Bio 502, Lectures #19&20: Cranial nerves & targets

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  1. If an arterial blockage occurred on the left side of the body at the C5 level in the carotid system, which portions of the dura mater would experience compromised blood flow and why?
    All three portions (anterior, middle and posterior) portions of the dura would experience compromised blood flow because an arterial blockage in the carotid system at the C5 level would mean that the common carotid artery would be blocked. the primary blood supplies to the three dural sections is from the anterior meningeal arteries (to the anterior cranial fossa off of the opthalmic and ethmoidal arteries, from the internal carotid artery), the middle meningeal artery (to the middle cranial fossa, off of the maxillary/external carotid artery) and the posterior meningeal artery (to the posterior cranial fossa, also off of the external carotid artery, via the ascending pharyngeal artery). Plus you would be dead since the brain is largely supplied by arteries derived from the internal carotid arteries.
  2. Why is the term "muscles of facial expression" a bit of a misnomer for the muscles of the face?
    Because their actual function is to act as sphincters and/or dilators of the orifices of the face (mouth, nose and eyes). Facial expressions are a secondary function.
  3. True or false (if false, provide the correct information):
    special afferent impulses travel out from the CNS, which is why they are categorized as "special afferent"
    FALSE. They travel into the CNS, as do all afferent impulses. They are special b/c they conduct afferent impulses from the organs of special sense: the eyes, organs of balance and hearing, nose, and tongue
  4. True or false (if false, provide the correct information):

    The general visceral efferent impulses conducted by occulomotor (CN VII) and glossopharyngeal (CN IX) are sympathetic to the lacrimrimal, submandibular and sublingual glands and to the parotid gland, respectively.
    FALSE. Sympathetic impulses exit CNS between T1 and L2. And all sympathetics bound for the head exit the CNS at T1. Parasympathetic impulses exit from among some of the cranial nerves and S2-S4. Additionally, occulomotor is CN III not VII and it doesn't supply the glands, its visceral efferent impulses supply the sphincter pupillae and cilliary muscles in the eye. However, those parasympathetics may travel with sympathetics bound for dialator pupillae. Also, glossopharyngeal does not innervate the submandibular and sublingual glands. Or the lacrimal gland. So...this is wrong for a whole bunch of reasons...
  5. What structure conducts the saliva produced by the structure innervated by the glossopharyneal nerve (CN IX) into the mouth?
    The parotid duct
  6. Why do surgeons have to be careful when working on the region of the parotid gland?
    • Because a number of important structures travel through or around the parotid gland which can be damaged during surgery. These structures are: 
    • 1) the terminal branches of the facial nerve
    • 2) the parotid duct
    • 3) the retromandibular vein and some of its tribuiteries
    • 4) the external carotid artery and some of its branches, including maxillary and many of its branches
  7. True of false (if false, provide the correct information):

    Trigeminal (CN V) conducts the following types of impulses:
    general somatic afferent
    special somatic efferent
    FALSE: trigeminal (CN V) conducts general somatic afferent and special visceral efferent. Special somatic efferent impulses do not exist. It does help get special afferent to the tongue, but those are really from the Facial nerve VII (chroda tempani)
  8. If the posterior trunk of the motor root of the mandibular division of the trigeminal nerve were 100% blocked, the function of which muscles participating in mastication would be compromised? Explain your answer.
    None of the "classic" muscles of mastication would be affected b/c they are all innervated by branches that come off of the anterior trunk or by nerves that branch off of the mandibular division before it divides into anterior and posterior divisions. However, the anterior belly of digastric and mylohyoid are both active during mastication and swallowing, and they are innervated by the nerve to mylohyoid which is a branch of the inferior alveolar nerve from the posterior trunk. So abduction (depression) of the mandible would be compromised and swallowing (i.e., raising the floor of the mouth) would be compromised.
  9. True of false (if false, provide the correct information):

    Buccal nerve from trigeminal nerve (CN V) always carries general somatic afferent fibers whereas the buccal branch from the facial nerve (CN VII) always carries special visceral efferent fibers.
    FALSE: buccal nerve from trigeminal always carries GSA and it MAY carry special visceral efferent fibers targeting temporalis and/or lateral pterygoid muscles. However buccal branch from facial does indeed consistently conduct BE impulses.
  10. True of false (if false, provide the correct information):

    In dissection, the external carotid artery lies anterior to the internal carotid artery.
  11. Which type of impulses innervate the muscles of mastication and what does this indicate about their derivation?
    They are innervated by special visceral efferent (BE) fibers, indicating that they are derived from the pharyngeal arches (1st arch).
  12. Trace the efferent nerve supply of the medial pterygoids from the brain. Include branching pattern and major structural components of the path.
    Pons / motor root of mandibular / mixes with sensory root to form mixed mandibular trigeminal nerve / pass through the foramen ovale into the infratemporal fossa / nerve to medial pterygoid
  13. True or false (if false, provide the correct information):
    vestibulocochlear nerve (CN IX) passes into the internal accoustic meatus with the facial nerve (CN VII)
    FALSE: vestibulocochlear nerve is CN VIII. However, the two nerves do enter the internal acoustic meatus together.
  14. A patient presents unable to produce tears, but with complete sensation around the eyes and full ability to open and close the eye lids. Which cranial nerve(s) appear affected, where and why? Which cranial nerves appear to be unaffected and why?
    The greater petrosal nerve of facial (CN VII) appears compromised. The problem would have to occur after it branches from the geniculate ganglion b/c the terminal nerves of facial (CN VII) must be fine if the patient can open and close the eye lids. The opthalmic (V1) and maxillary (V2) divisions of trigeminal are also OK, b/c sensation around the eyes is not impaired. The specific unaffected branches of trigeminal that are unaffected are: supra-orbital & supratrochlear (eyelids, forehead and scalp), infratrochlear (nose, eyelids and skin around the eyes), lacrimal (skin around eyelids and around eyes) and potentially zygomaticofacial and infra-orbital, depending on their distribution.
  15. List all of the nerves responsible for producing:
    1) movements of the eyeball
    2) movements of the eyelids
    3) changes in the shape of the lens
    4) changes in the amount of light able to enter the eye

    for each nerve, list the targets
    • 1) occulomotor nerve (CN III): 
    • All but two of the extraoccular muscles (Levator palpebrae, superior rectus, inferior rectus, medial rectus, inferior oblique)
    • changes in lens: ciliary muscles
    • changes in light: sphincter pupillae
    • 2) Trochlear nerve (CN IV):
    • An extraoccular muscle (superior oblique muscle)
    • 3) Abducent nerve (CN VI):
    • the last extraoccular muscle (lateral rectus muscle)
    • 4) Temporal & zygomatic branches of facial nerve (CN VII):
    • sphincters of the eye (we did not go over the muscles of facial expression that act on the eye, so simply saying "facial CN VII" is sufficient)
    • 5) sympathetics from T1: dialator pupillae
  16. Which nerve is described by the geographic path below:

    External ear / parotid gland / posterior trunk / infratemporal fossa / foramen ovale / mixed mandibular nerve / trageminal ganglion / sensory root / pons
    Auriculotemporal nerve
  17. True of false (if false, provide the correct information):
    The intermediate nerve is the sensory root of the facial nerve (CN VII), and as such it carries only sensory fibers.
    FALSE: even though it is considered the sensory root, it also carries general visceral efferent fibers (e.g., to the greater petrosal nerve)
  18. For the following question, select
    a) if 1 is correct
    b) if 1&2 are correct
    c) if 2&3 are correct
    d) if all are correct
    e) if none are correct

    1) the olfactory nerve (CN I) originated on the ethmoid bone
    2) CNs I, II, VII, VIII, IX & X carry special afferent fibers
    3) Accessory nerve (CN XI) carries only motor impulses to the trapezius and sternocleidomastoid muscles
    4) Accessory nerve (CN XI), vagus nerve (CN X), glossopharyngeal nerve (CN VIII) all travel through the foramen magnum
  19. For the following question, select
    a) if 1 is correct
    b) if 1&2 are correct
    c) if 2&3 are correct
    d) if all are correct
    e) if none are correct

    1) The tendon of the temporalis muscle passes superficial to the zygomatic arch
    2) Starting from their cranial origin, the lingual nerve (mandibular division of trigeminal, V3) is joined by chorda tympani (facial nerve, CN VII) before lingual nerve passes through the foramen ovale
    3) the superficial and deep temporal arteries form a network along the sagital suture to supply the crown of the head
    4) three of the four muscles of mastication take a portion of their origin from some aspect of the sphenoid bone
  20. True or false (if false, provide the correct information):

    Vagus nerve (CN X) is solely responsible for supplying impulses responsible for detecting changes in blood chemistry and blood pressure.
    FALSE: glossepharyngeal nerve (CN IX) also provides impulses for these functions
  21. True or false (if false, provide the correct information):

    three nerves are responsible for conducting impulses to and from the tongue.

    • five nerves are responsible for conducting impulses to the tongue:
    • chorda tympani (Facial nerve, CN VII)
    • lingual nerve (mandibular division of trigeminal nerve, CN V3)
    • glossopharyngeal nerve (CN IX)
    • vagus nerve (CN X)
    • hypoglossal nerve (CN XII)
  22. Match the cranial nerve and the target structures or areas: 
    A) Cochlear nerve (CN VIII)
    B) Carotid body
    C) frontal lobe
    D) organs of hearing
    E) Olfactory nerve (CN I)
    F) Falx cerebri
    G) glossopharyngeal nerve (CN IX) 
    H) Opthalmic division of trigeminal nerve (CN V1)
    • A&D
    • B&G
    • C&E
    • F&H
Card Set
Bio 502, Lectures #19&20: Cranial nerves & targets
Muscles of facial expression & mastication
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