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{{Infobox Brain
| Name = Hipotàlem
| Latin = hypothalamus
| GraySubject = 189
| GrayPage = 812
| Image = LocationOfHypothalamus.jpg
| Caption = Localització de l'hipotàlem humà
| Image2 = 1806 The Hypothalamus-Pituitary Complex.jpg
| Caption2 = Localització de l'hipotàlem, en relació amb la pituïtària i la resta del cervell
| IsPartOf =
| Components =
| Artery =
| Vein =
| BrainInfoType = hier
| BrainInfoNumber = 358
| MeshName = Hypothalamus
| MeshNumber = A08.186.211.730.385.357
| NeuroLex = Hypothalamus
| NeuroLexID = birnlex_734
}}
 
L''''hipotàlem''' (del [[grec antic|grec]] ὑπό, sota, i θάλαμος, [[tàlem]]) és una porció del cervell que conté una petita quantitat de [[Nucli (neuroanatomia)|nuclis]] amb funcions ben diverses. Una de les més importats és enllaçar el [[sistema nerviós]] amb el [[sistema endocrí]] a través de la [[glàndula pituïtària]] (la hipòfisi).
 
Aquesta part del cervell es troba situada a sota del tàlem i forma part del [[sistema límbic]].<ref>{{ref-web|cognom=Boeree|nom=C. George|url=http://webspace.ship.edu/cgboer/limbicsystem.html|consulta=21 desembre 2016|títol=The emotional nervous system}}</ref> En terminologia neuroanatòmica, forma la part ventral del [[diencèfal]]. Tots els vertebrats tenen hipotàlem. En humans és de la mida d'una ametlla.
 
L'hipotàlem és s'encarrega de dirigir certs processos biològics i altres funcions del [[sistema nerviós autònom]]. [[Biosíntesi|Sintetitza]] i secreta [[Neurohormona|neurohormones]] anomenades [[Hormones alliberadores i inhibidores|hormones alliberadores]] o hormones de l'hipotàlem que estimulen o inhibeixen la secreció d'hormones per part de la glàndula pituïtària. L'hipotàlem controla la [[temperatura corporal]], la [[gana]], aspectes importants dels lligams familiars i maternals, la [[Set (fisiologia)|set]],<ref>{{ref-web|url=http://www.cancer.gov/dictionary?CdrID=46359|consulta=21 desembre 2016|títol=Definition of the hypothalamus|obra=NCI Dictionary of Cancer Terms|editor=National Cancer Institute}}</ref> la [[fatiga]], el [[son]] i el [[ritme circadià]].
 
<!--
==Structure==
[[File:Hypothalamus small.gif|thumb|right|[[Human]] hypothalamus (shown in red)]]
The hypothalamus is a brain structure made up of distinct nuclei as well as less anatomically distinct areas. It is found in all vertebrate nervous systems. In mammals, [[magnocellular neurosecretory cell]]s in the [[paraventricular nucleus]] and the [[supraoptic nucleus]] of the hypothalamus produce [[neurohypophysial hormone]]s, [[oxytocin]] and [[vasopressin]]. These hormones are released into the blood in the [[posterior pituitary]].<ref name=williams>{{cite book|last1=Melmed|first1=S|last2=Polonsky|first2=KS|last3=Larsen|first3=PR|last4=Kronenberg|first4=HM|title=Williams Textbook of Endocrinology|date=2011|publisher=Saunders|pages=107|isbn=978-1437703245|edition=12th}}</ref> Much smaller [[parvocellular neurosecretory cell]]s, neurons of the paraventricular nucleus, release [[corticotropin-releasing hormone]] and other hormones into the [[hypophyseal portal system]], where these hormones diffuse to the [[anterior pituitary]].
 
===Nuclei===
The hypothalamic nuclei include the following:<ref>[http://www.psycheducation.org/emotion/pics/big%20hypothalamus.htm Diagram of Nuclei (psycheducation.org)]</ref><ref>[http://universe-review.ca/I10-80-nuclei.jpg Diagram of Nuclei (universe-review.ca)]</ref><ref>[http://www.utdallas.edu/~tres/integ/hom3/display13_04.html Diagram of Nuclei (utdallas.edu)]</ref>
{| class="wikitable"
|-
|'''Region'''
|'''Area'''
|'''Nucleus'''
|'''Function'''<ref>Unless else specified in table, then ref is: Guyton Twelfth Edition</ref>
|-
|rowspan=8|Anterior
| Preoptic<!--Per neurolex--> || [[Preoptic area|Preoptic nucleus]]
|-
|rowspan=5|Medial
| [[Medial preoptic nucleus]] ||
*Regulates the release of gonadotropic hormones from the adenohypophysis
*Contains the [[sexually dimorphic nucleus]], which releases GnRH, differential development between sexes is based upon in utero testosterone levels
*Thermoregulation<ref>{{cite journal|last1=Yoshida|first1=K.|last2=Li|first2=X.|last3=Cano|first3=G.|last4=Lazarus|first4=M.|last5=Saper|first5=C. B.|title=Parallel Preoptic Pathways for Thermoregulation|journal=Journal of Neuroscience|date=23 September 2009|volume=29|issue=38|pages=11954–11964|doi=10.1523/JNEUROSCI.2643-09.2009}}</ref>
|-
| [[Supraoptic nucleus]] ||
*[[Vasopressin]] release
*[[Oxytocin]] release
 
|-
| [[Paraventricular nucleus]] ||
*[[thyrotropin-releasing hormone]] release
*[[corticotropin-releasing hormone]] release
*[[oxytocin]] release
*[[vasopressin]] release
*[[somatostatin]] release
 
|-
| [[Anterior hypothalamic nucleus]] ||
*[[thermoregulation]]
*[[Thermoregulation|panting]]
*[[sweating]]
*[[thyrotropin]] inhibition
|-
| [[Suprachiasmatic nucleus]] ||
 
*[[Circadian rhythms]]
|-
|rowspan=2|Lateral
|-
| [[Lateral hypothalamic nucleus|Lateral nucleus]] || See [[Lateral hypothalamus#Function]] – primary source of [[orexin]] neurons throughout the brain and spinal cord
|-
|rowspan=5|Tuberal
|rowspan=3|Medial
| [[Dorsomedial hypothalamic nucleus]] ||
*[[Blood Pressure]]
*[[Heart Rate]]
*[[gastrointestinal tract|GI]] stimulation
|-
| [[Ventromedial nucleus]] ||
*[[satiety]]
*[[neuroendocrine]] control
|-
| [[Arcuate nucleus]] ||
* [[Growth hormone-releasing hormone]] (GHRH)
* [[feeding]]
* [[Dopamine]]-mediated [[prolactin]] inhibition
|-
|rowspan=2| Lateral || [[Lateral hypothalamic nucleus|Lateral nucleus]] || See [[Lateral hypothalamus#Function]] – primary source of [[orexin]] neurons throughout the brain and spinal cord
|-
| [[Lateral tuberal nuclei]] ||
|-
|rowspan=4|Posterior
|rowspan=2|Medial
|Mammillary nuclei (part of [[mammillary body|mammillary bodies]]) ||
*[[memory]]
|-
| [[Posterior nucleus (hypothalamus)|Posterior nucleus]] ||
*Increase [[blood pressure]]
*[[pupil]]lary dilation
*[[shivering]]
*[[vasopressin]] release
|-
| rowspan=2 | Lateral
| [[Lateral hypothalamic nucleus|Lateral nucleus]] || See [[Lateral hypothalamus#Function]] – primary source of [[orexin]] neurons throughout the brain and spinal cord
|-
| [[Tuberomammillary nucleus]]<ref name="Histamine pathways">{{cite book |vauthors=Malenka RC, Nestler EJ, Hyman SE |veditors=Sydor A, Brown RY | title = Molecular Neuropharmacology: A Foundation for Clinical Neuroscience | year = 2009 | publisher = McGraw-Hill Medical | location = New York | isbn = 9780071481274 | pages = 175–176 | edition = 2nd | chapter = Chapter 6: Widely Projecting Systems: Monoamines, Acetylcholine, and Orexin | quote = Within the brain, histamine is synthesized exclusively by neurons with their cell bodies in the tuberomammillary nucleus (TMN) that lies within the posterior hypothalamus. There are approximately 64000 histaminergic neurons per side in humans. These cells project throughout the brain and spinal cord. Areas that receive especially dense projections include the cerebral cortex, hippocampus, neostriatum, nucleus accumbens, amygdala, and hypothalamus. &nbsp;... While the best characterized function of the histamine system in the brain is regulation of sleep and arousal, histamine is also involved in learning and memory&nbsp;... It also appears that histamine is involved in the regulation of feeding and energy balance.}}</ref> <!--Per neurolex and ref for this entry-->||
* [[arousal]] (wakefulness and attention)
* feeding and [[energy balance (biology)|energy balance]]
* learning
* memory
* sleep
|}
 
''See also:'' [[ventrolateral preoptic nucleus]], [[periventricular nucleus]].
 
<gallery>
HIGHPVN.jpg|A cross section of the monkey hypothalamus displays 2 of the major hypothalamic nuclei on either side of the fluid-filled 3rd ventricle.
HypothalamicNuclei.PNG|Hypothalamic nuclei
3D-Hypothalamus.JPG|Hypothalamic nuclei on one side of the hypothalamus, shown in a 3-D computer reconstruction<ref>Brain Research Bulletin 35:323-327, 1994</ref>
</gallery>
 
===Neural connections===
{{Further|Lateral hypothalamus#Orexinergic projection system|Tuberomammillary nucleus#Histaminergic outputs}}
The hypothalamus is highly interconnected with other parts of the [[central nervous system]], in particular the brainstem and its [[reticular formation]]. As part of the [[limbic system]], it has connections to other limbic structures including the [[amygdala]] and [[septum]], and is also connected with areas of the [[autonomous nervous system]].
 
The hypothalamus receives many inputs from the [[brainstem]], the most notable from the [[nucleus of the solitary tract]], the [[locus coeruleus]], and the [[ventrolateral]] [[Medulla oblongata|medulla]].
 
Most nerve fibres within the hypothalamus run in two ways (bidirectional).
*Projections to areas [[Anatomical terms of location|caudal]] to the hypothalamus go through the [[medial forebrain bundle]], the [[Mammillotegmental fasciculus|mammillotegmental tract]] and the [[dorsal longitudinal fasciculus]].
*Projections to areas rostral to the hypothalamus are carried by the [[mammillothalamic tract]], the [[Fornix of brain|fornix]] and [[terminal stria]].
*Projections to areas of the [[Sympathetic nervous system|sympathetic motor system]] ([[lateral horn of spinal cord|lateral horn]] spinal segments T1-L2/L3) are carried by the [[hypothalamospinal tract]] and they activate the sympathetic motor pathway.
 
===Sexual dimorphism===
Several hypothalamic nuclei are [[sexually dimorphic]]; i.e., there are clear differences in both structure and function between males and females.{{citation needed|date=February 2013}}
 
Some differences are apparent even in gross neuroanatomy: most notable is the [[sexually dimorphic nucleus]] within the [[preoptic area]]. However most of the differences are subtle changes in the connectivity and chemical sensitivity of particular sets of neurons.{{citation needed|date=February 2013}}
 
The importance of these changes can be recognised by functional differences between males and females. For instance, males of most species prefer the odor and appearance of females over males, which is instrumental in stimulating male sexual behavior. If the sexually dimorphic nucleus is lesioned, this preference for females by males diminishes. Also, 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.{{citation needed|date=February 2013}}
 
;Responsiveness to ovarian steroids
Other striking functional dimorphisms are in the behavioral responses to [[ovarian steroids]] of the adult. Males and females respond to ovarian steroids in different ways, 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.{{citation needed|date=February 2013}}
 
[[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. Estrogen and progesterone bind to their cognate [[nuclear hormone receptor]]s, which translocate to the cell nucleus and interact with regions of DNA known as [[hormone response element]]s (HREs) or get tethered to another [[transcription factor]]'s binding site. [[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. In general, ERs and [[progesterone receptor]]s (PRs) are gene activators, with increased mRNA and subsequent protein synthesis following hormone exposure.{{citation needed|date=February 2013}}
 
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:{{citation needed|date=February 2013}}
*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).
 
===Development===
[[File:Gray654.png|thumbnail|Median sagittal section of brain of human embryo of three months]]
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.{{citation needed|date=February 2013}}
 
*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).{{citation needed|date=February 2013}}
*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 behavior]]).{{citation needed|date=February 2013}}
 
In primates, the developmental influence of [[androgens]] is less clear, and the consequences are less understood. Within the brain, testosterone is aromatized to ([[estradiol]]), which is the principal active hormone for developmental influences. 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. Estrogen from the maternal circulation is relatively ineffective, partly because of the high circulating levels of steroid-binding proteins in pregnancy.{{citation needed|date=February 2013}}
 
[[Sex steroid]]s are not the only important influences upon hypothalamic development; in particular, [[Puberty|pre-pubertal]] stress in early life (of rats) determines the capacity of the adult hypothalamus to respond to an acute stressor.<ref>{{cite journal | last = Romeo | first = Russell D |author2=Rudy Bellani |author3=Ilia N. Karatsoreos |author4=Nara Chhua |author5=Mary Vernov |author6=Cheryl D. Conrad |author7=Bruce S. McEwen | title = Stress History and Pubertal Development Interact to Shape Hypothalamic-Pituitary-Adrenal Axis Plasticity | journal = Endocrinology | volume = 147 | issue = 4 | pages = 1664–1674 | publisher = The Endocrine Society | year = 2005 | url = http://endo.endojournals.org/cgi/content/short/147/4/1664 | doi = 10.1210/en.2005-1432 |pmid = 16410296 |deadurl=no |accessdate=3 November 2013}}</ref> Unlike gonadal steroid receptors, [[glucocorticoid]] receptors are very widespread throughout the brain; in the [[paraventricular nucleus]], they mediate negative feedback control of [[Corticotropin-releasing hormone|CRF]] synthesis and secretion, but elsewhere their role is not well understood.
 
==Function==
 
===Hormone release===
[[File:Endocrine central nervous en.svg|thumbnail|Endocrine glands in the human head and neck and their hormones]]
The hypothalamus has a central [[neuroendocrine]] function, most notably by its control of the [[anterior pituitary]], which in turn regulates various endocrine glands and organs. [[Releasing hormone]]s (also called releasing factors) are produced in hypothalamic nuclei then transported along [[axons]] to either the [[median eminence]] or the [[posterior pituitary]], where they are stored and released as needed.<ref>{{cite web|last1=Bowen|first1=R.|title=Overview of Hypothalamic and Pituitary Hormones|url=http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/hypopit/overview.html|accessdate=5 October 2014}}</ref>
 
;Anterior pituitary
In the hypothalamic–adenohypophyseal axis, releasing hormones, also known as hypophysiotropic or hypothalamic hormones, are released from the median eminence, a prolongation of the hypothalamus, into the [[hypophyseal portal system]], which carries them to the anterior pituitary where they exert their regulatory functions on the secretion of adenohypophyseal hormones.<ref name=MelmedJameson>{{cite book |vauthors=Melmed S, Jameson JL |veditors=Kasper DL, Braunwald E, Fauci AS |title=Harrison's Principles of Internal Medicine|edition=16th |year=2005 |publisher=McGraw-Hill |location=New York, NY |isbn=0-07-139140-1 |pages=2076–97 |chapter=Disorders of the anterior pituitary and hypothalamus|display-editors=etal}}</ref>
These hypophysiotropic hormones are stimulated by parvocellular neurosecretory cells located in the periventricular area of the hypothalamus. After their release into the capillaries of the third ventricle, the hypophysiotropic hormones travel through what is known as the hypothalamo-pituitary portal circulation. Once they reach their destination in the anterior pituitary, these hormones bind to specific receptors located on the surface of pituitary cells. Depending on which cells are activated through this binding, the pituitary will either begin secreting or stop secreting hormones into the rest of the bloodstream. (Bear, Mark F. "Hypothalamic Control of the Anterior Pituitary." Neuroscience: Exploring the Brain. 4th ed. Philadelphia: Wolters Kluwer, 2016. 528. Print.)
 
{| class="wikitable" width=100%
! width=25% | Secreted hormone !! width=6% | Abbreviation !! width=17% | Produced by !! Effect
|-
! [[Thyrotropin-releasing hormone]] <br>(Prolactin-releasing hormone)
| TRH, TRF, or PRH || [[Parvocellular neurosecretory cell]]s of the [[paraventricular nucleus]] || Stimulate [[Thyroid-stimulating hormone|thyroid-stimulating hormone (TSH)]] release from [[anterior pituitary]] (primarily) <br>Stimulate [[prolactin]] release from [[anterior pituitary]]
|-
! [[Corticotropin-releasing hormone]]
| CRH or CRF || Parvocellular neurosecretory cells of the paraventricular nucleus || Stimulate [[Adrenocorticotropic hormone|adrenocorticotropic hormone (ACTH)]] release from [[anterior pituitary]]
|-
! [[Dopamine]] <br>(Prolactin-inhibiting hormone)
| DA or PIH || [[Arcuate nucleus|Dopamine neurons of the arcuate nucleus]] || Inhibit [[prolactin]] release from [[anterior pituitary]]
|-
! [[Growth-hormone-releasing hormone]]
| GHRH || [[Neuroendocrine]] neurons of the [[Arcuate nucleus]] || Stimulate [[Growth hormone|growth-hormone (GH)]] release from [[anterior pituitary]]
|-
! [[Gonadotropin-releasing hormone]]
| GnRH or LHRH || [[Neuroendocrine]] cells of the [[Preoptic area]] || Stimulate [[Follicle-stimulating hormone|follicle-stimulating hormone (FSH)]] release from [[anterior pituitary]] <br>Stimulate [[Luteinizing hormone|luteinizing hormone (LH)]] release from [[anterior pituitary]]
|-
! [[Somatostatin]]<ref>{{cite journal|last=Ben-Shlomo|first=Anat|author2=Melmed, Shlomo|title=Pituitary somatostatin receptor signaling|journal=Trends in Endocrinology & Metabolism|date=28 February 2010|volume=21|issue=3|pages=123–133|doi=10.1016/j.tem.2009.12.003|pmc=2834886|pmid=20149677}}</ref> <br>(growth-hormone-inhibiting hormone)
| SS, GHIH, or SRIF || [[Neuroendocrine]] cells of the [[Periventricular nucleus]] || Inhibit [[Growth hormone|growth-hormone (GH)]] release from [[anterior pituitary]] <br>Inhibit (moderately) [[Thyroid-stimulating hormone|thyroid-stimulating hormone (TSH)]] release from [[anterior pituitary]]
|}
 
Other hormones secreted from the median eminence include [[vasopressin]], [[oxytocin]], and [[neurotensin]].<ref name=horn>{{cite journal|last=Horn|first=A. M.|author2=Robinson, I. C. A. F. |author3=Fink, G. |title=Oxytocin and vasopressin in rat hypophysial portal blood: experimental studies in normal and Brattleboro rats|journal=Journal of Endocrinology|date=1 February 1985|volume=104|issue=2|pages=211–NP|doi=10.1677/joe.0.1040211|pmid=3968510}}</ref><ref>{{cite journal|last=Date|first=Y|author2=Mondal, MS |author3=Matsukura, S |author4=Ueta, Y |author5=Yamashita, H |author6=Kaiya, H |author7=Kangawa, K |author8= Nakazato, M |title=Distribution of orexin/hypocretin in the rat median eminence and pituitary.|journal=Brain research. Molecular brain research|date=Mar 10, 2000|volume=76|issue=1|pages=1–6|pmid=10719209|doi=10.1016/s0169-328x(99)00317-4}}</ref><ref>{{cite journal|last=Watanobe|first=H|author2=Takebe, K|title=In vivo release of neurotensin from the median eminence of ovariectomized estrogen-primed rats as estimated by push-pull perfusion: correlation with luteinizing hormone and prolactin surges.|journal=Neuroendocrinology|date=April 1993|volume=57|issue=4|pages=760–4|pmid=8367038|doi=10.1159/000126434}}</ref><ref>{{cite journal|last=Spinazzi|first=R|author2=Andreis, PG |author3=Rossi, GP |author4= Nussdorfer, GG |title=Orexins in the regulation of the hypothalamic-pituitary-adrenal axis.|journal=Pharmacological reviews|date=March 2006|volume=58|issue=1|pages=46–57|pmid=16507882|doi=10.1124/pr.58.1.4}}</ref>
 
;Posterior pituitary
In the hypothalamic-neurohypophyseal axis, [[neurohypophysial hormone]]s are released from the posterior pituitary, which is actually a prolongation of the hypothalamus, into the circulation.
 
{| class="wikitable" width=100%
! width=25% | Secreted hormone !! width=6% | Abbreviation !! width=17% | Produced by !! Effect
|-
! [[Oxytocin]]
| OXY or OXT || [[Magnocellular neurosecretory cell]]s of the paraventricular nucleus and [[supraoptic nucleus]] || [[Uterine contraction]] <br>[[Letdown reflex|Lactation (letdown reflex)]] <!--Not effects from hypothalamus: sexual arousal, bonding, trust, material behavior-->
|-
! [[Vasopressin]] <br>(antidiuretic hormone)
| ADH or AVP || Magnocellular and parvocellular neurosecretory cells of the paraventricular nucleus, magnocellular cells in supraoptic nucleus || Increase in the permeability to water of the cells of [[distal tubule]] and [[collecting duct]] in the kidney and thus allows water reabsorption and excretion of concentrated urine
|}
 
It is also known that [[hypothalamic-pituitary-adrenal axis]] (HPA) hormones are related to certain skin diseases and skin homeostasis. There is evidence linking hyperactivity of HPA hormones to stress-related skin diseases and skin tumors.<ref>{{cite web|title=Expression of Hypothalamic-Pituitary-Adrenal Axis in Common Skin Diseases: Evidence of its Association with Stress-related Disease Activity|url=http://web.b.ebscohost.com/ehost/pdfviewer/pdfviewer?sid=8239d5d4-8cd4-48b0-b25c-e1218229f462%40sessionmgr115&vid=11&hid=122|publisher=National Research Foundation of Korea|accessdate=4 March 2014|author1=Jung Eun Kim |author2=Baik Kee Cho |author3=Dae Ho Cho |author4=Hyun Jeong Park |year=2013}}</ref>
 
===Stimulation===
The hypothalamus coordinates many hormonal and behavioural circadian rhythms, complex patterns of [[neuroendocrine]] outputs, complex [[homeostasis|homeostatic]] mechanisms, and important behaviours. The hypothalamus must, therefore, respond to many different signals, some of which generated externally and some internally. [[Delta wave]] signalling arising either in the thalamus or in the cortex influences the secretion of releasing hormones; [[GHRH]] and [[prolactin]] are stimulated whilst [[TRH]] is inhibited.
 
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 Nervous System|Autonomic]] inputs
*Blood-borne stimuli, including [[leptin]], [[ghrelin]], [[angiotensin]], [[insulin]], [[pituitary hormones]], [[cytokines]], plasma concentrations of glucose and osmolarity etc.
*[[Stress (medicine)|Stress]]
*Invading microorganisms by increasing body temperature, resetting the body's thermostat upward.
 
====Olfactory stimuli====
Olfactory stimuli are important for [[sexual reproduction]] 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]]). Thus, during coitus, a female mouse forms a precise 'olfactory memory' of her partner that 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 disputed.
 
====Blood-borne stimuli====
[[Peptide]] hormones have important influences upon the hypothalamus, and to do so they must pass through the [[blood–brain barrier]]. The hypothalamus is bounded in part by specialized brain regions that lack an effective blood–brain barrier; the [[Capillary#Types|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]]. However, others are sites at which the brain samples the composition of the blood. Two of these sites, the SFO ([[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 [[Cerebrospinal fluid|CSF]]. These structures are densely vascularized, and contain osmoreceptive and sodium-receptive neurons that control [[drinking]], [[vasopressin]] release, sodium excretion, and sodium appetite. They also contain neurons with receptors for [[angiotensin]], [[atrial natriuretic factor]], [[endothelin]] and [[relaxin]], each of which important in the regulation of fluid and electrolyte balance. Neurons in the OVLT and SFO project to the [[supraoptic nucleus]] and [[paraventricular nucleus]], and also to preoptic hypothalamic areas. The circumventricular organs may also be the site of action of [[interleukins]] to elicit both fever and ACTH secretion, via effects on paraventricular neurons.{{citation needed|date=February 2013}}
 
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 the blood into the [[cerebrospinal fluid]] (CSF). 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. There is also evidence for central actions of [[prolactin]].{{citation needed|date=February 2013}}
 
Findings have suggested that [[thyroid hormone]] (T4) is taken up by the hypothalamic [[glial cells]] in the [[infundibular nucleus]]/ [[median eminence]], and that it is here converted into [[Triiodothyronine|T3]] by the type 2 deiodinase (D2). Subsequent to this, T3 is transported into the [[thyrotropin-releasing hormone]] ([[TRH]])-producing [[neurons]] in the [[paraventricular nucleus]]. [[Thyroid hormone receptor]]s have been found in these [[neurons]], indicating that they are indeed sensitive to T3 stimuli. In addition, these neurons expressed [[SLC16A2|MCT8]], a [[thyroid hormone]] transporter, supporting the theory that T3 is transported into them. T3 could then bind to the thyroid hormone receptor in these neurons and affect the production of thyrotropin-releasing hormone, thereby regulating thyroid hormone production.<ref>{{cite journal|last=Fliers|first=Eric|author2=Unmehopa, Alkemade|title=Functional neuroanatomy of thyroid hormone feedback in the human hypothalamus and pituitary gland|journal=Molecular and Cellular Endocrinology|date=7 June 2006|volume=251|issue=1–2|pages=1–8|doi=10.1016/j.mce.2006.03.042|pmid=16707210}}<!--|accessdate=7 July 2011--></ref>
 
The hypothalamus functions as a type of [[thermostat]] for the body.<ref name=Harrisons>{{cite book
|authorlink=Anthony Fauci
|author=Fauci, Anthony|title=Harrison's Principles of Internal Medicine
|edition=17
|publisher=McGraw-Hill Professional
|year=2008
|isbn=978-0-07-146633-2
|pages=117–121
|display-authors=etal}}</ref> It sets a desired body temperature, and stimulates either heat production and retention to raise the blood temperature to a higher setting or sweating and [[vasodilation]] to cool the blood to a lower temperature. All [[fever]]s result from a raised setting in the hypothalamus; elevated body temperatures due to any other cause are classified as [[hyperthermia]].<ref name=Harrisons /> Rarely, direct damage to the hypothalamus, such as from a [[stroke]], will cause a fever; this is sometimes called a ''hypothalamic fever''. However, it is more common for such damage to cause abnormally low body temperatures.<ref name=Harrisons />
 
====Steroids====
The hypothalamus contains neurons that react strongly to steroids and [[glucocorticoids]] – (the steroid hormones of the [[adrenal gland]], released in response to [[ACTH]]). It also contains specialized glucose-sensitive neurons (in the [[arcuate nucleus]] and [[ventromedial hypothalamus]]), which are important for [[appetite]]. The preoptic area contains thermosensitive neurons; these are important for [[TRH]] secretion.
 
====Neural====
[[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 body]] and [[aortic arch]], and from low-pressure [[atrial volume receptors]], is mediated by others. In the rat, stimulation of the [[vagina]] also causes [[prolactin]] secretion, and this results in [[pseudo-pregnancy]] following an infertile mating. In the rabbit, coitus elicits reflex [[ovulation]]. In the sheep, [[cervix|cervical]] stimulation in the presence of high levels of estrogen can induce [[maternal bond|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 [[Luteinizing hormone|LH]] and [[Follicle-stimulating hormone|FSH]].
 
Cardiovascular stimuli are carried by the [[vagus nerve]]. The vagus also conveys a variety of visceral information, including for instance signals arising from gastric distension or emptying, to suppress or promote feeding, by signalling the release of [[leptin]] or [[gastrin]], respectively. Again this information reaches the hypothalamus via relays in the brainstem.
 
In addition hypothalamic function is responsive to—and regulated by—levels of all three classical [[monoamine neurotransmitter]]s, [[noradrenaline]], [[dopamine]], and [[serotonin]] (5-hydroxytryptamine), in those tracts from which it receives innervation. For example, noradrenergic inputs arising from the locus coeruleus have important regulatory effects upon [[corticotropin-releasing hormone]] (CRH) levels.
 
===Control of food intake===
{| class="wikitable sortable" style="width:40%; float:right"
|+ Peptide hormones and neuropeptides that regulate feeding<ref name="Feeding peptides table">{{cite book |vauthors=Malenka RC, Nestler EJ, Hyman SE |veditors=Sydor A, Brown RY | title = Molecular Neuropharmacology: A Foundation for Clinical Neuroscience | year = 2009 | publisher = McGraw-Hill Medical | location = New York | isbn = 9780071481274 | page = 263 | edition = 2nd | chapter = Chapter 10: Neural and Neuroendocrine Control of the Internal Milieu – Table 10:3 }}</ref>
! scope="col" style="width:50%"| Peptides that increase<br />feeding behavior
! scope="col" style="width:50%"| Peptides that decrease<br />feeding behavior
|-
| [[Ghrelin]] || [[Leptin]]
|-
| [[Neuropeptide Y]] || (α,β,γ)-[[Melanocyte-stimulating hormone]]s
|-
| [[Agouti-related peptide]] || [[Cocaine and amphetamine regulated transcript|Cocaine- and amphetamine-regulated transcript peptides]]
|-
| [[Orexin]]s (A,B) || [[Corticotropin-releasing hormone]]
|-
| [[Melanin-concentrating hormone]] || [[Cholecystokinin]]
|-
| [[Galanin]] || [[Insulin]]
|-
| || [[Glucagon-like peptide 1]]
|-
|}
The extreme [[anatomical terms of location|lateral]] part of the [[ventromedial nucleus]] of the hypothalamus is responsible for the control of [[food]] intake. Stimulation of this area causes increased food intake. Bilateral [[lesion]] of this area causes complete cessation of food intake. 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. 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:<ref>{{cite journal|author=Theologides A|title=Anorexia-producing intermediary metabolites|journal=Am J Clin Nutr|volume=29|issue=5|pages=552–8 |year=1976 |pmid=178168}}</ref>
 
#Lipostatic hypothesis: This hypothesis holds that [[adipose]] [[biological tissue|tissue]] produces a [[humoral immunity|humoral]] signal that is proportionate to the amount of fat and acts on the hypothalamus to decrease food intake and increase energy output. It has been evident that a [[hormone]] [[leptin]] acts on the hypothalamus to decrease food intake and increase energy output.
#Gutpeptide hypothesis: [[gastrointestinal tract|gastrointestinal]] hormones like Grp, [[glucagon]]s, [[cholecystokinin|CCK]] and others claimed to inhibit food intake. The food entering the gastrointestinal tract triggers the release of these hormones, which act on the brain to produce satiety. The brain contains both CCK-A and CCK-B receptors.
#Glucostatic hypothesis: The activity of the satiety center in the ventromedial nuclei is probably governed by the [[glucose]] utilization in the neurons. 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-deoxy-D-glucose|2-deoxyglucose]] therefore decreasing glucose utilization in cells.
#Thermostatic hypothesis: According to this hypothesis, a decrease in body temperature below a given set-point stimulates appetite, whereas an increase above the set-point inhibits appetite.
 
===Fear processing===
 
The medial zone of hypothalamus is part of a circuitry that controls motivated behaviors, like defensive behaviors.<ref name="swanson2000">{{cite journal| author=Swanson, L.W.|title= Cerebral Hemisphere Regulation of Motivated Behavior|journal=Brain Research|volume=886|pages=113–164|year=2000|doi=10.1016/S0006-8993(00)02905-X}}</ref> Analyses of [[c-Fos|Fos]]-labeling showed that a series of nuclei in the "behavioral control column" is important in regulating the expression of innate and conditioned defensive behaviors.<ref name="canteras2002">{{cite journal|author=Canteras, N.S.| title=The medial hypothalamic defensive system:Hodological organization and functional implications| journal=Pharmacology, Biochemistry & Behavior|volume=71|pages=481–491|year=2002|doi=10.1016/S0091-3057(01)00685-2}}</ref>
 
;Antipredatory defensive behavior
 
Exposure to a predator (such as a cat) elicits defensive behaviors in laboratory rodents, even when the animal has never been exposed to a cat.<ref name="ribeiro2005">{{cite journal|author=Ribeiro-Barbosa, E.R.|title=An alternative experimental procedure for studying predator-related defensive responses.|journal=Neuroscience & Biobehavioral Reviews|volume=29|issue=8|pages=1255–1263|year=2005|doi=10.1016/j.neubiorev.2005.04.006|display-authors=etal}}</ref> In the hypothalamus, this exposure causes an increase in [[c-Fos#Applications|Fos-labeled]] cells in the anterior hypothalamic nucleus, the dorsomedial part of the ventromedial nucleus, and in the ventrolateral part of the premammillary nucleus (PMDvl).<ref name="cezario2008">{{cite journal|author=Cezário, A.F.|title=Hypothalamic sites responding to predator threats--the role of the dorsal premammillary nucleus in unconditioned and conditioned antipredatory defensive behavior.|journal=European Journal of Neuroscience|volume=28|issue=5|pages=1003–1015|year=2008|doi=10.1111/j.1460-9568.2008.06392.x}}</ref> The premammillary nucleus has an important role in expression of defensive behaviors towards a predator, since lesions in this nucleus abolish defensive behaviors, like freezing and flight.<ref name="cezario2008"/><ref name="blanchardpmd"/> The PMD does not modulate defensive behavior in other situations, as lesions of this nucleus had minimal effects on post-shock freezing scores.<ref name="blanchardpmd">{{cite journal|author=Blanchard, D.C.|title=Dorsal premammillary nucleus differentially modulates defensive behaviors induced by different threat stimuli in rats|journal=Neuroscience Letters|volume=345|issue=3|pages=145–148|year=2003|doi=10.1016/S0304-3940(03)00415-4}}</ref> The PMD has important connections to the dorsal [[periaqueductal gray]], an important structure in fear expression.<ref name="canteras1992">{{cite journal|author1=Canteras, N.S. |author2=Swanson, L.W. |title=The dorsal premammillary nucleus: an unusual component of the mammillary body.|journal=PNAS|volume=89|issue=21|pages=10089–10093|year=1992|url=http://www.pnas.org/content/89/21/10089.long|doi=10.1073/pnas.89.21.10089}}</ref><ref name="behbehani1995">{{cite journal|author=Behbehani, M.M.|title=Functional characteristics of the midbrain periaqueductal gray.|journal=Progress in Neurobiology|volume=46|issue=6|pages=575–605|year=1995|doi=10.1016/0301-0082(95)00009-K}}</ref>
In addition, animals display risk assessment behaviors to the environment previously associated with the cat. Fos-labeled cell analysis showed that the PMDvl is the most activated structure in the hypothalamus, and inactivation with [[muscimol]] prior to exposure to the context abolishes the defensive behavior.<ref name="cezario2008"/> Therefore, the hypothalamus, mainly the PMDvl, has an important role in expression of innate and conditioned defensive behaviors to a predator.
 
;Social defeat
 
Likewise, the hypothalamus has a role in [[social defeat]]: Nuclei in medial zone are also mobilized during an encounter with an aggressive conspecific. The defeated animal has an increase in Fos levels in sexually dimorphic structures, such as the medial pre-optic nucleus, the ventrolateral part of ventromedial nucleus, and the ventral premammilary nucleus.<ref name="motta2009">{{cite journal|author=Motta, S.C.|title=Dissecting the brain's fear system reveals the hypothalamus is critical for responding in subordinate conspecific intruders.|journal=PNAS|volume=106|issue=12|pages=4870–4875|year=2009|url=http://www.pnas.org/content/106/12/4870.full.pdf+html|doi=10.1073/pnas.0900939106|display-authors=etal}}</ref> Such structures are important in other social behaviors, such as sexual and aggressive behaviors. Moreover, the premammillary nucleus also is mobilized, the dorsomedial part but not the ventrolateral part.<ref name="motta2009"/> Lesions in this nucleus abolish passive defensive behavior, like freezing and the "on-the-back" posture.<ref name="motta2009"/>
 
===Sexual orientation===
According to [[Dick Swaab|D. F. Swaab]], writing in a July 2008 paper, "Neurobiological research related to sexual orientation in humans is only just gathering momentum, but the evidence already shows that humans have a vast array of brain differences, not only in relation to gender, but also in relation to sexual orientation."<ref>{{cite journal |author=Swaab DF |title=Sexual orientation and its basis in brain structure and function |url=http://www.pnas.org/content/105/30/10273.full |journal=PNAS |volume=105 |issue=30 |pages=10273–10274 |year=2008 |doi=10.1073/pnas.0805542105 |pmid=18653758 |pmc=2492513}}</ref>
 
Swaab first reported on the relationship between sexual orientation in males and the hypothalamus's "clock", the [[Suprachiasmatic nucleus| suprachiasmatic nucleus (SCN)]]. In 1990, Swaab and Hofman<ref>{{cite journal |vauthors=Swaab DF, Hofman MA |title=An enlarged suprachiasmatic nucleus in homosexual men |journal=Brain Res. |volume=537 |issue=1–2 |pages=141–8 |year=1990 |pmid=2085769 |doi=10.1016/0006-8993(90)90350-K}}</ref> reported that the suprachiasmatic nucleus in homosexual men was significantly larger than in heterosexual men. Then in 1995, Swaab et al.<ref>{{cite journal |vauthors=Swaab DF, Slob AK, Houtsmuller EJ, Brand T, Zhou JN |title=Increased number of vasopressin neurons in the suprachiasmatic nucleus (SCN) of 'bisexual' adult male rats following perinatal treatment with the aromatase blocker ATD |journal=Developmental Brain Research |volume=85 |issue=2 |pages=273–279 |year=1995 |doi=10.1016/0165-3806(94)00218-O |pmid=7600674}}</ref> linked brain development to sexual orientation by treating male rats both pre- and postnatally with ATD, an [[aromatase]] blocker in the brain. This produced an enlarged SCN and bisexual behavior in the adult male rats. In 1991, LeVay showed that part of the [[Sexually dimorphic nucleus#Sexually Dimorphic Nucleus in Medial Preoptic Area|sexually dimorphic nucleus (SDN)]] known as the 3rd interstitial nucleus of the anterior hypothalamus (INAH 3), is nearly twice as large (in terms of volume) in heterosexual men than in homosexual men and heterosexual women.
However, a study in 1992 has shown that the sexually dimorph nucleus of the preoptic area, which include the INAH3, are of similar size in homosexual males who died of AIDS to heterosexual males, and therefore larger than female. This clearly contradicts the hypothesis that homosexual males have a female hypothalamus. Furthermore, the SCN of homosexual males is extremely large (both the volume and the number of neurons are twice as many as in heterosexual males). These areas of the hypothalamus have not yet been explored in homosexual females nor bisexual males nor females. Although the functional implications of such findings still haven't been examined in detail, they cast serious doubt over the widely accepted Dörner hypothesis that homosexual males have a "female hypothalamus" and that the key mechanism of differentiating the "male brain from originally female brain" is the epigenetic influence of testosterone during prenatal development.<ref>http://www.hiim.unizg.hr/images/knjiga/CNS41.pdf - Judaš, M., Kostović, I., The Fundamentals of Neuroscience, ch. 41, Neurobiology of emotions and sexuality, p. 408 (in Croatian)</ref><ref>{{cite journal | pmid = 1292983 | volume=38 Suppl 2 | title=Gender and sexual orientation in relation to hypothalamic structures. | year=1992 | journal=Horm Res | pages=51–61 | doi=10.1159/000182597}}</ref>
 
In 2004 and 2006, two studies by Berglund, Lindström, and Savic<ref>{{cite journal |vauthors=Savic I, Berglund H, Lindström P |title=Brain response to putative pheromones in homosexual men |journal=PNAS |volume=102 |issue=20 |pages=7356–7361 |year=2005 |doi=10.1073/pnas.0407998102 |pmid=15883379 |pmc=1129091}}</ref><ref>{{cite journal |vauthors=Savic I, Berglund H, Lindström P |title=Brain response to putative pheromones in lesbian women |journal=PNAS |volume=103 |issue=21 |pages=8269–8274 |year=2006 |doi=10.1073/pnas.0600331103 |pmid=16705035 |pmc=1570103}}</ref> used [[positron emission tomography]] (PET) to observe how the hypothalamus responds to smelling common odors, the scent of testosterone found in male sweat, and the scent of estrogen found in female urine. These studies showed that the hypothalamus of heterosexual men and homosexual women both respond to estrogen. Also, the hypothalamus of homosexual men and heterosexual women both respond to testosterone. The hypothalamus of all four groups did not respond to the common odors, which produced a normal olfactory response in the brain.
 
==See also==
*[[Copeptin]]
*[[Hypothalamic-pituitary-adrenal axis]] (HPA axis)
*[[Hypothalamic–pituitary–gonadal axis]] (HPG axis)
*[[Hypothalamic–pituitary–thyroid axis]] (HPT axis)
*[[John Leonora]]
*[[Incertohypothalamic pathway]]
*[[Neuroendocrinology]]
*[[Neuroscience of sleep]]
 
==Additional images==
<gallery>
Image:Illu_diencephalon.jpg
Image:Human brain left dissected midsagittal view description 2.JPG|Human brain left dissected midsagittal view
File:Blausen 0536 HypothalamusLocation.png|Location of the hypothalamus
</gallery>
 
==References==
{{reflist|30em}}
Bear, Mark F. "Hypothalamic Control of the Anterior Pituitary." Neuroscience: Exploring the Brain. 4th ed. Philadelphia: Wolters Kluwer, 2016. 528. Print.
 
==Further reading==
*de Vries, GJ, and Sodersten P (2009) Sex differences in the brain: the relation between structure and function. Hormones and Behavior 55:589-596.
 
==External links==
*{{BrainMaps|Hypothalamus}}
*[http://www.endotext.org/neuroendo/neuroendo3b/neuroendo3b.htm The Hypothalamus and Pituitary at endotexts.org]
*[https://www.neuinfo.org/mynif/search.php?q=Hypothalamus&t=data&s=cover&b=0&r=20 NIF Search - Hypothalamus] via the [[Neuroscience Information Framework]]
*Space-filling and cross-sectional diagrams of hypothalamic nuclei: [http://www.netterimages.com/image/8535.htm right hypothalamus], [http://www.netterimages.com/image/8584.htm anterior], [http://www.netterimages.com/image/8586.htm tubular], [http://www.netterimages.com/image/8588.htm posterior].
 
{{Diencephalon}}
{{Endocrine system}}
{{Use dmy dates|date=September 2011}}
 
[[Category:Endocrine system]]
[[Category:Limbic system]]
[[Category:Hypothalamus]]
[[Category:Neuroendocrinology]]
[[Category:Human female endocrine system]]
 
 
 
 
 
 
L''''hipotàlem''' és una [[glàndula]] del [[sistema nerviós central]]. Forma part del [[diencèfal]] i està situada en la base cerebral per sota del [[tàlem]], més concretament en la part ventral del tàlem. Per la seva part basal s’uneix a la hipòfisi.
[[Fitxer:Hypothalamus.jpg|thumb|Localització de l'hipotàlem en una fotografia feta amb un [[escànner fMRI|escàner fMRI]].]]
Linha 4 ⟶ 360:
A l'hipotàlem, es regulen parts importants de la vida vegetativa.
L'hipotàlem, a més de participar en moltes funcions nervioses, també desenvolupa un paper molt important en el control del sistema endocrí, ja que a partir de la secreció de neurohormones actua sobre la hipòfisi (eix hipotàlem-hipofisiàri), controlant aquesta la secreció hormonal de moltes glàndules del cos.
 
-->
 
== Vegeu també ==
Obtingut de «https://ca.wikipedia.org/wiki/Hipotàlem»