GI 2

Question 1

What bridges the gap/connects the autonomic and enteric NS

Answer 1

The sensory afférents of the ENS also report to the ANS, usually medulla or spinal cord, and the medulla can then send out a response that will land on an ENS neuron again such that it can then elicit an appropriate response form the tissue

Question 2

Where do parasympathetic and sympathetic responses to ENS sensory neurons come from

Answer 2

Parasympathetic neurons come from the medulla and the sympathetic ones from the spinal cord
When these are triggered they will transmit wtv response is warranted by communicating it to teh ENS neurons in the plexuses, so they can then tell the tissues

Question 3

Long extrinsic reflexes

Answer 3

Called long because they venture outside the ENS, its basically any response not entirely mediated by the ENS, so any spinal cord/medulla intervention is ANS and therefore extrinsic

Question 4

What other factors can trigger the ANS intervention of the ENS (other than ENS sensory neurons)

Answer 4

Sight, smell of taste of food, these are stimuli that come in not by the ENS system, but they still have effects on the GIT, kind of in preparation of food almost
Emotional state: some people stress eat, linked

Question 5

GIT hormones

Answer 5

These are hormones produced in the gut that have effects outside of it, may also have effects on the GIT, depends
Mostly peptide hormones

Question 6

Ghrelin

Answer 6

À GIT hormone, made in gut but acts elsewhere
This hormone is released by glands in the stomach when fasting, signal travels thru blood as usual, but when it reached hypothalamus it triggers the response of increased appetite/hunger

Question 7

Leptin

Answer 7

Not a GIT hormone, made in fat cells in teh context of over eating, counteracts the effect of ghrelin, travels to hypothalamus, triggers the feeling of fullness

Question 8

DES

Answer 8

Diffuse endocrine system
Endocrine cells scattered in the GIT mucosa, they will secrete the GI hormones
Very large and very diverse endocrine system

Question 9

5 most important hormones in GIT regulation

Answer 9

Gastrin
CCK
Somatostatin
Secretin
GIP/VIP

Question 10

Where do GIT hormones go as they are released

Answer 10

Released from GI cells, from mucosa, enter portal blood (the hepatic portal vein), goes through the liver, makes sure its all good, goes back to the heart, enters the systemic circulation, eventually reaching the target cells

Question 11

GIT hormones with respect to each other

Answer 11

They can work together for a common goal: synergistically
They can work against each other, fine tuning, regulation: antagonistically

Question 12

Propulsion as flow

Answer 12

Propulsion is the forward movement of food down the GI tract
As with any flow, its affected by pressure and resistance (very minimally by resistance)
Overall a slow flow going out by anus

Question 13

Pressure in the GI tract

Answer 13

Often generated by muscle of the muscularis externa, 2 main types of motion: segmentation and peristalsis
Segmentation: a decrease in the diameter of the tracts lumen, caused by the coordinated contraction of the circular layer of SM in the tract
Peristalsis: same ring of contraction by circular muscle layer but this time its coordinated to push in one direction, down and out, generates a forward force aka pressure

Question 14

Segmentation (main purpose)

Answer 14

Main purpose is to mix the content, done in a coordinated way such that it alternates between front and back, goes back and forth until its being mushed more and more and mixed

Question 15

Resistance in the GI tract

Answer 15

Not much generally speaking, theres are sphincters between organs that do add a stop sign, but past that diameter isnt controlled in that way
These are points of resistance, but its not a continuous thing

Question 16

Phases of deglutition (brief)

Answer 16

Oral: only phase with a voluntary component
Pharyngeal: when the food reaches the pharynx (bridge from mouth to esophagus), just after the initial pushing back of bolts by tongue, air passes here too
Esophageal: bolus travels down esopahgus
Gastric: enters the stomach

Question 17

Bounds of the esophagus

Answer 17

Delimited by 2 sphincters, the upper and lower esophageal sphincters
Upper is the transition from pharynx to esophagus and lower is teh transition from esophagus to stomach

Question 18

Deglutition (the process)

Answer 18

Starts with oral phase, food is chewed up and covered in saliva, when you voluntarily choose to swallow your tongue reaches the hard palate to force the bolus back, starts the swallowing reflex, thats the end of the voluntary aspect, food reaches pharynx, now is pharyngeal phase, as it goes down pharynx it trigger stretch receptors, this triggers teh deglutition reflex at the medulla, passes upper eso sphincter (sphincter relaxes), travels down, passes lower eso sphincter, enters stomach

Question 19

What controls the voluntary component of the oral phase of deglutition

Answer 19

The choice is made in the cortex, no particular area for us to know just the higher order brain is sufficient

Question 20

What controls the involuntary components of deglutition

Answer 20

Controlled by the deglutition center of the medulla, it coordinates the reflexes and the movements of the muscles post oral phase
Parasympathetic and travels via the vagus nerve
Involuntary

Question 21

What other reflexes are triggered by pharyngeal stretch receptors in the pharyngeal phase

Answer 21

Triggers other reflexes to close of the airway portion of the pharynx so it doesnt get mixed up
The pharyngeal muscles contract, push bolus down, this bolus with push down on glottis which covers the hole to the larynx (air)
Whole vocal chords will contract and move the larynx upwards and forward to protect the airways further
Basically passage to nose mouth and trachea are all blocked to protect food from entering
All caused by medulla in response to pharynx stretch receptors

Question 22

Deglutition apnea

Answer 22

It’s a temporary stopping in breathing due to the reflexes closing off the nose, mouth and trachea in deglutition
Caused by medulla in response to stretch of pharynx