The major effector mechanisms are:

• Thirst 

• ADH (anti-diuretic hormone).

Control of Water Input : Thirst
Thirst is a mechanism for adjusting water input via the GIT.

Control of Water Output : ADH & the Kidney
ADH provides a mechanism for adjusting water output via the kidney. Note that ADH is often called 'vasopressin' - this term refers to the vasoconstrictive properties of very large doses ('pharmacological doses') of the hormone

Both thirst and ADH can increase when water is needed by the body and the usual physiological outcome is to repair the water deficit. These effector mechanisms are discussed in the next 2 sections. The whole system for control of water balance as outlined in this chapter is frequently referred to as "the thirst-ADH mechanism" though this really only refers to the effector part of the control system.

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