ABOUT HYPOTHALAMUS AND BLOOD BRAIN BARRIER

1. HYPOTHALAMUS
DR NIYATI N PATEL
MPT IN NEUROLOGICAL CONDITIONS
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2. INTRODUCTION
O Hypothalamus is a diencephalic structure. It
is situated just below thalamus in the
ventral part of diencephalon.
O It is formed by groups of nuclei, scattered in
the walls and floor of third ventricle. It
extends from optic chiasma to mamillary
body.
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6. NUCLEI OF
HYPOTHALAMUS
O Nuclei of
hypothalamus are
divided into three
groups:
O 1. Anterior or
preoptic group
O 2. Middle or tuberal
group
O 3. Posterior or
mamillary group.
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8. CONNECTIONS OF
HYPOTHALAMUS
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10. FUNCTIONS OF
HYPOTHALAMUS
O 1. SECRETION OF POSTERIOR PITUITARY
HORMONES
O Hypothalamus is the site of secretion for the
posterior pituitary hormones. Antidiuretic
hormone (ADH) and oxytocin are secreted by
supraoptic and paraventricular nuclei.
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11. O 2. CONTROL OF ANTERIOR PITUITARY
O Hypothalamus controls the secretions of anterior
pituitary gland by secreting releasing hormones
and inhibitory hormones. It secretes seven
hormones.
O i. Growth hormone-releasing hormone (GHRH)
O ii. Growth hormone-releasing polypeptide (GHRP)
O iii. Growth hormone-inhibiting hormone (GHIH) or
somatostatin
O iv. Thyrotropin-releasing hormone (TRH)
O v. Corticotropin-releasing hormone (CRH)
O vi. Gonadotropin-releasing hormone (GnRH)
O vii. Prolactin-inhibiting hormone (PIH).
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12. O 3. CONTROL OF ADRENAL CORTEX
O Anterior pituitary regulates adrenal cortex by
secreting adrenocorticotropic hormone
(ACTH).
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13. O 4. CONTROL OF ADRENAL MEDULLA
O Dorsomedial and posterior hypothamic
nuclei are excited by emotional stimuli.
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14. O 5. REGULATION OF AUTONOMIC NERVOUS
SYSTEM
O Hypothalamus controls autonomic nervous
system (ANS). Sympathetic division of ANS is
regulated by posterior and lateral nuclei of
hypothalamus.
O Parasympathetic division of ANS is
controlled by anterior group of nuclei. The
effects of cerebral cortex on ANS are
executed through hypothalamus
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15. O 6. REGULATION OF HEART RATE
O Hypothalamus regulates heart rate through
vasomotor center in the medulla oblongata.
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16. O 7. REGULATION OF BLOOD PRESSURE
O Hypothalamus regulates the blood pressure
by acting on the vasomotor center.
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17. O 8. REGULATION OF BODY TEMPERATURE
O Body temperature is regulated by
hypothalamus, which sets the normal range
of body temperature.
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18. O 9. REGULATION OF HUNGER AND FOOD
INTAKE
O Food intake is regulated by two centers
present in hypothalamus:
O i. Feeding center
O ii. Satiety center
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19. O 11 & 10 REGULATION OF SLEEP AND
WAKEFULNESS AND WATER BALANCE
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20. O 12. ROLE IN BEHAVIOR AND
O EMOTIONAL CHANGES
O The behavior of animals and human beings
is mostly affected by two responding
systems in hypothalamus and other
structures of limbic system. These two
systems act opposite to one another.
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23. BLOOD-BRAIN BARRIER
O Blood-brain barrier (BBB) is aneuroprotective
structure that prevents the entry of many
substances and pathogens into the brain
tissues from blood.
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24. STRUCTURE OF BLOOD-
BRAIN BARRIER
O Tight junctions in the endothelial cells of
brain capillaries are responsible for BBB
mechanism.
O In capillaries of other organs, adjacent
endothelial cells leave the cleft called
fenestra, which allows transcytosis of
several substances through endothelium
O However, in capillaries of brain, fenestra are
absent because, the endothelial cells fuse
with each other by tight junctions
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25. FUNCTIONS OF BLOOD-
BRAIN BARRIER
O BBB acts as both a mechanical barrier and
transport mechanisms. It prevents
potentially harmful chemical substances
and permits metabolic and essential
materials into the brain tissues.
O By preventing injurious materials and
organisms, BBB provides healthy
environment for the nerve cells of brain.
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26. Substances which can Pass
through
Blood-Brain Barrier
O 1. Oxygen
O 2. Carbon dioxide
O 3. Water
O 4. Glucose
O 5. Amino acids
O 6. Electrolytes
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27. O 7. Drugs such as L-dopa, 5-
hydroxytryptamine sulfona mides,
tetracycline and many lipid-soluble drugs
O 8. Lipid-soluble anesthetic gases such as
ether and nitrous oxide
O 9. Other lipid-soluble substances.
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28. Substances which cannot
Pass through
Blood-Brain Barrier
O 1. Injurious chemical agents
O 2. Pathogens such as bacteria
O 3. Drugs such as Penicillin and the
catecholamines. Dopamine also cannot
pass through BBB. So, parkinsonism is
treated with L-dopa, instead of dopamine.
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