Hunger notes

Hunger and Thirst

Introduction

Fundamental Needs for Survival:

• Hunger and thirst.

Israel Kamakawiwoʻole - ‘Izzy’

• Career Overview: Iconic cover of ‘Somewhere Over the Rainbow’, reached #1 on the German singles chart in 2010.

• Honors: Hawai'i State Flag flown at half-staff at his funeral, a unique honor for a private citizen.

• Physical Struggles: Struggled with obesity, weighing up to 757 pounds.

• Death: Passed away at age 38 from heart failure in 1997.

  

Homeostasis and Thirst Mechanisms

Negative Feedback Systems

• Definition: Main mechanisms for homeostasis.

• Behavioral Response: Actions like eating and drinking occur when deviating from a set point.

Thirst Types

• Osmotic Thirst: Triggered by high extracellular solute concentration.

• Hypovolemic Thirst: Triggered by low extracellular/intravascular volume.

  

Mechanisms of Hypovolemic Thirst

• Detection: Baroreceptors in blood vessels and heart sense decreased water volume.

• Response: Brain activates thirst and salt craving; arteries constrict to elevate blood pressure.

  

Hormonal Response

• Vasopressin: Released during hypovolemia; constricts blood vessels and reduces urine output.

  

• Angiotensin Cascade Process: Low blood volume triggers renin release from kidneys, producing angiotensin II, causing blood vessel constriction and stimulating drinking.

  

Brain Control of Drinking

• Mechanism: Angiotensin II acts in the subfornical organ, signaling brain areas for drinking behavior.

  

Osmotic Thirst Mechanism

• Process: Osmosensory neurons in the anterior hypothalamus respond to increased blood osmotic pressure. Na+ channels open as membranes shrink; neurons activate pituitary to release ADH.

  

Dehydration & Rehydration Summary

• Increased blood osmolarity prompts ADH release, leading to thirst and dry mouth. Drinking water rehydrates blood and reduces salivation.

  

Hunger Awareness

Cultural Quotations: Complexities of managing hunger.

Dieting Challenges

• Metabolism Adjustment: Energy expenditure declines when dieting, reducing basal metabolic rate (BMR). Longevity studies show restricted food intake may benefit rats but are uncertain for humans.

Obesity and Metabolism

• BMR: Energy needed for basic functions, comprising 75% of daily energy for sedentary students; genetics also play a role.

Energy Storage and Utilization

• Primary Energy Source: Glucose; glycogen serves as short-term storage.

• Metabolic Rate Insights: Peaks in infancy, slows in youth, stabilizes until age 60, then declines.

Food Intake Regulation

• Neurotransmitter Influences: Brain signals (NPY, a-MSH) regulate hunger and satiety, influenced by hormones and nutritional status.

Leptin and Ghrelin

• Leptin: Produced by fat cells; informs the brain about body fat. Resistance leads to obesity.

• Ghrelin: An appetite stimulant, elevated during fasting, low post-eating; dysregulated in Prader-Willi syndrome.

Hypothalamus and Appetite Control

• Dual Functionality: Two neuron types exist; one stimulates appetite (NPY/AgRP) and the other inhibits it (POMC/CART).

Obesity Effects on Brain

• Consequences of Overeating: Leads to hypothalamic inflammation, inhibiting neurogenesis and resetting hunger signals.

Eating Disorders

Anorexia Nervosa

• Criteria: Refusal to maintain body weight, intense fear of weight gain; highest mortality rate among psychiatric disorders.

Bulimia

• Criteria: Characterized by recurrent binge eating and inappropriate behaviors to counter it.

Co-occurrence with Other Disorders

• High anxiety and depression rates associated with anorexia and bulimia; significant suicide rates among afflicted individuals.

Children and Eating Disorders

• Survey reveals concerning rates of dieting and disordered eating behaviors among students in grades 5 to 8.

Treatment of Obesity (Effective Strategies)

Eating Habits:

• Creating a caloric deficit of 200 calories/day requires lifestyle changes and monitoring.

Exercise:

• Engaging in more than 200 minutes of strenuous aerobic activity weekly is effective combined with dietary changes.

New Drug Treatments

• GLP-1 receptor agonists: Drugs like Mounjaro and Ozempic show significant long-term weight loss effects by modulating appetite and metabolic responses.