Introduction Irritability Stimuli Response Co-ordination Reception Irritability in Plants Tropisms Tactic Movement in Plants and Other Organisms Nastic Movements Production of Auxins and their Effects on Plant Growth Reception, Responses and Coordination in Animals Receptors Effectors The Nervous System Simple And Conditioned Reflex Actions The Role of Endocrine System in Human Beings Comparison between Endocrine and Nervous System Structure and Function of Parts of the Human Eye Structure and Functions of Parts of the Human Ear Practical Activities To Investigate Tactic Responses To Investigate Tropisms in Plants Experiment to Determine Distance of the Blind Spot The Knee Jerk Experiment\ Introduction The structures involved in detecting the changes may be located far away from the ones that respond. There is need for a communication system within the body. The nervous system and the endocrine system perform this function, i.e. linking the parts of the body that detect changes to thos