5. Appetite Flashcards

1
Q

Digestion

A

Food is broken down by our gut microbiome (bacteria and other organisms in our intestines) and we absorb nutrients from it

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2
Q

Forms of Energy

A

Lipids - fats
Amino acids - proteins
Glucose - sugar from carbs

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3
Q

Energy storage

A

Fat (main, more energy per gram)
Glycogen
Proteins

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4
Q

3 Stages of Metabolism

A

Cephalic phase
Absorptive phase
Fasting phase

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5
Q

Cephalic phase

A

Sight/smell of food
Ends with absorption of nutrients into bloodstream
A lot of insulin, small amounts of glucagon

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6
Q

Absorptive phase

A

Energy is absorbed, body’s immediate needs are met
A lot of insulin, small amounts of glucagon

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7
Q

Fasting phase

A

The body withdraws energy from its reserves
Energy from the previous meal has been used up
Ends at the beginning of the next cephalic phase
High glucagon levels

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8
Q

Skipping of fasting phase

A

Fast weight gain occurs

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9
Q

Metabolic Phases/Cycle (hormones)

A
  1. Insulin is released
    Enabling glucose to enter cells
    Fuel conversion for storage is promoted
  2. Blood glucose levels decline, insulin stays the same
  3. Rapid return of hunger
    Insulin levels are low, so glucagon cannot enter cells
    Glucagon goes to the brain instead, stopping it from being the body’s main energy source
    Free fatty acids are used as the main source
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10
Q

Hunger related hormone

A

Galanin - triggers hunger for fats
Ghrelin

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11
Q

Ghrelin

A

Neurotransmitter, binds to the same receptors as growth hormones
Increases hunger

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12
Q

Galanin

A

Hunger related hormone
Triggers hunger for fats

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13
Q

Satiety Related Hormones

A

CCK
Leptin

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14
Q

CCK - satiety related hormone

A

In the short-term

  1. Constricts the sphincter muscle, leading to the stomach being constricted and filling more quickly
  2. Stimulates the vagus nerve, sending signals to the hypothalamus, signals satiety
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15
Q

Leptin - satiety related hormone

A

Satiety related hormone

Function is to decrease appetite and increase fat metabolism

Released after meals

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16
Q

Orexin/Hypocretin - hunger related hormone

A

Released in the hypothalamus

Two roles in feeding
Increase in seeking food
Reward response

17
Q

Sensory specific satiety

A

The number of different tastes influences meal size
More tastes = eating more

18
Q

Cafeteria diet

A

Positive incentive value
Satisfied with one food but still crave other tastes

19
Q

Set-point theory

A

The motivation to eat comes from energy deficits, eating is a method of returning to our normal levels of energy

We eat until this ‘set-point’ is obtained/we reach homeostasis

Lots of evidence against

20
Q

Criticism of set-point theory

A

Inconsistent with basic related evolutionary theories
That we eat as much as possible to survive

Obesity

Unaccounted for:
Tastes
Social influences

21
Q

Appetizer Effect

A

Hunger is increased after eating appetizers as the cephalic phase responses are increased

22
Q

Lateral Hypothalamus

A

Releases orexin, making you seek food
Controls insulin secretion
Alters taste responsiveness, enhancing the taste of food

23
Q

Paraventricular Hypothalamus

A

Gathers all information and provides it to the lateral nucleus
Inhibitory effect

24
Q

Sham eating experiments

A

Food is chewed and swallowed but not taken to the stomach, redirected by a tube inserted into the body
If set-point was true, the rats would’ve eaten huge meals as the energy threshold was not being met but this was not the case
Rats ate a relatively normal amount of food
After several meals, rats ate more
Showed that people enjoy physical eating

25
Causes of Obesity
Related to taste preferences, cephalic responses, culture, genetic factors (predisposition) etc. Drugs Surgeries Differences in energy expenditure Not everyone exercises the same amount Differences in the basal metabolic rate in each person Diet induced thermogenesis Social influences
26
Diet induced thermogenesis
Mechanism by which the body adjusts the efficiency of energy utilization in response to body fat Less body fat - more efficient energy usage
27
Leaky Barrel Model
There has to be balance between all factors (food intake, energy expenditure, satiety signals etc.) Remember the image with the hole in the barrel & the barrel on the hose
28
Glucostatic set-point theory
The set-point involves glucose intake Short-term (energy)?
29
Lipostatic set-point theory
Lipid set-point Long-term (energy?) Evidence: adults body weight is relatively consistent
30
Conditioning
Conditioned taste aversion, can determine what we do and don't eat
31
Preferences
High calorie foods like sweets (reminiscent of Mother's milk) Foods high in minerals and vitamins (usual choice but with so many options our bodies find it hard to differentiate and choose the best one)
32
Arcuate Nucleus
One set of hunger neurons and one set of satiety neurons that affect the paraventricular nucleus
33
Paraventricular Nucleus
Output stimulates satiety
34
Lateral Nucleus
Output stimulates feeding
35
Ventromedial hypothalamus
Output inhibits feeding