4 Autonomic Nervous System and Salivary Glands
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Questions and Answers

What is the primary function of saliva in the process of mastication?

  • To neutralize stomach acid
  • To lubricate food for easier swallowing (correct)
  • To enhance the taste of food
  • To break down carbohydrates

    • Which phase of swallowing follows the oral phase?

  • Gastric phase
  • Digestive phase
  • Esophageal phase
  • Pharyngeal phase (correct)

    • What does xerostomia refer to?

  • Altered taste sensation
  • Swallowing difficulties
  • Dry mouth due to lack of saliva (correct)
  • Excessive salivation

    • Which of the following factors can contribute to vomiting?

    <p>Overeating</p> Signup and view all the answers

    How is the secretion of saliva primarily controlled?

    <p>By the autonomic nervous system</p> Signup and view all the answers

    Which component is not typically found in saliva?

    <p>Cholesterol</p> Signup and view all the answers

    What role does the lower esophageal sphincter play during swallowing?

    <p>It controls the passage of food into the stomach</p> Signup and view all the answers

    What condition is described by the inability of the lower esophageal sphincter to relax properly?

    <p>Achalasia</p> Signup and view all the answers

    What is the primary component of saliva?

    <p>Mucins</p> Signup and view all the answers

    What is the typical volume of saliva produced per day?

    <p>1-2 L</p> Signup and view all the answers

    Which enzyme in saliva initiates the digestion of starches?

    <p>Salivary α-amylase</p> Signup and view all the answers

    How does the osmolality of saliva compare to that of plasma?

    <p>Saliva is hypo-osmolal compared to plasma.</p> Signup and view all the answers

    What is the primary role of mucins in saliva?

    <p>Lubrication</p> Signup and view all the answers

    What is the typical pH range of saliva?

    <p>6.0 - 8.0</p> Signup and view all the answers

    What cells secrete saliva in the salivary glands?

    <p>Acinar cells</p> Signup and view all the answers

    Which of the following components in saliva is involved in immune defense?

    <p>IgA</p> Signup and view all the answers

    What is the primary enzymatic activity of salivary amylase?

    <p>Digestion of dietary starches</p> Signup and view all the answers

    How does saliva contribute to oral hygiene?

    <p>By buffering acids with bicarbonate</p> Signup and view all the answers

    What is the effect of β-AR activation in salivary glands?

    <p>Increases amylase content</p> Signup and view all the answers

    Which statement about mastication is true?

    <p>It mechanically breaks up food into smaller pieces.</p> Signup and view all the answers

    What primary role does saliva play in the swallowing process?

    <p>It facilitates lubrication and swallowing.</p> Signup and view all the answers

    Which bactericidal component in saliva helps maintain oral microbiota?

    <p>Lysozyme</p> Signup and view all the answers

    What physiological role does α-AR activation in salivary glands suggest?

    <p>Increased blood resistance in ducts</p> Signup and view all the answers

    In which condition might mastication be severely affected due to loss of function?

    <p>Neuromuscular defects after strokes</p> Signup and view all the answers

    What happens during deglutition apnoea?

    <p>Breathing is inhibited for approximately 1 second.</p> Signup and view all the answers

    What is the primary function of the upper esophageal sphincter (UES) during swallowing?

    <p>To relax and allow the bolus to enter the esophagus.</p> Signup and view all the answers

    Which phase of swallowing occurs after the bolus has been pushed into the esophagus?

    <p>Oesophageal phase</p> Signup and view all the answers

    What initiates secondary peristaltic waves in the esophagus?

    <p>Stimulation of mechanoreceptors in the esophagus.</p> Signup and view all the answers

    What is the normal speed of the primary peristaltic wave within the esophagus?

    <p>4 cm/sec</p> Signup and view all the answers

    Which nerves are primarily involved in controlling the peristaltic contractions of the esophagus?

    <p>Vagal (X) and intrinsic reflex nerves.</p> Signup and view all the answers

    How long does it typically take for the bolus to reach the lower esophageal sphincter (LES)?

    <p>10 seconds</p> Signup and view all the answers

    What effect does increased salivary secretion have during swallowing?

    <p>Enhances lubrication of the bolus.</p> Signup and view all the answers

    What is the primary function of the Lower Oesophageal Sphincter (LES)?

    <p>Prevents reflux and heartburn</p> Signup and view all the answers

    In which condition is swallowing impaired due to excess LES tone?

    <p>Achalasia</p> Signup and view all the answers

    Which neurotransmitters are released to inhibit the smooth muscle of the LES before peristaltic contraction?

    <p>VIP and nitric oxide</p> Signup and view all the answers

    What is the primary secretion of the esophagus that aids in lubrication and protection?

    <p>Mucus</p> Signup and view all the answers

    What is a common cause of xerostomia, or dry mouth?

    <p>Dehydration and anxiety</p> Signup and view all the answers

    What is the primary composition of saliva by percentage?

    <p>99.5% H2O and 0.5% electrolytes and protein/enzymes</p> Signup and view all the answers

    Which enzyme in saliva is responsible for initiating the digestion of dietary lipids?

    <p>Lingual lipase</p> Signup and view all the answers

    Which statement best describes the osmolality of saliva compared to plasma?

    <p>Saliva is hypo-osmotic compared to plasma.</p> Signup and view all the answers

    What is the typical pH range of saliva?

    <p>6.0 - 8.0</p> Signup and view all the answers

    Which component of saliva plays a role in immune defense?

    <p>IgA</p> Signup and view all the answers

    What is the maximum flow rate of saliva during stimulation?

    <p>5 ml/min</p> Signup and view all the answers

    How does the concentration of potassium ions in saliva typically compare to that in plasma?

    <p>Higher than in plasma</p> Signup and view all the answers

    What is the spontaneous basal flow rate of saliva in milliliters per minute?

    <p>0.5 ml/min</p> Signup and view all the answers

    What effect does the parasympathetic nervous system have on salivary secretion?

    <p>It increases salivary flow rate via acetylcholine.</p> Signup and view all the answers

    Which receptors are primarily involved in salivary secretion stimulation by the parasympathetic system?

    <p>M3 muscarinic receptors</p> Signup and view all the answers

    What is the relationship between salivary flow rate and electrolyte concentration in saliva?

    <p>Higher flow rates lead to increased salivary electrolyte concentrations.</p> Signup and view all the answers

    What type of salivary reflex occurs in response to the presence of food in the mouth?

    <p>Simple (unconditioned) reflex</p> Signup and view all the answers

    Which statement correctly distinguishes between simple reflex and conditioned reflex in salivation?

    <p>Conditioned reflex is based on prior experience, while simple reflex is not.</p> Signup and view all the answers

    What effect does atropine have on salivary secretion?

    <p>It causes dry mouth by blocking parasympathetic activity.</p> Signup and view all the answers

    What physiological mechanism causes the relaxation of the lower oesophageal sphincter (LES) before peristaltic contraction?

    <p>Inhibition by VIP and nitric oxide</p> Signup and view all the answers

    Which cranial nerves are primarily involved in the transmission of salivary reflex actions?

    <p>Cranial nerves VII, IX, and V</p> Signup and view all the answers

    What primarily stimulates the increase in salivary secretion in response to taste stimuli?

    <p>Reflex action from taste buds</p> Signup and view all the answers

    In achalasia, which of the following issues contributes to impaired swallowing?

    <p>Excessive contraction of the LES</p> Signup and view all the answers

    What happens to the final composition of saliva as flow rate increases?

    <p>It resembles plasma more closely in ionic content.</p> Signup and view all the answers

    Which condition can impair swallowing due to its impact on striated muscle function?

    <p>Myasthenia gravis</p> Signup and view all the answers

    Which component of saliva contributes to antibacterial action?

    <p>Lysozyme</p> Signup and view all the answers

    What primary mucosal secretion protects the esophagus from harmful substances?

    <p>Mucus</p> Signup and view all the answers

    What is the effect of vasodilatation on the salivary glands?

    <p>Increases oxygen and glucose supply</p> Signup and view all the answers

    Which role does saliva play in digestion?

    <p>Solubilizes food molecules for taste</p> Signup and view all the answers

    What common physiological cause can lead to xerostomia (dry mouth)?

    <p>Decreased salivary gland function</p> Signup and view all the answers

    What primary function does the mechanical action of mastication serve?

    <p>Initiate enzymatic digestion</p> Signup and view all the answers

    Which of the following is NOT a function of saliva?

    <p>Digestion of protein</p> Signup and view all the answers

    What types of receptors are involved in the sympathetic stimulation of salivary glands?

    <p>α-AR and β-AR</p> Signup and view all the answers

    How does saliva contribute to oral hygiene?

    <p>By buffering acid and destroying pathogens</p> Signup and view all the answers

    What anatomical structure separates the nasopharynx from the oropharynx?

    <p>Soft palate</p> Signup and view all the answers

    Which phase of swallowing is primarily controlled involuntarily?

    <p>Pharyngeal phase</p> Signup and view all the answers

    Which muscle is responsible for pulling the epiglottis to close off the trachea during swallowing?

    <p>Pharyngeal muscle</p> Signup and view all the answers

    In which region of the pharynx do the palatine tonsils reside?

    <p>Oropharynx</p> Signup and view all the answers

    The contraction of which muscle helps in maintaining the closure of the nasopharynx during swallowing?

    <p>Palatal muscle</p> Signup and view all the answers

    Which region of the pharynx is continuous with the esophagus?

    <p>Laryngopharynx</p> Signup and view all the answers

    What is the sequence of motor events in swallowing initiated by?

    <p>A coordinated sequence of both voluntary and involuntary controls</p> Signup and view all the answers

    Which part of the brain coordinates the reflex actions during the pharyngeal phase of swallowing?

    <p>Medulla oblongata</p> Signup and view all the answers

    Study Notes

    Autonomic Nervous System

    • The gastrointestinal tract is innervated by the autonomic nervous system (ANS).
    • The ANS is responsible for extrinsic and intrinsic innervation of the GI tract.
    • Extrinsic branches of the ANS include the sympathetic and parasympathetic nervous systems.
    • The intrinsic nervous system of the gastrointestinal tract is also known as the enteric nervous system.

    Salivary Glands

    • There are three pairs of salivary glands: parotid, submandibular, and sublingual.
    • The parotid gland is the largest and secretes primarily serous saliva.
    • The submandibular gland is the second largest and secretes a mix of serous and mucous saliva.
    • The sublingual gland is the smallest and secretes primarily mucous saliva.
    • All glands have ducts that carry saliva to the oral cavity.

    Composition of Saliva

    • Saliva flow rate is typically ~1-2 L/day, with spontaneous basal rate ~0.5 ml/min and a max flow of ~5 ml/min.
    • Saliva is primarily water (~99.5%), with a small percentage of electrolytes and proteins/enzymes.
    • Key salivary enzymes include:
      • α-amylase (initiates digestion of starches)
      • lingual lipase (initiates digestion of dietary lipids)
      • mucins (glycoproteins, act as lubricants)
    • Salivary components include:
      • IgA and lysozyme (immune defence)
    • Saliva is hypo-osmolal compared to plasma, with lower [Na+] and [Cl-], higher [K+] and [HCO3-].
    • The pH of saliva is between 6.0 - 8.0.

    Regulation of Saliva Production

    • Salivary secretions are stimulated by both parasympathetic and sympathetic nerves.
    • Parasympathetic stimulation leads to increased salivation, mediated by acetylcholine acting on muscarinic receptors.
    • Parasympathetic stimulation increases blood flow to salivary glands via vasodilatation.
    • Sympathetic stimulation has a more complex role with limited physiological impact.
      • α-adrenergic receptor activation may increase flow, possibly due to resistance in the duct.
      • β-adrenergic receptor activation increases amylase content.

    Functions of Saliva

    • Digestion: Saliva starts the digestion of starches (α-amylase) and lipids (lipase).
    • Lubrication: Saliva lubricates food, facilitating swallowing.
    • Taste: Saliva solubilizes food molecules for tasting.
    • Speech: Saliva facilitates speech by helping with the movement of lips and tongue.
    • Oral Hygiene: Saliva plays a role in maintaining oral health by:
      • Buffering: Neutralizing acid and maintaining pH (6-8).
      • Antibacterial: Lysozyme and IgA help to fight bacteria and maintain oral microbiota homeostasis.

    Mastication (Chewing)

    • Mastication breaks down food into smaller pieces, increasing surface area for enzymatic digestion.
    • The tongue lubricates food and mixes it with saliva.
    • Taste buds are stimulated, triggering reflex increases in salivary, gastric, pancreatic, and bile secretion.

    Swallowing

    • Swallowing is a complex process divided into three phases:
      • Oral phase: Voluntary, involving the tongue pushing the bolus towards the pharynx.
      • Pharyngeal phase: Involuntary, involving the pharynx contracting and propelling the bolus towards the esophagus.
      • Oesophageal phase: Involuntary, involving peristaltic waves moving the bolus through the esophagus.
    • The upper esophageal sphincter (UES) contracts, preventing regurgitation of food.
    • The lower esophageal sphincter (LES) relaxes briefly before peristaltic waves reach the stomach.
    • The vagus nerve (X) and intrinsic reflexes are involved in controlling swallowing.

    Oesophageal Phase Control

    • Primary peristaltic waves, initiated by swallowing, move the bolus at 4cm/sec.
    • Secondary peristaltic waves are triggered by stimulation of mechanoreceptors in the esophagus when a bolus fails to reach the stomach.
    • The LES is tonically active, preventing reflux and heartburn.
    • The LES relaxes to allow the bolus to pass into the stomach, then contracts again.

    Swallowing Complications

    • Conditions affecting striated muscle can impair swallowing, such as stroke, myasthenia gravis, Parkinson's disease, and multiple sclerosis.
    • Dysphagia (difficulty swallowing) is a common concern in older adults.
    • Achalasia is a condition characterized by excess LES tone, weak oesophageal peristalsis, and failure of LES relaxation resulting in difficulty swallowing.

    Xerostomia (Dry Mouth)

    • Xerostomia is characterized by reduced or absent saliva flow due to various medical conditions, decreased salivary gland function, dehydration, anxiety, and medications.

    Ptyalism (Hypersalivation)

    • Ptyalism is excessive salivation, often caused by nausea or vomiting.
    • This can also be due to conditions like salivary gland tumors, and medications, such as those used to treat epilepsy.

    Vomiting

    • Vomiting is a complex reflex regulated by the vomiting center in the medulla oblongata.
    • The vomiting center receives input from:
      • The gastrointestinal tract (stretch receptors, chemoreceptors)
      • The chemoreceptor trigger zone (CTZ)
      • The vestibular system
    • The vomiting reflex involves:
      • Deep inspiration followed by closing of the glottis
      • Contraction of the abdominal muscles
      • Relaxation of the lower esophageal sphincter
      • Reverse peristaltic waves in the stomach and esophagus

    Saliva

    • Saliva flow rate: 1-2 L/day
      • Varies with time of day and stimulus
      • Basal rate (0.5 ml/min) to peak flow (5 ml/min)
    • Composition: 99.5% water, 0.5% electrolytes, proteins, and enzymes
      • Salivary amylase (digests starches)
      • Lingual lipase (digests lipids)
      • Mucins (lubricant)
      • IgA and lysozyme (immune defense)
    • Hypo-osmolal compared to plasma
      • Saliva ~130 mosmol/kg vs. plasma 280 mosmol/kg
      • Lower [Na+] and [Cl-], higher [K+] and [HCO3-]
      • pH 6.0 - 8.0 (optimal for amylase = 7.0)

    Regulation of Salivary Secretion

    • Autonomic nervous system control (no hormonal regulation)
      • Parasympathetic branch (ACh) increases flow
    • Chemoreceptors and pressure receptors respond to food
      • Simple (unconditioned) salivary reflex
    • Action potentials transmitted to the salivary center in the brainstem
      • Stimulates PNS efferents to the salivary glands (cranial nerves: VII, IX, and V)
      • ACh increases salivation
    • Acquired (conditioned) salivary reflex
      • Salivation occurs as a learned response (thinking, smelling)

    Autonomic Control of Secretion

    • Parasympathetic (ACh) stimulation is dominant
      • Anti-muscarinics (e.g., atropine) cause dry mouth
    • Increases salivary flow rate
      • Increased flow and decreased electrolyte reabsorption along the duct
      • Salivary electrolyte concentrations increase
      • Higher flow rate = closer similarity to plasma in ionic content
      • Vasodilation increases blood flow to salivary gland (O2, glucose)
    • Sympathetic: complex, limited physiological role
      • α-adrenergic activation may increase flow (duct resistance)
      • β-adrenergic activation increases amylase content

    Function of Saliva

    • Digestion
      • Begins digestion of starches (amylase) and lipids (lipase)
      • Minimal digestion in the mouth due to time
      • No nutrient absorption
    • Lubrication
      • Moistens food and provides lubrication (mucus) for bolus formation
      • Solubilizes food molecules for tasting
      • Facilitates speech (lips, tongue movement)
    • Oral Hygiene
      • Buffering: neutralizes acid, maintains pH (6-8)
      • Antibacterial action: lyses and destroys certain bacteria (lysozyme)
      • Antibacterial action: responds to bacteria, maintains oral microbiota homeostasis (IgA)

    Mastication (Chewing)

    • Mechanical breakdown of food
      • Grinds and breaks food into smaller pieces
      • Increases surface area for salivary enzymatic digestion
    • Lubricates food (tongue)
      • Mixes food with saliva (salivary amylase) for enzymatic digestion
      • Facilitates swallowing by softening and lubricating food (mucus)
    • Stimulates taste buds
      • Reflex increase in salivary, gastric, pancreatic, and bile secretion

    Xerostomia (Dry Mouth)

    • Reduced or absent saliva flow
      • Medical conditions
      • Decreased salivary gland function (hyposalivation)
      • Physiological causes (dehydration, anxiety)
      • Medications (e.g., antihistamines, antidepressants)

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    Explore the intricacies of the autonomic nervous system, focusing on its role in the gastrointestinal tract and the various salivary glands. This quiz delves into the structure and function of the ANS, as well as the composition and flow rate of saliva. Test your knowledge on these essential biological systems!

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