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Human Body
33 cord and brainstem and outgoing fibres to the cerebral cortex.
All sensations from the periphery of the body (head, limbs and trunk) are conveyed to the thalamus. It is bere that very crude, uncritical sensations reach consciousness. Critical interpretation of these occur in sensory area of the cerebral cortex. If it is damaged, one loses the ability to localize sensations precisely.
Hypothalamus is a mass of grey matter situated below the thalamus, at the base of the brain. Its importance seems quite out of proportion to its size. Although it constitutes only about 1/300 of the total mass of the brain, it is a vital link in the physical and emotional life of the body. It has neural connections to the posterior lobe and vascular connections to the anterior lobe of the pituitary gland. Hypothalamus contains numerous specialized controlcentres including
(i) Cardio-vascular regulation through participation in autonomic responses, regulation of heart-rate, cardiac output, blood-pressure etc. The activities of both components (sympathetic & parasympathetic) are coordinated and controlled.
(ii) Body temperature regulation-regulation of production and loss of heat by stimulating shivering and sweating.
(iii) Regulation of food intake (both hunger and satiating centres) and gastro-intestinal activity.
(iv) Regulation of water balance it contains receptors which are sensitive to changes of salt concentration in the blood and controls intake or output of water via ADH (anti-diuretic hormone) and thirst centre.
(v) Control of circadian rhythms which include wakefulness and sleeping, body temperature cycle etc. and which occur with a periodicity of about 24 hours. Hypothalamus exerts overall control over these rhythms.
(vi) Stimulation of sexual activity in concert with the limbic system.
(vii) Emotional feeling and expression. Feelings and
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