control of alimentary system Flashcards
what controls the alimentary system?
nerves and hormones
which 2 types of nerves control the alimentary system?
somatic and autonomic
which 2 types of somatic nerves control the alimentary system?
sensory and motor
which 2 types of autonomic nerves control the alimentary system?
parasympathetic and sympathetic
give examples of somatic control of the alimentary system
eating, doing toilet, mastication
what influence does the sympathetic NS have on the alimentary system?
directs blood away from gut towards essential organs
what influence does the parasympathetic NS have on the alimentary system?
kicks in when we rest, stimulates gut motility
which hormones control the GIT?
cholrcystokinin (CCK), gastrin, gastric inhibitory peptide (GIP), secretin
what is the function of cholecystokinin?
bile sack mover, stimulates production of bile to digest fat
where is gastrin produced? and what cells produce it?
produced by G cells in the stomach
what is the function of gastrin?
activates parietal cells which produce HCl
when is gastro inhibitory peptide (GIP) produced?
in response to insulin regulation
which structure releases secretin into the bloodstream?
duodenum
what is the function of secretin?
reduces gastrin secretions and neutralises acid coming from the duodenum
which type of nervous control is most active at the top (mouth) and bottom (anal canal) of the GIT?
somatic
which nervous control is most active at the middle of the GIT?
autonomic
At which structures in the GIT do most hormones work?
stomach and small intestine
what is the function of the mouth and pharynx?
secretion - saliva
motility - chewing and swallowing
secretary control of saliva is completely neural via which nerves?
cranial
which two stimuli stimulate saliva production?
chemical and mechanical
which chemical stimuli stimulate saliva production?
gustation and olfaction
which cranial nerves are responsible for gustation?
CN VII, IX
which cranial nerves are responsible for olfaction?
CN I
which 2 mechanical stimuli stimulate saliva production?
chewing and psychic
which cranial nerve is responsible for chewing?
CN V
which salivary stimuli has the greatest strength?
chemical
which muscles are involved in chewing?
jaw, facial, and tongue
which muscles are involved in swallowing?
jaw, tongue, pharyngeal
what does the ‘swallowing centre’ contain?
brain, nerves and muscles
which types of muscle are in the oesophagus?
smooth and skeletal
which secretion does the stomach produce?
gastric juice
state the 3 phases of gastric secretion
cephalic phase, gastric phase and intestinal hase
what stimulates cephalic phase of gastric activity?
mechanical - chewing
chemical - taste, smell
psychic - visual, emotional
what stimulates gastric phase of gastric activity?
mechanical - distension
chemical - food in stomach
what stimulates intestinal phase of gastric activity?
mechanical - distension
chemical - acid or protein in duodenum
what controls cephalic phase of the gastric cycle?
nerves (long)
what controls gastric phase of the gastric cycle?
nerves (long and short) and hormones (gastrin)
what controls intestinal phase of the gastric cycle?
nerves (long and short) and hormones (GIP and secretin)
describe what happens during cephalic phase of the gastric cycle?
. taste, smell, though or sensation of food sends impulses to medulla oblongota of brain
. these impulses cause PNS neutrons via vagus nerves to stimulate secretion of HCl, pepsin and gastrin
describe what happens during gastric phase of the gastric cycle?
. food enters and distends stomach, activating PNS reflex via vagus nerves
. this reflex results in continued secretion of HCl and pepsin
describe what happens during intestinal phase of the gastric cycle?
. chyme enters duodenum, low pH and lipids I’m chyme stimulate PNS neurons in vagal nerves to inhibit gastric secretion, local reflexes that decrease gastric secretion are also stimulated
. release of hormones which travel in blood to gastric glands inhibiting their secretion are stimulated
what does the small intestine secrete?
intestinal juices (bile, pancreatic juice, chyme)
in which way does the small intestine carry out motility?
mixing, segmentation contractions, peristalsis and villus movement
what controls the small intestine?
local nerves in response to intra-luminal stimuli (distension)
during which stage of gastric activity is most of the pancreatic juice produced?
intestinal phase
which hormone is the main stimulator of enzyme-rich pancreatic juice?
CCK
which hormone is the main stimulator of bicarbonate-rich pancreatic juice?
secretin
where is secretin produced and what triggers its production?
released from duodenum in response to acid
what is the function of the bicarbonate in pancreatic juice?
makes pancreatic juice highly alkaline in order to neutralise acid
where is CCK produced and what triggers its production?
produced from duodenum in response to fat
in what way does the cephalic phase of gastric secretion stimulate the production of bile?
the vagus nerve causes relaxation of the sphincter of oddi (allowing secretions to enter duodenum)
in what way does the intestinal phase of gastric secretion stimulate the production of bile?
. CCK is released from duodenum in response to fat/protein, this stimulates contraction of gall bladder and relaxation of sphincter of oddi
what secretions does the large intestine and rectum produce?
mucus, water and electrolytes
in what way does the large intestine and rectum carry out motility?
mixing, mass movement and defeacation
name the 3 extrinsic reflexes of the gastrointestinal tract
long reflexes, gastro-ileac reflex, gastro-colic reflex
what is the function of long nerves in the anal canal?
allow us to decide when to go to the toilet
what is the function of local nerves in the anal canal?
tell us we need the toilet