Chapter 3 Study Guide

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21 Feb 2011
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Ch. 3 The motivation and organization of Behavior
Key Points
-Behaviors can be thought of having underlying motivations. These may be internal or
external to the individual (or both). Levels of motivation relating to homeostasis are
regulated in accordance to need by a range of physiological mechanisms. Variations in
motivation tend to increase fitness.
-*** Variations in motivation tend to increase fitness
-Many behaviors are expressed according to a distinct temporal pattern. They occur with a
regular periodicity and are controlled by biological clocks
-There is a genetic component to the control of biological rhythms, but their cycling is also
controlled to some extent by internal and external environmental cues.
Motivation
Homeostatis and the motivation to drink
-Our bodies have a built in system of regulators that maintain our internal environment at
the peak of operating efficiency.
-Homeostasis: being the coordinated physiological processes that maintain an animals
body at a steady state relative to its environment. It involves the cooperative actions of the
sensory system, the brain, and the organs of the body
- Whether anticipatory or responsive, conditions cause a change in behavior
-Motivation: internal urges. Uncnonsious (in animal behavior)
-if you decide to drink before playing a sport it could be said that you were motivated to
drink or that your motivation to drink changed.
-Loss of water from the body of a mammal is recorded by specialist cells termed
osmoreceptors that are located in the hypothalamus of the brain.
-Changes in the internal water balance of the body (as a result of drinking or dehydration
due to excretion, sweating, respiration, etc.) alter the osmotic environment of the cells.
-A water deficits results in the loss of water from cells
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- a loss of water causes cell shrinkage, as turgor is lost
- Osmoreceptors use their own shrinkage as a cue to both initiate hormonally controlled
water conservation measures (release of antidiuretic hormone which decreases urine
production in the kidneys), and to motivate the onset of drinking behavior.
-This is an example of a negative feedback system: when there is a lack of
something needed (body fluid), behavior occurs to increase the levels (drinking).
- Other than simple physiological needs to response there are other cues that can be used to
trigger behaviors (in this case drinking)
-Both rats and pigeons will increase their drinking levels in response to a rise in air
temperature even though their internal fluid balance has not in fact changed. There can
therefore be a behavioral component to homeostasis, both in response to current need and
in anticipation of a future requirement. This could imply that animals learn to associate
warmer conditions with a dehydration risk on the basis of past experience.
The motivation to eat
-Hunger: response of the organism to a hormonal signal. High levels of leptin = no
secretion of ghrelin and no motivation to eat. Decreased levels of leptin = secretion of
ghrelin (high levels of ghrelin) and motivation to eat.
-leptin is released by fat storage cells. Thus increased fat storage results in higher
leptin levels and indicate the adequacy of the bodys stored energy reserves. Levels of leptin
are measured by areas of the hypothalamus.
-If leptin levels are high appetite is suppressed.
- If leptin levels are low the stomach secretes the hormone ghrelin. This acts
upon the same three areas of the brain but its effect to stimulate appetite to signal
hunger.
Hyperphagic behavior
-Hyperphagia: overeating
-fish experiment. 1 group not fed for 40 days, other for 20. Predicted the 1st group to have a
greater intensity of hyperphagia (eat more, more quickly) or (eat more, for longer).
-Results: starvation resulted in a strong motivation to feed in both groups, but that the
result of their higher energy deficit the very hungry fish were motivated to feed at higher
levels for a longer period (eat more for longer).
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