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What initiates a long reflex in the digestive system?

A.

Release of hormones from the pancreas

B.

Local distension of the stomach

C.

Movement of food into the small intestine

D.

External stimuli such as the sight or smell of food

Answer and Explanation

The Correct Answer is D

 What initiates a long reflex in the digestive system?

  1. Release of hormones from the pancreas
  2. Local distension of the stomach
  3. Movement of food into the small intestine
  4. External stimuli such as the sight or smell of food

Correct answer: D

A. Release of hormones from the pancreas: Pancreatic hormones like insulin and glucagon regulate systemic glucose metabolism rather than initiating gastrointestinal long reflexes. They respond to absorbed nutrients in the blood. They do not trigger the initial neural phases of digestion.

B. Local distension of the stomach: This mechanical stimulus typically triggers short reflexes mediated by the enteric nervous system within the gut wall. While it can involve long reflexes, it is primarily a local sensory input. It occurs after ingestion has commenced.

C. Movement of food into the small intestine: This process triggers the intestinal phase of gastric regulation, primarily involving the enterogastric reflex. While this involves long pathways, it is a response to chyme. It does not initiate the digestive sequence.

D. External stimuli such as the sight or smell of food: These sensory inputs trigger the cephalic phase of gastric secretion via the vagus nerve. This long reflex originates in the central nervous system before food enters the stomach. It prepares the stomach for digestion.


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Related Questions

Correct Answer is A

Explanation

A. Larynx:The glottis consists of the vocal apparatus and the space between the vocal folds. It serves as the entrance to the lower respiratory tract. It is protected by the epiglottis during the act of swallowing.

B. Pharynx:This is a muscular funnel that serves as a common pathway for both the digestive and respiratory systems. The glottis is a specific structure located within the larynx, which sits inferior to the oropharynx. It is not the pharynx.

C. Esophagus:The opening to this muscular tube is the upper esophageal sphincter, located posterior to the larynx. The glottis leads to the trachea, while the esophagus leads to the stomach. These are distinct anatomical pathways.

D. Nasal cavity:This cavity is located superior to the oral cavity and connects to the nasopharynx via the choanae. The glottis is located much further down in the neck. There is no direct anatomical connection between them.

Correct Answer is C

Explanation

A. They close off the nasopharynx:The closure of the nasopharynx is performed by the elevation of the soft palate and uvula during the pharyngeal phase. This occurs before the bolus enters the esophagus. It is a muscular, not a glandular, function.

B. They produce enzymes for digestion:The esophagus is a conduit and does not participate in chemical digestion. No significant digestive enzymes are secreted by its mucosa. Its primary function is the rapid transport of the bolus to the stomach.

C. They lubricate the bolus to reduce friction:Esophageal glands secrete mucus that coats the luminal wall and the food bolus. This lubrication is essential for smooth peristaltic transit and protects the mucosa from mechanical abrasion. It facilitates an efficient, low-resistance passage.

D. They control the lower esophageal sphincter:The lower esophageal sphincter is a physiological high-pressure zone controlled by smooth muscle tone and vagal innervation. Glandular secretions do not influence the contraction or relaxation of this sphincter. It is regulated neurally and hormonally.

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