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Chapter 10

Psychology 1000 Chapter Notes - Chapter 10: Basal Metabolic Rate, Anorexia Nervosa, Fixed Action Pattern

Course Code
PSYCH 1000

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Instinct Theory and Modern Evolutionary
-instinct (also called a fixed action pattern): an inherited characteristic, common to all
members of a species, that automatically produces a particular response when the
organism is exposed to a particular stimulus
-modern evolutionary psychologists propose many motives have evolutionary
underpinnings expressed through the actions of significance of behaviour is a key to
understand motivation
Homeostasis and Drive Theory
-homeostasis: a state of internal equilibrium that the body strives to maintain
-drive theory: physiological disruptions to homeostasis produce drives, internal tension
that motivates an organism to behave in ways that reduce this tension
Incentive and Expectancy Theories
-incentives: represent environmental stimuli that “pull” a organism toward a goal
- modern incentive theory emphasizes the “pull” of external stimuli and how stimuli with
high incentive value can motivate behaviour
-expectancy X value theory: proposes that goal directed behaviour is jointly determined
by two factors: the strength of the person’s expectation that particular behaviours will
lead to a goal, and the value the individual places on that goal (the incentive value)
motivation = expectancy X incentive value
-extrinsic motivation: performing an activity to obtain an external reward or to avoid
-intrinsic motivation: performing an activity b/c you want to
-overjustification hypothesis: giving ppl extrinsic rewards to perform activities they
intrinsically enjoy may “overjustify” that behaviour and reduce intrinsic mot.
Psychodynamic and Humanistic Theories
-Freud much of our behaviour results from a battle between unconscious impulses and
our defenses keeping them under control “dual-instinct” model
-Maslow distinguished between deficiency needs (concerned with physical and social
survival), and growth needs (uniquely human and motivate us to develop our potential)
-Need hierarchy: a progression of needs containing deficiency needs at the bottom and
growth needs at the top
-Self actualization: represents the need to fulfill our potential (ultimate human motive)
The Physiology of Hunger
-metabolism: the body’s rate of energy consumption, and about 2/3 of our energy usually
goes to support the basal metabolism, the resting, continuous work of body cells
-“short term” signals start meals by producing hunger and stop food intake by producing
satiety (the state in which we no longer feel hungry)
- “long term” signals adjust appetite and metabolism to compensate for times when you
overeat or eat too little
-set point: a standard around which body weight is regulated homeostatic mechanisms
will return us to our original weight if we eat too much or too little

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Signals that Start and Terminate a Meal
-Washburn swallowed a balloon found stomach contractions corresponded to
subjective feelings of hunger
- research indicates that “hunger pangs” can happen even if you don’t have a stomach
-when you eat, digestive enzymes break down food into various nutrients glucose: a
simple sugar and major source of immediate usable fuel
- most of the glucose is transferred to liver and fat cells and stored
-when blood glucose levels decrease, the liver responds by converting stored nutrients
back into glucose produces a drop-rise glucose pattern
ousually a drop-rise pattern before experiencing hunger
-stomach and intestinal distention are “satiety signals” walls of these organs stretch as
food fills them up, sending nerve signals to the brain
-the intestines respond to food by releasing several hormones, called peptides help
terminate a meal CCK (cholecystokinin) released into blood and stimulates receptors
in brain that decrease eating
Signals that Regulate General Appetite and Weight
-fat cells actively regulate food intake and weight by secreting leptin, a hormone that
decreases eating
- as we gain fat and secrete more leptin, we tend to eat less b/c leptin increases the potency
of satiety factors, making us feel full sooner
-ob gene
directs fat cells to produce leptin, but mutations cause a lack of leptin
-db gene
mutations cause the brain to be insensitive to leptin
othese mutations cause mice to continue eating, but is rare in humans
Brain Mechanisms
- lateral hypothalamus thought to be “hunger on” center
- vertromedial hypothalamus thought to be “hunger off” center
olater studies proved that they were not, but lesions caused other effects such as
trouble swallowing and digesting
-paraventricular nucleus (PVN): a cluster of neurons packed with receptor sites for
various transmitters that stimulate or reduce appetite appears t integrate several
different short-term and long-term signals that influence metabolic and digestive
-neuropetide Y: powerful appetite stimulant when leptin reaches the hypothalamus, it
seems to inhibit the activity of neurons that release neuropeptide Y into the PVN, thereby
reducing appetite
Psychological Aspects of Hunger
-objectification theory: Western culture teaches women to view their bodies as objects
- 1 in 5 adolescent and young adult females report being happy with their weight
- a body mass index (BMI) over 30 is considered obese
- 33% of adult Canadians are overweight, and 15% are obese
- often blamed on a lack of willpower, weak character, etc
- hypothesize that obese ppl eat to cope with stress, or react more strongly to food cues
-heredity influences our basal metabolic rate and tendency to store energy as either fat or
lean tissue genetic factors account for about 40-70% of body mass variation
- over 200 genes have been identified as possible contributors to obesity
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