PSYA02H3 Chapter Notes -Normative Social Influence, Lateral Hypothalamus, Microexpression

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13 Feb 2014
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Chapter 11: Hunger and Eating
Motivation: concerns the physiological and psychological processes underlying the initiation of
behaviors that direct organisms toward specific goals
o Initiating factors/ motives -> thoughts, feelings, sensations, bodily process that lead to
goal- directed behavior
o Essential to individual’s survival -> contributes to homeostasis: body’s physiological
processes that allow it to maintain consistent internal states in response to outer
environment
! Physiological needs -> appropriate body temp, hunger, thirst
! Social in nature -> form social bonds -> achieving success at school or work
Drives: the physiological triggers that tell us we may be deprived of something and cause us to
seek out what is needed, such as food
We also respond to incentives (or goals): the stimuli we seek to reduce the drives such as social
approval and companionship, food, water, and other needs
Satiation: the point in a meal when we are no longer motivated to eat
o Homeostasis of food intake is balanced between hunger motives & satiation
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On/ off switches involved in hunger -> hypothalamus
o Researches found that electrically stimulating the lateral hypothalamus causes rats to
begin to eat -> this structure serves as “on” switch
o The ventromedial region of hypothalamus -> serve as “off” switch
! Damage to this area -> obesity in lab animals
o The paraventricular nucleus of hypothalamus -> signals time to stop eating by
inhibiting lateral hypothalamus
Hypothalamus -> doesn’t work alone
o Busy hub of activity that sends & receives signals throughout body
o When it comes to eating/ hunger -> receives info about tastes, textures, smells through
nerves coming from mouth & nose & exchanges this info with front cortex
o Monitoring blood chemistry for indicators of levels of sugars & hormones involved in
energy
! Hypothalamus detects changes in level of glucose: a sugar that serves as a
primary energy source for the brain and rest of the body
Vital energy source for human body; it’s levels monitored by nervous
system
! Highly specialized neurons called glucostats -> can detect glucose levels in fluid
outside of cell
! When glucose level drops, glucostats signal hypothalamus that energy supplies =
low => hunger increases
After food reaches stomach & intestines, sugars absorbed into bloodstream
& transported throughout body
Insulin: hormone secreted by the pancreas -> helps cells store this
circulating glucose for future use
As insulin level rise in response of meal -> hunger decreases & so does
glucose levels -> hunger eventually rises a few hours later
Ghrelin: hormone secreted in stomach that stimulates stomach
contractions & appetite
o Also released by hypothalamus => functions to decrease appetite
Another key chemical in regulating hunger -> cholecystokinin (CKK)
o As intestines expand -> neurons release CKK -> communicates to
hypothalamus that it’s time to stop eating
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Food can be more powerful reinforcer than highly addictive drugs
o Cravings for a “sugar fix– a term that seems to imply that addiction to candy bars is
comparable to an addiction to a drug like heroin
! Possible that sugar act like a drug?
! Ordinary sucrose- plain white granulated sugar- can stimulate release of
neurotransmitter dopamine in nucleus accumbens, brain region associated with
reinforcing effects of substances such as amphetamines & cocaine
Taste -> another powerful force to motivate
o Eating more than just maintaining homeostasis
Scientists not 100% sure -> we crave fats because we have specialized receptors on the tongue
that are sensitive to fat content of food
o Experiments -> used brain imaging technology -> participants tasted various substances -
> overall; they rated fatty substance favorably & brain scans showed activation in regions
of brain associated with pleasure sensations when they tasted fat
Scientific studies -> confirmed health risks brought on by high-fat diets
When chemical receptors in mouth & nose are detecting tastes & smells -> touch receptors in
mouth are detecting textures of food & relaying this info to the orbitofrontal cortex ->
contributes info to overall sensation of eating
o These cells help distinguish runny spaghetti sauce from thick one
o Other cells -> between fatty & lean meats -> spicy and bland foods
Tube feeding: technique used with hospitalized patients who cannot chew or swallow on their
own
o Satisfies body’s nutritional needs by delivering nutrients directly to stomach
o Experiment -> even tough the tube-fed volunteers received all the nutrition they needed,
they were still motivated to eat
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