Psy 340 chapter 9 Homeostasis and motivation
I. Homeostasis and motivation
a. Homeostasis = physiological state of equilibrium or balance
b. Set points
... [Show More] = value defended by regulatory systems, such as core temperature or a particular body
weight
i. Deviation from set point initiate behaviors that return the system to homeostasis
ii. Temperature, fluid levels, body weight
c. Motivation = process of activating and directing behavior
i. Regulatory systems help us identify a problem, but our reaction to this information
involves a complicated set of psychological and biological processes
II. Regulating body temperature
a. Involves defined set point, mechanisms for detecting deviation away from set point, and internal
and behavioral elements to regain set point
b. High temperature = proteins needed for carrying out cell function become unstable
c. Low temperature = ice crystals form within cells and damage cell membrane
III. Adaptations maintain temperature
a. Endotherms = animal that use internal methods, such as perspiration or shivering to maintain
body temperature
b. Ectotherms = animal that relies on external methods such as moving into sun or shade for
maintaining body temperature
c. Maintenance of body temperature influenced by animal’s surface to volume ratio
i. The larger the overall volume of body, the more heat is produced by metabolic activity
ii. Smaller animals have more surface area relative to overall body volume so they use much
more energy to maintain constant body temperature
d. Populations of animals evolve features that fit a particular environmental niche
i. Cold climates = surface area and heat loss are reduced in animals that have compact
bodies; conserve heat by having compact body
ii. Warm climes = animals have greater surface area in the form of slim bodies; disperse heat
by having slim bodies
IV. Behavioral responses to heat and cold
a. Simple behavioral strategy for regulating temperature is to move to the right type of environment
b. Body position adjusted in response to change in temperature
V. Endothermic responses to heat and cold
a. Demonstrate a variety of automatic internal responses to deviations from temperature set point
b. responses to lower temperatures
i. shiver, blood vessels constricts
ii. thyroid hormone increases to boost metabolic rates
iii. newborn animals increase activity of brown fat cells
c. responses to higher temperature
i. perspiration, licking, panting
ii. blood vessels dilate near skin surface
d. defend temperature set point of 37 degrees Celsius (98.6 F)
i. below = shiver which results from muscle twitches and produce that cost high energy
blood vessels constrict which heat loss is the greatest
e. Raynaud’s disease
i. Sudden spasms in arteries, in fingers and toes in response to cold that affect digit and
appear white
f. Sympathetic nervous system responds to brown fat cells – located in torso, close to vital organs.
Appear brown due to large numbers of mitochondria
g. Perspiration cools skin through evaporation
VI. Deviations in human core temperature [Show Less]