This document provides information about the hypothalamus including its: - Anatomy, boundaries, subdivisions and nuclei - Connections including tracts that regulate the pituitary gland - Main functions like controlling the endocrine system, autonomic nervous system, and roles in regulating behaviors such as food intake, circadian rhythms, temperature, and sexual dimorphism - Some hypothalamic disorders including hypothalamic obesity and memory dysfunctions

1. 22/11/2013
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Dr. Hareesh krishnan HYPOTHALAMUS

2.  Part of Diencephalone which lies below
the thalamus.
 Forms the floor and lower parts of the
lateral walls of the 3rd ventricle.
 Small in size weighning only4gm, forms
only 0.3 % of total brain mass.
 Mainly acts through 3 systems._ ANS
,endocrine system and the limbic system
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3. ANATOMY_
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4. boundaries
 Anteriory_ lamina terminalis( extends from
the optic chiasma to the ant.commissure)
 Posteriorly_subthalamus
 Inferiorly_ structures in the floor of the 3rd
ventricle.ie, tuber cinereum,infundibulam
and mammillary bodies.
 Superiorly_ thalamus
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5.  Lateral boundary_ internal
capsule.
 Medially bounded by the cavity
of 3rd ventricle.
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6. subdivisions
 Divided into 2 lateral halves by the cavity of 3rd ventricle.
 The ant. Column of fornix divides the hypothalamus into medial and
lateral zones. The mamillo thalamic tract passes through this plane.
 The medial zone again divided into a thin periventricular zone and a
thick intermediate zone.
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7. Antero_posteriorly divided into
 Preoptic region_ area adjoining the lamina
terminalis.
 supra optic region __above the optic chiasma
 tubreal region includes the tuber
cinereum,infundibulam and area around it.
 mammillary region_ includes the mammillary
bodies and area around it.
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8. Hypothalamic nuclei
 Hypothalamus is made up of
numerous small nuclear masses called
hypothalamic nucleus.
 They are divided into groups acco. To
their regional distribution and they
differ in their functions also.
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9. Region nucleus functions
Preotic region Preoptic nucleus Contains the sexually dimorphic
nucleus, which releases GnRH
Supraoptic region Supra optic nucleus Vassopressin release
Anterior nucleus Thermo regulation,sweating
Paraventricular nucleus TRH,CRH&OXYTOCIN release
Tuberal region Arcuate( infundibular nucleus) GHRH,feeding and Dopamine release
Ventromedial nucleus Satiety centre
Dorsomedial nucleus Controls BP,HR and GI stimulation
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10. Connections of hypothalamus_ afferent
 FORNIX_ Connects hippocampus to the mammillary body.
 Stria terminalis_ connects amygdaloid body to preoptic and ant. Nu. Of
hippocampus.
 Mamillary peduncle _transmits sensory impulses from spinal cord and brain stem
the lateral nu. Of hypothalamus.
 Medial forebrain bundles _ connects hippocampus with autonomic & limbic
structures of forebrain.
 Others include thalamo_hypothalamic,pallido_hypothalamic and sub thalamo
hypothalamic tracts.
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11. Efferent connections
 Mamillo_thalamic tract_ connects mammillary body to the
ant. Nu. Of thalamus which inturn connected to the
cingulate gyrus.
 Mamillo_tegmental tract_ mammillary body with reticular
formation of brain stem.
 Descending fibres to the brain stem_ trough this fibres hypo.
Can influence the peripheral neurones of the ANS.
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12.  HYPOTHALAMUS IS ALSO CONNECTED TO THE
PREGANGLIONIC SYMPATHETIC NEURONES IN THE LATERAL
HORNES T1_L2 SPINAL SEGMENTS.
 ALSO TO THE PRE GAANGLIONIC PARASYMPATHETIC
NEURONES IN THE LATERAL HORNES OF S2-S4 SEGMENTS.
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13. HYPOTHALAMO_
HYPOPHYSEAL TRACT
 Connects hypo. To neurohypophysis(post.
Pituitary).
 The fibres originate from supra optic &
paraventricular nu. Of hypothalamus which
secrets vasopressin and oxytocin
respectively.
 These hormones then transported to
post_pituitary along the fibres of this tract
by axoplasmic flow and get stored in post.
Pituitary.
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14. Tubero_infundibular tract
 The releasing hormones and release
inhibiting hormones are produced in the
cells of tuberal and infundibular nuclei.
 And are transported upto the median
eminence along the tubero infundibular
tract.
 From here ,these hormones are carried by
the hypothalamo_hypophyseal portal
system
 to adeno hypophyis (
ant.pituitary).
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15. Tubero infundibular tract
Releasing hormones
 TRH
 CRH
 GnRH & LHRH
Release inhibiting hormones
 DOPAMINE- prolactin
inhibition
 GHIH_ inhibits GH
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16. Functions of
hypothalamus
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17. ENDOCRINE
CONTROL#
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18. HPT AXIS
 The hypothalamic–pituitary–thyroid
axis ( aka thyroid homeostasis or
thyrotropic feedback control) is part of
the endocrine system responsible for
the regulation of metabolism.
 As its name suggests, it depends upon
the hypothalamus the pituitary gland
and the thyroid gland#
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19. HPA AXIS
 The hypothalamic-pituitary-adrenal
axis (HPA or HTPA axis) is a complex set of direct
influences and feedback interactions among
the hypothalamus the pituitary gland and
the adrenal glands.
 The interactions among these organs constitute
a major part of the neuroendocrine system that
controls reactions to stress and regulates many
body processes, including digestion
,the immune system, mood and emotions,
sexuality and energy storage and expenditure.
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20. Dexamethasone suppression test.
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21. HPG AXIS
 The hypothalamic–pituitary–gonadal axis is
a critical part in the development and
regulation of a number of the body's
systems, such as the reproductive and
immune systems.
 This axis controls development,
reproduction, and aging in animals.
 The hypothalamus
produces gonadotropin-releasing
hormone (GnRH). The anterior portion of
the pituitary gland produces luteinizing
hormone (LH) and follicle-stimulating
hormone (FSH), and
the gonads produce estrogen and testoster
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22. Autonomic control of body
 Hypothalamus controls autonomic functions of body through
sympathetic as well as parasympathetic fibres including cardiac, and
respiratory activity, vasomotor tone of blood vessels ,digestive process
.
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23. Part of limbic system
The limbic system is a complex set of
structures that lies on both sides of the
thalamus, just under the cerebrum. It
includes the hypothalamus, the hippocampus,
the amygdala, and several other nearby
areas. It appears to be primarily responsible
for our emotional life, and has imp. Role in
formation of memories.
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24. Regulation of sleep
 Key role in regulation of sleep
 Has GABAergic neurones in the VLPO
area and wakefulness promoting
orexinergic neurones in the lateral
hypothalamus.
 These orexinergic neurones projects
from the hypothalamus to a no. of
monoaminergic centres including the
locus ceruleus,raphe nu. And ventral
tegmentum.
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25. Regulation of Food & water intake
 The extreme 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.
 The ventromedial nucleus of medial
hypothalamus acts as satiety centre.
 Bilateral lesion of the medial part of the
ventromedial nucleus causes
hyperphagia and obesity of the animal.
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26. Temperature regulation
 the cold and heat sensors located in the
hypothalamus respond appropriately to
maintain the body temperature at
optimum level in diverse conditions.
 The ant. Portion of hypothalamus
prevents the rise in body temperature
while,
 Posterior portion promotes heat
conservation and heat production.
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27. Circadian rhythm
 Hypothalamus regulates the cyclic
activities of the body ,viz sleeping and
waking cycle but itself affected by
diurnal rhythm.
 The circadian rhythm for many body
functions is of about 24 hours.
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28. Sexual dimorphism
 Several hypothalamic nuclei are sexually dimorphic i.e. there
are clear differences in both structure and function between
males and females.
 Some differences are apparent even in gross anatomy most
notable is the sexually dimorphic nucleus within the preoptic
area.
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29.  The importance of these changes can be recognised by differences in
sexual behaviour between males and females.
 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.
 Hypothalamus also regulates the sexual behaviour and reproduction by
influencing the secretion of gonadotrophic hormones by the pituitary
gland.
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30. Responses to ovarian steroids
 Other striking functional dimorphisms are in the behavioral
responses to ovarian steroids of the adult. Males and females
respond differently to ovarian steroids, partly because the
expression of estrogen-sensitive neurons in the
hypothalamus is sexually dimorphic.
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31. Other functions
 EMOTIONAL EXPRESSION:_ Hypothalamus
regulates the expression of emotions
through its control over the ANS
(laughting,crying,sweating,crying etc.)
 Fear processing:_The medial zone of
hypothalamus is part of a circuitry that
controls motivated behaviors, like
defensive behaviors.
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32. Hypothalamic
disorders
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33. causes
 Anorexia
 Bleeding
 Bulimia
 Genetic disorders
 tumors(craniopharyngiomas)
 Head trauma
 Infections and swelling
(inflammation)
 Malnutrition
 Radiation
 Surgery
 Too much iron
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34. Hypothalamic obesity
 Has been asso. With lesions of the
ventromedial nu.
 Initially involves aggressive behaviour and
hyperphagia until a new set weight is
reached.
 Rage reactions are well describe in animals
with similar lesion.
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35. Memory dysfunctions
 Short term memory dysfunction has been reported in lesions of
the ventromedial and premamillary areas of the hypothalamus.
 Extensive hypothalamic lesions may produce features consistent
with a dementing illness.
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36. Abnormalities of thermoregulation
 Acute lesions such as haemorrhage, infarction or those from surgical
procedures may result from acute or paroxysmal hypothermia.
 Posterior hypothalamic lesions may result in paroxysmal hyperthermia
with associated fever and rigors.
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37. Diencephalic syndrome
 Caused by tumours invading the anterior and basal hypothalamus such as
gliomas, midline cerebellar astrocytomas and supracellar ependymomas.(
childhood tumours).
 Symptoms manifest as motor hyperactivity, euphoria(or inappropriate
affect),increased alertness and emaciation despite normal caloric intake.
 In adulthood slow growing tumours usually result in a dementia syndrome
,endocrine dysfunction and food intake dysregulation.
 Also may present as disturbances of consciousness ,temperature and
autonomic dysregulation.
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38. craniopharyngioma
 Congnital tumour which develops
from the remenants of the Rathke’s
pouch.
 MCC of hypopituitarism in children.
 Compresses both optic chiasma and
hypothalamus.
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39. Clinical features_craniopharyngioma
Optic chiasma compression
 Visual abnormalities(bitemporal
hemianopia).
 Headache.
Hypothalamic compression
 Hypogonadism
 Hyperprolactinemia
 Diabetes insipidus
 Weight gain
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40. Kallmann syndrome
 This syndrome characterised by failure to start puberty, primary
amenorrhoea and anosmia.
 The GnRH neurones originate in an area of the developing brain called
the olfactory placode they then pass through the cribriform plate and
into olfactory bulb where the sense of smell is generated. From there they
migrate into hypothalamus.
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41.  Any problems with the development of the olfactory bulb will
prevent the progression of the GnRH releasing neurones through it.
If the GnRH releasing neurones are prevented from reaching the
hypothalamus no GnRH will be released.
 so in turn no FSH or LH will be released which results in the failure
of puberty and deficient production of testosterone in men, and
oestrogen and progesterone in women.#
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42. NARCOLEPSY
 Narcolepsy is a sleep disorder characterized by
 Excessive day time somnolence
 Cataplexy( a sudden loss of muscle tone ,often trigerred by
strong emotional reactions)
 REM sleep disorders_ hypnogogic hallucinations,automatic
behaviour and sleep paralysis.
 Asso. With low orexin levels in the CSF
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43. references
 Comprehensive textbook of psychiatry_Kaplan& sadocks .
 Synopsis of psychiatry_ Kaplan & sadocks 10th edi.
 Textbook of Clinical neuroanatomy- vishram singh 2nd edi.
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