A diencephalic (bilateral) structure. It represents less than 1 % of the brain mass. Small in size but has two way communicating system with all levels of limbic system.
Subdivision & nuclei of Hypothalamus
Hypothalamus is connected to several areas of brain to serve several functions autonomic , visceral etc. Apart from neural connection hypothalamus also acts by releasing secretion into blood stream, into CSF.
FUNCTIONS OF HYPOTHALAMUS
Strong stimulation of PUNISHMENT CENTRES results in this. It is kept in check by counterbalancing activity of VENTROMEDIAL N of hypothalamus, hippocampus, amygdala & ant portion of Limbic Cortex. Rage reaction is characterised by –
- Development of defence posture
- Extension of limbs
- Lifting of tail
- Hissing and splitting
- Wide opening of eyes
- Dilation of pupil
- Severe savage attack, even on mild provocation
Normally, animals & human beings maintain a balance between the rage & calm stage. this is maintained due to reciprocal connection between cerebral cortex & hypothalamus. if this connection is lost then animal exhibits outburst of rage — called SHAM RAGE. EMOTIONS associated are ABSENT.Sham rage is due to release of hypothalamus from Cortical control, and can be abolished by lesioning the caudal hypothalamus.
Lesions of Hypothalamus
- Inflammation (or encephalitis)
- Ischaemia due to vascular disorder
- Damage due to surgical operations in these area