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Chapter 11.1

PSY100H1 Chapter Notes - Chapter 11.1: Family Reunion, Eating Disorder, Nucleus Accumbens

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Dan Dolderman

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The study of motivation concerns the physiological and psychological processes underlying the initiation
of behaviours that direct organisms toward specific goals. These initial factors, or motives, include the
thoughts, feelings, sensations, and bodily processes that lead to goal-directed behavior. A drive is a
biological trigger that tells u we may be deprived of something and causes us to seek out what is
needed, such as food or water. When a drive is satisfied, reward centers in our brain become activated.
This reinforces our behavior, making it more likely that we will respond to these drives. Motivation is
essetial for a idiidual’s surial eause at its ost asi leel it otriutes to homeostasis, the
od’s phsiologial proesses that allo it to aitai osistet iteral states i respose to the
outer environment. However, sometimes humans and animals are motivated to engage in behaviours
that cannot be explained by homeostasis. Ex. The experience of anxiety uses a lot of energy, as does the
effort to otrol our eotios. If Jaie ho as stressed aout her ea the et da did’t irease
her food consumption to meet these new energy demands, her energy level would quickly drop below
the level that homeostasis was trying to maintain. Motivation is not only influenced by current needs,
but also by the anticipation of future needs. This process is known as allostasis. This process is not
perfect, which is why physiological variables can have such a strong influence on behavior.
Huger is’t ol a hoeostati ehais. The otrols of huger are found in the hypothalamus.
Electrically stimulating the lateral hypothalamus causes rats to eat, and stimulating the ventromedial
region of the hypothalamus causes them to stop eating. Removal of the ventromedial region causes
obesity in rats. The activity of the hypothalamus is influenced by hormones that are released in response
to the energy needs of your body. Thus, your brain influences your body and your body influences your
brain. The hypothalamus monitors blood chemical levels. The hypothalamus detects changes in levels of
glucose, a sugar that serves as a primary energy source for the brain and the rest of the body. Glucostats
can detect glucose in fluid outside the cells. If the glucose levels are too low, the hypothalamus will
trigger a feeling of hunger. Insulin helps cells store glucose for later use. As insulin levels increase in
response to consumption of food, hunger decreases, but so do glucose levels, which after a few hours,
leads to hunger again. A full stomach is a cue for satiation, the point in a meal where we are no longer
motivated to eat. The feeling of satiation can also influence how rewarding we find a food. In one
experiment, researchers scanned peoples brains while feeding them chocolate. At first, the people said
it was good, and they observed activity in the orbitofrontal cortex, a brain area that judges the reward
value of foods. Activity was also found in the insula, which receives information about taste, and the
basal ganglia, which responds to physical rewards. But after being fed the chocolate for quite some
time, their reactions to it became aversive. After this negative rating, brain area activity dealing with
reward decreased and was replaced by activity in other areas of the frontal lobes. This study shows that
a number of different brain areas are involved when we are motivated to eat, it is not simply just the
hypothalamus. This also shows that our physiological and psychological motivations to eat influence
Over history our bodies have adapted to like high energy foods. Scientists suggest that we crave fats
because we have specialized receptors on the tongue that are sensitive to the fat content food. In one
experiment, people had their brain scanned while tasting various foods. At different times, they tasted
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