PSYC 280 Chapter Notes - Chapter 13: Preoptic Area, Negative Feedback, Lateral Hypothalamus
9 Feb 2019
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PSYC 280 - Textbook - Chapter 13
Homeostasis Maintains a Consistent Internal Environment
● Homeostasis - active regulation of monitored physical attributes at appropriate levels
○ Resulting in relatively stable, balanced internal environment
● Alterations in internal env can have effect on motivation - drive state prompting
homeostatic behaviors
● Obligatory losses - unavoidable loss of regulated variables such as energy, water,
temperature
● Thermoregulation - active process of closely regulating body temperature around set
value
Homeostatic Systems Share Several Key Features
● Endotherms - animals whose body temp regulated chiefly by internal metabolic
processes
● Ectotherms - animals whose body temperature regulated by & whose heat comes mainly
from env
Negative Feedback
● Negative feedback - property by which some of output of system feeds back to reduce
effect of input signals
● Set point - point of reference in feedback system
● Set zone - range of variable that feedback system tries to maintain
● Some animals that cannot avoid subfreezing temperatures - produce antifreeze
○ Suppress formation of ice crystals & prevent damage to membranes
Redundancy
● Loss of function in one part of system can usually be compensated for by remaining
parts
○ Attests to importance of maintaining stable inner environment
● Diff hypothalamic sites controlled 2 separate thermoregulatory systems
○ Lesions in preoptic area - impaired physiological responses to cold but did not
interfere w/ behaviors such as pressing levels to control heating lamps
○ Lesions in lateral hypothalamus of rats abolished behavioral regulation of temp
but did not affect physiological responses
Behavioral Homeostasis
● In general, ectotherms & endotherms can
○ Change exposure of body surface
Document Summary
Homeostasis - active regulation of monitored physical attributes at appropriate levels. Resulting in relatively stable, balanced internal environment. Alterations in internal env can have effect on motivation - drive state prompting homeostatic behaviors. Obligatory losses - unavoidable loss of regulated variables such as energy, water, temperature. Thermoregulation - active process of closely regulating body temperature around set value. Endotherms - animals whose body temp regulated chiefly by internal metabolic processes. Ectotherms - animals whose body temperature regulated by & whose heat comes mainly from env. Negative feedback - property by which some of output of system feeds back to reduce effect of input signals. Set point - point of reference in feedback system. Set zone - range of variable that feedback system tries to maintain. Some animals that cannot avoid subfreezing temperatures - produce antifreeze. Suppress formation of ice crystals & prevent damage to membranes.
