Not unchanging: dynamic state of equilibrium involving many systems: 

• adequate blood levels of vital nutrients
• heart activity/ blood pressure monitors & adjusted as needed
• wastes don't accumulate
• body temperature 

1. receptor: senses change (stimulus)& sends info (afferent pathway) to:
2. control centre: determines set point for variable maintenance; analyzes info & determines correct response
3. effector: provides means for response (output along efferent pathway)

Allows for regulation within a range/ enhanced response

• enhances original stimulus
• change occurs in same direction as original response
• goal to be attained

Output reduces or shuts off stimulus- 2 options:

1. 1 hormone or neural pathway regulating a process: negative feedback decreases secretion
2. process regulated in opposite directions by 2 different hormones or neural pathways (eg: blood glucose)

Goal: prevent sudden/severe changes 

Disease: most diseases seen as a disturbance of homeostasis = homeostatic imbalance

Aging: associated w/ progressive decrease in our ability to maintain homeostasis    greater risk for illness