GIT and Saliva Study Quiz

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Questions and Answers

What is the average daily secretion of saliva?

2000-2500 mL

800-1500 mL (correct)

1500-2000 mL

500-800 mL

Which of the following is NOT a function of saliva?

Moistens the mouth

Inhibits bacterial growth

Acts as a digestive buffer

Provides nutrients to teeth (correct)

Which gland is primarily responsible for producing serous secretion?

Submandibular glands

Parotid glands (correct)

Smaller mucosal glands

Sublingual glands

What is the pH range of saliva?

6.8 to 7.0 Signup and view all the answers

Which enzyme in saliva helps initiate starch digestion?

Ptyalin Signup and view all the answers

What substance in saliva is responsible for killing bacteria?

Lysozymes Signup and view all the answers

Which salivary gland is NOT a major salivary gland?

Minor glands in the tongue Signup and view all the answers

What type of reflex triggers the secretion of saliva during food stimulation?

Simple reflex Signup and view all the answers

Which of the following ions is present in high concentration in saliva?

Potassium Signup and view all the answers

Which component in saliva helps lubricate food for easier swallowing?

Mucus Signup and view all the answers

What is the primary function of acetylcholine in the enteric nervous system?

Stimulating smooth muscle contraction Signup and view all the answers

Which neurotransmitter is primarily responsible for inhibitory effects in the gastrointestinal tract?

Norepinephrine Signup and view all the answers

What role do the sympathetic fibers play in gastrointestinal function?

Causing inhibition of secretion and motor activity Signup and view all the answers

Which statement about the enteric nervous system is true?

It can operate independently from the central nervous system. Signup and view all the answers

How does the sight of appealing food influence the digestive system?

It initiates secretion in the stomach. Signup and view all the answers

Which statement best describes the composition of enteric neurons?

They are composed of both excitatory and inhibitory neurons. Signup and view all the answers

What effect does parasympathetic stimulation have on gastrointestinal functions?

It stimulates digestive secretions and motility. Signup and view all the answers

What type of neurons predominantly secrete acetylcholine in the digestive system?

Enteric neurons Signup and view all the answers

What happens to intestinal motility when norepinephrine is released?

It inhibits intestinal motility. Signup and view all the answers

What is the relationship between the enteric nervous system and the central nervous system?

They have communication links that influence function. Signup and view all the answers

What is the primary function of the myenteric plexus?

Controlling gastrointestinal movements Signup and view all the answers

Which statement accurately describes the submucosal plexus?

It primarily controls intestinal secretions and local blood flow. Signup and view all the answers

What type of neuron structure is primarily found in the submucosal plexus?

Bipolar and unipolar neurons Signup and view all the answers

Which of the following is NOT controlled by the myenteric plexus?

Local contraction of sub-mucosal muscle Signup and view all the answers

The enteric nervous system is primarily confined within which structure?

The gastrointestinal wall Signup and view all the answers

Which part of the gastrointestinal tract does the myenteric plexus extend from?

Upper esophagus to anus Signup and view all the answers

How does the myenteric plexus influence gastrointestinal movements?

By altering muscle contractions across segments Signup and view all the answers

What is one primary role of the enteric nervous system?

Regulation of gastrointestinal functions Signup and view all the answers

Which mechanism is primarily influenced by the submucosal plexus?

Local intestinal secretions Signup and view all the answers

What type of nerve fibers predominantly compose both the myenteric and submucosal plexuses?

Un-myelinated nerve fibers Signup and view all the answers

Study Notes

GIT & Saliva

The gastrointestinal (GIT) tract and saliva are topics for study.
Objectives include differentiating between mesenteric and submucosal plexuses, explaining the autonomic nervous system's role in GIT function, and discussing saliva composition and secretion mechanisms.
The enteric nervous system is entirely within the GIT wall.
The system extends from the upper esophagus to the internal anal sphincter.
It's composed of two plexuses: the myenteric (Auerbach's) and submucosal (Meissner's) plexuses.
Both plexuses comprise intricate networks of fine, unmyelinated nerve fibers and neuronal cell bodies forming ganglia.

Enteric Nervous System

The myenteric plexus (Auerbach's plexus) lies between the outer longitudinal and inner circular smooth muscle layers and extends from the upper esophagus to the anus.
It's principally responsible for controlling gastrointestinal movements.
Its neurons are multipolar.
The submucosal plexus (Meissner's plexus) lies between the inner circular smooth muscle and the muscularis mucosae, also extending from the stomach to the anus.
It primarily regulates gastrointestinal secretions and local blood flow.
This plexus's neurons are bipolar or unipolar (sensory) and multipolar (interneurons).

Neurotransmitters

Enteric neurons release a variety of neurotransmitters.
Acetylcholine (ACh) is a key neurotransmitter, generally acting as an excitatory signal, stimulating smooth muscle contraction and increasing intestinal secretions.
Norepinephrine (NE), derived from extrinsic sympathetic neurons, usually has an inhibitory effect, opposing ACh's actions.

Role of the Autonomic Nervous System

The enteric nervous system functions autonomously but needs communication with the central nervous system.
Parasympathetic and sympathetic fibers connect with the CNS and/or the enteric nervous system to affect the GIT.
This connection allows signals from outside the digestive system to influence it, like the sight of food stimulating stomach secretions.
Sympathetic stimulation usually inhibits GIT function and constricts blood vessels. Conversely, parasympathetic stimulation promotes digestive activity.
The autonomic system modulates the enteric nervous system's activities in most cases.

Saliva

Saliva is mostly water (approximately 99%), with a pH of 6.8–7.0.
Important components include salivary amylase (for starch digestion), lingual lipase (activated by stomach acid to digest fat), mucus (lubrication and binding), lysozymes (antibacterial), and IgA (also antibacterial).
Electrolytes like sodium, potassium, chloride, phosphate, and bicarbonate ions are present.
Average daily saliva production is around 1000 mL.

Salivary Glands

The main salivary glands are parotid, submandibular, and sublingual.
Smaller glands are also located in the mouth's mucosa.
Saliva has a critical role in oral health:
- Moisten the mouth.
- Digest starches and fat.
- Cleanse the teeth.
- Inhibit bacterial growth.
- Dissolve molecules for taste.
- Dilute and buffer food.
- Moisten food & bind particles for swallowing

Saliva Secretion

The major types of secretion in saliva include aqueous (serous) fluid containing water, ions, and digestive enzymes like ptyalin.
The serous part is produced by the parotid, submandibular, and sublingual glands.
Mucin-rich saliva (mucous secretion) is mainly created by the submandibular and sublingual glands.
Parasympathetic signals are primary drivers of saliva production.

Simple and Conditioned Reflexes

Simple reflexes involve direct stimulation within the oral cavity (e.g., food presence), triggering salivation.
Conditioned reflexes (like mouth-watering from the smell of food) are associated with acquired responses.

Saliva Characteristics

Aqueous fluids are also called serous secretions. These fluids contain water, ions and enzymes.
Mucous secretions are rich in mucin.

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Description

Test your knowledge on the gastrointestinal tract and saliva. This quiz focuses on the differences between the mesenteric and submucosal plexuses, the role of the autonomic nervous system in GIT function, and the mechanisms behind saliva composition and secretion. Perfect for students of physiology and anatomy.