1.  If both the nervous system and the endocrine system are involved in regulating and controlling changes within the body, don’t the two systems just duplicate each other?

 It’s true that both systems do send out “messages” to the body  but here are some differences.

 The signaling system of the nervous system is nerve impulses.

 The signaling system of the endocrine system is chemical “messengers”  (that is, hormones) released into the blood or to near-by cells.

 The time it takes for the impulse to travel to its destination and cause some effect is in milliseconds.
 
 The time it takes from the when the hormone is released until its effects occur may take minutes or days.

 The duration of the effect of the nerve impulse is quite short.  For example, a nerve impulse causes a muscle in the leg to contract, & then the contraction will end unless there is further stimulation by more nerve impulses.  This again just occurred in milliseconds.
 
 The duration of the effect of hormones is rather prolonged.  For example, adrenalin released into the blood stream will stimulate the heart to increase its rate of contraction.  This rate increase may continue for several minutes until the adrenalin is processed out of the blood.

 These are some of the ways that the nervous system and the endocrine system differ in their influence over the regulation and control of the body.