Exam 4 LO Flashcards
Major roles of saliva
Starch breakdown
Food solubilization
Protection
Absorption
Lubrication
Major digestive enzyme present in the saliva, responsible for starch breakdown
alpha amylase
Alpha amylase’s ability to function depends on…
how well food is chewed
Starch breakdown is important in the mouth because…
amylase is deactivated in the stomach due to acidic environment
Breaking down food releases chemicals that activate…
taste receptors in mouth, if something doesn’t get broken down then you cannot taste it as well
In food solubilization, dissolved chemicals diffuse into…
pores in tongue, sensed by taste hairs that depolarize the membrane—activating NS
Protects against chewing of sharp material
Mucins producing thick mucus
pH of saliva and it’s role
Alkaline pH buffers against acidic foods and stomach acid
Absorption of what molecules can occur directly in the mouth? What happens when molecules are absorbed directly in the mouth?
Low molecular weight. they bypass (bypass hepatic portal vein) the first round of liver metabolism and go straight into the bloodstream
What do mucins produce and how it is relevant for lubrication?
glycoproteins that coat the food so you can move it around and important for swallowing
Swallowing is what kind of reflex
Long reflex
Explain the voluntary phase of swallowing
Tongue pushes food bolus back and upward’s towards the back of the mouth, once food touches the soft palate and back of mouth which triggers swallowing reflex
Explain the pharyngeal phase of swallowing
Medulla initiates swallowing reflex, causing soft palate to elevate, closing the glottis and opening the esophageal sphincter (once food moves into esophagus and sphincter closes, glottis opens and breathing continues)
Explain reflex arc of swallowing
Controlled variable:
Stimulus:
Sensor:
Input:
Controlled center:
Output:
Effectors:
Response:
Negative feedback:
Controlled variable: open and clear back of mouth
Stimulus: food touching palate
Sensor: mechanoreceptor
Input: afferent neuron
Controlled center: medulla
Output: somatic motor neuron
Effectors: skeletal muscle
Response: contract,elevate soft palate; larynx closes and epiglottis moves down; opening of UES (relaxation)
Negative feedback: moves bolus to clear back of mouth
What occurs in the esophageal phase
food moves down esophogus by peristalsis
As food moves into the stomach, the LES…
relaxes and opens allowing food to enter into stomach
If food gets stuck what occurs?
Short reflexes will continue peristalsis
Distinguish between the walls of the esophagus and those represented by small intestine
GI tract has smooth muscle
Upper 3rd of esophogus has skeletal muscle
Lower 2/3rds of esophogus has smooth muscle
Stretch of smooth muscle responds by contraction in ENS
myogenic reflex
Explain what happens at the cellular level with stretching of smooth muscle
stretch activates mechanically gated channels, allowing calcium to enter the cell
Higher calcium concentration where?
Outside the cell
Explain what happens at the subcellular level with stretching of smooth muscle
- calcium in cell binds to calmodulin forming the ca-calmodulin complex
- Ca-calmodulin complex activates MLCK
- Active MLCK binds to and phosphorylates myosin
- Myosin binds to actin, initiating contraction
If MLCK is elevated what occurs:
If you inhibit phosphorylation of myosin:
more likely to be contracted
Predict it will lead to muscle relaxation
Explain the reflex arc in esophogus that responds to stretch
Controlled variable:
Stimulus:
Sensor:
Input:
Controlled center:
Output:
Effectors:
Response:
Negative feedback:
Controlled variable: Muscle length
Stimulus: Stretch
Sensor: Mechanoreceptor (sensitive to stretch)
Input: Sensory neuron
Controlled center: ENS (interneuron)
Output:Myenteric plexus (innervate smooth muscle)
Effectors: Smooth muscle (contracts in response to ENS input)
Response: Contraction
Negative feedback: Moves bolus and restores muscle length