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Questions and Answers
What is the respiratory quotient (RQ) for a mixed diet?
What is the respiratory quotient (RQ) for a mixed diet?
- 0.8 (correct)
- 1.0
- 0.9
- 0.7
What factor does not affect the Basal Metabolic Rate (BMR)?
What factor does not affect the Basal Metabolic Rate (BMR)?
- Altitude (correct)
- Sex
- Weight
- Age
Which macronutrient requires the most oxygen for oxidation?
Which macronutrient requires the most oxygen for oxidation?
- Sugars
- Carbohydrates
- Fats (correct)
- Proteins
In individuals with diabetes, what change occurs in the RQ?
In individuals with diabetes, what change occurs in the RQ?
What is the minimum energy requirement for the body at rest called?
What is the minimum energy requirement for the body at rest called?
What effect does leptin have on feeding behavior?
What effect does leptin have on feeding behavior?
Which neuropeptides are considered orexigenic?
Which neuropeptides are considered orexigenic?
Which of the following peptides is NOT associated with increasing appetite?
Which of the following peptides is NOT associated with increasing appetite?
Where are first-order neurons that produce orexigenic neuropeptides located?
Where are first-order neurons that produce orexigenic neuropeptides located?
What is the role of cholecystokinin (CCK) in feeding regulation?
What is the role of cholecystokinin (CCK) in feeding regulation?
What does the calorimetry process measure in terms of food?
What does the calorimetry process measure in terms of food?
What is the specific heat capacity of water as stated in the content?
What is the specific heat capacity of water as stated in the content?
What is defined as 1 dietary calorie?
What is defined as 1 dietary calorie?
The respiratory quotient (RQ) is calculated using which formula?
The respiratory quotient (RQ) is calculated using which formula?
What does a higher respiratory quotient (RQ) value indicate?
What does a higher respiratory quotient (RQ) value indicate?
What does the calorimeter directly measure during the combustion of food?
What does the calorimeter directly measure during the combustion of food?
Which of the following best explains the relationship between food combustion and metabolism?
Which of the following best explains the relationship between food combustion and metabolism?
What is the main purpose of measuring the respiratory quotient (RQ)?
What is the main purpose of measuring the respiratory quotient (RQ)?
What is the primary action of Leptin in the body?
What is the primary action of Leptin in the body?
Which orexigenic peptide is identified as the most potent in stimulating food intake?
Which orexigenic peptide is identified as the most potent in stimulating food intake?
What initiates the signaling for hunger when fat stores are low?
What initiates the signaling for hunger when fat stores are low?
Which neurons does Leptin modulate to exert its anorexigenic effects?
Which neurons does Leptin modulate to exert its anorexigenic effects?
Which gene is involved in the production of the leptin hormone?
Which gene is involved in the production of the leptin hormone?
What is the effect of increased leptin levels in the body?
What is the effect of increased leptin levels in the body?
What role does Neuropeptide Y (NPY) play in energy regulation?
What role does Neuropeptide Y (NPY) play in energy regulation?
Which of the following peptides is secreted from the lateral hypothalamus and is orexigenic?
Which of the following peptides is secreted from the lateral hypothalamus and is orexigenic?
What is a characteristic feature of ob/ob mice?
What is a characteristic feature of ob/ob mice?
What contributes to leptin resistance in obese individuals?
What contributes to leptin resistance in obese individuals?
Which treatment directly targets the feeding centers in the brain?
Which treatment directly targets the feeding centers in the brain?
What is one method of non-surgical treatment for obesity that acts on the gut?
What is one method of non-surgical treatment for obesity that acts on the gut?
What is the primary function of sodium-glucose transporter 2 (SGLT2) inhibitors?
What is the primary function of sodium-glucose transporter 2 (SGLT2) inhibitors?
What type of surgical procedure involves the removal of a large part of the stomach?
What type of surgical procedure involves the removal of a large part of the stomach?
Which drug is known to decrease hunger by stimulating POMC neurons?
Which drug is known to decrease hunger by stimulating POMC neurons?
Inanition is best defined as what?
Inanition is best defined as what?
What happens to leptin levels when adipose stores are enlarged?
What happens to leptin levels when adipose stores are enlarged?
What is one potential outcome of dysregulation in leptin expression?
What is one potential outcome of dysregulation in leptin expression?
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Study Notes
Energy Available in Foods
- Nutrients that provide energy include carbohydrates, proteins, and fats.
- Stored chemical energy is released through cellular respiration.
Determining Energy Content of Food
- Calorimetry measures energy through the combustion of food, producing heat that raises water temperature.
- Specific heat of water: 4.2 J or 1 calorie (cal) raises 1 g of water by 1ºC.
- 1 dietary calorie (Cal) = 1000 calories (1 kcal).
- Energy obtained from food combustion parallels energy utilized by the body during metabolism.
Respiratory Quotient (RQ)
- RQ = Volume of CO2 produced / Volume of O2 consumed indicates which macronutrient is oxidized.
- Carbohydrates: RQ = 1 (complete oxidation).
- Fats: RQ = 0.7 (more O2 required for oxidation).
- Proteins: RQ = 0.8.
- Mixed diet RQ approximates to 0.8; RQ decreases in conditions like Diabetes Mellitus.
Basal Metabolic Rate (BMR)
- BMR represents minimum energy needed for physiological functions at rest (12-14 hrs post-meal).
- Average BMR: 2000 kcal/day; expressed as Cal/m²/hr.
- Factors affecting BMR include height, weight, surface area, sex, age, muscular exertion, and environmental temperature.
Hypothalamic Networks in Feeding Regulation
- Neuropeptidergic networks in the arcuate nucleus regulate appetite.
- Orexigenic (hunger-inducing) neuropeptides: Agouti-related protein (AgRP) and Neuropeptide Y (NPY).
- Anorexigenic (appetite-suppressing) neuropeptides: Pro-opiomelanocortin (POMC) and Cocaine-and-amphetamine-regulated transcript (CART).
- Hypothalamic second-order neurons produce orexigenic peptides (orexin) or anorexigenic factors (oxytocin, TRH, CRH).
Influential Neurotransmitters & Hormones
- Anorexigenic: α-MSH, Leptin, Serotonin, Insulin, CCK, CRH.
- Orexigenic: NPY, AgRP, MCH, Orexins, Endorphins, Cortisol, Ghrelin.
- NPY is the most potent orexigenic peptide, activated by decreased leptin levels.
Role of Leptin in Energy Regulation
- Leptin is a peptide hormone from white adipose tissue signaling energy storage levels.
- Low leptin indicates reduced fat stores, promoting hunger and energy conservation; high leptin signals increased energy expenditure and decreased hunger.
- Genes involved: ob gene (leptin production) and db gene (leptin receptor signaling).
Leptin and Obesity
- Obesity leads to leptin desensitization; weight gain is linked to leptin resistance.
- Leptin resistance causes include disrupted receptor signaling, altered leptin production, and impaired transportation across the blood-brain barrier.
- Mouse models: ob/ob mice (leptin gene mutation) and db/db mice (leptin receptor mutation).
Treatment of Obesity
- Pharmacological:
- Amphetamines to inhibit feeding.
- Bupropion (Dopamine and NE reuptake inhibitor) stimulates POMC neurons for satiety.
- GLP-1 agonists.
- SGLT2 inhibitors prevent renal glucose reabsorption.
- Orlistat reduces lipid absorption (lipase inhibitor).
- Surgical options:
- Gastric bypass, vertical sleeve gastrectomy, and gastric banding.
Inanition, Anorexia, and Cachexia
- Inanition represents the extreme opposite of obesity, indicating a state of starvation or severe weight loss.
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