GIT - Lecture 2 Flashcards
Endocrine secretions move into the…
blood
Exocrine secretions move into the…
lumen of the gut
ANS – “modulates” ENS activity via
LONG, EXTRINSIC REFLEXES
ENS regulates GIT via
ANS – “modulates” ENS activity via LONG, EXTRINSIC REFLEXES – synaptic connections with ENS neuronsSHORT, INTRAMURAL REFLEXES
What causes activation of the ANS?
signals at the level of the gut that send sensory afferents to the CNS
What is the pathway of long extrinsic reflexes?
- chemoreceptors, osmoreceptors, mechanoreceptors
- afferent neurons
- central nervous system
- efferent autonomic neurons (S or PS)
- nerve plexus
Where do efferent autonomic neurons synapse?
nerve plexus
Where do long extrinsic reflexes happen?
outside the gut wall
What are 2 direct ways we can activate the ANS?
- sight, smell, taste of food
- emotional state
The ___ modulates the activity of the ENS.
ANS
Parasympathetic is ___, whereas sympathetic is ___.
excitatory, inhibitory
Parasympathetic may also ___ inhibitory neurons.
excite
Sympathetic may also ___ inhibitory neurons.
inhibit
The activities of the GIT are integrated for high functional efficiency by which 2 mechanisms?
neural and hormonal mechanisms
What do non-GIT hormones influence?
growth and development of GIT
What do GIT hormones influence?
activities outside the GIT
What is released by glands in the stomach during fasting?
ghrelin
What does ghrelin activate?
hypothalamic “feeding centre”
What does ghrelin stimulate?
hunger and increases apetite
What is released by fat cells with overeating?
leptin
What does leptin activate?
hypothalamic “feeding centre”
What does leptin induce?
satiety and decreases apetite
What is DES?
diffuse endocrine system
Where is the DES scattered?
among cells in the mucosa
What is the largest, most diverse endocrine system in the body?
DES
What are the 5 important GI hormones?
- gastrin
- CCK
- secretin
- GIP
- VIP
What are the 3 different modes of hormone regulation?
autocrine, paracrine and endocrine effects
What is the autocrine effect?
the hormone released by an endocrine cells have effects on cells that release that hormone
What is the paracrine effect?
the hormone released by paracrine cells have effects on nearby cell
What is the endocrine effect?
the hormone released by the endocrine cells move through the capillary and have effects on target tissues
What are GIT regulatory hormones classified as?
peptides
Where are GIT regulatory hormones released from? Where do they go?
mucosa into portal blood
How do GIT regulatory hormones go to portal blood?
through the hepatic portal vein
What is the pathway of GIT regulatory hormones?
- mucosa
- portal blood
- liver
- heart
- systemic circulation
- target cells
What are the 2 targets of GIT regulatory hormones?
excitatory and inhibitory
What do GIT regulatory hormones interact with?
one another and with neurotransmitters
What are the 2 effects that GIT regulatory hormones have?
- synergistic
- antagonistic
What happens during motility?
propulsion and physical breakdown
Which layer of the GIT is important during motility?
muscularis externa (longitudinal and circular fibers)
What contributes to variations of flow in the GIT?
- gradients of pressure
- variations in resistance
What creates gradients of pressure in the GIT?
coordinated contractions of muscular elements in the GIT wall
What are the 2 types of motility that the circular muscles produce?
segmentation and peristalsis
What is segmentation good for?
mixing
What is peristalsis good for?
propulsion
What is flow in the GIT mainly driven by?
gradients in pressure
Normally, is there resistance in the GIT?
there is little to none
Why are sphincters closed at rest?
to prevent the contents moving from one part of the GIT to another
What would happen if the lower esophageal sphincter was open?
there will be stomach acid moving to the esophagus which could lead to heartburn
What kind of flow is in the GIT?
slow
What direction does food move in the GIT?
aboral direction
What does aboral mean?
food is moving away from the mouth
Why is there little/no resistance in the GIT?
because the sphincters always open at the appropriate time
Why is swallowing highly regulated?
because we don’t want food to move up into our nose
What is the scientific term for swallowing?
deglutition
What are the 4 phases of deglutition?
- oral
- pharyngeal
- esophageal
- gastric
Which phase of deglutition is the only one that is voluntary?
oral
What conveys food from the mouth to the esophagus through a process called deglutition?
the pharynx
What organ transports food into the stomach?
esophagus
What 2 sphincters of the esophagus must be relaxed in order for food to be transported?
the upper and lower esophageal sphincters
What happens during the oral phase?
transport of food from the mouth to the pharynx
What is a sticky mass of food called?
bolus
What closes off the nose during the oral phase so that food doesn’t go up to the nose?
the soft palate
What closes off the airway when swallowing food?
the epiglottis
The voluntary aspect of swallowing happens via what kind of processing?
cortical processing
What is activated when you decide you want to swallow?
deglutition center
What kind of reflexes is found in the deglutition centre?
involuntary reflexes
Where in the brain is the deglutition centre found?
medulla
What happens to the pharyngeal receptors during the pharyngeal phase?
they stretch
What is the pharynx?
the region where respiratory and digestive tracks cross
Why do people who have strokes have trouble swallowing?
because it involves a lot of coordination
What happens to the vocal chords in the larynx during the pharyngeal phase?
reflective contraction
What happens to the glottis when the larynx closes it?
it becomes closed
During the pharyngeal phase, UES ___ and pharyngeal muscle ___.
relaxes, contracts
Why do pharyngeal muscles contract?
to push bolus across the relaxed UES into the esophagus
What are the steps during the pharyngeal phase?
- passages to nose, mouth, and trachea blocked
- apnea
- UES relaxes
- pharynx muscles contract
What happens to respiration during the pharyngeal phase?
it is briefly inhibited
