what is the difference between allostasis and homeostasis ​
Allostasis
The concept of allostasis was proposed by Sterling and Eyer in 1988 to describe an additional process of reestablishing homeostasis , but one that responds to a challenge instead of to subtle ebb and flow . This theory suggests that both homeostasis and allostasis are endogenous systems responsible for maintaining the internal stability of an organism . Homeostasis , from the Greek homeo , means `` similar , '' while stasis means `` stand ; '' thus , `` standing at about the same level . '' ( The term was not coined as `` homostasis '' or `` standing the same '' because internal states are frequently being disturbed and corrected , thus rarely perfectly constant . ) Allostasis was coined similarly , from the Greek allo , which means `` variable ; '' thus , `` remaining stable by being variable '' ( Sterling & Eyer 1988 ; Klein 2004 ) . Allostatic regulation reflects , at least partly , cephalic involvement in primary regulatory events , in that it is anticipatory to systemic physiological regulation ( Sterling & Eyer 1988 ; Schulkin 2003 ) . The term Heterostasis is also used in place of Allostasis , particularly where state changes are finite in number and therefore discrete ( e.g. computational processes ) . 
The concept of allostasis was proposed by Sterling and Eyer in 1988 to describe an additional process of reestablishing homeostasis , but one that responds to a challenge instead of to subtle ebb and flow . This theory suggests that both homeostasis and allostasis are endogenous systems responsible for maintaining the internal stability of an organism . Homeostasis , from the Greek homeo , means `` similar , '' while stasis means `` stand ; '' thus , `` standing at about the same level . '' ( The term was not coined as `` homostasis '' or `` standing the same '' because internal states are frequently being disturbed and corrected , thus rarely perfectly constant . ) Allostasis was coined similarly , from the Greek allo , which means `` variable ; '' thus , `` remaining stable by being variable '' ( Sterling & Eyer 1988 ; Klein 2004 ) . Allostatic regulation reflects , at least partly , cephalic involvement in primary regulatory events , in that it is anticipatory to systemic physiological regulation ( Sterling & Eyer 1988 ; Schulkin 2003 ) . The term Heterostasis is also used in place of Allostasis , particularly where state changes are finite in number and therefore discrete ( e.g. computational processes ) .
The concept of allostasis describes an additional process of reestablishing homeostasis, but one that responds to a challenge instead of to subtle ebb and flow.   Homeostasis, from the Greek homeo, means "similar," while stasis means "stand;" thus, "standing at about the same level."   Allostasis was coined similarly, from the Greek allo, which means "variable:" thus, "remaining stable by being variable."
The concept of allostasis was proposed by Sterling and Eyer in 1988 to describe an additional process of reestablishing homeostasis , but one that responds to a challenge instead of to subtle ebb and flow . Homeostasis , from the Greek homeo , means `` similar , '' while stasis means `` stand ; '' thus , `` standing at about the same level . '' Allostasis was coined similarly , from the Greek allo , which means `` variable ; '' thus , `` remaining stable by being variable '' ( Sterling & Eyer 1988 ; Klein 2004 ) .