Gastrointestinal motility Flashcards
Describe the hormones that regulate appetite
Leptin - produced by fat cells - signals to brain when there is sufficient energy stores - suppresses appetite
Ghrelin - secreted by stomach - stimulate hunger
How can diet affect appetite?
Protein-rich diets promote satiety (fullness)
How does metabolic rate affect appetite?
high metabolic rate creates a stronger drive to eat due to increased energy requirements
What environmental factors can affecte appetite?
Taste and smell of food
Social facts - availability of food, feeding in groups, presence of dominant individual
Health
Feeding schedules - leads to anticipation of food
Age - younger animals have higher energy requirement for growth
Time of year - temp and season can affect metabolic rate
Describe the effects of sympathetic stimulation on the GIT
Describe the effects of parasympathetic stimulation of the GIT
Describe the layout of the SNS in the abdomen and pelvis
Describe the layout of the PNS in the abdomen and pelvis
Identify the positions of the autonomic plexuses in the abdomen and pelvis
Describe the distribution of the enteric nervous system
What is the function of the enteric nervous system?
Describe the extrinsic autonomic innervations and intrinsic enteric innervations of the GIT
Describe the relationship between extrinsic autonomic inntervations and intrinsic enteric innervations of the GIT
What is the importance of electrical coupling in the GIT
Describe the anatomical characteristics of the GIT smooth muscle
Unstriated
Spindle-shaped cells - allows for close packing and efficient force generation
2 layers (longitudinal and circular) for multidirectional contractions
Gap junctions between cells allow electrical coupling
No tendons - integrated into walls of digestive organs
Cytoplasm contains dense bodies - anchor the actin and intermediate filaments to maintain cell structure
Describe the biophysical characteristics of GIT smooth muscle
Describe segmentation
Describe the hormonal control of gastric motility
Gastrin from G cells - increase force of contractions and promotes relaxation of pyloric sphincter allowing for controlled passage of chyme into SI
Motilin from duodenal cells between meals - stimulates gastric motility - promotes initiation of the migrating motor complex (MCC) which helps clear the stomach and upper SI of residual material
Cholecystokinin (CKK) - inhibits gastric emptying, slow movement of chyme from stomach to SI to allow more time for digestion and absorption
How can osmotic pressure affect gastric emptying
When chyme in stomach is hypertonic it can draw water into stomach lumen which makes chyme less viscous
Elevated osmotic pressure in stomach can lead to delayed gastric empyting to allow for more thorough digestion and absorption
How can chemical composition affect gastric emptying?
Describe the integrated reflexes that initiate vomiting
Vomiting centre in medulla oblongate receives info from sensory receptors in GIT and CTZ (chemoreceptor trigger zone in brainstem)
Vomiting centre activates efferent nerve fibres to coordinate muscle contractions involving diaphragm, abdominal muscles and GI muscles to create retrograde peristalsis
Sphincters along the GIT relax
What is the source, stimuli and function of gastric inhibitory peptide?
Produced by K cells in duodenum and jejunum
Stimuli: presence of glucose, fatty acids and amino acids in SI
Function: inhibits gastric motility and acid secretion and stimulates insulin release
What is the source, stimuli and function of secretin?
Describe the source, stimuli and function of somatostatin
What is the source, stimuli and function of enteroglucagon?
What is the affect of cholecytokinin (CKK) on the pancreas?
stimulates acinar cells to secrete enzyme-rich pancreatic juices
Stimulates bicarbonate cells to be released from pancreatic duct cells to neutralize acidic chyme
What is the effect of cholecytokinin on the gall bladder?
causes it to secrete bile into duodenum to aid digestion and absorption of fats
What is the affect of secretin on the pancreas?
stimulates bicarbonate ions to be released from pancreatic duct cells to neutralise acidic chyme
Small effect on enzyme secretion from acinar cells
