Gastrointestinal System Flashcards
How is smell (olfaction) detected?
Dissolved by fluid near olfactory receptors. Sensory signals delivered to CNS via cranial nerves. Chemicals detected by dendrites of olfactory nerves - depolarises in response to certain chemicals.
How does the olfactory system work in the NS?
Olfactory receptors form olfactory nerve which reaches into olfactory bulb. Continues as olfactory tract, delivering signals to the olfactory cortex. This signals other areas of the brain, and the hypothalamus triggers responses.
What are the different cranial nerves involved in gustation?
Facial, vagus and glossopharyngeal.
What are the different types of papillae on the tongue?
Filiform = most common. No tastebuds as detect textures.
Foliate - vertical folds.
Vallate - half tastebuds here.
Fungiform - projections on sides of tongue.
What are the functions of the GI system?
- mechanically break down food
- dissolve soluble components and emulsify lipids
- catalyse hydrolysis reactions
- absorb biological monomers
- remove waste products
What are the components of the GI system?
Digestive tract: mouth, oesophagus, stomach, SI, LI, rectum
Accessory organs: salivary glands, liver, pancreas, gallbladder
What are the 2 phases of swallowing?
Conscious phase/buccal - bolus of food pushed to back of mouth into pharynx. Tongue pressed against back of pharynx.
Autonomic/pharyngeal - nasal cavity closed by soft palate and larynx closed. Bolus pressed into oesophagus.
Define gastrin.
A peptide hormone produced in stomach and duodenum. Increase H+ and K+ ATPase production into cell membrane, so stomach acid increases.
Released in response to stomach stretching.
What is the function of the duodenum?
Receives partially digested food from stomach and is the major site of absorption. Site of major duodenal papilla.
What is the function of the liver and gallbladder?
Liver detoxifies blood and produces bile, stored in gallbladder. Neutralises stomach acid and emulsifies fats in food to increase SA for lipase.
What is the function of the pancreas?
Exocrine organ with some endocrine function. Produces enzymes and secretes into duodenum.
What is the function of the colon?
Removes excess water via an osmotic gradient as ions are absorbed, so water follows.
What is the enteric NS?
Independently functioning nerve network. Receives sensory input and transmits motor instructions to control muscles and secretion.
How are glucose and aa absorbed by cotransport with Na+?
- Na+ pumped out cells lining intestine into blood
- conc decreases
- Na+ comes in from gut, down electrochemical gradient. Only in if attached to glucose.
What are the 3 regions of the GI tract?
Foregut. Oesophagus, stomach, pancreas etc.
Midgut.
Hindgut.
