Histamines are chemicals released by the body as an allergic response.They help the body by reacting when their are "intruders" so when enters, histamine acts as a messenger and sends out a signal for the body to create a reaction helping to get rid of teh intruder through some type of reaction.
I think the thalamus is the gateway to the cerebral cortex. Thalamus is a small structure within the brain located just above the brain stem between the cerebral cortex and the mid brain and has extensive nerve connections to both. Its main function is to relay motor and sensory signals to the cerebral cortex. A sensory impulse travels from the body surface towards the thalamus, which receives it as a sensation, which is then passed onto the cerebral cortex for interpretation as touch, pain or temperature.
