Neural Control of Food Intake

Neural Control of Food Intake

• Neural control of food intake is a complex process involving multiple neural and chemical systems.
• Appetite is the desire to eat and select food based on hunger and interest.
• The sensation of hunger is associated with cravings, stomach contractions, and restlessness, driving the search for food.
• Appetite is a desire for food, often a specific type, aiding in food quality selection.
• Satiety occurs following a successful food quest.

Role of Hypothalamus

• The hypothalamus contains hunger and satiety centers.
• Several neuronal centers within the hypothalamus are involved in food intake regulation.
• The lateral nuclei of the hypothalamus act as a feeding center, stimulating eating and voracious eating (hyperphagia).
• Excessive eating (hyperphagia) results from increased hunger or appetite.
• Damage to the lateral hypothalamus leads to a lack of desire for food and inanition (marked weight loss, muscle weakness, and decreased metabolism).
• The ventromedial nuclei act as the satiety center, inhibiting eating when full, and electrical stimulation can cause complete satiety (aphagia).
• Damage to the ventromedial nuclei can cause voracious eating and obesity.
• Paraventricular, dorsomedial, and arcuate nuclei also have roles in regulating food intake.

Role of Hormones

• Besides neural centers, hormones play a significant role in regulating food intake.
• Gastrointestinal hormones suppress feeding.
• Increased food intake is orexigenic, decreased food intake is hypophagic.

Ghrelin

• Often called the "hunger hormone."
• Produced in the stomach.
• Ghrelin levels increase when the stomach is empty, signaling the need to eat.
• Ghrelin levels decrease after eating, reducing hunger.

Glucagon-like Peptide-1 (GLP-1)

• An incretin hormone secreted by L-cells in the small intestine.
• Released in response to food intake, particularly carbohydrates and fats.
• Plays a critical role in appetite regulation.
• Suppresses appetite, acts on hypothalamic and brainstem receptors.
• Slows stomach emptying, increasing satiety.

Cholecystokinin (CCK)

• A peptide hormone primarily produced in the small intestine.
• Released in response to nutrients (especially fats and proteins).
• Functions as a satiety signal, interacting with gut and brain receptors to reduce food consumption.
• Stimulates the release of digestive enzymes and bile to aid digestion.
• Activates vagal afferent nerves, communicating with the hypothalamus to induce feelings of fullness and reduce meal size.
• Short-term regulator, doesn't affect long-term energy balance. Effectiveness is influenced by individual factors and food composition.

Peptide YY (PYY)

• A gut hormone secreted by L-cells in the distal small intestine and colon.
• Released shortly after eating, with levels peaking 1–2 hours post-meal.
• Released based on caloric content of meal, highest with high fat content.
• Acts on the hypothalamus and brainstem to reduce appetite.
• Inhibits orexigenic NPY/AgRP neurons and activates anorexigenic POMC neurons.
• Slows gastric emptying, increasing satiety and prolonging the feeling of fullness.

Neural Centres Influencing Food Intake

• Brain centres below the hypothalamus but above the mesencephalon control the mechanical processes like chewing, swallowing, and salivation.
• Centres above the hypothalamus (amygdala, prefrontal cortex) are closely tied to the hypothalamus and play roles in appetite control, food preference, and type/quality of food consumed. Damaging these areas can affect appetite control.

Physiology Assignment

• The assignment is related to understanding the various processes of food intake regulation.
• Factors include hormonal regulation mechanisms like ghrelin, GLP-1, CCK, and PYY.
• The control of food intake is influenced by short-term and long-term physiological, psychological, and environmental factors.

Obesity Treatment

• Obesity is defined as an excess of body fat.
• A common measure of excess body fat in humans is BMI.
• Methods like skinfold measurements, bioelectrical impedance, and underwater weighing can measure body fat percentage.
• Treatment depends on decreasing energy intake and increasing energy expenditure to create an energy imbalance until the desired weight loss is achieved.

Lifestyle Changes

• Dietary modifications: Eat a balanced diet with varied nutrients.
• Sleep and stress management: Aim for 7-9 hours of sleep and engage in stress-reducing activities.
• Increased physical activity: Aim for at least 150 minutes of moderate-intensity aerobic exercise per week.

Medications

• Most of the medications help to control food intake and energy expenditure.

Surgery

• Surgical options include gastric bypass surgery, gastric banding, and sleeve gastrectomy, each targeting specific aspects of food intake or energy balance.

Conclusion, Obesity, Eating Disorders

• Hormones play important roles in regulating food intake, affecting appetite, satiety, and energy balance.
• Disruptions in hormonal signaling can lead to overeating/undereating and weight gain or loss.
• Understanding these relationships can help develop effective strategies for managing conditions like obesity, eating disorders, and metabolic diseases.

Cachexia

• Cachexia is a metabolic disorder characterized by increased energy expenditure and weight loss beyond that explained by reduced food intake.
• This condition often occurs with cancer, AIDS, and chronic inflammatory disorders.
• Central and peripheral factors contribute to cachexia, with inflammatory cytokines being important players.

Pica

• Pica is a psychological eating disorder characterized by an appetite for non-nutritive substances that persist for more than one month.
• Symptoms can include a range of problems, such as intoxication, intestinal obstructions, and other health problems, often tied to emotional/mental needs.