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psy290 lecs 8-10 (chp9,12-15).pdf

123 pages78 viewsFall 2012

Department
Psychology
Course Code
PSY290H1
Professor
Junchul Kim

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Eating, Sex & Hormones 12-05-22 1:30 PM
Eating
Believe:
o hunger & eating are normally triggered when body’s energy
resources fall below prescribed optimal level (set point)
Assume:
o hunger & eating system evolved to supply body with right
amount of energy
Digestion
Purpose of hunger:
o inc probability of eating
Purpose of eating:
o supply body with molecular building blocks & energy needed
to survive & function
Digestion:
o gastrointestinal process of breaking down food & absorbing its
constituents into the body
! Chewing breaks up food & mixes it with saliva
! Saliva lubricates food & begins digestions
! Swallowing moves food & drink down esophagus to
stomach
! Stomach functions as a storage reservoir, hydrochloric
acid breaks food into small particles, pepsin breaks down
protein into aa
! Stomach empties contents through pyloric sphincter into
duodenum
! Digestive enzymes in duodenum break down proteins to
aa, starch & complex sugars into simple sugars, simple
sugars & aa pass through duodenum wall into
bloodstream to liver
! Fats emulsified by bile (manufactured by liver, stored in
gall bladder), carried by small ducts in duodenum wall
into lymphatic system
! Remaining water & electrolytes absorbed from waste in
large intestines, rest ejected from anus
Energy Storage
Lipids (fat), Amino acid (protein), Glucose (carbohydrates)
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o Most stored as fats, little as glycogen & protein
Changes in body weight:
o changes in amount of stored body fat
Glycogen:
o stored in liver & muscles (easily converted into glucose)
Fats preferred:
o 1g of fat stores 2x as much energy as 1g glycogen, glycogen
holds water
3 Phases of Energy Metabolism
Cephalic phase
o Preparatory phase: sight, smell, thought of food
o Ends when food starts to be absorbed into blood stream
Absorptive phase
o Energy absorbed into bloodstream from meal is meeting
body’s immediate energy needs
Fasting phase
o Unstored energy from previous meal has been used & body is
withdrawing energy from reserves to meet its immediate
energy req
Flow of energy controlled by 2 pancreatic hormones
Insulin: lots in cephalic & absorptive phase,
o Promotes use of glucose,
o Conversion of bloodborne fuels to forms that can be stored
o Storage of glycogen in liver & muscle, fat in adipose tissue,
protein in muscle
! Cephalic:
" lower levels of bloodborne fuel
! Absorptive:
" minimize increasing levels of bloodborne fuels
(use & store them)
Glucagon: high in fasting phase
o Low levels of insulin:
! Glucose saved for brain cells (doesn’t req insulin to enter)
! Gluconeogenesis: conversion of glycogen & protein into
glucose
o High levels of glucagon:
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! Release of free fatty acids from adipose tissue
" used as main fuel
! Conversion of free fatty acids to ketones
" used by muscles, later brain
Theories of hunger & Eating: Set Points
People attribute hunger to:
o presence of energy deficit
o view eating as means by which energy resources of body
returned to optimal level
After meal:
o energy resources assumed to be near set point & decline
Energy falls below set point:
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