PHYSIO B GI TRACT Flashcards
What are the two main categories of signals?
Short term: hypoglycemia, sensed by hepatic and central receptors.
Long term: starving, revealed by hepatic receptors.
What are the two hunger receptors?
Hepatic receptors: sense low levels of glucose in blood and send information through the vagus nerve to CNS.
Central receptors: located at the level of solitary nucleus, their firing frequency is proportional to glucose level inside BBB.
In terms of satiety, what are the four short term signals?
Cephalic: related to info coming from visual, olfactory and the taste of food.
Gastric signal.
Intestinal: receptors in the duodenum that sense lipids, glucose or AA, they send signals to the CNS.
Hepatic: give info about final absorption of food and about the level of energy.
How are long term signals sent?
They arise from adipose tissue and they are delivered by a hormone called Leptin which is secreted by adipocytes.
How is leptin regulated?
It is regulated by the ob gene. Its secretion is stimulated by high insulin level, so the body is able to stop appetite by triggering sense of satiety.
What are catabolism and anabolism?
Catabolism is the break down of molecules to obtain ATP. Anabolism is the synthesis of all compounds needed by the cell.
What are the two main metabolic processes?
Glycolysis which occurs in the cytoplasm, no CO2 produced.
TCA which occurs in the mitochondria, CO2 is produced and is connected to oxidative phosphorylation.
What are some general notions of the enteric nervous system?
Enteric nervous system is composed by neurons and projections that are completely located inside the GI tract. Enteric nervous system can control and modulate in complete autonomy the functions of GI tract, even without the action of the autonomic nervous system. Enteric nervous system is also referred as gastrointestinal brain and it lays at the level of the gut, it has about 100 millions neurons. It is highly developed and specialized and is important to control motility patterns inside the GI tract and secretion.
What are the two coordinated plexi in the GI tract?
The submucosa or Meissner’s plexus and the myenteric or Auerbach’s plexus.
What is meissner’s plexus?
It lies between longitudinal and circular muscle layers and it is involved in control of the function of the inner wall of intestine. In
this plexus, many sensory signals originating from the lumen are integrated. It acts in controlling local intestinal secretion, absorption, contraction and local blood flow.
What is Auerbach’s plexus?
It consists of a linear chain of interconnected neurons that
extend for the entire length of the GI tract. It controls muscular activity along the gut and when stimulated, it increases the tonic contraction of gut walls and is responsible for increasing the intensity of movement patterns, rate and speed of the conduction of excitatory waves that run along the gut walls.
Inside this plexus there are also inhibitory neurons.
What are the three groups of neurons in the enteric system?
Intrinsic primary afferent neurons also called IPANs, effector neurons and interneurons.
What are IPAN neurons?
They are multimodal sensory neurons, they have a sensory ending for stimuli that originate in the lumen of intestine and can carry also
thermal information. IPAN send the signal to enteric nervous system that will release acetylcholine, substance P, neurokinin A and PACAP.
What are effector neurons?
They are motor neurons involved in control of smooth muscle cells, secretory cells and blood vessels. These neurons have both excitatory (if acetylcholine is released) and inhibitory action (in case of NO, VIP and ATP release).
What are interneurons?
They are located between IPAN and effector neurons. Interneurons form a connection between those neurons and are part of reflex arches located completely inside gut walls.
