Flashcards in Physiology Deck (66):
Enteric nervous system comprises what
Myenteric and submucosal plexuses
Vagal-Vagal reflex: afferents go where
Vagal vagal reflex: Efferents come from where?
NTS: Nucleus Tractus Solitarius
Stimuli of secretion
-G cells of stomach
-small peptides and aa
-vagal stimulation (via GRP)
Stimuli of secretion?
I cell of duodenum and jejunum
-Small peptides and a.a.
Stimuli of secretion?
S cell of the duodenum
-H+ in duodenum
-Fatty acids in duodenum
stimuli of secretion?
What does it do?
Duodenum and jejunum
What does the NT VIP do?
-relaxation of smooth muscle
-increase intestinal and pancreatic secretion
what does the NT GRP do?
-increases Gastrin secretion
What 2 NTs are used for food intake regulation
What is it called when the GI smooth muscle, even subthreshold depolarizes and can produce weak contraction
Sub thrshold depolarization and repolarization of the GI membrane potential
What 3 things stimulate depolarization of the slow waves?
what stimulates hyper polarization?
pacemaker for GI smooth muscle
Interstitial cells of Cajal (ICC)
slow waves occur spontaneously in the ICC and spread how
Smooth muscle cells response to slow wave depolarization with increased what?
Ca2+ channel open probability
3 phases of swallowing
involuntary swallowing reflex is controlled by what?
What nerve sends afferent sensory input due to food in the pharynx to the swallowing center in the medulla?
Esophageal phase of swallowing contains what 2 types of peristaltic waves?
primary and secondary
Which wave of the esophageal phases can still occur after a vagotomy
Receptive relaxation occurs in what region of the stomach
What does CCK do to the contractions and distensibility of orad region upon reception of food
how long does gastric emptying take
What secretion from the duodenum inhibits gastric emptying
Large particles of undigested residue remaining in the stomach are emptied by what
Migrating myoelectric complexes (MMC)
-intervals for MMCs
-when do they occur?
-what mediateds them?
-when are they inhibited?
-inhibited by feeding
What type of contractions:
-back and forth movements
-No forward propulsive movement
What type of contrations:
-Circular and longitudinal muscles work in opposition and are reciprocally innervated
what does the myenteric plexus do?
regulates relaxation/contraction of intestinal wall
What does submucosal plexus (Meissner) plexus do?
sense the lumen environment
what inhibits contraction in small intestine via and interneuron and causes relaxation DISTAL (caudad) to the signal of distention
VIP and NO
what excites and stimulates contraction in the small intestine via and interneuron and causes relaxation PROXIMAL (Orad) to the signal of distention
ACh and substance P
What is released by ECCs and binds to receptors in IPANs, initiating peristaltic reflex
Colon Absorbs what?
water and vitamins
What 2 things can cause achalasia
-Lack of VIP
-enteric system has been knocked out
LES stays closed during swallowing and elevation of LES resting pressure
-slow emptying of stomach/paralysis of stomach
-20% of type 1diabetics have this
Causes of Gastroparesis
Damage to vagus nerve from:
-high blood glucose (diabetic gastroparesis)
Ganglion cells absent from segment of colon
Failure to pass meconium
what levels are low in Hirschsprung
What is saliva composed of
Tonicity of saliva
HYPOtonic compared to plasma
-K+ and HCO3 in saliva
-Na and Cl?
What cells form isotonic plasma like solution in the first step of salivary secretion
What cells modify the isotonic solution that was created by Acinar cells to make it hypotonic
How do vasopressin and aldosterone modify the composition of saliva
-decreases its Na
-increases its K
Parasympathetics to acinar and ductal cells for salivary secretions
-Vagus and Glossopharyngeal
-IP3 and Ca
Sympathetic to Acinar and ductal cells for salivary secretions
What are the 2 unusual features in the regulation of salivary secretion
-EXCLUSIVELY under control of ANS
-increase by BOTH parasympathetics and sympathetics
What is required for absorption of vitamin B12 in the ileum
What kind of gland is in the proximal 80% (body and fundus) of the stomach and secretes acid
What kind of gland has chief cells?
These secrete what?
What kind of gland is in the distal 20% (antrum) and synthesizes and releases gastrin
What kind of gland has D cells?
These secrete what?
What are the 2 Gq pathways leading to increase in IP3/Ca2 and H+ secretion in gastric parietal cells
-G cells -->Gastrin --> CCKB receptor
-Vagus -->Ach -->M3 receptor
What is the Gs pathway leading to increased cAMP and H+ secretion in gastric parietal cells
-ECL cells--> Histamine --> H2 receptor
What are the 2 Gi inhibitory pathways that decrease cAMP and inhibit secretion of H+ in gastric parietal cells
-D cells --> somatostatin
Falling pH inhibits what?
gastrin release so decreases HCl secretion
what are the 2 pathways that the vagus nerve uses to stimulate HCl secretion from parietal cells
-Directly on parietal cells
-indirectly through GRP and G cells --> gastrin --> to parietal cells (atropine doesn't block this pathway)
What is in the protective layer of the mucosa to protect stomach from H+ and pepsin?
What secretes each?
mucus .. . mucous neck cells
HCO3- . . . Gastric epithelial cells
Unconjugated Jaundice diseases
Conjugated Jaundice diseases
transporter for fructose from lumen to cell?
cell to blood?