Digestive Flashcards
Where is NaHCO3 made?
Pancreas, Small intestines, liver
What substance neutralizes chyme as it enters the duodenum?
NaHCO3 (Sodium bicarbonate)
Increase of digestive processes is typically signaled by what division of the autonomic nervous system?
Parasympathetic
Long digestive reflexes are made by what nervous system?
Central
Short digestive reflexes are mediated by what branch of the nervous system?
Enteric
What are the effects of gastrin?
Increases stomach contractility and increases HCl secretion
What hormone decreases stomach contractility?
CCK
What vagal neurotransmitter increases H+ secretion?
Acetylcholine
What paracrine signal molecule causes HCl secretion?
Histamine
What two things convert pepsinogen to its active form?
HCl
An active pepsin initiating autocatalyzing
What organ secretes most of the hydrolytic digestive enzymes?
Pancreas
What are the breakdown products of fat before absorption?
Glycerol (monoglyceride), fatty acid
What salivary enzyme breaks down starch and glycogen?
Salivary amylase
What is the name of the gastric protease and what is its optimal pH range?
1.5-2.5
What is the luminal membrane transport mechanism of glucose in the small intestine?
Secondary active transport
What sets up glucose absorption?
A sodium concentration gradient
What transport mechanism is typically used for monosaccharides at the basolateral membrane?
Facilitated diffusion
What are the enzymes used to complete the very last steps of catabolism of carbohydrates and peptides during absorption?
Brush border enzymes
What are the cholesterol-based molecules that increase lipid surface area and water solubility for further digestion?
What is this process called?
Bile Salts
Emulsification
What are the structures that transport fat breakdown products on the luminal side of absorptive cells
Micelles
What is the packing structure of peptides and fats combined that transport those breakdown products across the basolateral membrane?
Chlyomicrons
What part of the lymphatic system is responsible for the absorption of fat and protein byproducts?
Lacteals
What are the pancreatic proteases and how are they activated?
Trypsin, Chynotrylsin, Procarboxylpeptidase
They are activated by enterochase cleaving their activation peptides
What are two advantages humans receive from their microbiome?
Digestive support, with the breakdown of cellulose
Immune support
Besides diverting blood away from the digestive system how does stress negatively affect digestion?
Limits motility and rate of HCl production
Cortisol causes breakdown of food already stored in the body
What are the layers if the alimentary canal from deep to superficial?
Mucosa (lines the lumen)
Submocasa (areolar CT)
Muscularia externa
Serosa
What GI activities take place in the oral cavity?
Ingestion, Propulsion, Mechanical Digestion, Chemical Digestion
What GI activities take place in the esophagus?
Propulsion
What GI activities take place in the stomach?
Propulsion, Mechanical Digestion, Chemical Digestion
What GI activities take place in the small intestine?
Absorption, Propulsion, Mechanical Digestion, Chemical Digestion
What GI activities take place in the lathe intestine?
Absorption, Defecation
What is the main form of movement in the small intestine?
Segmentation
What are the methods for regulation of the digestive tract activity?
Autonomous smooth muscle control
Mechanical and chemical stimuli (stretch receptors, osmolarity, presence or absence of substrate)
GI hormones
Extrinsic nerve control (CNS)
Intrinsic nerve control locally (ENS)
True or False: Visceral smooth muscle is autonomous and has its own pacemaker cellsz
True
How does one describe smooth muscle action potentials?
Slow Wave Potential
True or False: The force and duration of muscle contraction are directly related to the amplitude and frequency of action potentials
True
What are the long reflexes of the GI Tract?
Involve integration with CNS:
Alter muscle/gland activity
Alter levels of hormone secretion
Modify intrinsic activity
Coordinate different parts of the GI (ie chewing food increases gastric secretions)
What are the short reflexes of the GI Tract?
Involves the enteric nervous system:
Within the GI Tract
Coordinates local activity but can involves the extrinsic nerve because they are linked
What does the myenteric plexus control?
Motility of the stomach
What does the submucosal plexus control?
Gastral secretions?
What is a paracrine signal?
Affects neighboring cells instead of entering the bloodstream
What is a gastrointestinal peptide?
Digestive hormones that excite or inhibit motility or secretions and act on the brain to trigger hunger or satiety
What is the term for chewed food mixed with saliva?
Bolus
What is saliva made of?
97-99% water
Digestive enzymes; salivary amylase and salivary lipse
Mucus
Lysozyme and IgA (antibacterials)
What three glands secrete salvia?
Parotid
Sublingual
Submandibular
What is the difference between the simple and acquired salivary reflex?
Simple: Ingested food triggers barioreceptors and chemoreceptors, triggers salivary center of medulla
Acquired: Thought of food triggers cerebral cortex, triggers same
What is the difference between nervous centers for control of saliva
PSNS - larger volume, watery, enzyme rich
SYMP - smaller volume, more mucus
What structures are involves in swallowing?
Tongue, Soft Palate, Pharynx, Esophagus
What is the difference between the two deglutition (swallowing) reflexes?
Buccal phase - voluntary
Pharyngeal-esophageal - Involuntary
How does food enter the stomach?
Through the gastroesophageal sphincter
What is food called after it is mixed with gastric juices in the stomach?
Chyme
Besides pepsin, what hormone does the stomach produce and what is its purpose?
Intrinsic factor; the absorption of vitamin B12
What are the 4 phases of gastric motility?
Gastric Filling
Storage
Mixing
Emptying
True or False. The most peristaltic contractions happen during gastric storage.
False. Little mixing occurs here
What causes gastric mixing?
Chyme is propelled by the muscular antrum against the closed pyloric sphincter
What are the exocrine stomach secretions?
Mucus - to protect walls from acid
HCl - from parietal cells
Intrinsic factor - from parietal cells
Pepsinogen and gastric lipase - from Chief cells, becomes pepsin in stomach
What hormones inhibit and stimulate gastric acid secretion, respecitively
Somatostatin and Gastrin
What are the breakdown components of proteins?
Peptides then amino acids
What are the stimulations of the 3 phases of gastric juice secretion?
Cephalic (thought if food, stimulation of taste receptors - vagal nerve)
Gastric (stomach distention activates stretch receptors, rising pH and caffeine activate chemoreceptors and G cells)
Intestinal (presence of low pH stimulates gastrin release)
What are the inhibitory impulses of the Gastric Phases?
Cephalic (depression causes cerebral cortex to block stimulation)
Gastric (excessive acidity, emotional upset causes SNS to override PSNS)
Intestinal (distention of duodenum, irritants in chyme stimulate entero-gastric reflex)
Which controls the rate of stomach emptying: the stomach or the duodenum?
Both
How long does it take the stomach to empty?
4 hoursish
What are the gastric factors that increase gastric emptying?
The amount of chyme in the stomach (empties at proportional rate)
Fluidity if chyme
Signaling from vagus nerve
Gastrin
What are the dudoenal factors that decrease gastric emptying?
Fatty chyme
High acidity (chyme has to be complete neutralized)
Hypertonicity
Distention
What are the hormonal mechanisms that inhibit gastric motility?
Chloecystokinin (CCK) and secretin
What is the name of the reflex that closes the pyloric sphincter as the duodenum fills?
Enterogastric Reflex
Activities of the digestive system are stimulated by what?
Intrinsic nerve plexi
hormones
parasymp. impulses
symp. impulses
the contents of the GI tract
Salivary glands contain enzymes for the breakdown of what substance?
Polysaccharides
Is lactase secretes by the pancreas?
No
What does the gastroileal reflex do?
Moves chyme into the colon
What does CCK do?
Causes the gallbladder to contract, releasing stored bile
What does secretin cause?
Pancreas to release fluid rich in bicarbonate
