This is power point talks about the science of eating and drinking

1. Motivation and
Regulation of the
Internal States

2. Motivation and Homeostasis
• Motivation literally means “to set in motion”
Psychologists were not able to define it solely in
terms of external stimuli. There various kinds of
motivation such as achievement or hunger.
• Motivation is a concept psychologists
invented. Do not expect to find a motivation
center in the brain.

3. Theoretical Approaches to Motivation
• Instinct : it is a complex behavior that is
automatic and unlearned and occurs in all the
members of a species
Example: Maternal instincts or migration in
animals.
At any rate we need to be extremely careful
about how we use the term instinct and to avoid
the temptation to label any behavior that is
difficult to explain as an instinct.

4. The drive theory has fared much better in
explaining motivation than the instinct theory
Drive: the body maintains a condition of
homeostasis in which any particular system is in
balance or equilibrium. Any departure from
homeostasis such as depletion of nutrients or
drop in temperature causes an aroused
condition or Drive

5. Simple Homeostatic Drives
• Temperature regulation
In mammals the major thermostat is
located in the preoptic area of the
hypothalamus, which contains warmth-
sensitive and cold-sensitive cells directly
to the temperature of the blood flowing
through the areas

7. • Others receive input from temperature
receptors in other parts of the body, including
the skin.
• The preoptic area of
The brain integrates
Regulatory responses
Such as sweating,
Panting, or shivering.

8. • Thirst
Water is needed to maintain the cells of the
body to keep the blood flowing through the
veins and arteries and to digest food.
There are two types of thirst:
1. Osmotic thirst
2. Hypovolemic thirst

9. • Osmotic thirst
This occurs when the fluid content decreases
inside the cells. This happens when the blood
becomes more concentrated than usual, usually
because the individual has not taken in enough
water to compensate for food intake.
This is detected by the bordering third ventricle
particularly in the organum vasculosum lamina
terminalis or OVLT

10. • Hypovolemic thirst
This occurs wen the blood volume drops due to
a loss of extracellular water. This can be due to
sweating, vomiting, and diarrhea.
Hypovolemia is detected by receptors located
where the large veins enter the atrium of the
heart.

12. Hunger
• Eating provides energy for activity, fuel for
maintaining body temperature, and materials
needed for growth and repair of the tissues.
The set point is varies with demands on our
resources caused by exercise, stress, growth
and so on.

13. The role of taste
• Taste receptors are
located on taste buds
which in turn are
found on the surface
of the papilla.
• Besides the 4 primary
tastes the newest
one added is called
umami.

15. • The taste neurons travel through the thalamus to
the insula, the primary taste area in the frontal
lobes, but on their way they pass through the
medulla.
• Each of the primary taste stimuli is detected by
receptors that are specialized for that stimulus .
• Information from the different receptors travels
to the brain via separate pathways to distinct
areas in the insular cortex.

16. • The taste sense contributes to dietary
selection in three additional ways:
1. Sensory specific satiety
2. Learned taste aversion
3. Learned taste preferences

17. Sensory-specific satiety
• This means that the more of a
particular food an individual
eats, the less appealing the food
becomes.
• The effect sounds trivial but it is
not; Sensory-specific satiety is
the brains way of encouraging
you to vary your food choices,
which is necessary for a
balanced diet.

18. Learned taste aversion
• Learned taste aversion is the avoidance of
foods associated with illness or poor nutrition.
• Learned taste aversion helps wild animals and
primitive-living humans avoid dangerous
foods.

19. Learned taste preferences
• This is the preference for the flavor of a food
that contains a particular nutrient.
Taste: the experience you get from your taste
receptors
Flavor: depends on the combination of taste and
smell.

20. The digestive process

21. • Digestion begins in the mouth where food is
ground and mixed with saliva.
• After reaching the stomach it mixes with HCL
and if the food is not favorable the stomach
responds by regurgitating it.
• If the toxins make their way into the blood
stream, the postrema in the brain induces
vomiting.

22. • Digestion primarily occurs in the duodenum
where the food is broken down into usable forms.
Carbohydrates
Proteins
Fats
• The products of digestion are absorbed through
the intestinal wall and transported to the liver via
the hepatic portal vein
• This process is under the control of the
autonomic nervous system
Simple sugars such as glucose
Converted into amino acids
fatty acids and glycerol

23. The Two Phases of Metabolism
• The absorptive phase: For a few hours
following a meal, the body lives off the
nutrients arriving from the digestive system.
• The fasting phase: Eventually the glucose level
in the blood drops. Now the body must fall
back on its energy stores, which is why it is
called the fasting phase.

26. Signals That Start a Meal
• Did you know that the stomach is not necessary
to feel hunger?
• There are three major signals for hunger:
1. Glucoprivic hunger : tells the brain there is a low
supply of glucose.
2. Lipoprivic hunger: indicates a deficit in fatty
acids
3. Informs us that the stomach’s store
of nutrients has been depleted.

27. The role of Ghrelin
• It is part of the third major signal for hunger. It
is synthesized in the stomach and released
into the bloodstream as the stomach empties
during fasting .
• Signals of glucose and fatty acid deficits are
carried by the vagus nerve from the liver to
the NST(Pg. 171) in the medulla.

28. • Three of these hunger signals exert their
influence through neurons in the arcuate
nucleus which excite the lateral hypothalamus
and increase eating and reduce metabolism.

29. Signals That End a Meal
• Just as with drinking there must be a satiety
mechanism that ends a mean well before
nutrients reach the tissues.
• Optimal satiation requires the interaction of
mouth, stomach, and intestinal factors. The
best known of these satiety signals is
Cholecystokinin (CCK), a peptide hormone
released as food passes into the duodenum.

30. Long term controls
• Over long periods humans and animals
regulate their eating behavior by monitor in
their body weight or more precisely their body
fat but how they do it is unclear.
• How much we eat at a meal is also regulated
by the amount of fat we have stored indicated
by leptin and insulin levels.

31. • An additional contributor to the control of
feeding and body weight is orexin or
hypocretin, a neuropeptide that increases
appetite and induces eating.

32. Obesity
• Obesity is measured in BMI (Body mass index)
It is calculated by dividing the person’s weight in
kilograms by the square height in meters.
• Obesity is most important because of its
health risks. As overweight and obesity
increase, so does the incidence of diabetes.

33. • Obesity increases the likelihood of high blood
pressure, heart disease, stroke and colon
cancer. Obesity is also linked to cognitive
decline and risk for Alzheimer’s diseases

34. Myths of obesity
• Simply put the cause of obesity is energy in
exceeds energy out.
#1 caused by inability to control appetite.
#2 Inability to delay gratification
#3 Maladaptive eating styles
#4 It runs in the family
Obesity does run in families and it is moderately to
family members but research shows that
environmental effects are stronger

35. • All the known genes account for only a small
proportion of obesity, and heritability
measures leave room for significant
environmental influence.
• Indeed we must recognize that the recent
surge in obesity is due to non-genetic factors
such as diet and activity.

36. Contributions of the heredity and the
Environment to obesity
• Sleep deprivation : sleep loss reduces leptin
levels and increases ghrelin secretion which
makes you crave for high calorie foods.
• Certain types of infection: Bacteria of the
phylum Firmicutes are most likely the culprit.
This bacteria can be found in the gut.

37. Obesity and Reduced Metabolism
• Differences in basal metabolism may be a key
element in explaining differences in weight.
However a person’s metabolism can shift
when the person gains or loses weight.
• The energy expenditure changes are greater
than the weight changes required, which
means the individual’s bodies defend their
original weight.

38. • So why doesn’t this defense of body weight
prevent people from becoming obese?
The body reserves excess nutrients for a time of
starvation.
• A second reason is that people vary
tremendously in the strength of their defense
response making some people more
vulnerable to being overweight than others.

39. Treating obesity
• The standard treatment for obesity is of
course dietary restriction.
• Another option is medication. But the
problem with drugs is that they manipulate
metabolic and other important body systems
and often have adverse side effects. Drugs
such as Belviq and Qsymia are examples are
drugs used.

40. • Researchers have also looked into treatment
with hormones. The leptin treatment however
only benefits 5% to 10% of the obese people
who are leptin deficient. The rest of the
population are resistant to leptin’s effects.
• A more recent therapeutic approach involves
treating eating disorders as other addictions.
Some drugs used in addiction treatment have
shown promise for treating obesity.

41. Leptin deficiency

42. • The most effective procedure is the gastric
bypass. It reduces the stomach to a small
pouch which is then reconnected at a lower
point on the intestine. This limits the meal size
and the nutrient absorption in the digestive
tract.

44. Anorexia, Bulimia and Binge Eating
Disorders
Anorexia
• Anorexia nervosa is known as the “starving
disease” because the individual restricts food
intake to maintain weight at a level so low that
can be life threatening.
• If Anorexia continues long enough, it leads to
cessation of ovulation, loss of muscle mass,
heart damage and reduction in bone density.
This is more prevalent among females.

45. Bulimia
• Bulimia nervosa also involves weight control, but
the behavior is limited to bingeing and purging.
Binge eating disorder
• In this the individual frequently eats large
amounts of food during a short period of time
and they feel like they cannot control it. They are
often obese because they do not attempt to
control weight.

46. Causes
• Many of these eating disorders, especially in
the western society where more emphasis is
given on thinness and beauty has been
deemed to be an environmental cause of
these disorders.
• Other psychological problems could also
trigger disordered eating, starvation or
overeating.

47. The role of Serotonin, Dopamine and
Cannabinoids
• Imaging studies indicate that anorexia and
bulimia patients have an imbalance activity at
Serotonin receptors. These receptors are of
interest because of their role in anxiety
depression, compulsive behaviors and harm
avoidance.
• Dopamine is associated with lowering anxiety.
Because eating increases Dopamine release, this
finding lends additional support to the idea that
food restriction serves to reduce anxiety.

48. • Cannabinoid
Both anorexic and bulimic patients have larger
numbers of cannabinoid receptors in the insula
whose functions include the rewarding effects of
food and responses to hunger.