Hypothalamus (2)

HYPOTHALAMUS

1. DR NILESH KATE
MBBS,MD
ASSOCIATE PROF
DEPT. OF PHYSIOLOGY
HYPOTHALAMUS.

2. OBJECTIVES
Physiological
Anatomy.
Functions of
Hypothalamus.
Applied Aspects.
Monday, March 14, 2016

3. HYPOTHALAMUS
Latin word – Hypo- below; Thalamus – room or
chamber
Very small part of brain weighing about 4 gms.
Regulate all vegetative & endocrine process.
Main organ of integration of homeostasis.
Bilateral diencephalic structure, diffuse nuclear
mass below the thalamus.
Monday, March 14, 2016

4. HYPOTHALAMUS
The most ventral part of diencephalon which lies
below the thalamus
 4 gram in weight (whole brain wt 1400gms)
0.3 to 0.5% of total brain
Sherrington regarded as head ganglion of ANS
Nauta describes as the nodal region in the
maintenance of Homeostasis.
Monday, March 14, 2016

5. Physiological Anatomy.
External features.
Subdivisions & Nuclei
of Hypothalamus.
Connections of
Hypothalamus.
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6. External features.
Boundaries.
Superior.
Inferior
Medial
Lateral
Anterior
Posterior.
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9. Subdivisions & Nuclei of
Hypothalamus.
Zones
Medial zone & lateral
zone.
Regions
Preoptic
Supraoptic
Tuberal
Mammilary.
Nuclei.
Preoptic N.
Suprachiasmatic,
supraoptic anterior,
paraventricular.
Dorsomedial, lateral,
tuberal, ventromedial
and arcuate nucleus.
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15. Region wise descriptions of Nuclei
A.Preoptic
Region: Lies
anterior to
hypothalamus
along with
lamina
terminalis
between optic
chiasma &
ant.commissure
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16. Supra optic
Region:
1.Supra optic Nucleus: Medial,
lateral and periventricular
part. It is Sexually
dimorphic Nuclei.
2.Suprachiasmatic: Involves
circadian rhythm
3.Anterior Nucleus: Thirst
Center
4.Paraventricular
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17. C. Tuberal Region
1.Arcuate or
infundibular nucleus:
composed of small
neurons. Controls
emotional behaviors
and endocrine function
2.Ventromedial: Satiety
centre
3.Ventrolateral
4.Lateral nucleus:
feeding centre
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18. Mammilary Region
1.Mammilary bodies:
i) Medial intercalated N.:
small neurons. Forms the
bulk of mammilary bodies.
ii) Lateral intercalated N.:
Receive termination of
fornix and provide origin
to mamilothalamic tract
and mamilotegmental tract
1.Posterior hypothalamic
nucleus
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19. Connections of Hypothalamus.
Afferent connections.
Efferent connections.
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20. Afferent connections.
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21. Efferent connections.
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22. Functions of Hypothalamus.
(AS-RESPECT)
Autonomic functions.
Sleep –wake cycle.
Reward & punishment
centre.
Endocrinal functions.
Sexual behaviour &
reproduction.
Ph(F)ood intake
regulation.
Emotional & Instinctual
behaviour.
Circadian Rhythm
control.
Temperature regulation.
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23. Autonomic functions.
Sherrington –
describes as Head
Ganglion.
Ant –
Parasympathetic
Post – Sympathetic.
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24. AUTONOMIC FUNCTIONS.
Cardiovascular
regulation.- Post & lat
N stimulation –
tachycardia ,HT &
Cutaneous
vasoconstriction.
Preoptic area opposite.
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25. AUTONOMIC FUNCTIONS.
Pupil size – post & Lat –
dilatation. And Preoptic &
supraoptic opposite.
Peristaltic &
Secretomotor functions
of GIT – POST & LAT N
decreases secretions &
motility.
Ant & medial opposite.
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26. Sleep –wake cycle.
Ant hypothalamus –
sleep fascilitatory
Post hypothalamus –
waking centre.
Sleep – negative
Phenomenon. Inhibition
of waking centre in post
hypothalamus by ant
hypothalamus – leads to
sleep.
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27. Food intake regulation.
Feeding Centre.
Lat Hypothalamic N.
Stimulations increases
food intake.
Its destruction –
anorexia.
Satiety Centre.
Feeling of fulfillment after
food intake.
Ventromedial N of
Hypothalamus.
Stimulation causes fulfillment
– stop food intake
Destruction – Hyperphagia.
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28. PRINCIPAL HYPOTHALAMIC
POLYPEPTIDE.
Food intake
increased by
Neuropeptide Y.
Orexin – A
Orexin –B
Melanin concentrating
hormone. (MCH)
Ghrelin.
Food intake
decreased by
Cocacine &
amphetamine
regulated
transcript.
(CART)
CRH.
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30. Endocrinal functions.
Anterior Pituitary.(through
Tubero-infundibular tract &
hypophyseal portal system)
Controls Thyroid G.
Controls Metabolism through
adrenal gland.
Keep gonads inhibited.
Control formation of milk by
prolactin secretion.
Posterior Pituitary
regulate water balance
through ADH.
Regulation Of Uterine
Contractility &
regulation of Milk
Ejection from breast
through oxytocin.
Monday, March 14, 2016

31. HYPOTHALAMO-HYPOPHYSIAL TRACT
The
hypothalamus
is a
neuroendocrin
e area which
acts as a
"transducer"
to convert
neuronal
activity into
hormonal
secretions
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32. Controls anterior pitutary
Several trophic factors or
hormones are released
that influence the
production of hormones
in adenohypophysis.
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34. Neuro-secretory cells
1. Receive and process
stimuli from
all parts of the CNS,
2. Conduct action potentials
along their axons, and
3. Synthesize and release
hormones into the
circulatory system.
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35. Neuro-secretory cells
4. produce peptide Prohormones
by mRNA on ribosomes in their
nerve cell bodies, and then
convert these Prohormones to
active hormones during the
process of axoplasmic
transport along axon filaments.
5. They store the hormones in
vesicular granules at their axon
terminals until depolarization
of the plasma membrane
causes Exocytosis.
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36. HORMONES RELEASED
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38. CONTROLS POSTERIOR PITUTARY
It controls Neurohypophysis
through HYPOTHALAMO-
HYPOPHYSEAL tract.
Approx. 100,000
Nonmyelinated fibers extend
from the SON & PVN of the
hypothalamus to the
fenestrated capilary bed of the
Neurohupophysis.
These fibers convey 2 peptide
hormones; ADH & oxytocin
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40. Circadian Rhythm control.
Common rhythmic
variations in
Secretion of ACTH.
Secretion of Growth
Hormone.
Secretion of melatonin.
Sleep wake cycle.
Body-temp rhythm.
Rhythmic Gonadotrophins
secretion.
Basis of circadian
rhythm.
Supra-chiasmatic N. main
site
Biological clock
Receives inputs from
Eye – retinohypothalamic
fibres.
Lateral geniculate N.
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41. Circadian Rhythm control.
Effect of
environmental
factors on circadian
rhythm.(HINTS)
Light dark cycle
Temperature.
Meal timing.
Physiological significance.
Enables homeostatic
mechanism to be used
immediately & automatically.
Have effect on body’s
resistance to drugs.
Disturbance of circadian
rhythm.
Speed jet travel – Jet lag.
Monday, March 14, 2016

42. Temperature regulation.
Heat loss centre.
Anterior Hypothalamus,
Preoptic area.
Stimulation causes
Cutaneous
vasodilatation &
sweating.
Lesion – abolishes
response.
Heat gain
centre.
Posterior
hypothalamus.
Stimulation –
Cutaneous
vasoconstriction
& shivering.
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44. SEXUAL BEHAVIOUR &
REPRODUCTION.
Given by Brookhart &
dey (1941)
Pathway-Amygdala –
Stria terminalis -
Preoptic area –
Tuberal region.
Connection maintains
basal secretion of
GnRH.
Stimulation of
Preoptic – cyclical
surge – Ovulation.
Lesion – prevents
Ovulation.
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46. Emotional & Instinctual
behaviour.
Limbic cortex.
Concerned with
affective nature of
sensory impulses.
Whether pleasant or
unpleasant.
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48. Reward & Punishment centre.
Site
Reward centre –
Lateral &
Ventromedial N.
Punishment centre –
Medial Hypothalamus.
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49. ROLE OF REWARD &
PUNISHMENT CENTRE.
Controllers of our
bodily activities, drives,
aversions & motivation.
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50. RAGE
Rage – violent & aggressive
emotional state by strong
stimulation of Punishment
Centre.
Kept in check by
counterbalancing activity of
Ventromedial N of
hypothalamus, hippocampus,
amygdala & ant portion of limbic
cortex.
Characterized by –
Development of
defense posture.
Extension of limbs
Lifting of tail.
Hissing & splitting
Piloerection.
Wide openings of eye.
Pupil dilation.
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51. SHAM RAGE.
Outburst of rage on
mild peripheral
stimulation.
Due to release of
hypothalamus from
cortical control.
Emotions are not
associated with it.
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52. REGULATION OF WATER
BALANCE.
Through thirst centre
Through
osmoreceptors in
supraoptic nucleus.
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Decreased Body water
Plasma Hypertonicity.
Thirst Center Osmoreceptors in
supraoptic nucleus
Raised water injestion Post pituitary
ADH
Decreased urinary water
NORMAL RESTORATION OF BODY WATER.

54. APPLIED ASPECTS.
Lesions of Hypothalamus.
Disturbances in Hypothalamic lesions.
Clinical conditions in hypothalamic lesions.
Monday, March 14, 2016

55. LESIONS OF HYPOTHALAMUS.
Tumour.
Inflammation or
encephalitis.
Ischemia.
Damage due to
surgical operation
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56. DISTURBANCES IN
HYPOTHALAMIC LESIONS.
Disturbance of all
hypothalamic
functions.
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57. CLINICAL CONDITIONS IN
HYPOTHALAMIC LESIONS.
Diabetes Insipidus-
supraoptic N damage.
Deficiency of ADH
Excessive thirst &
Polydipsia.
Narcolepsy.
Sudden attack of
unresistable desire of
sleep during day time.
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58. Clinical conditions in
hypothalamic lesions.
Cataplexy.
Sudden emotional
outburst of anger,
fear & excitement
associated with
narcolepsy.
Consciousness is
not lost.
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