axis)
• Neuroendocrinology
• John Leonora

Additional images

Median sagittal section of brain of human embryo of three months. The hypothalamic-pituitary-adrenal axis ( HPA or HTPA axis) also known as the Limbic -hypothalamic-pituitary-adrenal axis (LHPA axis is a complex set of direct influences The hypothalamic-pituitary-adrenal axis ( HPA or HTPA axis) also known as the Limbic -hypothalamic-pituitary-adrenal axis (LHPA axis is a complex set of direct influences Neuroendocrinology is the study of the interactions between the Nervous system and the Endocrine system. John Leonora ( January 30, 1928 - February 17, 2006) is notable for his research into the critical role of hypothalamic "factors" for

Human brain left dissected midsagittal view

References

External links

• BrainMaps at UCDavis Hypothalamus

• The Hypothalamus and Pituitary at endotexts.org

BrainMaps is an NIH -funded interactive zoomable high-resolution digital brain atlas and virtual microscope that is based on more than 20 million megapixels (50 terabytes

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