Regulation of Digestive Function Flashcards
what 4 factors affect Control of Motility and Secretion
- Autonomous smooth muscle function
- Intrinsic nerves
- Extrinsic nerves
- Gastrointestinal
hormones
what innervates the digestive organs
enteric nervous system- autonomic nervous system
what are short reflexes in the digestive system
reflexes of intrinsic nerves -receptors in digestive tract
what are long reflexes in the digestive system
reflexes of extrinsic nerves - external stimuli
describe autonomic contol of GI activity
sympathetic - inhinitionof GI tract contraction and secretion
parasympathetic - increases GI motility and secretion of digestive enzymes and hormones (via vagus nerve)
describe neural control of Salivary Secretion
*Low-level parasympathetic stimulation induces production of basal salivary secretion
Salivary secretion may be increased by two types of salivary reflexes
- simple and conditioned
what is the simple reflex in salivary secretion
an unconditioned autonomic reflex that occurs in response to direct stimulation of the oral cavity e.g. chemical change in mouth
where is the salivary center in the brain
medulla
what is the conditioned reflex in salivary secretion
does not require chemical changes in mouth/stimuli to act - learned response where salivation occurs without direct stimulation of the mouth.
e.g. when we smell food we start to salivate
describe the Mechanism of the Simple Salivary Reflex
- Stimulus - activates sensory receptors on the tongue and oral mucosa.
- Afferent Pathway (Sensory Input) - Sensory receptors send signals via the afferent fibers to the salivary center in the medulla oblongata.
- Processing in the Salivary Center
- Efferent Pathway (Motor Output) - The autonomic nervous system (ANS) sends signals to the salivary glands
- Saliva Secretion
what are the three phases of gastric secretion
- cephalic phase
- gastric phase
- intestinal phase
what is the cephalic phase
stimuli in head (occurs before food eneters stomach)- senses/thought of food sends sensory signals to the hypothalamus and medulla oblongata which activates vagus nerve
intrinstic nerves stimulates parietal cells, chief cells and muscous cells for gastric gland stimulation
The vagus nerve stimulates G cells in the stomach to release gastrin which stimulates ECL cells to produce histamine
what is gastrin secereted into
blood
what is histamine secreted into
lamina propria
what is pepsinogen and HCI secreted into
lumen
what is the gastric phase
occurring when food enters the stomach, activating stretch receptors in the stomach wall.
These signals travel via the vagus nerve to the medulla oblongata, stimulating gastric secretions
.
what is the intestinal phase
occurring when chyme enters the small intestine. It plays a role in inhibiting gastric secretion to regulate digestion and protect the small intestine
Stretch receptors and chemoreceptors in the duodenum detect excessive distension and acidity
Sensory signals are sent to the medulla oblongata, reducing vagal stimulation to the stomach.
Secretin – Released in response to acidic chyme, it inhibits gastric acid secretion and stimulates the pancreas to release bicarbonate to neutralize acid.
Cholecystokinin (CCK) – Released due to fat and protein in chyme, it reduces gastric motility and stimulates enzyme secretion from the pancreas.
what stimulates the parietal cells
acetycholine, gastrin and histamine
g cells secrete gastrin which binds to CCK cells in parietal cells and stimulates HCI
gastrin causes histamine to be released from ECL cells and Strongly enhances HCl secretion
Ach released by neurons also causes histamine to be released
what do duct cells secrete in the pancreas
bicarbonate
what do acinar cells secrete in the pancreas
enzymes - amylase/lipase/protease
what do the islets of langerhans secrete into the pancreas
-Insulin & glucagon
what causes pancreatic acinar cells to secrete
cholecystokinin (CCK) released from duodenal mucosa caused by fat and protein products in the duodenal lumen
what causes the release of pancreatic duct cells
secretin released from duodenal mucosa caused by acid in the duodenal lumen
what does CCK stimulate
causes pancreatic acinar cells to secrete
stimulates contraction of gallbladder
and relaxation of the sphincter of Oddi
describe the neural track of the GI tract
internal stimuli -> receptors -> local intrinsic nerve plexus -> effectors (smooth muscle or glands) -> response (chnage in contracile or secretory activity
external stimuli -> CNS -> extrinsic visceral efferents-> local intrinsic nerve plexus -> effectors (smooth muscle or glands) -> response (chnage in contracile or secretory activity
describe the Mechanism of the Conditioned Salivary Reflex
- External Stimulus (Learned Trigger) activates sensory receptors
- Sensory signals are sent to the higher brain centers, including the cerebral cortex and the hypothalamus.
- The brain signals the salivary center in the medulla oblongata, which controls salivation.
- Efferent Response via the Autonomic Nervous System
