Gastric Secretions: Cephalic and Gastric Phases

These flashcards cover key terms and concepts related to gastric secretions, focusing on the cephalic and gastric phases, their stimuli, mechanisms, and regulatory hormones.

Cephalic Phase

The initial phase of gastric secretion triggered by the sight, thought, smell, or taste of food, accounting for about one-third of gastric juice production.

Gastric Phase

The phase of gastric secretion that occurs when food enters the stomach and stretches its walls, accounting for about two-thirds of gastric juice production.

Stimuli for Cephalic Phase

Includes the sight, thought, smell, and taste of food, which stimulate gastric juice production before food enters the stomach.

Hydrochloric Acid (HCl)

A strong acid produced by parietal cells in the stomach, crucial for digestion and maintaining low pH.

Pepsinogen

The inactive form of the proteolytic enzyme pepsin, secreted by chief cells and activated by acidic conditions.

Gastrin

A hormone secreted by G cells in response to partially digested proteins, stimulating gastric acid secretion and pepsinogen release.

Somatostatin

A hormone that inhibits gastric acid secretion and gastrin release, especially when there is a high concentration of protons.

Vagus Nerve

The nerve that innervates the stomach, stimulating gastric secretions through parasympathetic pathways.

G cells

Endocrine cells located in the gastric glands that secrete the hormone gastrin.

D cells

Cells located in the gastric mucosa that secrete somatostatin to regulate gastric secretion.

Mucosal Barrier

A protective layer in the stomach composed of mucus and bicarbonate that prevents damage from gastric acid and pepsin.

Enteric Nervous System

A part of the autonomic nervous system that controls the functions of the gastrointestinal system.

Acidic Chyme

Partially digested food mixed with gastric juices that enters the small intestine.

Proton Pump

A protein pump located on parietal cells that secretes protons into the stomach, facilitating the production of hydrochloric acid.

Vago-Vagal Reflex

A reflex involving both afferent and efferent fibers of the vagus nerve, regulating gastric secretions in response to stomach distension.

Intrinsic Factor

A glycoprotein secreted by parietal cells necessary for the absorption of vitamin B12 in the intestine.

What is the approximate contribution of the cephalic phase to total gastric juice production?

About one-third.

What types of sensory input trigger the cephalic phase?

The sight, thought, smell, or taste of food.

What is the approximate contribution of the gastric phase to total gastric juice production?

About two-thirds.

What physical event in the stomach initiates the gastric phase?

When food enters and stretches its walls.

What is the chemical nature of Hydrochloric Acid (HCl) in the stomach?

It is a strong acid.

Which specific cells in the stomach are responsible for producing Hydrochloric Acid (HCl)?

Parietal cells.

What is a crucial function of Hydrochloric Acid (HCl) besides digestion?

Maintaining a low pH.

What active enzyme is Pepsinogen normally converted into?

Pepsin.

What type of enzyme is pepsin?

A proteolytic enzyme (breaks down proteins).

What kind of cells secrete Pepsinogen?

Chief cells.

What environmental condition is necessary for the activation of Pepsinogen?

Acidic conditions.

What specific type of cells secrete Gastrin?

G cells.

What substance primarily stimulates the release of Gastrin?

Partially digested proteins.

What are the two main gastric secretions whose release is stimulated by Gastrin?

Gastric acid and pepsinogen.

What is the primary action of Somatostatin on gastric secretion?

It inhibits gastric acid secretion and gastrin release.

What specific chemical concentration triggers the release of Somatostatin?

A high concentration of protons (H^+).

What type of cells secrete Somatostatin?

D cells.

What part of the nervous system is the Vagus Nerve associated with in stimulating gastric secretions?

Parasympathetic pathways.

What does the Vagus Nerve do by 'innervating the stomach'?

It supplies nerve fibers to control its functions, including secretions.

What are the two primary components of the stomach's mucosal barrier?

Mucus and bicarbonate.

What is the main protective role of the gastric mucosal barrier?

It prevents damage from gastric acid and pepsin.

What specific body system's functions does the Enteric Nervous System control?

The gastrointestinal system.

The Enteric Nervous System is a division of what larger nervous system?

The autonomic nervous system.

What does Acidic Chyme consist of?

Partially digested food mixed with gastric juices.

Where does Acidic Chyme typically go after leaving the stomach?

It enters the small intestine.

On which specific cells is the Proton Pump located?

Parietal cells.

What ion is secreted into the stomach by the Proton Pump?

Protons (H^+).

The secretion of protons by the Proton Pump facilitates the production of what important gastric substance?

Hydrochloric acid.

What types of vagus nerve fibers are involved in the Vago-Vagal Reflex?

Both afferent and efferent fibers.

What is the primary stimulus for the Vago-Vagal Reflex?

Stomach distension.

What specific physiological activity does the Vago-Vagal Reflex regulate?

Gastric secretions.

What is the chemical classification of Intrinsic Factor?

A glycoprotein.

Which cells in the stomach secrete Intrinsic Factor?

Parietal cells.

What essential vitamin's absorption is dependent on Intrinsic Factor?

Vitamin B12.

Where does the absorption of vitamin B12, facilitated by Intrinsic Factor, primarily occur?

In the intestine.