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Lecture 2

Physiology 3120 Lecture Notes - Lecture 2: Curvatures Of The Stomach, Medulla Oblongata, Vasodilation


Department
Physiology
Course Code
PHYSIO 3120
Professor
Tom Stavraky
Lecture
2

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Physiology 3120
Dr. Woods
Lecture 2
Clinical Scenario
- You are working in the pediatric ER you get a patient that has increased vomiting following
eating
- This baby was born 3 weeks overdue at a weight of 9 pounds and 11 ounces
- The baby is starting to lose weight after having a normal predicted weight gain
- Blood work shows that the baby is dehydrated and there is an electrolyte imbalance
Neural Regulation of Salivary Secretions
- Unlike other digestive tract organs, the salivary glands are completely under the control of
neurons
o The rest of the digestive tract has both a component of neural regulation and hormonal
regulation
- There is both sympathetic and parasympathetic innervation that is +ive
o This is unlike other organs where sympathetic and parasympathetic innervation is
reciprocal
1. Parasympathetic (PSYN)
o Major pathway to stimulate saliva secretion
o Initiates and sustains high levels of saliva
o When it comes to the initiation of salivary secretion and the flow rate of salivary
secretion (the actual quantity of saliva) its parasympathetic innervation that is the most
important
o The PSYN does this by dilating the blood vessels that are around the salivary glands
o So by dilating the blood vessels, we increase blood flow and the more blood flow at the
salivary glands means we have more blood to draw fluid from to create saliva
2. Sympathetic (SYN)
o Can’t initiate saliva secretion but potentiates effects of PSYN
o It activates another receptor on the acinar cells and by causing neurotransmitter release
and activating a separate cascade, we increase and potentiate the saliva
o We don’t actually know how the SYN innervation helps the saliva production
- Hormones can control composition but not flow rate, ie. ADH and aldosterone
o Hormones in high levels for a long period of time can modify the type of saliva you are
able to produce
o ADH and aldosterone change the composition of our saliva
o ADH is released when you want to increase water reabsorption so when you have
ADH present in higher amounts, you will produce less saliva bc there is less water being
able to be secreted
o Aldosterone you have low Na+ in the blood plasma when aldosterone is present in the
body and is persistent for a while, saliva will have less Na+ in it bc aldosterone causes
increased Na+ reabsorption in the salivary acinar cells
- We want salivary production to increase when we are eating food bc that will cause less
abrasions from the food we are digesting and it helps to form a bolus (makes it easier to
swallow)
Mastication (aka chewing)
- Mastication is a mechanical type of digestion
- Mechanical digestion converting food into a bolus (soft type of food that is soft enough for us to
swallow)
- Chemical digestion (enzymes that breakdown bonds, producing smaller units)
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o salivary amylase
active in our mouth, especially more active in the presence of Cl-
o lingual lipase
breaks down fat)
does not function until it reaches the stomach this is bc lingual lipase needs to
be activated it is activated by proper folding, which is done in an acidic
environment
so lipid digestion from the lingual lipase that came from your saliva doesn’t start
working until you have swallowed the bolus and its in your stomach
Stages of Swallowing
- swallowing is important and controlled by neurons
- we only have control of the voluntary stage we don’t have control of the pharyngeal stage or
the esophageal stage
1. Voluntary stage
o We decide how many times we chew our food and where in the mouth we chew our
food
o When we are distracted in this stage, we might inappropriately end this stage without
realizing it in this situation, we would push the bolus to the back of the pharynx
against the pallet
o Here, there is sensory neurons that will detect the pressure
o It will then circumvent the voluntary stage and initiate the pharyngeal stage
2. Pharyngeal stage
o There is complex innervation that happens where we have to coordinate movement of
positions in our mouth
o Specifically, we have to get the pallet to be pulled upwards so there is innervation that
causes the pallet to be moved upwards, closing off your nasal cavity (if this isn’t closed,
you get it in your sinuses)
o Eating too fast or laughing at the same time, you can get parts of the bolus into the sinus
cavity
o We then need to block off the airway using the larynx the larynx is opening up the
back of the throat and the closing of the larynx by the epiglottis prevents the trachea
from receiving any bolus
3. Esophageal stage
o Stage where we now permit the food to go down our esophagus
o This stage is initiated by the opening of the upper esophageal sphincter, permitting the
bolus to go down the esophagus
o From the esophagus, we have other neurons that take over to control the movement
from the top of the esophagus to the bottom
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