eating behavior

Question 1

steps in digestion

Answer 1

1. chewing breaks up food and mixes w saliva which lubricates and begins digestion
2. swallowing moves food down esophagus to to stomach
3. hydrochloric acid in stomach breaks down food into small particles & pepsin being breaking down protein to AA
4. stomach gradually empties out contents through pyloric sphincter into duodenum where most absorption takes place
5. digestive enzymes in duodenum break down protein, starch & sugar which move through duodenum wall into bloodstream then liver
6. fats are emulsified by bile - cannot pass through duodenum & is carried into the lymphatic system
7. most remaining water & electrolytes are absorbed from waste in LI & remainder is excreted from anus

Question 2

how do glucose, insulin & glucagon relate?

Answer 2

glucose = an important source of energy from food

insulin & glucagon = pancreatic hormones that regulate the flow of glucose into cells

Question 3

role of insulin

Answer 3

before & during a meal - pancreas increases release of insulin = enables glucose to enter cells
some of the excess glucose enters the liver - coverts to glycogen & stores
some also enters fat cells - converts to fat & stores

Question 4

role of glucagon

Answer 4

after a meal - blood glucose falls - insulin levels drop - glucose enters cells slowly = hunger increases
pancreases increases release of glucagon = liver converts some of stored glycogen back to glucose for energy

Question 5

what is leptin

Answer 5

a hormone that signals your brain about your fat reserves

when fat decreases - leptin decreases = you eat more & become less active to save energy

leptin return to normal = eat less & exercise more

Question 6

what are the 3 phases of energy metabolism

Answer 6

cephalic: begins with sight, smell or thought of food & ends when food starts to be absorbed into bloodstream

absorptive: the period where the energy absorbed meets the body’s immediate energy needs

fasting: the period where all the unstored energy from previous meal has been used & body uses energy from reserves to meet energy needs

Question 7

insulin & glucagon during the cephalic & absorptive phases

Answer 7

during these phases the pancreas releases lots of insulin & little glucagon

inulin promotes:
- use of glucose as primary energy source
- the conversion of bloodbourne fuels to forms that can be stored
- the storage of glycogen in liver, fat in adipose tissue & protein in muscles

Question 8

insulin & glucagon during the fasting phase

Answer 8

during this phase the pancreas releases lots of glucagon and little insulin

low levels of insulin = glucose cant enter most body cells = stops being primary fuel + promotes conversion of glycogen & protein into glucose

high levels of glucagon = conversion of fats to free fatty acids = uses it as source of energy

Question 9

ghrelin

Answer 9

period of food deprivation - stomach releases ghrelin = triggers stomach contractions & acts on hypothalamus to increase appetite

Question 10

what is the arcuate nucleus of the hypothalamus

Answer 10

an area that is very important in controlling appetite

has one set of neurons sensitive to hunger signals & one set sensitive to satiety signals

Question 11

paraventricular nucleus vs lateral nucleus of the hypothalamus

Answer 11

PVN promotes satiety
LN promotes hunger

hunger neurons are activated - inhibits inhibitory neurons in the PVN = decreases breaks on the LN = we feel hungry

satiety neurons are activated - excites inhibitory neurons in the PVN - increases breaks of LN = feel less hungry

hunger neurons in the AN inhibit the PVN which inhibits the LN

Question 12

set point theories general idea

Answer 12

state that after a meal - resources are at/near their set point
this declines after as the body uses energy
when energy levels are far enough below set point - you become hungry
you eat until energy levels are restored to set point and you feel satiated

Question 13

glucostatic theory

Answer 13

states that eating is regulated by a system designed to maintain a blood glucose set point

we become hungry when blood glucose levels drop below set point
we become satiated when eating returns blood glucose levels to set point

Question 14

lipostatic theory

Answer 14

states that every person has a set point for body fat & deviations from this produce compensatory changes that return body fat levels to set point

Question 15

3 major weakness of set point theories

Answer 15

1. they are inconsistent with basic eating related evolutionary processes
2. major predictions of these theories have not been confirmed
3. they fail to recognize that major influences social & personal factors on hunger and eating

Question 16

positive-incentive theory

Answer 16

humans are driven by pleasure of eating not because of energy deficits
presence and anticipation of good food makes us feel hungry
2 ways: good food would be eaten over and over again, food that makes you sick would not be eaten again

Question 17

factors that contribute to obesity

Answer 17

• differences in energy input & output
• genetics
• basal metabolic rate
• culture & taste preferences (influence what & how much)

Question 18

3 types of heritability for obesity

Answer 18

1. syndromal obesity: when a gene causes a medical problem that causes obesity
2. monogenic obesity: when a single gene cause obesity without other physical or mental abnormalities
3. polygenic/common: when many genes slightly increase probability of obesity