Podcast
Questions and Answers
What role does the oculomotor nerve have in the eye?
What role does the oculomotor nerve have in the eye?
How does the parasympathetic system affect gastrointestinal function?
How does the parasympathetic system affect gastrointestinal function?
What is the role of the facial nerve in secretion?
What is the role of the facial nerve in secretion?
Which function is associated with the glossopharyngeal nerve?
Which function is associated with the glossopharyngeal nerve?
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What is the effect of the vagus nerve on the heart?
What is the effect of the vagus nerve on the heart?
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What is the primary effect of the vagus nerve on the heart?
What is the primary effect of the vagus nerve on the heart?
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Which of the following accurately describes the role of the parasympathetic nervous system in the gastrointestinal tract?
Which of the following accurately describes the role of the parasympathetic nervous system in the gastrointestinal tract?
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What is the primary function of the facial nerve in relation to salivary secretions?
What is the primary function of the facial nerve in relation to salivary secretions?
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Which function is associated with the glossopharyngeal nerve?
Which function is associated with the glossopharyngeal nerve?
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Which of the following statements about sympathetic and parasympathetic interaction in salivary secretion is true?
Which of the following statements about sympathetic and parasympathetic interaction in salivary secretion is true?
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What effect does the vagus nerve have on the bronchi and bronchioles?
What effect does the vagus nerve have on the bronchi and bronchioles?
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Which of the following is NOT a function of the parasympathetic nervous system in the pelvic region?
Which of the following is NOT a function of the parasympathetic nervous system in the pelvic region?
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Which of these areas receives sympathetic innervation only?
Which of these areas receives sympathetic innervation only?
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What is a primary function of the oculomotor nerve in the parasympathetic nervous system?
What is a primary function of the oculomotor nerve in the parasympathetic nervous system?
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Which nerve is primarily involved in the secretion of saliva from the submandibular and sublingual glands?
Which nerve is primarily involved in the secretion of saliva from the submandibular and sublingual glands?
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What is one of the key functions of the glossopharyngeal nerve in the parasympathetic system?
What is one of the key functions of the glossopharyngeal nerve in the parasympathetic system?
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The vagus nerve primarily influences which of the following in the parasympathetic nervous system?
The vagus nerve primarily influences which of the following in the parasympathetic nervous system?
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What physiological action is controlled by the facial nerve in the context of mucosal management?
What physiological action is controlled by the facial nerve in the context of mucosal management?
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What effect does the vagus nerve have on the gastrointestinal tract?
What effect does the vagus nerve have on the gastrointestinal tract?
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What function does the constrictor pupillae muscle perform when activated by the oculomotor nerve?
What function does the constrictor pupillae muscle perform when activated by the oculomotor nerve?
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Which cranial nerve is responsible for triggering vasodilation of blood vessels in the face?
Which cranial nerve is responsible for triggering vasodilation of blood vessels in the face?
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Study Notes
Parasympathetic Nervous System
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The parasympathetic nervous system (PNS) regulates a wide range of bodily functions, typically promoting "rest-and-digest" responses.
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Objectives: The lecture aims to cover the origin and components of the parasympathetic nervous system (PNS). It also touches on the parasympathetic tone, the functions of the PNS in various areas of the body, its relation to the sympathetic nervous system, and its roles in functions like micturition.
Cranial Outflow
- Cranial nerves 3, 7, 9, and 10 are part of the parasympathetic system
- III - Oculomotor nerve
- VII - Facial nerve
- IX - Glossopharyngeal nerve
- X - Vagus nerve
Sacral Outflow
- The sacral outflow originates from the lumbar spinal cord segments 2, 3, and 4
- The preganglionic fibers form the pelvic nerve
Parasympathetic Supply to Head and Neck
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III - Oculomotor nerve: The PNS, via this nerve, causes pupil constriction (miosis) and facilitates focusing the eye for near vision (accommodation). This process occurs at the ciliary ganglion.
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VII - Facial nerve (Chord tympanic branch): PNS stimulation via this nerve increases salivary secretion (true saliva) in submandibular & sublingual salivary glands, and causes vasodilation in the blood vessels of the face and anterior 2/3 of the tongue. This action takes place within the submandibular ganglion.
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IX - Glossopharyngeal nerve: PNS stimulation by this nerve triggers true salivary secretion in the parotid salivary gland and vasodilation in the blood vessels of the parotid gland and posterior 1/3 of the tongue, happening at the otic ganglion.
Parasympathetic to Thorax and Abdomen
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X - Vagus nerve: The vagus nerve represents a significant portion (75%) of the parasympathetic supply to the thorax and abdomen.
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Relay occurs in terminal ganglia within the thoracic and abdominal viscera.
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Thorax (heart and lungs): Parasympathetic functions in the thorax include reducing heart rate, decreasing conductivity, contractility, excitability, & rhythmicity, constricting the coronary blood vessels, reducing blood flow to the cardiac muscle. The vagus nerve also causes bronchoconstriction in the lungs, increasing mucous secretion and vasodilation.
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Abdomen (GI tract, liver, pancreas): The parasympathetic system stimulates motility in the gastrointestinal tract, increases secretions (HCl and mucus) in the gastric glands, causes vasodilation in the blood vessels, stimulates bile secretion in the liver, and stimulates pancreatic juice secretion and insulin secretion in the pancreas.
Parasympathetic to the Pelvis
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Origin: Sacral segments 2, 3, and 4.
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Relay: Terminal ganglia
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Urinary bladder: The PNS contracts the bladder wall and relaxes the internal urethral sphincter, facilitating urination.
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Rectum and anal canal: The PNS contracts the rectum and relaxes the internal anal sphincter, promoting defecation.
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Sex organs: Parasympathetic activity supports vasodilation in the blood vessels of the sex organs.
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Autonomic Nervous System Control: Autonomic functions are controlled by reflexes. Reflexes are routed through the spinal cord, brain stem (medulla oblongata, pons, midbrain), and the hypothalamus (temperature, water balance, eating, & behavior).
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The cerebral cortex has higher controls over micturition and defecation, and the hypothalamus controls the activity of autonomic centers in the brain stem.
Sympathetic and Parasympathetic Tone
- The tone is the basal rate of activity of both the sympathetic and parasympathetic systems.
- Sympathetic tone is responsible for maintaining the constriction of blood vessels. The sympathetic tone is continuously stimulated through sympathetic fibers and by the level of adrenaline and noradrenaline secretion from the adrenal medulla.
- Parasympathetic tone is critical for heart rate control and GI function (decreasing SA node's high rhythm, and maintaining normal functioning of the GI tract).
Structures Supplied Primarily by Each System
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Sympathetic Systems: Supplies dilator pupillae muscle, ventricles of the heart, most blood vessels, spleen, adrenal medulla, and skin
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Parasympathetic Systems: Supplies sphincter pupillae muscles, stomach glands, pancreas.
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Description
This quiz explores the origin and components of the parasympathetic nervous system, focusing on its functions and relation to the sympathetic nervous system. Key areas discussed include cranial and sacral outflows, as well as the specific roles of cranial nerves in regulating bodily functions. Test your understanding of the PNS and its significance in maintaining homeostasis.
