thirst and hunger

Homeostasis

The body's process of maintaining internal balance through negative feedback systems.

Osmotic Thirst

Thirst triggered by high extracellular solute concentration, such as salt intake.

Hypovolemic Thirst

Thirst triggered by low blood volume, often caused by blood loss or dehydration.

Osmosensory Neurons

Neurons in the anterior hypothalamus that detect osmotic pressure changes and regulate ADH release.

Baroreceptors

Sensors in blood vessels and the heart that detect drops in blood volume and signal the brain to initiate thirst responses.

Angiotensin II

A hormone that regulates thirst and blood pressure by acting in the subfornical organ.

Basal Metabolic Rate (BMR)

The amount of energy used to maintain body functions at rest, accounting for 75% of energy expenditure.

Glycogenesis

The process of converting glucose into glycogen for short-term energy storage in the liver.

Leptin

A hormone produced by fat cells that suppresses appetite and signals energy storage to the brain.

Ghrelin

A hunger-stimulating hormone released by the stomach, increasing before meals and decreasing after eating.

Lateral Hypothalamus (LH)

A region in the hypothalamus that stimulates hunger; lesions can cause refusal to eat.

Ventromedial Hypothalamus (VMH)

A region in the hypothalamus that suppresses hunger; lesions can cause overeating.

NPY/AgRP Neurons

Neurons that stimulate appetite and lower metabolism, leading to weight gain.

POMC/CART Neurons

Neurons that suppress appetite and increase metabolism, leading to weight loss.

Overeating Effects on Brain

Overeating leads to hypothalamic inflammation, inhibiting neurogenesis and resetting the body’s weight set point.

Prader-Willi Syndrome

A genetic disorder characterized by excessive hunger due to elevated ghrelin levels.

Anorexia Nervosa

An eating disorder marked by severe food restriction, fear of weight gain, and body image disturbances.

Bulimia Nervosa

An eating disorder characterized by binge eating followed by compensatory behaviors such as vomiting or excessive exercise.

Eating Disorders and Mental Health

90% of individuals with eating disorders suffer from depression; 30% attempt suicide.

Treatment for Obesity

Effective strategies include calorie reduction (200 kcal/day deficit), strenuous exercise (200+ min/week), and long-term lifestyle changes.

GLP-1 Receptor Agonists

A class of drugs (e.g., Ozempic, Mounjaro) used to regulate appetite and support weight loss.