abnormal nervous system physiology abnormal hypothalamus physiology any functional anomaly of the ventral and medial region of the diencephalon forming the walls of the ventral half of the third ventricle, which is normally involved in the functions of the autonomic (visceral motor) nervous system and, through its vascular link with the anterior lobe of the pituitary gland, in endocrine mechanisms MPheno.ontology MP:0005645