Hypothalamus

Hypothalamus

1. HYPOTHALAMUS
Dr.K.Jaiganesh
Professor of Physiology
MGMC & RI

2. Objectives
The nuclei,connections and functions of
Hypothalamus
Disorders of Hypothalamic functions

5. Hypothalamusis
described as “The Head
ganglion of the autonomic
nervous system”by
“Sherrington”.
Stimulation of the
hypothalamus produces
autonomic response.
It is a small bilateral
structure extends from the
region of the optic chiasma to
the caudal border of the
mammillary bodies

6. It lies below the Thalamus
Forms the floor and inferior part of the lateral
walls of the 3rd ventricle.
It is an integrative centre for
regulation of cardiovascular system,
body temperature,
food and water intake and
endocrine secretion.
HT is only 0.3% of brain weight.(10 gms)

7. Hypothalamic Nuclei
It is typically divided into 4 regions from
rostral to caudal
Pre optic area
Supra optic area (anterior)
Tuberal area (middle )
Mamillary area( posterior)

8. Hypothalamic Nuclei

10. 1.Preoptic area:
Medial preoptic nucleus, Lateral preoptic nucleus
2. Anterior (supraoptic) region:
Anterior hypothalamic nucleus, Supraoptic nucleus,
Paraventricular nucleus, Suprachiasmatic nucleus
3. Middle (tuberal) region:
Arcuate nucleus, Ventromedial nucleus,
Dorsomedial nucleus
4. Posterior (mammillary) region:
Mammillary nuclei, Posterior hypothalamic nucleus

11. Preoptic area:medial preoptic nucleus, lateral
preoptic nucleus

12. Pre optic area:
Medial pre optic (bladder contraction, HR, BP )
Lateral pre optic

13. Anterior (supraoptic) region:anterior hypothalamic
nucleus, supraoptic nucleus, paraventricular
nucleus, suprachiasmatic nucleus

14. Supra optic area:
Supra optic ( vasopressin release)
Supra chiasmatic (optic nerve)
Paraventricular (oxytocin release,
water conservation)
Anterior (Body Temperature,
panting, sweating)

15. Middle (tuberal) region:arcuate nucleus,
ventromedial nucleus, dorsomedial nucleus

16. Tuberal area (middle )
Ventromedial (satiety, neuroendocrine)
Dorso medial ( GI stimulation)
Arcuate (neuroendocrine )
Lateral (hunger & thirst )

17. Posterior (mammillary) region: mammillary nuclei,
posterior hypothalamicnucleus

18. Mamillary area:
Mammilary body (feeding reflexes)
Posterior Hypothalamic N ( BP, Pupillary dilation,
Shivering )

19. Afferent Connections
From Olfactory area
Frontal lobe cortex
Hippocampus
Thalamus
Amygdala
Lemniscal system
Reticular Activating system
Raphe nucleus
Locus ceruleus

21. Efferent connections
Adenohypophysis
Neurohypophysis
Orbital cortex
Cerebral cortex
Septal nuclei
Thalamus
Mamillo thalamic
tract
Amygdala
Brain stem
spinal cord

23. hypothalamus
Olfactory area
Frontal lobe
Of cortex
Hippocampus
Thalamus
RAS
Amygdala
Spinal cord
Brainstem
ANS
Pituitary
Afferent and efferent connection

25. Cortex
Sub cortical
structure
Cortex
Sub cortical
structure
Hypothalamus
Homeostatic mechanism

26. Functions of
Hypothalamus

27. Functions of hypothalamus
Autonomic system
Food intake
Temperature
Thirst –Fluid regulation
Endocrine
Reproduction
Sleep and wakefulness
Emotion
Stress
Circadian rhythm
Visceral function
Somatic
Reward & Punishment

28. 1.Hypothalamic Control of the
Anterior Pituitary
Hormonal control rather than
neural.
Hypothalamic neurons
synthesize releasingand
inhibitinghormones.
Hormones are transported to
axon endings of median
eminence.
Hormones secreted into the
hypothalamo-hypophyseal
portal systemregulate the
secretions of the anterior
pituitary

29. Releasing hormones
Thyrotropin-releasing hormones (TRH)
Corticotropin-releasing hormones (CRH)
Growth hormone-releasing hormones(GHRH)
Gonadotropin-releasing hormones(GnRH)
Prolactin inhibitory hormone (PIH)

30. Pituitary Hormones

31. 2. Hypothalamic Control of
Posterior Pituitary
Hypothalamic neuron cell
bodies produce:
ADH: supraoptic nuclei.
Oxytocin:para
ventricular nuclei.
Transported along
hypothalamo-hypophyseal
tract.
Storedin posterior
pituitary.
Releasecontrolled by
neuroendocrine reflexes.

32. Figure 7-12: Synthesis, storage, and release of posterior pituitary hormones

34. 3. Hypothalamic Control of the Autonomic
Nervous System
Descending projections from HT to autonomic
centers:
Paraventricular nuclei →via medial forebrain
bundle →to dorsolateral brainstem &
periaqueductal gray area
to parasympathetic & sympathetic
preganglionic neurons.
Controls CVS, GIT, Excretion, Respiration
and Reproduction

35. Other brainstem nuclei are also origins of descending
pathways controlling autonomic centers:
-Nucleus solitarius,
-noradrenergic nuclei (locus coeruleus),
-raphe nuclei,
-pontomedullary reticular formation
Inputs to HT that affect autonomic function
come mostly from the amygdala and limbic
cortex.

36. Hypothalamus
SNS
PSNS
•Heart
•Blood vessel
•Visceral organ
•GIT,Bladder
•Heart
•Blood vessels
•Visceral organ
•Lungs

37. Hypothalamus
Autonomic nervous system
Posterior hypothalamus
•HR
•BP
•Pupillary dilatation
•piloerection
Anterior hypothalamus
•HR
•Hcl secretion
•Urination
+
+

38. 4. Hypothalamic –Limbic Pathways
Amygdala has reciprocal connections with HT
via two pathways:
-Stria terminalis
-Ventral amygdalo fugal pathway
-participation in the eloboration of emotional
behavior, and experience of emotion.
Limbic –hypothalamic interconnections explain
why emotional behavior is often accompanied by
autonomic activation:
eg:-blushing when embarassed
-sweaty palms & dry mouth when anxious or
afraid
-HT functions in sexual desire / sex
preference

39. 5. Control of Hunger & Feeding
Feeding centre -Lateral hypothalamus
Stimulation increases the appetite
Lesion in this Nucleus makes the animal to starve and
cechaxic
Satiety centre –Ventromedial Nucleus
Stimulation suppresses appetite by inhibiting Lateral
nucleus
Lesion makes the animal to become Obese due to
voracious appetite –”Hypothalamic Obesity”
Both centres were described byB.K.Anand &
J.R.Brobeck

40. Glucose Control Theory
Ventromedial nucleus (VMN)
Lateral nucleus (LN)
Glucose
Feeding Center
Satiety Center

41. Hypothalamus and body weight
regulation:
Satiety
center
Electrolytic lesions:
Ventromedial nucleus (VMN)
Hyperphagia
Lateral hypothalamic area
(LHA)
Hunger
center
Anorexia

42. Hypothalamic Obesity

43. Hypothalamic
Obesity

44. Lesion in Lateral Hypo Nucleus-
Cechaxic Animal

47. Mechanism
Hypothalamus regulates the setpoint for body
weight rather than food intake.
1.Glucostat Hypothesis:
Glucostat cells inside the satiety centre are
stimulated by ↑ blood glocose level
Satiety centre inhibits feeding centre →
↓ appetite → ↓ blood glucose
Satiety centre is depressed by ↓ blood
glucose level → feeding centre is activated
→
↑ appetite → ↑ blood glucose.

48. In Diabetes MellitusVentro Medial Nucleus
(VMN) is deprived of glucose due to the
deficiency of Insulin →↑ activity of Feeding
centre → Hyperphagia
In lesions of Amygdala–moderate
hyperphagia for adulterated ,tainted food

49. Experimental Evidence in Rats
100
100
100100
0
200
0
100
200
0
3 690396 03 6 9
F
o
o
d
Int-
-ake
%
Body
W
e
i
g
h
T
%
(a) (b) ( c )
Time ( weeks )
( a ) Force fed
( b ) Partially
Starved
( c ) Lesion made
At
Bilateral
Ventromedial
&
allowed for
free food

50. 2.Aminostatic Hypothesis
Food in the GIT releases polypeptides which
inhibit the food intake by acting on the
Hypothalamus (Gut peptide Hypothesis)
GI Hormones like CCK , GRP ,Glucagon, &
Somatostatin inhibit the food intake
Injection of CCK into the Hypothalamus
inhibit the food intake

51. 3.Lipostatic Hypothesis
Increased level of Fatty acids & Ketoacids also
act like glucose
Protein hormone LEPTINis produced by fatty
tissues proportionate to the amount of Adipose
tissues in the body, acts on the Hypothalamus
& inhibits the food intake ( feed back
mechanism in obesity)

52. Leptin-deficient obesity
(ob/obmouse)
+/+ob/ob
Leptin
Energy intake
Energy expenditure

53. 4.Thermostatic Hypothesis
The thermostatic SET POINTin the
Hypothalamus may also be involved in the
regulation food intake
Appetite is increased by fall in the temperature
below the set point, & supressed when it rises
above the set point.

54. Modulators of feeding behavior
Name Site of productionEffect
1. a-MSH Hypothalamus Inhibition
2 .Cocaine-
amphetamine-
Regulated
transcript (CART) Hypothalamus Inhibition
3. Leptin Adipose tissue Inhibition

55. 4.Neuropeptide Y
(NPY) Hypothalamus Stimulation
5.Melanin
Concentrating
hormone (MCH) Hypothalamus Stimulation
6.Agouti-related
peptide (AGRP) Hypothalamus Stimulation

56. 6. Regulation of Body temperature
Anterior HTdetects increased body temp and
activates systems ofheat dissipation ,like
vasodilation, sweating, & panting
Lesion here causes hyperthermia.
Posterior HTfunctions to conserve heat, by
vasoconstriction,& shivering heat gain
Lesions here cause poikilothermia,where body temp
matches environment temp.
Preoptic region acts as Thermostat while Post HT
nuclei correct any deviation in the thermostat

57. Pre optic region
warm cold
•Panting
•Sweating
•vasodilation
•Vasoconstriction
•Piloerection
•shivering

58. Temperature
Body temp
Cold receptor
Heat conservation
(Thermostat on)
Posterior hypo
Seratonergic
pathway
Body temp
Warm receptor
Thermostat off
Anterior hypo
Adrenergic pathway

59. 7. Control of Water intake & Thirst
By two mechamisms:
1.Osmoreceptors in the Supraoptic Nare
sensitive to osmolarity changes of plasma &
ECF.
Excess water loss, & dehydration, causes an
in osmolarity of ECFstimulates osmo
receptors release ADH water
reabsorption normal osmolarity of ECF
Excess water intakeosmoreceptors 
ADH

60. 2.By thirst mechanism
A thirst centreis in the Lateral
Hypothalamus-stimulated by intracellular
dehydration –causes water drinking
Increase in plasma osmolarity, decrease in
ECF volume, Haemorrhage, Angiotensin II &
dryness of mouth promote water drinking &
thirst mechanism thus maintains water balance

61. ECF volume
Baroreceptor
Thirst centre
ADH secretionAngiotensin -II
AldosteroneADHThirst
Volume restored

62. Water intake
Hypertonicity Hypovolemia
Baroreceptor
Angiotensin-II
Osmo receptors
Hypothalamus
Intake of water

63. 8. Functions of Selected Regions of
Hypothalamus
Suprachiasmatic nucleus regulates circadian
rhythms, biological clock
GABA neurons in ventral part of lateral
preoptic area function in non REM
sleepby inhibiting histamine neurons in tubero
mammillary nucleus.

64. Cerebral cortex
Limbic system
Hypothalamus
Adrenal medullaSNS
catecholamines
Adrenal
cortex
glucocorticoids
Stress
Internal
External
9.Role in stress

65. 10.Role in memory
Hippocampus
Mamillary body
Ant.,nucleus of thalamus
Cingulate gyrus

66. 11.Reproduction control
Hypothalamus
Gn RH
Gonodotrophin
Male
-Spermatogenesis
-Growth of accessory organ
Female
-Ovulation
-Menstrual cycle
-Secondary sexual
character

68. Role in reproduction
Reproduction
Hypothalamus
Limbic system
Cerebral cortex
+
_
integrate

69. 12.Role in emotion
Emotion
Limbic system
Cerebral cortex
Hypotalamus
_
_
+

71. 13.Circadian rhythm
In animal and in humans certain body functions
are tuned to the day & night cycle. These
fluctuation are referred to as diurnal or circadian
rhythm,which is mediated through retino –
hypothalamo –pineal system.
Example:
Cortisol secretion
Body temperature
ACTH secretion
Sleep and wakefulness

72. Retina
Optic chiasma
Hypothalamus
Pineal body
Melatonin secretion
Important physiological connection

73. Circadian Rhythm

74. Sleep and wakefulness
Hypothalamus
•Posterior hypothalamus
•Intra laminar
•Anterior hypothalamus
•Pre optic area
stimulation
8 Hz
14.Role in sleep and wakefulness

75. Hypothalamus
Reward and punishment
Cerebral cortex
Limbic system
15.Role in reward and punishment

76. B. F. Skinner

78. Disorders of Hypothalamus
Function affected
Sleep-lesion-Mammil.body
Emotional disturbances due
to Lesion in VMN & Post
lat N
Autonomic disturbances
Body temperature
disturbances
Endocrine-Hypogonadism,
hypothyroidism
Disturbances in water
balance
Sexual disfunction
Disturbance seen
Disorders of sleep-Narcolepsy
“Sham rage”
Diabetes Insipidus
Lesion in midhypothalamus