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FHB - GI/Metabolism - Exam 3 > Lecture 3 - Response to a meal > Flashcards

Lecture 3 - Response to a meal Flashcards

1
Q

What are the 3 integrated responses to a meal?

A
  1. Cephalic
  2. Oral
  3. Esophageal
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2
Q

In the Cephalic phase, what is the type of stimuli?

Can you name the 4 stimuli that trigger responses in GI system?

What is unique about the Cephalic phase?

A
  1. Cognitive

2.

  • Idea of food
  • Olfaction
  • Visual Stimuli
  • Auditory Stimuli

All of these trigger responses in the ABSENCE of food ingestion

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3
Q

Unlike other aspects of the GI systems the Salivary Secretions (or cephalic phase) are strictly what?

  1. Endocrine
  2. Neural
  3. Paracrine
A

Neural!

Integrated via CN 7 and CN 9

  • no actual input of food
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4
Q

Describe how the sensory inputs are relayed to prepare the GI tract to receive and digest food.

(where does it travel through in the brain, which Autonomic nerves, what is the effector response in terms of secretion etc)

(6)

A
  1. Sensory Input
  2. Cortex and Hypothalamus
  3. Lower Pons/Upper Medulla
    (DMX –> Dorsal Motor Nucleus of Vagus)
    = vagal preganglionic neurons
  4. Parasympathetic (Vagal) Stimulation
  5. Salivary, gastric, pancreatic secretion
    - gallbladder contraction
    - relaxation of sphincter of Oddi
  6. Preparation of GI tract to receive food
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5
Q

How is the Oral Phase different from the Cephalic Phase?

A
  1. Difference: FOOD IS IN THE MOUTH
  2. Activation from taste buds and mechanical receptors in mouth & upper pharynx

ORAL PHASE MOSTLY ACTIVATES the digestive system, not a significant portion of digestion itself

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6
Q

What are the main functions of the Oral Phase?

What secretions?
What aids in lubrication?

Does absorption occur here?(if yes, what?)

A
  1. Breaking down of food –> MECHANICAL disruption
  2. Mixing food w/ enzymes:
    - salivary amylase
    - lingual lipase
    - MUCIN (lubrication)**
  3. NO ABSORPTION
    - except alcohol and some drugs
  • mouth is not a major site of absorption or digestion since the amylase digests carbs but is inactivated once it reaches the stomach due to the low pH (same with Lipase)
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7
Q

What is a clinical problem that occurs often during the ORAL phase?

Why is this an issue of concern?

A

Xerostomia

  • dry mouth, impaired salivary secretion
  • DECREASE IN pH!

= tooth decay, esophageal erosions, difficulty swallowing

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8
Q

What muscles are involved in chewing and what innervates them?

A

Temporalis (Most Important)
Masseters
Lateral Pterygoids
Medial Pterygoids

V3 (trigeminal nerve)

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9
Q

What ELICITS secretions? (stimulates secretion)

A

Secretagogues
- any substance that stimulates secretion

  • work as endocrine, paracrine, or neurocrine
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10
Q

What is mostly secreted from the duodenum? Which gland is in the GUT WALL and is responsible for secretions?

What glands are associated with the GI tract?

A
  1. BICARBONATE
  2. Brunner’s Glands in the duodenum
  3. Salivary, Pancreas, Liver
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11
Q

What are the 3 major salivary glands in the mouth?

A
  1. Parotid (largest)
  2. Submandibular
  3. Sublingual
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12
Q

What are the two types of secretions and which glands fall into these categories? (3)

A
  1. Serous (water, electrolytes, enzymes)
    = PAROTID
  2. Mucous:
    Mucin glycoprotein
    = SUBLINGUAL
  3. MIXED:
    SUBMANDIBULAR*
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13
Q

What are the units of secretion in the mouth called?

What empties the secretory juice into the gut from the secretory unit?

A
  1. Acini
    - composed of serous an mucous cells or mixed
  2. Collecting Ducts
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14
Q

Where is initial saliva produced?

What is it composed of?

Where does saliva pass through (2)

What cells provide the FINAL MODIFICATION of initial saliva?

What do they change?

A
  1. Acinus - acing cells
  2. Water, ions, enzymes, mucus
  3. Intercalated Duct
    Striated Duct lined w. DUCTAL CELLS
  4. DUCTAL CELLS!
    - modify saliva by altering solutes & electrolyte concentrations
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15
Q

The following describes what type of cells?

  1. present in the acini & intercalated ducts
  2. Contain ACTIN & MYOSIN

What is the main function of these cells when stimulated by NEURAL input?

A
  1. Myoepithelial Cells
  2. Contract
    - expel saliva in FORWARD direction
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16
Q

What is the most common site of tumors in the mouth? (which gland)

A

Parotid Gland!

80%
- lose the serous acing structure & become mostly mucous

17
Q

Which gland had many striations and is rich in pumps, ion, and fluid transport?

A

Submandibular!

18
Q

What are serous demilunes? Where are these mostly found

  1. Parotid
  2. Submandibular
  3. Sublingual
A

Serous Demilunes –> mucous cells with a cap that contains serous cells

  • found mainly in submandibular
  • some in sublingual

( Parotid Gland = mostly serous, no demilunes)

19
Q

What is the clinical correlate in the mouth of a viral infection like MUMPS?

A

Causes swelling of the salivary glands

in acinar

20
Q

What are the 3 main functions of saliva?

State what components are important to these functions.

A
  1. Lubrication
    - MUCIN!
  2. Protection
    - dilute & buffer food
    * *especially important in vomiting –> salivary excretions increase to buffer the gastric acid & pepsin that enters the mouth
  • also has LYSOZYME to degrade bacterial cell wall
  1. Initial Digestion
    - starches & lipids by enzymes
21
Q

The inorganic composition of Saliva mostly depends on what two aspects?

What are the major inorganic components?(8)

What are the 5 major ORGANIC components of saliva?

A
  1. Stimulus
  2. Salivary Flow

Water, bicarb, Na, K Ca, Mg, Cl
- Fluoride

  1. Saliary Amylase - starch digestion initiated
  2. Lingual Lipase - lipid digestion
  3. Glycoprotein (mucin)
  4. Lysozyme - attacks bacterial wall
  5. Kallikrein - converts plasma protein into bradykinin (vasodilator)
22
Q

In comparison to plasma, salivary secretions are what to plasma?

  1. Isotonic
  2. Hypotonic
  3. Hypertonic
A

HYPOtonic

  • high K & HCO3-
  • low NA & Cl
23
Q

What cells form the initial saliva? What is the solute composition in relation to plasma?

What cells modify the saliva?

What is the final solute concentration relative to plasma?

A
  1. Acinar cells
  2. ISOTONIC
    - Na, K, CL, HCO3- concentrations all = to plasma
  3. Ductal Cells
  4. Hypotonic –> final saliva
24
Q

What substances are absorbed by ductal cells and which are secreted?

What is the NET result?

A
  1. NA & Cl absorbed
    K & HCO3 - secreted
  2. NET ABSORPTION of NaCl
    (NaCl abso.> K/HCO3- Secretion)
25
Q

What part of the salivary cells are water impermeable? Are they permeable to solutes?

What is the purpose for this?

A
  1. Ductal cells are H20 impermeable

NaCl permeable & K/HCO3 -

  1. HYPOTONIC saliva
26
Q

At which flow rates is the solute concentration most similar to plasma?

When is it most dissimilar?

What is the exception?
In which flow states? (fast/slow)

A
  1. HIGHEST flow (4ml/min)
    saliva = plasma
  2. LOW flow (<1ml/min)
    - saliva is much different from plasma
  • increased flow means less time for modification by Ductal Cells, thus less reabsorption/secretion

EXCEPTION: HCO3 - secretion increases when production of saliva increases (flow)

27
Q

Salivary secretions are both sympathetic & parasympathetic.

True or False?

A

TRUE!

  • acinar & ductal cells stimulated by both!
  • parasympathetic is dominant
28
Q

What are the 3 main results of salivary stimulation?

A

Stimulation of salivary cells results in:

  1. increased saliva production
  2. increased HCO3- and enzyme secretions
  3. contraction of myoepithelial cells.
29
Q

Describe the action of parasympathetic salivary innervation.
(5)

MAIN: What is produced by stimulation of Muscarinic receptors with Ach?

A

Parasympathetic Innervation:

  1. branches of Facial (CN VII) and Glossopharyngeal (CN IX):
  2. post-ganglionic neurons release Ach
  3. Muscarinic receptors stimulated by ACh
  4. production of IP3 and increased intracellular Ca++
  5. increased saliva secretion.
30
Q

Describe the action of Sympathetic salivary innervation. (6)

MAIN: What is produced by stimulation of B-adrenergic receptors with NE?

A
  1. originates in thoracic segments T1-T3
  2. preganglionic nerves synapse in the superior cervical ganglion
  3. postganglionic neurons release NE
  4. interacts with -adrenergic receptors
  5. production of cAMP
  6. increased saliva secretion

FHB - GI/Metabolism - Exam 3 (21 decks)

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