Chapter 3: Hunger, Satiety, and the Digestive System

Vocabulary flashcards covering human digestion, hunger, satiety mechanisms, hormones, and GI tract anatomy based on Chapter 3 lecture notes.

Hunger

The non-specific physiological drive for food that occurs when the body senses a need to eat, which can be satisfied by a variety of foods.

Appetite

The psychological desire to consume specific foods, which is triggered by environmental cues.

Hypothalamus

The region of the brain responsible for prompting us to seek food by integrating signals from GI nerve cells, hormones, and nutrient levels.

Feeding Center

A cluster of nerve cells in the hypothalamus whose stimulation triggers feelings of hunger.

Satiety Center

A cluster of nerve cells in the hypothalamus that inhibits feeding center cells and prompts us to stop eating.

Hormones

Chemical messenger molecules secreted into the bloodstream by endocrine glands that bind to target cell receptors to trigger specific responses.

Insulin

A hormone produced by the pancreas that lowers blood glucose levels by enabling cells to take up glucose from the bloodstream for energy.

Glucagon

A hormone produced by the pancreas that raises blood glucose levels by signaling the liver to break down stored glycogen into glucose.

Ghrelin

A hunger hormone produced by the stomach that increases before meals and stimulates the hypothalamus to prompt eating.

Cholecystokinin (CCK)

A hormone produced in the small intestine that stimulates the satiety center in response to food entry and signals the gallbladder to contract.

Leptin

A protein hormone produced by adipose tissue that acts on the hypothalamus to suppress hunger and increase metabolism over time.

Satiety Value

The capacity of a food to sustain fullness; highest in protein-rich foods, followed by fat, bulky fiber-rich foods, and solid foods over semisolid foods.

Cephalic Phase of Digestion

The preliminary preparation phase during which hunger and appetite trigger the nervous system to release digestive juices prior to food consumption.

Digestion

The process by which consumed foods are broken down into their smaller component molecules through mechanical and chemical means.

Absorption

The physiological process by which the products of digestion move through the intestinal wall into the blood or lymphatic system.

Elimination

The process of removing undigested portions of food and waste products from the body as feces.

Gastrointestinal (GI) Tract

The continuous organ path through which food travels, consisting of the mouth, pharynx, esophagus, stomach, small intestine, and large intestine.

Accessory Organs

Organs that assist with GI tract processing by providing digestive secretions, including the salivary glands, liver, gallbladder, and pancreas.

Sphincters

Rings of muscle located along the GI tract that open in response to nerve signals to regulate the flow of food between organs.

Mechanical Digestion

The physical breakdown of food into smaller particles through actions such as mastication in the mouth and churning in the stomach.

Chemical Digestion

The enzymatic breakdown of complex nutrient molecules into simple units that can be absorbed by the body.

Saliva

A fluid mixture of water, mucus, enzymes, and other chemicals secreted by salivary glands that moistens food, binds particles, and begins carbohydrate digestion.

Salivary Amylase

An enzyme produced by the salivary glands that initiates the chemical breakdown of carbohydrates in the mouth.

Lingual Lipase

An enzyme secreted by cells on the tongue during chewing that begins the chemical breakdown of lipids in the mouth.

Enzymes

Protein compounds that catalyze chemical reactions to induce structural changes and accelerate bodily processes.

Epiglottis

A flap of tissue that closes over the trachea during swallowing to ensure food enters the esophagus rather than the airway.

Peristalsis

Rhythmic, wave-like muscular contractions that propel food and chyme along the gastrointestinal tract.

Gastrin

A hormone secreted by the stomach that prepares it to receive food by stimulating the release of acid and digestive enzymes.

Gastric Juice

An acidic fluid secreted by the stomach containing hydrochloric acid, pepsin, gastric lipase, and mucus.

Pepsin

An enzyme in gastric juice that initiates protein digestion in the stomach.

Gastric Lipase

An enzyme present in gastric juice that digests a portion of lipids in the stomach.

Chyme

The liquid mixture of partially digested food and gastric juices produced by the stomach's mixing and churning actions.

Pyloric Sphincter

The muscular valve regulating the release of chyme from the stomach into the small intestine.

Small Intestine

The primary site of digestion and nutrient absorption, measuring about $20\text{ feet}$ in length and comprising the duodenum, jejunum, and ileum.

Ileocecal Valve

The muscular sphincter connecting the ileum of the small intestine to the large intestine.

Large Intestine

The tubelike structure framing the small intestine—comprising the cecum, colon, rectum, and anal canal—that reabsorbs water, salts, and vitamins and compacts waste into feces.

GI Flora

Beneficial bacterial populations living in the large intestine that digest food residues, ferment fibrous wastes to produce vitamins, and inhibit harmful pathogen growth.

Probiotic Foods

Foods containing live beneficial bacteria (such as Lactobacillus and Bifidobacterium) that temporarily adhere to the intestinal wall to support health.

Prebiotic Foods

Nondigestible food components (such as inulin and fructo-oligosaccharides) that nourish and stimulate the growth or activity of probiotics.

Pancreatic Bicarbonate

An alkaline secretion produced by the pancreas that neutralizes acidic chyme as it enters the small intestine.