HYPOTHALAMUS – DIVISIONS & FUNCTIONS
Location:
- Diencephalic structure
- Below hypothalamic sulcus in ventral part of diencephalon.
- Formed by groups of nuclei, scattered in walls & floors of 3rd ventricle
- Forms major & central element of limbic system surrounded by other structures of limbic system.
Divided by sagittal & coronal planes into 3 regions & 3 zones each,
By Sagittal plane (regions):
- Anterior – Supraoptic
- Middle – Tuberal
- Posterior – Mamillary
By Coronal plane (zones):
- Lateral
- Medial
- Periventricular (surrounding 3rd ventricle)
NUCLEI OF HYPOTHALAMUS:
Divided into three groups,
- Anterior or preoptic group
- Middle or tuberal group
- Posterior or mamillary group.
- Supraoptic nucleus
- Suprachiasmatic nucleus
- Paraventricular nucleus
- Lateral preoptic nucleus
- Medial preoptic nucleus
- Anterior nucleus
- Lateral hypothalamic area
- Ventromedial nucleus
- Dorsomedial nucleus
- Arcuate nucleus
- Mamillary nucleus
- Posterior hypothalamic nucleus
FUNCTIONS OF HYPOTHALAMUS:
Two types of functional effects majorly,
- Endocrinal effects
- Neuronal effects
REGULATION OF NEURONAL FUNCTIONS:
1. Regulation of body temperature:
- Controlled by Pre-optic nucleus
- Anterior hypothalamus – Respond to heat
- Posterior Hypothalamus – Respond to cold (Shivering center)
- Suprachiasmatic nucleus
- Feeding center
– Lateral hypothalamic nucleus
- Satiety center
– Ventromedial nucleus
- Lateral nucleus.
- Supra-optic nucleus
- Pressor effect
– Posterior & lateral nuclei
- Depressor effect
– Preoptic nucleus
6. Regulation of sexual function:
Anterior hypothalamus:
- In males:
– Medial preoptic nucleus
- In females:
– Lateral preoptic nucleus
- Anterior hypothalamus
- Posterior hypothalamus
- Sleep center
– Preoptic (Ventrolateral)
- Wakefulness center
– Reticular Activating System (RAS) in brainstem & hypothalamus
- Reward center
– Lateral & ventromedial nuclei of hypothalamus
- Punishment center
– Periventricular nuclei (mainly)
REGULATION OF ENDOCRINAL FUNCTIONS:
1. Control of anterior pituitary:
- Releases activator hormone somatostatin
- For Growth hormone secretion.
Preoptic nucleus
- Releases activator hormone Gonadotrophin Releasing Hormone (GnRH)
- For FSH & LH secretion
- Releases activator hormone Corticotropin-releasing hormone (CRH)
- For ACTH secretion.
- Releases Thyrotropin-releasing hormone (TRH).
- For thyroxine secretion
- Dorsal & posterior nucleus
- Releases activator hormone for Catecholamines secretion
- Supraoptic nuclei – ADH (majority)
- Paraventricular nucleus – Oxytocin (majority)
Exam Important
1. Regulation of body temperature:
- Controlled by Preoptic nucleus
- Anterior hypothalamus – Respond to heat
- Posterior Hypothalamus – Respond to cold (Shivering center)
- Suprachiasmatic nucleus
- Feeding center
– Lateral hypothalamic nucleus
- Satiety center
– Ventromedial nucleus
- Lateral nucleus
- Supra-optic nucleus
- Pressor effect
– Posterior & lateral nuclei.
- Depressor effect
– Preoptic nucleus
6. Regulation of sexual function:
Anterior hypothalamus:
- In males:
– Medial preoptic nucleus
- In females:
– Lateral preoptic nucleus
- Anterior hypothalamus
- Posterior hypothalamus
- Sleep center
– Preoptic (Ventrolateral)
- Wakefulness center
– Reticular Activating System (RAS) in brainstem & hypothalamus
- Reward center
– Lateral & ventromedial nuclei of hypothalamus
- Punishment center
– Periventricular nuclei (mainly)
REGULATION OF ENDOCRINAL FUNCTIONS:
1. Control of anterior pituitary:
- Releases activator hormone somatostatin
- For Growth hormone secretion.
Preoptic nucleus
- Releases activator hormone Gonadotrophin Releasing Hormone (GnRH)
- For FSH & LH secretion
- Releases activator hormone Corticotropin-releasing hormone (CRH)
- For ACTH secretion.
- Releases Thyrotropin-releasing hormone (TRH)
– For thyroxine secretion
- Dorsal & posterior nucleus
– Releases activator hormone for Catecholamines secretion
- Supraoptic nuclei – ADH (majority).
- Paraventricular nucleus – Oxytocin (majority).
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