Chapter 3 - The Human Body Flashcards
Appetite
Psychological desire to consume specific foods
Hunger
Physiological drive for food
Anorexia
Physiological need for food, yet no appetite
Hypothalamus
- Triggers feelings of hunger or satiation (fullness)
- Located above the pituitary gland and the brain stem in an area of the brain that regulates involuntary activities
- Integrates signals from nerve cells, chemical messengers (hormones), and the types of food consumed
Role of nerve cells and hunger
- Special sells lining the stomach and small intestine
- Detect changes in pressure which indicate whether the organ is empty or distended with food
Hormones
- Chemical messengers secreted into the bloodstream by endocrine glands to help regulate body functions
- -Pancreatic hormones, insulin and glucagon, maintain blood glucose levels
- -Feeling full results from signals from the stomach no a raise in blood glucose
Roles of food type on hunger (protein, high-fat diets, bulky meals, solid foods)
- Proteins have the highest satiety value
- High-fat diets have a higher satiety value that high-carb diets
- Bulky meals (high in fiber and water) distend the stomach and promote a sense of satiety
- Solid foods are more filling than semisolid foods or liquids
Why do we want to eat?
- Foods stimulate our senses (sight, smell, taste, texture, hearing)
- Social and cultural cues
- Learned experiences
Digestion
Large food molecules are broken down to smaller molecules, mechanically and chemically
Absorption
Process of taking the digested products through the intestinal wall
Elimination
Undigested portions of food and waste products are removed from the body
Gastrointestinal Tract
- A series of organs arranged in a long tube that work together to process foods
- Sphincters: muscles that control the passage of food material from one GI organ to the next
Cephalic phase of digestion
- Hunger and appetite work together to prepare the GI tract for digestion
- First thought of food (nervous system)’stimulates the release of digestive juices
Digestion begins in the mouth
- Chewing moisten the food and mechanically breaks it into smaller pieces
- Saliva contains digestive juices secreted by the salivary gland in the mouth
- Taste receptors detect distinct tastes
Components of saliva
- Enzymes are complex chemical that induce chemical changes in other substances to speed up bodily processes
- Bicarbonates neutralize acids
- Mucus moistens the food and oral cavity
- Antibodies and lysosomes fight oral bacteria
Bolus
The mass of food chewed and moistened in the mouth
Epiglottis
Covers the opening to the trachea during swallowing
Peristalsis
The muscular contraction that move food through the GI tract
The pH scale
- Stands for potential of hydrogen
- Measures the potential of a substance to release or take up hydrogen ions in solution
- Tissues lining the stomach are generally protected from the effects of acidity
Gastrin
A hormone secreted by stomach lining cells that stimulates the gastric glands to produce gastric juice
Gastric glands
- Parietal cells secrete HCL and intrinsic factor
- Chief cells secrete pepsinogen and gastric lipase
Contents of gastric juice
- HCl denatures proteins and activates pepsin
- Pepsin - enzyme to digest protein
- Gastric lipase - enzyme to digest fat
- Intrinsic factor - protein to absorb vitamin B12
Mechanical digestion
Occurs as the stomach mixes and churns the food and gastric juices
Chyme
Liquid product of mechanical and chemical digestion in the stomach
Components of the small intestine
Duodenum, jejunum, ileum
Ileocecal valve
A sphincter that connects the small intestine to the large intestine
Purpose of large intestine
- AKA colon
- Bacteria assist with final digestion
- Stores undigested food material and absorb water, short-chain fatty acids, and electrolytes
Enzymes
- Guide digestion through hydrolysis, a chemical reaction that breaks down substances by addition of water
- Specific to carbohydrate, protein, and fat digestion
How do hormones assist in digestion?
- Released into the bloodstream and act on specific target cells that contain the receptor protein for that given hormone
- Bind to receptor on the ell membrane and activate a second messenger system within the ells to achieve the targeted response
Gastrin (Key hormone involved in digestion)
- In the stomach
- Stimulates secretion of HCl and pepsinogen
- Stimulates gastric motility
- Promotes proliferation of gastric mucosal cells
Secretin (Key hormone involved in digestion)
In the small intestine (duodenum)
- -Pancreas - stimulates secretion of pancreatic bicarbonate
- -Stomach - decreases gastric motility
Cholecystokinin (Key hormone involved in digestion)
In the small intestine (duodenum and jejunum)
- -Pancreas - stimulates secretion of pancreatic digestive enzymes
- -Gallbladder - stimulates gallbladder contraction
- -Stomach - slows gastric emptying
Gastric inhibitory peptide (Key hormone involved in digestion)
In the small intestine
- -Stomach - inhibits gastric acid secretion; slows gastric emptying
- -Pancreas - stimulates insulin release
Purpose of the gallbladder
- Stores bile (produced by the liver)
- Bile emulsifies the lipids
Purpose of the pancreas
- Manufactures, holds, and secretes digestive enzymes
- Insulin and glucagon are produced to regulate blood glucose
- Bicarbonate is secreted to neutralize chyme
Purpose of the liver
- Synthesizes chemicals for metabolism
- Receives the products of digestion via the portal vein
- Releases glucose from glycogen stores
- Stores vitamins
- Manufactures blood proteins
- Filters the blood, removing wastes and toxins
