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CLASS NOTES FOR BIOLOGICAL AND PSYCHOLOGICAL BASES OF HUNGER, Lecture notes of Biological Psychology

University of MadrasBiological Psychology

THE CLASSES ARE BY VIDYA MA'AM A GUEST LECTURER IN THE DEPARTMENT OF COUNSELLING PSYCHOLOGY

Typology: Lecture notes

2018/2019

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UNIT – 4 BIOPSYCHOLOGY OF MOTIVATION- HUNGER, EATING, SEX HORMONES &
SLEEP
EATING:
• Eating is a behaviour that is of interest to virtually everyone.
• We all do it, and most of us derive great pleasure from it.
• Most eating-related health problems in industrialized nations are associated with eating too much.
• Hunger and eating are normally triggered when the body’s energy resources fall below a prescribed optimal level, or set
point.
• The primary purpose of hunger is to increase the probability of eating, and the primary purpose of eating is to supply the body
with the molecular building blocks and energy it needs to survive and function.
DIGESTION:
•Digestion is the gastrointestinal process of breaking down food and absorbing its constituents into the body.
• As a consequence of digestion, energy is delivered to the body in three forms:
(1) lipids (fats),
(2) amino acids (the breakdown products of proteins), and
(3) glucose (a simple sugar that is the breakdown product of complex carbohydrates, that is, starches and sugars).
Energy is stored in three forms:
•fats,
•glycogen,
•proteins.
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UNIT – 4 BIOPSYCHOLOGY OF MOTIVATION- HUNGER, EATING, SEX HORMONES &

SLEEP

EATING:

  • Eating is a behaviour that is of interest to virtually everyone.
  • We all do it, and most of us derive great pleasure from it.
  • Most eating-related health problems in industrialized nations are associated with eating too much.
  • Hunger and eating are normally triggered when the body’s energy resources fall below a prescribed optimal level, or set point.
  • The primary purpose of hunger is to increase the probability of eating, and the primary purpose of eating is to supply the bodywith the molecular building blocks and energy it needs to survive and function.

DIGESTION:

  • Digestion is the gastrointestinal process of breaking down food and absorbing its constituents into the body.
  • As a consequence of digestion, energy is delivered to the body in three forms: (1) lipids (fats), (3) glucose (a simple sugar that is the breakdown product of complex(2) amino acids (the breakdown products of proteins), and carbohydrates, that is, starches and sugars). Energy is stored in three forms:
  • fats,
  • glycogen,
  • proteins.

Most relatively little as and proteins are glycogen. of the body’s energy reserves stored as fats,

  • In contrast to the cephalic and absorptive phases, the fasting phase is characterized by high blood levels of glucagon and low levels of insulin.
  • The low levels of insulin also promote the conversion of glycogen and protein to glucose. (The conversion of protein to glucose is called gluconeogenesis.)

THEORIES OF HUNGER AND EATING: SET POINTS VERSUS POSITIVE INCENTIVES

  • Most people attribute hunger to the presence of an energy deficit, and they view eating as the means by which the energy resources of the body are returned to their optimal level—that is, to the energy set point.
  • Like a thermostat All set-point systems have three components:
  1. Set-point Mechanism,
  2. Detector Mechanism,
  3. Effector Mechanism.

The set-point mechanism defines the set point, the detector mechanism detects deviations from the set point, and the effector mechanism acts to eliminate the deviations.

  • All set-point systems arecompensatory effects in the opposite direction. negative feedback systems—systems in which feedback from changes in one direction elicit
  • Negative feedback systems are common in mammals because they act to maintain environment – which is critical for mammal’s survival. homeostasis—a stable internal

GLUCOSTATIC THEORY:

  • The idea being that we become hungry when our blood glucose levels drop significantly below their set point and that webecome satiated when eating returns our blood glucose levels to their set point.
  • The various versions of this theory are collectively referred to as the glucostatic theory. LIPOSTATIC THEORY:
  • Every person has a set point for body fat, and deviations from this set point produce compensatory adjustments in the level of eating that return levels of body fat to their set point.

POSITIVE-INCENTIVE PERSPECTIVE ON HUNGER AND EATING.

  • The central assertion of this perspective, commonly referred to as positive-incentive theory, is that humans and other animals are not normally driven to eat by internal energy deficits but are drawn to eat by the anticipated pleasure of eating—theanticipated pleasure of a behaviour is called its positive-incentive value.
  • Positive-incentive perspective on eating is that eating is controlled in much the same way as sexual behaviour: We engage in sexual behaviour not we have an internal deficit but because we have evolved to crave it.
  • The factors that influence the positive incentive value of eating
  • These include the following:
  • The flavour of the food you are likely to consume.
  • What you have learned about the effects of this food either from eating it previously or from other people.
  • (^) The amount of time since you last ate, the type.

FACTORS THAT INFLUENCE WHEN WE EAT:

  • Premeal^ hunger: According to Woods, the key to understanding hunger is to appreciate that eating meals stresses the body. Before a meal, thebody’s energy reserves are in reasonable homeostatic balance; then, as a meal is consumed, there is a major homeostasis-
  • disturbing influx of fuels into the bloodstream. The body does what it can to defend its homeostasis.Mealtime hunger is caused by the expectation of food, not by an energy deficit.

FACTORS THAT INFLUENCE HOW MUCH WE EAT

  • The motivational state that causes us to stop eating a meal when there is food remaining is satiety.
  • Satiety mechanisms play a major role in determining how much we eat.

SATIETY SIGNALS: Food in the gut and glucose entering the blood can induce satiety signals, which inhibit subsequent consumption.

  1. Appetizer effect and satiety.
  2. (^) Serving size and satiety.
  3. Social influences and satiety.
  4. Feelings Of Satiety
  5. Sensory-specific satiety.

THE CONCEPT OF HYPOTHALAMIC HUNGER AND SATIETY CENTERS:

  • In the 1950s, experiments on rats seemed to suggest that eating behaviour is controlled by two different regions of the

t

  • Hypothalamus: satiety by the ventromedial hypothalamus (vmh) and feeding by the lateral hypothalamus (lh)—
  • (^) Large bilateral electrolytic lesions to the ventromedial hypothalamus produce hyperphagia (excessive eating)
  • LH feeding centre.
  • Bilateral electron.
  • (^) Lytic lesions to the lateral hypothalamus produce aphagia—a complete cessation of eating THE HUNGER AND SATIETY PEPTIDES: - CCK (Cholecystokinin) known as satiety peptides (peptides that decrease appetite). - Severalin the brain, particularly in the hypothalamus. hunger peptides (peptides that increase appetite) have also been discovered. These peptides tend to be synthesized - The most widely studied of these are neuropeptide Y, galanin, orexin-A, and ghrelin. SEROTONIN AND SATIETY: - The monoaminergic neurotransmitter serotonin is another chemical that plays a role in satiety. - Serotonin agonists (e.g., fenfluramine, dexfenfluramine, fluoxetine) have been shown to reduce hunger, eating, and bodyweight in obese humans under some conditions. HUMAN OBESITY: CAUSES, MECHANISMS, AND TREATMENTS:
  • The development of numerous cultural practices and beliefs that promote consumption has augmented the effects of evolution.
  • The key to permanent weight loss is a permanent lifestyle change.
  • (^) Exercise has many health-promoting effect.
  • However, despite the general belief that exercise is the most effective method of losing weight, several studies have shown thatit often contributes little to weight loss.

LEPTIN AND THE REGULATION OF BODY FAT:

  • Fat is more than a passive storehouse of energy; it actively releases a peptide hormone called leptin.
  • Efforts to use leptin in the treatment of human obesity have not been a total failure. TREATMENT OF OBESITY: SEROTONERGIC AGONISTS: Gastric Surgery:
  • Cases of extreme obesity sometimes warrant extreme treatment.
  • Gastric bypass is a surgical treatment for extreme obesity that involves short-circuiting the normal path of food through the digestive tract so that its absorption is reduced.

ANOREXIA NERVOSA & BULIMIA NERVOSA:

  • Anorexia nervosa is a disorder of under-consumption.
  • Bulimia amounts of food in short periods of time) followed by efforts to immediately eliminate the consumed calories from the body Nervosa. Bulimia nervosa is a disorder characterized by periods of not eating interrupted by bingeing (eating huge
  • by voluntaryIndividuals with anorexia or bulimia both tend to have distorted body images, seeing themselves as much fatter and less^ purging^ (via^ vomiting^ or^ excessive^ use of laxatives, enemas, or diuretics) or by extreme exercise.
  • attractive than they are inIn practice, many patients seem to straddle the two diagnoses and cannot readily be assigned to one or the other categories, and many patients flip-flop between the two diagnoses as their circumstances change
  • Both anorexia and bulimia are highly correlated with obsessive-compulsive disorder and depression. DEVELOPMENTAL AND ACTIVATIONAL EFFECTS OF SEX HORMONES: Hormones influence sex in two fundamentally different ways. They are:
  1. by influencing the development from conception to sexual maturity of the anatomical, physiological, and behavioural characteristics that distinguish one as female or male (2) by activating the reproduction-related behaviour of sexually mature adults

NEUROENDOCRINE SYSTEM: The endocrine glands only the organs whose primary function appears to be the release of hormones.

GLANDS:

F 09 7 The two main classes of gonadal hormones are androgens and oestrogens; F 09 7 Testosterone is the most common androgen, and oestradiol is the most common oestrogen. F 09 7 The ovaries and testes also release a third class of steroid hormones called progestins. F 09 7 The most common progestin is progesterone, which in females prepares the uterus and the breasts for pregnancy

THE PITUITARY:

  • The pituitary gland is frequently referred to as the master gland because most of its hormones are tropic hormones.
  • Tropic hormones’ primary functions is to influence the release of hormones from other glands.
  • The pituitary gland is really two glands – the posterior pituitary and anterior pituitary.
  • Female gonadal hormone levels are cyclic; male gonadal hormone levels are steady.
  • The major difference between the endocrine function of females and males is that in human females, the levels of gonadaland gonadotropic hormones go through a cycle that repeats itself every 28 days or so - Menstrual cycle.

CONTROL OF THE ANTERIOR AND POSTERIOR PITUITARY BY THE HYPOTHALAMUS.

PITUITARY

POSTERIOR ANTERIOR

PARAVENTRICULAR SUPRAOPTIC NUCLEI HYPOTHALAMIC PORTAL