Comprehensive Physiology and Regulation of Energy Balance and Appetite

Define homeostasis in the context of physiology.

The process that maintains the internal environment of the body within a narrow physiological range.

What is the primary role of the hypothalamus regarding feeding behavior?

It acts as the master regulator of homeostasis, specifically regarding energy balance and regulation.

Distinguish between satiety and hunger in terms of their signaling effects.

Satiety signals are anorexigenic (inhibit eating), while hunger signals are orexigenic (promote eating).

What is basal metabolism?

The energy used for heat production, maintenance of membrane potentials, and other life-sustaining processes.

How does the body's basal metabolic rate (BMR) respond to a significant reduction in nutrition?

The BMR will fall to conserve energy and prevent weight loss.

What is the primary energy source for the human body and brain?

Glucose.

What is the function of glycogen?

It is a complex carbohydrate used for short-term energy storage in the liver and muscles.

Define glycogenesis.

The process of converting glucose into glycogen, which requires insulin.

What is the role of insulin in energy regulation?

It regulates the conversion of glucose to glycogen and enables cells to take up glucose from the blood.

Define glycogenolysis.

The process of converting stored glycogen back into glucose for energy.

What is the function of glucagon?

It is a pancreatic hormone that regulates the conversion of glycogen back into glucose.

Where are lipids primarily stored for long-term energy?

In adipose tissue.

What is gluconeogenesis?

The conversion of fats and proteins into glucose and ketones for fuel.

Do brain cells require insulin to utilize glucose?

No, brain cells do not require insulin to use glucose.

What is the difference between Type 1 and Type 2 diabetes mellitus?

Type 1 is caused by the pancreas stopping insulin production; Type 2 is caused by reduced sensitivity to insulin.

What is the Dual-Center Hypothesis of appetite?

The theory that the hypothalamus contains two specific appetite centers: the ventromedial hypothalamus (satiety) and the lateral hypothalamus (hunger).

What is the effect of a lesion in the ventromedial hypothalamus (VMH)?

It causes overeating because the satiety center is damaged.

What is the effect of a lesion in the lateral hypothalamus (LH)?

It causes reduced eating because the hunger center is damaged.

What is the role of the arcuate nucleus in the hypothalamus?

It acts as an appetite center whose activity is governed by peripherally released feeding-related hormones.

What happens to blood glucose levels if insulin is not working properly?

Glucose remains high in the blood, leading to hyperglycemia.

Which fuel source does the brain prioritize during periods of high cognitive demand?

Glucose.

Why is obesity often difficult to treat according to metabolic studies?

Significant weight loss can trigger a persistent metabolic suppression, making it difficult to maintain a lower weight.

What is the difference between hyperglycemic and hypoglycemic states?

Hyperglycemic means too much glucose in the blood; hypoglycemic means too little glucose in the blood.

What hormones are typically released during a 'fight or flight' response to mobilize energy?

Glucagon and adrenaline (epinephrine).

Can the brain use fatty acids for energy?

No, the brain can only use glucose for energy.

What is the primary function of leptin in appetite regulation?

Leptin is a long-term satiety signal released by fat cells that informs the brain about energy reserves, decreasing appetite and increasing energy expenditure.

What happens to mice with defective leptin genes (ob/ob) or leptin receptor genes (db/db)?

They become obese because they lack the signaling required to regulate body mass and suppress appetite.

What is the role of insulin in appetite regulation?

Insulin is secreted by the pancreas in response to glucose and acts as a short-term satiety signal.

How does ghrelin influence appetite?

Ghrelin is produced by the stomach and acts as a short-term hunger signal; its levels rise during fasting and fall after a meal.

What is the function of Peptide YY (PYY) in appetite regulation?

PYY is produced by the intestines and acts as a short-term satiety signal, with levels rising rapidly after a meal.

Which neurons in the arcuate nucleus are activated by leptin to suppress appetite?

Neurons that release POMC and CART peptides.

What are POMC and CART peptides considered in terms of appetite?

They are anorexigenic peptides, meaning they act as satiety signals to diminish appetite.

Which neurons are activated to stimulate appetite and reduce metabolism?

Neurons that release NPY and AgRP.

What are NPY and AgRP peptides considered in terms of appetite?

They are orexigenic peptides, meaning they act as hunger signals.

How does ghrelin affect NPY/AgRP neurons?

Ghrelin stimulates NPY/AgRP neurons, which increases appetite (anorexigenic effect).

How do POMC/CART neurons affect NPY/AgRP neurons?

POMC/CART neurons inhibit NPY/AgRP neurons, which leads to a decrease in appetite.

What is the effect of THC (cannabis) on appetite-regulating hormones?

THC can increase ghrelin levels and NPY/AgRP activity while reducing POMC neuron activity, leading to increased appetite.

What is the role of GLP-1 in appetite regulation?

GLP-1 is a short-term satiety hormone produced by the intestines that signals the body is full.

What are the physiological effects of GLP-1 receptor agonists?

They increase insulin secretion, inhibit glucagon secretion, lower blood sugar, slow gastric emptying, and promote weight loss.

How do GLP-1 receptor agonists affect food cravings?

By acting on the ventral tegmental area and nucleus accumbens, they decrease dopamine release in response to high-reward foods, reducing the 'wanting' or drive to seek food.

Why is obesity considered difficult to treat?

The body has multiple, redundant systems for energy management that are optimized for storing energy and actively fight against weight loss.

List four common clinical approaches to treating obesity.

1. Diet and exercise (lifestyle change), 2. GLP-1 agonists, 3. Liposuction, 4. Bariatric procedures.

Define Anorexia nervosa.

A syndrome characterized by severe restriction of energy intake, intense fear of gaining weight, and distorted body image.

Define Bulimia nervosa.

A syndrome marked by recurrent episodes of bingeing combined with a lack of control and compensatory purging behaviors.

Define Binge eating disorder.

A syndrome marked by recurrent binge eating episodes and a sense of lack of control.

What are common treatments for eating disorders?

Family-based therapy, cognitive behavioral therapy (CBT), nutritional counseling, and medications such as SSRIs.

What is the effect of insulin on POMC/CART neurons?

Insulin activates POMC/CART neurons, promoting satiety.

What is the effect of insulin on NPY/AgRP neurons?

Insulin inhibits NPY/AgRP neurons, suppressing hunger.

Where are GLP-1 receptors located in the brain?

They are found throughout the brain, including the hippocampus, cortex, hypothalamus, and cerebellum.

What are two examples of FDA-approved GLP-1 receptor agonists?

Ozempic and Wegovy.

What is the primary difference between orexigenic and anorexigenic peptides?

Orexigenic peptides stimulate appetite, while anorexigenic peptides suppress appetite.