5. Hypothalamus is
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)
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 releasing and
inhibiting hormones.
Hormones are transported to
axon endings of median
eminence.
Hormones secreted into the
hypothalamo-hypophyseal
portal system regulate the
secretions of the anterior
pituitary
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.
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 by B.K.Anand &
J.R.Brobeck
41. Hypothalamus and body weight
regulation:
Satiety
center
Electrolytic lesions:
Ventromedial nucleus (VMN)
Hyperphagia
Lateral hypothalamic area
(LHA)
Hunger
Anorexia
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 Mellitus Ventro 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 6 9 0 3 96 0 3 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 LEPTIN is 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)
53. 4.Thermostatic Hypothesis
The thermostatic SET POINT in 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 production Effect
1. a-MSH Hypothalamus Inhibition
2 .Cocaine-
amphetamine-
Regulated
transcript (CART) Hypothalamus Inhibition
3. Leptin Adipose tissue Inhibition
56. 6. Regulation of Body temperature
Anterior HT detects increased body temp and
activates systems of heat dissipation ,like
vasodilation, sweating, & panting
Lesion here causes hyperthermia.
Posterior HT functions 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 N are
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 centre is 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
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
sleep by inhibiting histamine neurons in tubero
mammillary nucleus.
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
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
