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CPG15 PHYSII L13
CPG15 PHYSII Midterm information (digestive system and respiratory)
| Question | Answer |
|---|---|
| What is the primary function of the digestive system? | Transfer nutrients/water/electrolytes from food into the body's internal environment |
| What % of ingested food is available as use of energy source for the body? | 95% |
| What are the four digestive processes performed by the digestive system? (MADS!) | Motility, Absorption, Digestion, Secretion |
| What is tone? | When smooth muscle in GI tract exerts a steady low level of contraction |
| Where does rapid propulsive transit occur? Where does slow propulsive transit occur? | Esophagus; small intestine |
| What are the four major tissue layers of the digestive tract wall? | Serosa, myenteric plexus, submucosa (plexus), and mucosa (outward in) |
| What are the three layers of the mucosa of the digestive tract? | Mucous membrane, lamina propria, and muscularis mucosa (inward out) |
| Is the digestive tract structure maintained throughout the body from mouth to anus? | Yes |
| What are the four factors involved with the regulation of digestive function? | autonomic smooth muscle, intrinsic nerve plexuses, extrinsic nerves, and GI peptides (PAEI) |
| What cells regulate the autonomic smooth muscle of the digestive tract? | Pacesetter cells |
| Where are pacesetter cells located? | the interstitial cells of Cajal, between longitudinal and circular smooth muscle in the myenteric plexus and muscular externa layer |
| What do pacesetter cells do? | Determine the rate of rhythmic contractions that varies throughout tract |
| Where are the intrinsic nerve plexuses located | In the myenteric and submucosal layers of the GI tract within the length of the wall |
| What is the intrinsic nerve plexuses also known as? | The enteric nervous system |
| What type of neurons secrete acetylcholine and what is its response? | Cholinergic neurons, contract smooth muscle in wall, relax sphincters, increased salivary, gastric, and pancreatic secretions |
| What type of neurons secrete norepinephrine and what is its response? | Adrenergic neurons, relaxation of smooth muscle, contractions of sphincters, increased salivary secretion |
| What type of neurons secrete vasoactive intestinal peptide (VIP) and what is its response? | Mucosal neurons and smooth muscle, relaxation of smooth muscle, increased intestinal and pancreatic secretions |
| What type of neuron secrets enkephalins (opiates) and what is its response? | Mucosal neurons and smooth muscle, contraction of smooth muscle, decreased intestinal secretions |
| What type of neuron secrets Neuropeptide Y and what is its response? | Mucosal neurons and smooth muscle, cause relaxation of smooth muscle, decreased intestinal secretions |
| What type of neuron secrets Substance P and what is its response? | Cholinergic neurons (same time as ACh), contraction of smooth muscle, increased salivary secretion |
| What three neuromodulators cause smooth muscle wall contration? | substance P, enkephalins, and ACh (SEA CONTRACTS) |
| What three neuromodulators cause smooth muscle wall relaxation? | norepinephrine, neuropeptide Y, vasoactive intestinal peptide (NNV RELAXES) |
| What two innervations from extrinsic nerves influence motility and secretions in digestive function? | The somatic nervous system and the peripheral nervous system |
| What does the somatic nervous system do with extrinsic nerves and digestion? | Slows GI tract secretion, stimulated by fight or flight response |
| What does the peripheral nervous system do with extrinsic nerves and digestion? | Increases motility and secretion by stimulating the vagus nerve (upper GIT) and pelvic nerve (lower GIT) |
| What are the three types of GI peptides that regulate digestive function? | Hormones, paracrines, and neurocrines |
| What are the roles of the GI peptides in regulating digestive function? | Contract/relax smooth muscle wall and sphincters, secrete digestive enzymes, secrete fluid and electrolytes |
| What are three hormone GI peptides? | CCK, Gastrin, and Secretin |
| What is one paracrine GI peptide? | Somatostatin |
| What are three neurocrine GI peptides? | ACh, NE, and VIP |
| What are the roles of the lips in digestion? | Guide food in mouth, speech, and sensory receptors |
| What links the mouth to the esophagus? | Pharynx |
| What are the three main purposes of chewing? | Grind and mix food with saliva, stimulate the taste buds, and reflexively increase salivary, gastric, and pancreatic secretions to prepare GIT for food |
| What three pairs of tissue discharge saliva into the mouth | parotid gland, submandibular gland, and sublingual gland |
| What does the parotid gland secrete? | Aqueous fluid from serous cells |
| What do the submandibular and sublingual glands produce? | Aqueous fluid from serous cells and mucin from mucosal cells |
| What does Kallikrein do? | Cleaves kininogen into bradykinin; found in salivary acinar cells |
| What is bradykinin? | A vasodilator that increases blood flow to salivary glands when there is increased salivary secretions |
| What is saliva mostly composed of? | mostly water, some electrolytes, and salivary proteins like amylase, mucus, and lysozyme |
| What does amylase do? | Breaks down carbohydrates like polysaccharides into maltose (2 glucoses) |
| What does lysozyme do? | Antibacterial action by lysing bacteria |
| What are the four functions of saliva? | solvent for molecules to stimulate taste buds, aids speech, keeps oral cavity clean, and contains bicarbonate buffers to neutralize acids from food and bacteria |
| What type of cells in salivary glands contract to eject saliva? | Myoepithelial cells |
| What are duct cells? | important in saliva secretion, are impermeable to water, have a net absorption of Na and Cl, and some secretion of K and HCO3 |
| How does the osmolarity change in the secretion of saliva? | Isotonic saliva is secreted around acinar cells, and becomes hypotonic (low osmolarity) surrounding ductal cells |
| How is bicarb in the saliva secreted? | Bicarb secretion is selectively stimulated when saliva production is stimulated by the PNS |
| How is saliva composition modified? | By the flow from acinar to ductal cells (longer time means more modification, more Na and Cl absorbed) |
| What is the average volume of saliva secreted on a daily basis? | about 1-2 Liters per day |
| What stimulates salivary secretion? | SNS and PSN stimulation (both cause increase) |
| What does the PNS do to salivary secretions? | Makes saliva more watery and enzyme rich (dominant normally); ACh, muscarinic, IP3, increased Ca |
| What does the SNS do to salivary secretions? | Decreases saliva volume, makes is richer in mucus (active with stress); NE, beta adrenergic, AC, increased CAMP |
| Who first described the conditioned salivary reflex? | Pavlov |
| What is the simple reflex for salivary secretion? | Pressure and chemoreceptors stimulate salivary center (medulla), stimulatory chain to AUTONOMIC NERVES to SALIVARY GLANDS to increase secretions |
| How does a conditioned (acquired) reflex differ for salivary secretion | Other inputs (PNS) such as increased food/smells and decreased fear, dehydration, and sleep directly stimulate the cerebral cortex; cortex stimulates salivary center (medulla), etc. |
| How is the salivary secretion reflex regulated? | Solely by the autonomic nervous system ("no hormones") |
| What is xerostomia? | Decreased saliva production |
| What can cause xerostomia? | staph or strep infection of glands, stones, mumps (VIRAL); radiation and chemo; blood pressure and depression medications |
| What are the symptoms of xerostomia? | dry mouth, difficulty chewing or swallowing, inarticulate speech, facial pain, increased dental caries |
| What are the treatments for xerostomia? | No alcohol/tobacco/caffeine, sip more water, take better care of teeth |
| What percentage of stones occur in the SUBMANDIBULAR gland? | 80% |
| What type of waves push food through the esophagus? | Peristaltic waves (fast transit) |
| What is the upper sphincter (UES) also called? | PharyngoESOPHAGEAL sphincter |
| What is the lower sphincter (LES) also called? | GastroESOPHAGEAL spincter |
| Is the LES open or closed when there is no esophageal peristalsis occurring? | The sphincter is closed to prevent gastric reflux (GERD) |
| What is achalasia? | A condition where the LES (lower sphincter) fails to relax during swallowing; does not allow food to enter the stomach |
| What treatments are available for achalasia? | Surgery, drugs to inhibit tone (constant contraction) |
| What drugs are used for the treatment of achalasia? | Botox (botulinum toxin) and calcium channel blockers (CCB!) |
| How fast is the esophageal phase in moving a bolus? | Less than ten seconds in transit time |
| How would you describe the swallowing reflex? | Sequentially programmed all or none reflex |
| What are the three phases of swallowing? | oral, pharyngeal, and esophageal phases |
| What happens during the oral phase of swallowing? | The swallowing reflex is initiated by presence of food from rear of mouth to pharynx |
| What type of receptors are activated during oral phase? | TACTILE receptors are stimulated, an afferent input to swallowing center in MEDULLA/PONS via vagus and glossopharyngeal nerves |
| What four events occur during the pharyngeal phase? | soft palate pulls up to prevent food reflux into nasopharynx, vocal cords and larynx move against epiglottis to prevent food reflux into trachea, UES relaxes to receive bolus, pharyngeal muscle contraction (peristalsis begins) |
| What happens during the esophageal phase of swallowing? | phase is controlled by swallowing center; after bolus passes UES it constricts, peristalsis moves food throughout esophagus, LES relaxes until food passes through it |
| How would you describe the swallowing? | highly COORDINATED, initiated in a regular pattern |
| Is swallowing initiated voluntarily? | YES, but once initiated, it can't be stopped (ALL OR NONE) |
| Is motility at either end of the GI tract under involuntary control? | NO, voluntary skeletal muscle |
| Are GI secretions only stimulated by neurons? | NO, hormones and modulators affect GI secretions |
| Does neural ACh cause relaxation of GIT smooth muscle? | NO, contraction (SEA CONTRACTS) |
| Does norepinephrine and VIP cause relaxation of GIT smooth muscle? | YES, (NNV RELAXES) |
| Is salivary secretions from both acinar and duct cells hypotonic? | NO, acinar is isotonic |
| Do low flow rates allow less time to modify saliva? | NO, allow more time (will have greater Na and Cl levels) |
| Is the mucosa layer comprised of circular and longitudinal smooth muscle? | NO, the mucosa layer is comprised of mucus membrane, lamina propria, and muscularis mucosa; MUSCULARIS EXTERNA contains it |
| Does swallowing consist of 3 phases? | YES, oral, pharyngeal, and esophageal |
Created by:
jgk25
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