Regulation of Food Intake — MCQs
The principal polypeptides that increase food intake are the following, EXCEPT:
Which of the following is NOT true about ghrelin?
All of the following are known functions of hypothalamus except
Which of these hormones activate catalytic receptors?
During starvation, which hormone level increases?
Which phase of gastric secretion is stimulated by sight and smell of food?
What percentage of gastric secretion is attributed to the cephalic phase?
Which phase of gastric secretion is stimulated by sight and smell of food?
All of the following cause the secretion of gastric juice during the cephalic phase EXCEPT:
Which hormone is secreted by the "Delta cells" of the stomach?
Regulation of Food Intake Indian Medical PG Practice Questions and MCQs
Question 1: 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 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: All of the following are known functions of hypothalamus except
- A. Temperature regulation
- B. Hypophyseal control
- C. Food intake
- D. Increase in heart rate with exercise (Correct Answer)
Explanation: ***Increase in heart rate with exercise*** - The **hypothalamus** has an indirect role in cardiovascular responses during exercise, primarily through its influence on the **autonomic nervous system** to maintain homeostasis. - However, the primary control of increased heart rate during exercise originates from the **medulla oblongata** and the **motor cortex**, which directly modulates the sympathetic nervous system to increase cardiac output. *Temperature regulation* - The **hypothalamus** contains thermoregulatory centers that monitor and adjust body temperature through mechanisms such as **sweating** and **shivering**. - This function is a fundamental aspect of maintaining **homeostasis**. *Hypophyseal control* - The **hypothalamus** directly controls the **pituitary gland** (hypophysis) by producing releasing and inhibiting hormones that regulate the secretion of pituitary hormones. - This neuroendocrine function is crucial for controlling various **endocrine axes**. *Food intake* - The **hypothalamus** plays a key role in regulating appetite and satiety, with specific nuclei like the **arcuate nucleus** integrating signals related to hunger and fullness. - This control is essential for maintaining **energy balance**.
Question 4: 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 5: 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 6: Which phase of gastric secretion is stimulated by sight and smell of food?
- A. Intestinal
- B. Cephalic (Correct Answer)
- C. Absorptive
- D. Gastric
Explanation: ***Cephalic*** - The **cephalic phase** of gastric secretion is initiated by the **sensory input** of food, such as its sight, smell, taste, or even the thought of it. - This phase involves the **vagus nerve** stimulating gastric glands to secrete acid and pepsinogen in anticipation of food arrival. *Intestinal* - The **intestinal phase** begins when partially digested food (chyme) enters the **duodenum**, either stimulating or inhibiting gastric secretion. - It primarily involves **hormonal mechanisms** like secretin and cholecystokinin (CCK) to regulate gastric emptying and secretion. *Absorptive* - The **absorptive phase** is not a common term used to describe gastric secretion. It typically refers to the **absorption of nutrients** within the small intestine after digestion. - Gastric secretion phases specifically relate to the **preparation and digestion of food in the stomach**, not its absorption. *Gastric* - The **gastric phase** is the largest phase of gastric secretion, triggered by the **presence of food in the stomach**. - This phase is stimulated by **distension of the stomach**, the presence of **peptides** and **amino acids**, and involves both neural and hormonal (gastrin) mechanisms.
Question 7: What percentage of gastric secretion is attributed to the cephalic phase?
- A. 20% (Correct Answer)
- B. 70%
- C. 10%
- D. 100%
Explanation: ***20%*** - The **cephalic phase** of gastric secretion is initiated by the sight, smell, taste, or even thought of food and accounts for approximately **20-30%** of total gastric acid secretion. - This phase is mediated by the **vagus nerve**, stimulating parietal cells (via acetylcholine) and G cells (via gastrin-releasing peptide) to release acid and gastrin, respectively. *70 %* - **70%** represents the approximate contribution of the **gastric phase** to total gastric secretion, which is the largest phase. - This phase is activated by the presence of food in the stomach, distension, and the presence of amino acids and peptides. *10%* - **10%** is a value that is too low for the cephalic phase; it typically accounts for a more significant portion of initial acid secretion. - This percentage is sometimes associated with the intestinal phase, which produces a smaller amount of acid secretion after chyme enters the duodenum. *100%* - **100%** is incorrect because gastric secretion is a complex process involving multiple phases (cephalic, gastric, intestinal), each contributing a portion of the total secretion. - Each phase has distinct stimuli and regulatory mechanisms, ensuring a coordinated digestive response.
Question 8: Which phase of gastric secretion is stimulated by sight and smell of food?
- A. Interdigestive
- B. Gastric
- C. Cephalic (Correct Answer)
- D. Intestinal
Explanation: ***Cephalic*** - The **cephalic phase** of gastric secretion is initiated by the **thought, sight, smell, or taste of food**. - This phase involves the vagus nerve stimulating the stomach to prepare for food intake, leading to increased **gastric acid and enzyme secretion** before food even reaches the stomach. *Interdigestive* - The **interdigestive phase** refers to the period between meals when the stomach is relatively inactive, primarily involved in clearing residual material. - This phase is characterized by basal or minimal gastric secretion, distinct from the active preparatory phase. *Gastric* - The **gastric phase** begins when food actually enters the stomach, causing distention and stimulating chemoreceptors. - This phase relies on local reflexes and the release of **gastrin**, intensifying the secretion initiated during the cephalic phase. *Intestinal* - The **intestinal phase** occurs when partially digested food (chyme) enters the small intestine. - This phase initially promotes some gastric secretion, but its primary role is to **inhibit gastric emptying and secretion** to allow for proper digestion and absorption in the small intestine.
Question 9: All of the following cause the secretion of gastric juice during the cephalic phase EXCEPT:
- A. Thought of food
- B. Food in mouth
- C. Sight of food
- D. Food in stomach (Correct Answer)
Explanation: ***Food in stomach*** - The presence of **food in the stomach** primarily stimulates the **gastric phase** of digestion, which occurs after the cephalic phase. - This phase involves stimuli like **stomach distension** and the presence of digested proteins, leading to further gastric juice secretion. *Food in mouth* - The taste and chewing of **food in the mouth** stimulate the **cephalic phase** through neural signals to the brainstem. - This initiates anticipatory gastric juice secretion via the vagus nerve. *Sight of food* - The **sight of food** is a powerful sensory input that triggers the **cephalic phase** of digestion. - This visual stimulus sends signals to the cerebral cortex, which then activates the vagus nerve to stimulate gastric secretion. *Thought of food* - The **thought of food**, even without direct sensory contact, can initiate the **cephalic phase**. - This cognitive stimulation reflects a conditioned reflex, where the brain anticipates a meal and prepares the digestive system, including gastric secretion.
Question 10: Which hormone is secreted by the "Delta cells" of the stomach?
- A. Cholecystokinin
- B. Gastrin-releasing peptide
- C. Somatostatin (Correct Answer)
- D. Secretin
Explanation: ***Somatostatin*** - **Delta cells (D cells)** in the stomach and pancreas secrete **somatostatin**, a potent inhibitory hormone. - Somatostatin **inhibits the release of gastrin**, histamine, secretin, cholecystokinin, and gastric acid secretion, acting as a "universal off switch." *Cholecystokinin* - **Cholecystokinin (CCK)** is primarily secreted by **I cells** in the duodenum and jejunum. - Its main functions include stimulating gallbladder contraction and pancreatic enzyme secretion. *Gastrin-releasing peptide* - **Gastrin-releasing peptide (GRP)**, also known as **bombesin**, is a neuropeptide released from **enteric neurons**. - It stimulates the release of **gastrin** from G cells. *Secretin* - **Secretin** is secreted by **S cells** in the duodenum in response to acidic chyme entering the small intestine. - Its primary role is to stimulate the pancreas to release **bicarbonate-rich fluid** to neutralize gastric acid.
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