Hunger and Satiety Regulation — MCQs
Orexins, which control appetite and food intake, are secreted from neurons located in:
Which of the following is NOT true about ghrelin?
Appetite is stimulated by all except
Which of the following inhibits appetite by counteracting the effects of neuropeptide Y?
The principal polypeptides that increase food intake are the following, EXCEPT:
Which of these hormones activate catalytic receptors?
Insulin secretion is normally stimulated by -
During starvation, which hormone level increases?
On insulin administration, what change is expected in the extracellular fluid (ECF)?
The primary hormone secreted by duodenal cells in response to dietary fats and proteins is:
Hunger and Satiety Regulation Indian Medical PG Practice Questions and MCQs
Question 1: Orexins, which control appetite and food intake, are secreted from neurons located in:
- A. Lateral hypothalamus (Correct Answer)
- B. Pons
- C. Adrenal medulla
- D. Central hypothalamus
Explanation: ***Lateral hypothalamus*** - The **lateral hypothalamus** contains neurons that produce **orexins** (also known as hypocretins), which are critical neuropeptides involved in the **regulation of appetite, wakefulness, and arousal**. - Stimulation of these orexin-producing neurons leads to feelings of **hunger and increased food intake**, playing a key role in energy homeostasis. *Pons* - The **pons** is a part of the brainstem primarily involved in relaying sensory information, regulating breathing, and sleep. - It does not contain the primary neurons responsible for secreting **orexins** related to appetite control. *Adrenal medulla* - The **adrenal medulla** is part of the adrenal gland and primarily secretes **catecholamines** (epinephrine and norepinephrine) in response to stress. - It has no role in the production or secretion of **orexins** or direct control of appetite. *Central hypothalamus* - While the hypothalamus is crucial for appetite regulation, the term "central hypothalamus" is not a specific anatomical region where orexin-producing neurons are primarily located. - The **arcuate nucleus** in the hypothalamus is involved in appetite regulation by producing other peptides like NPY/AgRP and POMC/CART, but orexins originate from the lateral hypothalamus.
Question 2: Which of the following is NOT true about ghrelin?
- A. Has anorexic effect (Correct Answer)
- B. Stimulates growth hormone release
- C. Secreted by gastric fundus cells
- D. Increases gastric motility
Explanation: ***Has anorexic effect*** - Ghrelin is known as the **"hunger hormone"** because it stimulates appetite and has an **orexigenic effect**, meaning it increases food intake. - Therefore, stating that it has an **anorexic effect** (reduces appetite) is incorrect. *Stimulates growth hormone release* - Ghrelin is a **natural ligand** for the **growth hormone secretagogue receptor (GHSR)**. - This binding leads to the stimulation of **growth hormone (GH)** release from the pituitary gland. *Secreted by gastric fundus cells* - The primary source of ghrelin in the body is the **P/D1 cells** found in the mucosa of the **gastric fundus**. - Smaller amounts are also produced in the small intestine, pancreas, and hypothalamus. *Increases gastric motility* - Ghrelin is involved in regulating stomach function and can **increase gastric motility** and acid secretion. - This action helps to prepare the digestive system for incoming food.
Question 3: Appetite is stimulated by all except
- A. Neuropeptide Y
- B. Agouti related peptide
- C. Melanocyte concentrating hormone
- D. Melanocyte stimulating hormone (Correct Answer)
Explanation: ***Melanocyte stimulating hormone*** - **Alpha-melanocyte stimulating hormone (α-MSH)** is a catabolic hormone that acts to reduce appetite and increase energy expenditure. - It is an **anorexigenic peptide** that suppresses feeding by binding to central melanocortin receptors, primarily MC4R. *Neuropeptide Y* - **Neuropeptide Y (NPY)** is a potent **orexigenic peptide** that stimulates appetite and food intake. - It plays a crucial role in regulating energy balance and is increased during fasting states. *Agouti related peptide* - **Agouti-related peptide (AgRP)** is a strong **orexigenic peptide** that increases food intake. - It acts as an **antagonist** at the MC3R and MC4R melanocortin receptors, counteracting the appetite-suppressing effects of α-MSH. *Melanocyte concentrating hormone* - **Melanin-concentrating hormone (MCH)** is an **orexigenic neuropeptide** that stimulates feeding behavior. - It is primarily expressed in the lateral hypothalamus and plays a significant role in promoting appetite and weight gain.
Question 4: Which of the following inhibits appetite by counteracting the effects of neuropeptide Y?
- A. Orexins
- B. Leptin (Correct Answer)
- C. Neuropeptide Y
- D. Ghrelin
Explanation: ***Leptin*** - **Leptin** is a hormone primarily produced by **adipose tissue** that signals satiety to the brain, effectively counteracting the appetite-stimulating effects of neuropeptide Y. - It acts on receptors in the **hypothalamus** to reduce food intake and increase energy expenditure, thereby inhibiting appetite. *Orexins* - **Orexins** (also known as hypocretins) are **neurotransmitters** involved in regulating **wakefulness** and appetite. - Their primary role related to appetite is typically to **stimulate hunger** and food seeking behavior, rather than inhibiting it. *Neuropeptide Y* - **Neuropeptide Y (NPY)** is a potent **orexigenic peptide**, meaning it **stimulates appetite** and food intake. - It promotes the consumption of carbohydrates and is a key mediator of hunger signals in the brain through its action on the **hypothalamus**. *Ghrelin* - **Ghrelin** is a hormone produced mainly in the **stomach** that acts as a strong **appetite stimulant**. - It is often referred to as the "**hunger hormone**" and its levels rise before meals, signaling the brain to initiate food seeking.
Question 5: The principal polypeptides that increase food intake are the following, EXCEPT:
- A. Neuropeptide-Y
- B. Orexin-A
- C. Endocannabinoid
- D. Leptin (Correct Answer)
Explanation: ***Leptin*** - **Leptin** is a hormone primarily produced by adipocytes (fat cells) that acts to **decrease food intake** and increase energy expenditure, signaling satiety to the brain. - High levels of leptin typically indicate sufficient stored fat, leading to a reduction in appetite and an increase in metabolism to maintain **energy homeostasis**. *Neuropeptide-Y* - **Neuropeptide-Y (NPY)** is a potent **orexigenic peptide** produced in the hypothalamus that directly stimulates food intake, especially carbohydrate consumption. - It plays a crucial role in the central regulation of appetite and **energy balance**, increasing hunger in response to energy deficits. *Orexin-A* - **Orexin-A** (also known as hypocretin-1) is a neuropeptide produced in the hypothalamus that strongly promotes **wakefulness** and **food-seeking behavior**. - It enhances appetite and food intake, particularly palatable foods, and is involved in the overall regulation of the **sleep-wake cycle** and reward system. *Endocannabinoid* - The **endocannabinoid system**, particularly through receptors like CB1, plays a significant role in stimulating appetite and **rewarding aspects of eating**. - Activation of this system by endocannabinoids such as **anandamide** and **2-arachidonoylglycerol (2-AG)** increases hunger and motivates food consumption.
Question 6: Which of these hormones activate catalytic receptors?
- A. All of these
- B. Leptin
- C. GH
- D. IGF1 (Correct Answer)
Explanation: ***Correct: IGF1*** - **IGF-1** binds to the **IGF-1 receptor (IGF-1R)**, which is a **receptor tyrosine kinase (RTK)** with **intrinsic catalytic activity** [1]. - Upon IGF-1 binding, the receptor undergoes **autophosphorylation** and directly phosphorylates intracellular substrates through its own tyrosine kinase domain [2]. - This qualifies as a **true catalytic receptor** because the enzymatic activity is intrinsic to the receptor itself [3]. *Incorrect: Leptin* - Leptin binds to the **leptin receptor (Ob-R)**, which is a member of the **cytokine receptor family**. - This receptor **lacks intrinsic enzymatic activity** and instead signals through **associated Janus kinases (JAKs)** via the JAK-STAT pathway. - Since the catalytic activity comes from associated proteins (JAKs) rather than the receptor itself, this is **not classified as a catalytic receptor**. *Incorrect: GH* - **Growth Hormone (GH)** binds to the **GH receptor**, another member of the cytokine receptor superfamily. - Like the leptin receptor, the GH receptor **does not have intrinsic catalytic activity** but relies on associated JAKs for signal transduction via the JAK-STAT pathway. - This is **not a catalytic receptor** because the enzymatic function is provided by associated kinases, not the receptor itself. **Key Distinction:** - **Catalytic receptors** = Receptors with intrinsic enzymatic activity (e.g., receptor tyrosine kinases, receptor serine/threonine kinases) [1], [3] - **Cytokine receptors** = Receptors that recruit associated kinases but lack intrinsic catalytic domains
Question 7: Insulin secretion is normally stimulated by -
- A. GLP-1 (Correct Answer)
- B. GLP-2
- C. α-adrenergic receptors
- D. VIP
Explanation: ***GLP-1*** - **Glucagon-like peptide-1 (GLP-1)** is an **incretin hormone** that stimulates glucose-dependent insulin secretion from pancreatic beta cells. - It also **suppresses glucagon secretion**, slows gastric emptying, and promotes satiety, all contributing to blood glucose regulation. *GLP-2* - **Glucagon-like peptide-2 (GLP-2)** primarily affects the **gastrointestinal tract**, promoting mucosal growth and nutrient absorption. - It does not directly stimulate **insulin secretion**. *α-adrenergic receptors* - Activation of **α-adrenergic receptors** on pancreatic beta cells by catecholamines like adrenaline and noradrenaline actually **inhibits insulin secretion**. - This response is part of the **stress response**, prioritizing glucose availability for vital organs. *VIP* - **Vasoactive intestinal peptide (VIP)** is a **neuropeptide** that acts as a potent vasodilator and stimulates intestinal water and electrolyte secretion. - While it has some effects on metabolism, it is not a primary or direct stimulator of **insulin secretion** under normal physiological conditions.
Question 8: During starvation, which hormone level increases?
- A. Leptin
- B. MSH
- C. Insulin
- D. Ghrelin (Correct Answer)
Explanation: ***Ghrelin*** - **Ghrelin** is often referred to as the "hunger hormone" because its levels typically rise during fasting or periods of starvation. - It stimulates **appetite** and signals the brain to increase food intake, playing a crucial role in energy balance. *Leptin* - **Leptin** is a hormone produced by **adipose tissue** that signals satiety and helps regulate long-term energy balance. - During starvation, **leptin levels typically decrease** as fat stores are depleted, which further increases appetite and reduces energy expenditure. *MSH* - **Melanocyte-stimulating hormone (MSH)** is involved in skin pigmentation and appetite regulation, but its levels do not primarily increase in response to starvation. - While MSH can influence appetite, it is often seen to decrease appetite when present in higher concentrations, which is counterintuitive during starvation. *Insulin* - **Insulin** is a hormone produced by the **pancreas** that helps regulate blood glucose levels by promoting glucose uptake into cells. - During starvation, blood glucose levels decrease, leading to a **reduction in insulin secretion** to preserve glucose for vital organs like the brain.
Question 9: On insulin administration, what change is expected in the extracellular fluid (ECF)?
- A. Hypoglycemia (Correct Answer)
- B. Hyperkalemia
- C. Hyponatremia
- D. Hypocalcemia
Explanation: **Hypoglycemia (Correct Answer)** - Insulin promotes the uptake of **glucose** from the ECF into cells, primarily muscle and adipose tissue - This action leads to a decrease in ECF **glucose concentration**, resulting in **hypoglycemia** if insulin levels are excessive or glucose intake is insufficient - This is the primary and most significant change in ECF composition after insulin administration *Hyperkalemia (Incorrect)* - Insulin actually stimulates the cellular uptake of **potassium**, moving it from the ECF into the intracellular fluid - Therefore, insulin administration typically causes **hypokalemia**, not hyperkalemia - This effect is sometimes used therapeutically to treat hyperkalemia by driving potassium into cells *Hyponatremia (Incorrect)* - Insulin primarily affects **glucose** and **potassium** metabolism and does not directly cause changes in sodium concentration in the ECF - **Hyponatremia** would be more associated with altered water balance or disorders of kidney function, not direct insulin effects - Sodium homeostasis is regulated by the renin-angiotensin-aldosterone system and ADH *Hypocalcemia (Incorrect)* - Insulin has no direct effect on **calcium** levels or its regulation in the ECF - **Calcium homeostasis** is primarily regulated by parathyroid hormone (PTH), vitamin D, and calcitonin, independent of insulin action - Changes in calcium concentration are not expected with insulin administration
Question 10: The primary hormone secreted by duodenal cells in response to dietary fats and proteins is:
- A. Secretin
- B. Gastrin
- C. CCK (Correct Answer)
- D. Motilin
Explanation: ***Correct Answer: CCK (Cholecystokinin)*** - **Cholecystokinin (CCK)** is primarily released from the **duodenal I-cells** in response to the presence of **fats and proteins** in the chyme entering the duodenum. - Its main functions include stimulating **gallbladder contraction** (releasing bile for fat emulsification) and **pancreatic enzyme secretion** (for nutrient digestion). *Incorrect: Secretin* - **Secretin** is primarily released in response to **acidic chyme** entering the duodenum, not directly by fats and proteins. - Its main roles are to stimulate the pancreas to release **bicarbonate-rich fluid** to neutralize gastric acid and to inhibit gastric acid secretion. *Incorrect: Gastrin* - **Gastrin** is secreted by **G-cells** in the stomach and duodenum, primarily in response to food (especially proteins) and vagal stimulation. - Its main function is to stimulate **gastric acid secretion** by parietal cells, not directly to dietary fats and proteins as a primary duodenal response. *Incorrect: Motilin* - **Motilin** is released from the small intestine during the **interdigestive period** (when fasting). - It plays a key role in initiating the **migrating motor complex (MMC)**, which sweeps undigested food and bacteria from the stomach and small intestine into the colon.
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