the limbic brain Flashcards
How does the body use energy?
Three primary ways:
Basal Metabolism (BMR): 55% of energy is used to maintain body heat and other resting functions.
Digestion of Food: 33% of energy is used to process food.
Active Behavioral Processes: 12-13% of energy is used for non-resting behaviors.
**Stored energy: **Remaining energy is typically stored as reserves.
What is the Kleiber function for calculating Basal Metabolic Rate (BMR)?
Kleiber’s formula: Kcal/day = 70 × weight^0.75
Purpose: Estimates the energy expenditure based on body weight.
What are the primary nutrients and their energy values?
Carbohydrates: ~4 kcal per gram. Converted to glucose, the primary energy source. Stored as glycogen in liver and muscles.
Amino Acids (Proteins): ~4 kcal per gram. Basic building blocks of cells. 9 out of 20 amino acids are essential (cannot be produced by the body).
Lipids (Fats): ~9 kcal per gram. Long-term energy storage and source of glucose.
Vitamins and Minerals: Essential for bodily functions but do not provide energy. Needed for digestion, homeostasis, and cell building.
What is glucose’s role in the body?
Primary fuel: Glucose is the main source of energy for the body, derived from carbohydrates.
What is the role of appetite in maintaining homeostasis?
Variable: The body needs to maintain balance in variables like glucose or body fat.
Set-point: The desired level of a specific variable (e.g., blood glucose or body fat).
Sensor: Measures the levels of variables.
**Effector mechanisms: **Control feeding behavior, metabolism, etc.
What is the glucostat theory?
Theory (Mayer, 1954): Blood glucose levels are a primary variable that needs to be at equilibrium.
**Outcome of low glucose: **Drive to eat (to restore glucose levels).
What is the lipostatic theory?
Theory: Eating is regulated by a hypothetical body-fat set-point.
Homeostasis: The body maintains a certain level of fat for long-term energy storage.
What is the dual-centre hypothesis?
Ventromedial Hypothalamus (VMH): Lesions cause increased feeding and weight. VMH is proposed as the satiety (stop eating) center.
Lateral Hypothalamus (LH): Lesions cause reduced feeding and weight. LH is proposed as the hunger (start eating) center.
What are the problems with the dual-centre hypothesis?
James Olds’ experiments: Self-stimulation of LH did not just lead to eating but also other behaviors (e.g., drinking, fighting, mating).
Elliot Valenstein: LH stimulation leads to various behaviors, not just eating, suggesting LH is involved in motivated behaviors, not just hunger.
What hormones are involved in hunger and satiety signals?
Hunger signals (e.g., Ghrelin, Orexin): Peptide hormones from the gut, adipose tissue, and hypothalamus that increase hunger.
Satiety signals (e.g., CCK, PYY, Leptin):
Cholecystokinin (CCK): Released in response to fat and inhibits feeding.
Peptide YY (PYY): Released after food intake and inhibits eating.
Leptin: Produced by adipose tissue, interacts with receptors in the hypothalamus to reduce hunger.
What is the role of Leptin in satiety?
Leptin: Produced by fat cells, signals the brain to reduce hunger.
Deficiency: Leads to obesity, as seen in leptin-deficient mice.
Action: Binds to receptors in the hypothalamus, particularly in the ventromedial nucleus, to regulate appetite.
What is appetite as a motivational system?
**Homeostatic system: **Competing hunger and satiety signals regulate eating behavior.
Hunger signals: Lateral Hypothalamus, Ghrelin, Orexin.
Satiety signals: Ventromedial Hypothalamus, CCK, PYY, Leptin.
Does motivation to eat always depend on homeostatic mechanisms?
Non-homeostatic factors: Learned associations, taste, smell, and anticipation can drive eating even when not hungry or full.
**Anticipatory eating: **For example, babies may eat before a long night’s sleep even if not hungry.
What is anticipatory eating in rats?
Study finding: Rats eat and drink before lights go off (before sleep), even if not hungry. This is driven by an internal clock rather than by hunger.
What is cue-potentiated feeding?
Pavlovian conditioning: A cue (CS+) paired with food delivery can trigger overeating, even when the animal is satiated.
Brain involvement: The amygdala influences hypothalamic processes related to hunger.
How do learned associations influence appetite?
Learned cues: Food-specific cues (visual or auditory) can trigger feeding behavior in humans and animals, even when not hungry.
Study (Birch et al., 1989): Food-related cues enhanced eating in children.
What is the role of the mesolimbic dopamine system in eating behavior?
Study findings: Rats that are deprived of food show pleasure responses to sweet solutions, which is dopamine-mediated.
**Dopamine’s role: **Dopamine promotes the “wanting” of food, though not necessarily the “liking.”
What is the dissociation between liking and wanting in eating behavior?
**Liking: **Mediated by opioid, GABA, and cannabinoid systems in the nucleus accumbens.
Wanting: Mediated by dopamine in the mesolimbic system.
**Study findings: **Genetically altered mice with high dopamine levels “want” more food, but do not “like” it more.
What brain areas are involved in motivation to eat and drink?
Limbic system: Includes the cingulate cortex, hippocampus, amygdala, and nucleus accumbens, which integrate homeostatic and non-homeostatic signals for feeding, drinking, and temperature regulation.
What is the motivation summary in relation to appetite?
Homeostatic mechanisms: Maintain temperature, hydration, and nutrient levels.
Hypothalamus: Critical in regulating homeostasis.
Limbic system: Non-homeostatic influences (e.g., learning, emotion) on feeding behavior.
