Which is INCORRECT regarding nerve supply to the gut?

Correct Answer: A

Rationale: The correct answer is A because blood vessels in the gut are primarily innervated by sympathetic and parasympathetic fibers, not by enteric nerves. Enteric nerves are confined to the gastrointestinal tract itself and are responsible for regulating gut motility, secretion, and blood flow. Sympathetic innervation typically causes vasoconstriction, while parasympathetic innervation promotes vasodilation. The myenteric plexus (Auerbach's plexus) lies between the longitudinal and circular muscle layers, regulating gut motility. Parasympathetic supply to the gut is mainly through the vagus nerve (cranial nerve X) and sacral nerves (pelvic splanchnic nerves). Sympathetic supply can either be inhibitory or excitatory, but generally, sympathetic fibers are inhibitory on cholinergic postganglionic fibers in the gut.

Correct Answer: D

Rationale: Correct Answer: D - The conversion of pyruvate to acetyl-CoA is irreversible because it is catalyzed by the enzyme pyruvate dehydrogenase. This step is a key regulatory point in carbohydrate metabolism as it commits pyruvate to enter the citric acid cycle for further energy production. Reversing this step would disrupt the normal flow of metabolic pathways. Summary of other choices: A: Glucokinase is not increased in starvation; it regulates glucose uptake in the liver. B: The breakdown of glycogen is called glycogenolysis, not glycolysis which is the breakdown of glucose. C: The direct oxidative pathway involves the breakdown of glucose through glycolysis, not triose.

Correct Answer: C

Rationale: The correct answer is C: Thyroid. The thyroid gland is located at the base of the throat, just inferior to the laryngeal prominence. It is responsible for producing hormones that regulate metabolism and growth. The pituitary gland (A) is located in the brain and controls other endocrine glands. The hypothalamus (B) is also in the brain and regulates hormone production. The pineal gland (D) is located in the brain and produces melatonin. Thyroid is correct due to its anatomical location and function in hormone regulation.

Correct Answer: C

Rationale: The correct answer is C: neural. In this scenario, the student experiences the fight or flight response, which is controlled by the sympathetic nervous system. The pupil dilation, increased heart rate, and rapid breathing are all physiological responses triggered by the activation of neural pathways in response to a perceived threat or stress. The other choices are incorrect because: A: Humoral stimuli involve changes in blood levels of certain substances triggering hormone release. B: Hormonal stimuli involve the release of hormones in response to other hormones. D: Positive feedback is a mechanism that amplifies a response, not directly related to the immediate physiological responses seen in this case.

Correct Answer: C

Rationale: The correct answer is C: Oesophagus. The oesophagus is the structure leading to the stomach that carries food from the mouth to the stomach through peristalsis. The pharynx (A) is the throat cavity, the epiglottis (B) is a flap that prevents food from entering the trachea during swallowing, and the larynx (D) is the voice box. Therefore, the oesophagus is the correct answer as it specifically functions to transport food to the stomach.