1. The PNS includes
    • cranial nerves
    • spinal nerves
    • ganglia
    • sensory receptors
    • *Includes all nervous system structures EXCEPT THE BRAIN AND SPINAL CORD
  2. Functions of the PNS
    • converting various forms of energy into sensory impulses
    • conducting these sensory impulses into the CNS
    • conducting motor impulses from the CNS to effector organs (muscles and glands)
  3. nerve
    a bundle of nerve fibers (axons) in the peripheral nervous system
  4. epineurium
    the connective tissue proper encasement surrounding the whole structure of a nerve
  5. perineurium
    partitions of connective tissue proper inside the epineurium which subdivide the groups into fasciculi
  6. fasciculi
    groups of axons
  7. endoneurium
    a conn. t.p. encasement surrounding each individual axon
  8. nerve fiber tracts
    • groups of nerve fibers in the brain and spinal cord (within the CNS)
    • *nerves, per se, do not exist in the CNS. Their called "nerve fiber tracts"
  9. cranial nerves
    nerves which originate directly from (attach to) the brain
  10. spinal nerves
    those nerves which originate directly from (attach to) the spinal cord
  11. mixed nerves
    • nerves which consist of both efferent and afferent FIBERS
    • (nearly all nerves)
  12. sensory nerves
    the few cranial nerves which contain ONLY afferent fibers
  13. cranial nerves
    • pairs numbered 1-12
    • distributed mainly to the head and neck
    • *with the exception of the vagus (and to a lessor extent, the accessory) nerves which supply a number of structures in the trunk
  14. cell bodies of motor fibers carried by cranial nerves are found in groups (nuclei) within....
    the mesencephalon, pons, and medulla oblongata of the brain
  15. cell bodies of sensory fibers carried by cranial nerves are located primarily in...
    sensory ganglia located along the course of the nerves near the brain
  16. memory aid to remember the names of all 12 cranial nerves
    • On Old Olympus' Towering Top, A Fine Victorian Gentleman Viewed A Hawk
    • (CN1) Olfactory nerve
    • (CN2) Optic nerve
    • (CN3) Oculomotor nerve
    • (CN4) Trochlear nerve
    • (CN5) Trigeminal nerve (Ophthalmic,Maxillary,Mandibular N)
    • (CN6) Abducens nerve
    • (CN7) Facial nerve
    • (CN8) Vestibulocochlear nerve
    • (CN9) Glossopharyngeal nerve
    • (CN10) Vagus nerve
    • (CN11) Accessory nerve
    • (CN12) Hypoglossal nerve
  17. cranial nerves that are sensory ONLY
    • 3 pairs
    • CN 1 - Olfactory n.
    • CN 2 - Optic n.
    • CN 8 - vestibulocochlear n.
  18. cranial nerves considered to be primarily motor
    • 5 pairs
    • CN 3 - oculomotor n.
    • CN 4 - trochlear n.
    • CN 6 - abducens n.
    • CN 11- accessory n.
    • CN 12 - hypoglossal n.
  19. cranial nerves that are relatively simple in that they only have one function
    • CN 1 = olfaction
    • CN 2 = vision
  20. cranial nerves considered to be mixed (motor/sensory)
    • 4 pairs
    • CN 5 - trigeminal n.
    • CN 7 - facial n.
    • CN 9 - glossopharyngeal
  21. memory aid for major roles of the cranial nerves as sensory, motor, or both
    • Six Sailors Made Merry But My Brother Said Bad Business, My Man
    • Where S = Sensory only, M = motor mainly, B = both
  22. CN 1
    • Olfactory nerve
    • Transmitting foramen: cribriform of ethmoid bone
    • Function: VA neurons - sense of smell (olfaction)
  23. olfactory epithelium
    a specialized part of the respiratory epithelium covering the superior third of the nasal septum and most of the superior nasal conchae of the ethmoid bone
  24. olfactory cells
    • bipolar neurons whose cell bodies are scattered among the regular columnar epithelial cells and goblet cells.
    • Only very small % of inhaled air comes in contact w/ olfactory mucosa (most pass inferior to it) but Olf. cells are extmly sensitive chemoreceptors
    • Moisture from goblet cells increase sensitivity
  25. cribriform foramina
    • where the axons of olfactory cells course through, synapse within the olfactory bulb of the rhinencephalon
    • these axons form the olfactory tracts which terminate in the olfactory areas of the temporal lobes of the cerebral cortex. That's where impulses are interpreted as odors
  26. CN II
    • Optic nerve
    • Trans. foramen: Optic canal of sphenoid bone
    • Function: SA neurons - vision
  27. rods and cones
    • photoreceptor cells in the retina of each eye which initiate nervous impulses in response to light
    • these synapse with bipolar neurons, which synapse with ganglion cells (all within the retina) the axons from the ganglion cells become the optic nerve, which passes throu the orbit and through the optic canal of the spheniod bone
  28. optic chiasm
    • on the ant. aspect of the hypothalamus
    • formed when the optic nerves join at the midline (after passing through the optic canal
    • *here the fibers from medial 1/2 of each retina cross over (decussate) to the opposite side.
  29. lateral geniculate bodies
    • of the thalamus
    • axons from these neurons continue to the visual cortex located in the occipital lobs of the cerebral hemispheres
    • *small % (20-30) of fibers in each optic tract course to the ipsilateral superior colliculus of the mesencephalon where they synapse on neurons involved in reflexes related to body/eye coordination
  30. CN III
    • Oculomotor nerve
    • Trans. foramen: superior orbital fissure
    • SE - motor to superior, medial and inferior rectus mm.c inferior oblique m. levator, palpebrae superioris m. of the eye
    • VE - motor to ciliary m. of eye and pupillary sphincter m. of the iris
  31. oculomotor nerves
    • CN III - innervate a # of muscles associated with the eye
    • nerve emerges to from the oculomotor sulcus (adjacent to pons), pass through orbital fissure, and divides into superior and inferior branches within the orbit
  32. superior branch of the oculomotor nerves
    • (CN III) - carries multipolar (SE) fibers to:
    • the superior rectus muscle which rotates the eyeball superiorly
    • the levator palpebrae superioris muscle which raises the upper eyelid to open the eye
  33. inferior branch of the oculomotor nerves
    • (CN III) supplies multipolar (SE) fibers to:
    • the medial rectus, inferior rectus, and inferior oblique muscles of the eye - which rotate the eyeball in various directions
  34. VE action of oculomotor nerves
    • (CN III)
    • supply smooth muscles within the eyeball
    • impulses are carried by nerves to the ciliary ganglion (located behind the eyeball)
    • axons from postganglionic fibers continue to eyeball within short ciliary nerves and supply the ciliary muscle (a smooth m. in the ciliary body which controls lens thickness) and the pupillary sphincter muscle (smooth m. in the iris, causes constriction of pupillary aperture)
  35. CN IV
    • trochlear nerve
    • Trans. foramen: superior orbital fissure
    • SE neurons - motor to superior oblique m. of the eye
  36. trochlear nerves
    CN IV - smallest cranial nerves, only pair that arise from the posterior/superior aspect of the brain
  37. CN V
    • trigeminal nerves, 3 subdivisions:
    • Ophthalmic n. : SA
    • Maxillary n.: SA
    • Mandibular n.: SA 
    • *largest cranial nerves (in diameter) are principal sensory nerves of the head
  38. ophthalmic n.
    • subdivision of CN V
    • Trans. foramen - superior orbital fissure
    • SA neurons - sensory from and around the eye (general sensation)
    • *after it courses throu the superior orbital fissure into the orbit, it divides into several sensory branches which are distributed to the nose, eye, upper eyelid, forehead, and vertex
  39. Maxillary n.
    • Subdivision of CN V
    • Trans. foramen: foramen rotundum of sphenoid bone
    • SA neurons: divides into several branches, sensory from upper lip, upper teeth palate, cheek, and lower eyelid
  40. infraorbital nerve
    • branch of the maxillary nerve (subdivision of CN V)
    • continues through the infraorbital forament to be distributed to the face
  41. mandibular nerve
    • subdivision of CN V
    • largest and most lateral branch
    • SA neurons: sensory from lower limp and surrounding skin, lower teeth and gums, tongue, and floor of oral cavity
    • SE neurons: motor to mm. of mastication
  42. inferior alveolar nerve
    • branch of the mandibular nerve
    • enters mandibular foramen to supply the inerior teeth with sensory fibers and then re-emerges at the mental foramen as the mental nerve to supply the lower lip
  43. chorda tympani
    • a branch of facial nerve with is RECEIVED by the mandibular nerve
    • includes the axons of taste fibers and the parasympathetic preganglionic fibers destined for the salivary glands
  44. trigeminal ganglion
    • contains the cell bodies of it's pseudounipolar (SA) neurons
    • three named subdivisions which attach to ganglion:
    • ophthalmic nerve
    • maxillary nerve
    • infraorbital nerve
  45. CN VI
    • abducens nerve
    • emerge from the brain within a groove called the bulbopontine sulcus
    • trans. foramen: superior orbital fissure
    • SE neurons: motor to lateral rectus m. of the eye
    • frequently traumatized resulting in the inability to rotate the eyeball laterally
  46. convergent strabismus
    • "cross eyes"
    • can happen from abducens nerve trauma, which results in the inability to rotate the eyeball laterally
  47. CN VII
    • Facial nerve
    • also emerges from the bulbopontine sulcus
    • trans. foramen - passes through both the internal acoustic meatus and stylomastoid foramen of temporal bone
    • VA neurons: taste sensation (gustation) from anterior 2/3rds of tongue
    • VE neurons: motor to lacrimal, sublingual, and submandibular glands (lacrimation and salivation) - lacrimation synapse on postganglionic neurons in the pterygopalatine ganglion; salivation synapse in sublingual and submandibular ganglia
    • SE neurons: motor to mm. of facial expressions and the stapedius m.
  48. geniculate ganglion
    (sensory), facial nerve widens here and gives off to several branches.
  49. chorda tympani
    • a branch of the facial nerve which courses across the medial side of the typanic membrane to join and be distributed with the lingual nerve (a branch of the mandibular nerve)
    • carry taste sensations from anterior 2/3rds of tongue
  50. CN VIII
    • Vestibulocochlear n.
    • trans. foramen: internal acoustic meatus of temporal bone (ONLY cranial nerve which does not emerge from skull)
    • SA neurons: sensory from cochlear part of internal ear (audition) and vestibular part of internal ear (balance and body position)
    • within meatus, divides into cochlear (auditory) nerve and vestibular(equilibrium) nerve portions of the internal ear
  51. CN IX
    • Glossopharyngeal n.
    • trans. foramen: jugular foramen
    • VA : taste sensation (gustation) from post. 1/3 of tongue, general sensation from back of tongue and pharyngeal region
    • VE : motor to parotid gland (salivation)
    • SA : sensory from a small cutaneous area behind the ear
    • SE : motor to some skeletal mm. of the pharynx
  52. otic ganglion
    • there the autonomic fibers of the parotid (salivary) gland synase
    • (glossopharyngeal nerve)
  53. CN X
    • Vagus nerve - longest cranial nerves, distributed throughout cervical, thoracic, and most abdomial regins
    • trans. foramen: jugular foramen
    • VA : sensory from respiratory and digestive systems, and a few taste fibers from the tongue
    • VE: motor to heart and to smooth muscle and glands of the respiratory and digestive systems
    • SA: sensory from skin in back of ear and post. wall of ext. acoustic meatus
    • SE: motor to muscles of the larynx and pharynx
  54. CN XI
    • Accessory nerve
    • trans. foreman: jugular foramen
    • SE : motor to trapexius and part of stenocleidomastoid muscles
  55. CN XII
    • Hypoglossal nerve
    • trans. foramen: hypoglossal conal of occipital bone
    • SE : motor to muscles of the tongue and infrahyoid muscles
  56. *Any cranial nerve which carry SE fibers (to skeletal muscle tissue.....
    will ALSO carry SA fibers (proprioceptive fibers) from that skeletal m.
  57. Which cranial nerves transmit from the superior orbital fissure
    • CN III - oculomotor n.
    • CN IV - trochlear n.
    • CN V  - trigeminal n.- ophthalmic n.
    • CN VI - abducens n.
  58. which cranial nerves transmits through jugular foramen
    • CN IX - glossopharyngeal n.
    • CN X  - vagus n.
    • CNXI - accessory n.
  59. which cranial nerves have all 4 SA, SE, VA, VE
    CN IX and X
  60. Which cranial nerves carry gustatory fibers
    • CN VII Facial nerve
    • CN IX  Glossopharyngeal nerve
  61. which cranial nerve does NOT emerge from the skull
    CN 8 Vestibulocochlear n.
  62. which CN supply the muscles which move the eyeball
    • CN 4 Trochlear nerve
    • CN 6 Abducens nerve
  63. which CN originate from the superior (posterior) aspect of the brain
    CN 4 trochlear nerve
  64. which CN carry impulses interpreted as sound
    CN 8 Vestibulocochlear n.
  65. which CN carry impulses interpreted as sight
    CN 2 Optic nerve
  66. which CN are distributed to the tongue
    CN 12 hypoglossal n
  67. which CN carry VA fibers which are distributed beyond the head
    CN 10 Vagus n.
  68. which CN supply involuntary effectors
    • VE -
    • CN 3 Oculomotor nerve
    • CN 7 Facial nerve
    • CN 9 Glossopharyngeal nerve
    • CN 10 Vagus nerve
  69. how many pairs of spinal nerves?
    • 31± pairs
    • 8 pairs from cervical part of spinal cord
    • 12 pairs from thoracic part
    • 5 pairs of lumbar portion
    • *# of sacral pairs typically 5, but is reduced to four in those individuals w/ only 4 sacral vert. seg.
    • 1-2 pairs of coccygeal spinal nerves
  70. posterior root/anterior root (spinal nerves)
    • posterior root carrying mostly sensory fibers INTO spinal cord
    • anterior root carrying mostly motor fibers OUT OF spinal cord
  71. sensory ganglia
    • contain cell bodies of pseudounipolar neurons (no bi-polar neurons in spinal nerves)
    • located on the posterior roots
  72. After emerging from the vertebral canal through intervertebral foramina (except for the first cervical spinal n's which course bt skull and the atlas)... each spinal nerve...
    is distributed as three branches: posterior, anterior, and ramus communicans
  73. posterior branch
    • "dorsal" - consists of sensory and motor fibers that are distributed primarily to epaxial structures (structures posterior to the vertebral column)
    • typically smaller than anterior branch
  74. anterior branch
    carries sensory and motor fibers that are distributed hypaxially
  75. ramus communicans
    (pl = rami communicantes) consists of pre- and postganglionic fibers of the autonomic nervous system
  76. sympathetic trunk
    • composed of two long nerve strands, one located on each side of vertebral column, extend from base of skull to coccyx.
    • are interconnected and form cervical, thoracic, lumbar, and sacral ganglia
    • receive preganglionic fibers from thoracic and upper lumbar anterior roots via the white rami communicantes and sent postgnaglionic fivers to anterior branches via the gray rami communicantes.
    • extend to adjacent viscera and blood vessels
  77. muscles supplied by musculocutaneous nerve
    • nerve supplying superior limb
    • nerve coming from C5-7
    • the coracobrachialis, biceps brachii, and brachialis muscles; the nerve continues as the lateral cutaneous antebrachial nerve to the skin on the radial aspect of the antebrachium
  78. muscles supplied by the median n.
    • nerve supplying superior limb
    • nerve coming from C6 - T1
    • the anterior antebrachial muscles (except the flexor carpi ulnaris m. and part of deep digital flexor m.) and to the thenar muscles of the hand
    • it is cutaneously distributed to the palmar aspect of the manus (except the medial part) and to the dorsum of the distal half of digits 1-3 and the lateral aspect of digit 4
  79. muscles supplied by the Ulnar n.
    • nerve supplying superior limb
    • coming from C7 - T1
    • the flexor carpi ulnaris muscle, part of the deep digital flexor muscle, the hypothenar and many of the intermediate muscles of the manus
    • is cutaneously distributed to the medial 3rd of the manus including all of digit 5 and the midal aspect of digit 4
  80. muscles supplied by the Radial n.
    • nerve supplying superior limb
    • coming form C5-8
    • the posterior muscles of the brachium and antebrachium (ex: the extensors of the elbow, carpal, and digital joints);
    • is cutaneously distributed to central part of post. aspect of antebrachium and to the dorsum of the manus except for digit 5, the ulnar aspect of digit 4, and the distal halves of digits 1-4
  81. muscles supplied by the obturator n.
    • nerve supplying inferior limb
    • coming from L2-4
    • distributed by ant., post., and muscular branches to the skin over the medial aspect of the thigh, to the medial muscles of the thigh (except pectineus m.) and to the external obturator muscles
  82. muscles supplied by the femoral n.
    • nerve supplying inferior limb (duh)
    • coming from L2-4
    • to pectineus, sartorius, and quadriceps femoris muscles
    • branches from these muscular rami supply coxal and genual joints
    • major cutaneous branch of femoral nerve is the saphenous nerve with supplies the kin over medial aspect of crus
  83. muscles supplied by the sciatic n.
    • derived from the sacral plexus
    • sciatic n. -largest nerve in the body
    • divides into the tivial nerve and the common fibular nerve
  84. tibial nerve
    • coming from L4-S3
    • to the semitendinous and semimembranous muscles, long head of the biceps femoris, and the adductor magnus muscles(these branches arise before the sciatic nerve divides)
    • to the henual joint, muscles and skin of the calf
    • at the foot, it divides into medial and lateral plantar nerves shich supply the sole of the foot and toes
  85. common fibular n.
    • derived from the sacral plexus
    • coming from L4-S2
    • to the short head of the biceps femoris muscle (this branch arises before the sciatic nerve divides)
    • to the genual and tibiofibular joints
    • to the tibialis anterior muscle
  86. cervical plexus
    • anatomoses of the anterior branches of the first five cervical nerves (C1-C5)
    • net-like structure innervates the skin of the scalp, neck and superior aspects of the shoulder and chest, muscles of the neck, and the diaphragm
  87. brachial plexus
    • branches of the nerves that supply each superior limb
    • involves last four and first thoracic spinal nerves (C5,C6,C7,C8,C1)
    • unite to form three named trunks after the emerge from v. canal:
    • upper (superior) trunk; fusion btwn C5 & C6
    • middle trunk ; consists of anterior branch C7
    • lower (inferior) trunk; formed by fusion of anterior branches C8 and T1
    • Trunks are located in cervical region above clavicle and divides into anterior and posterior divisions
  88. posterior division
    • division of trunks
    • posterior divisions of all three unite to for a posterior cord
  89. anterior divisions
    • division of trunks
    • upper and middle trunks form the lateral cord
    • the anterior div. of the lower trunk forms the medial cord
  90. ganglia
    • collections of neuron cell bodies in the PNS system
    • two types: sensory and autonomic
  91. sensory ganglia
    • contain the cell bodies of pseudounipolar or bipolar neurons
    • found on the posterior roots of the spinal nerves and in association with most of the cranial nerves
  92. antonomic ganglia
    • (motor, visceral)
    • formed by groups of neuron cell bodies in the autonomic nervous system
    • serve as synaptic sites brwn pre- and postganglionic neurons in the two neuron motor chain of the ANS
    • 3 groups occur: sympathetic trunk ("paravertebral") ganglia, named peripheral (prevertebral") ganglia, and terminal (intermural) ganglia
  93. Sympathetic trunk ganglia
    "paravertebral" - occur segmentally along the sympathetic trunks and serve as synaptic sites for pre- and postganglionic sympathetic neurons
  94. named peripheral ganglia
    • prevertebral - include those associated with cranial nerves 3, 7, 9 and 10 as well as named ganglia within the thoracic and abdominal cavites
    • some are strictly parasympathic and some contain both sympathic and parasympathic neurons
  95. terminal ganglia
    intramural ganglia - autonomic ganglia located within the walls of the organs innervated. typically too small to be grossly ovserved
  96. special senses/general senses
    • special = vision, audition, equilibrium, olfaction, and gustation
    • general = touch, pressure, pain, heat and cold
  97. sensory receptors can be categorized into 5 groups according to general type of stimulus which they respond:
    Photoreceptors, thermoreceptors, mechanoreceptors, chemoreceptors, and nociceptors
  98. photoreceptors
    • found only in the retina of the eye
    • when exposed to light, they form the impulses interpreted as vision
  99. thermoreceptors
    • occur primarily in the skin and in the mucosal linings of some of the visceral body dystems
    • some respont to heat and other types respond to cold
  100. mechanoreceptors
    a large and varied group of highly specialized receptors that trasduce pressure, movement, stretching motions, and touch
  101. chemoreceptors
    respond to specific chemical stimuli and include cells within the taste bus in the oral cavity as well as the olfactory cells in the olfactory mucosa of the nasal cavity
  102. nociceptors
    • respond to stimuli interpreted as pain
    • thought to actually be chemoreceptors in most cases because some of them have been shown to respond to chemicals relased with tissues are damages
  103. Sensory receptors can also be grouped by general location in the body where impulses originate;
    exteroceptors, visceroceptors, and proprioceptors
  104. exteroceptors
    • respond to stimuli from the external environment
    • include all the receptors of the skin as well as those associated with vision, hearing, taste, and smell
  105. visceroceptors
    (interoceptors) respond to stimuli in the deep body organs and carry sensations related to pain, hunger, thirst, fatigue, nausea, as well as fullness of the urinary bladder, stomach, etc.
  106. proprioceptors
    • initiate impulses realted to body position, balance, and movement
    • located in vestibular portion of the internal ear and within muscle bellies, tendons, and joint capsules
  107. cutaneous receptors
    those found in the skin
  108. kinestetic receptors
    the proprioceptors whose impulses are consciously perceived (impulses from some proprioceptors initiate reflexes at the subconscious level)
  109. encapsulated receptors
    those which are encased by supporting cells
  110. free nerve endings
    • consist of unadorned neuronal dendrites
    • simplest receptors, extend superficially into deep layers of cells in epidermis and respond to touch and pain.
  111. hair root endings
    type of free nerve endings, around base of hair follicles and respond to movement of the hair shaft
  112. menisci tacti
    (Merkel's cells) another form of free nerve endings, convey touch sensations
  113. Several kinds of sensory receptors consist of dendritic endings that are encapsulated by conn. tissue sheaths:
    • pacinian corpuscles
    • baroreceptors
    • organs of ruffini
    • lamellated corpuscles
    • corpusculi tactili
    • corpusculi bulboidea
  114. pacinian corpuscles
    • large encapsulated pressure receptors that are located in the skin and a few other places int he body
    • respond to vibrations as well as pressure
  115. baroreceptors
    • another kind of specialized pressure receptor
    • found in vessel walls where they respond to changes in blood pressure
  116. organs of ruffini
    (Ruffini corpuscles) similar structurally to baroreceptors but respond to heat
  117. Lamellated corpuscles
    official terms for baroreceptors and Organs of ruffini
  118. corpusculi tactili
    (meissner's corpuscles) encapsulated receptors which are located in the skin and respond to light touch
  119. corpusculi bulboidea
    (bulbs of Krause) integumentary receptors that respond to cold
  120. neuromuscular spindles
    • complex proprioceptors found in skeletal muscles
    • contain specialized skeletal m.cells that contract to various degrees to adjust the length of the spindle to a certain tension, depending on the degree of contraction of the whole muscle belly
    • stimulated by stretching muscle belly & initiate a spinal reflex that results in subsequent contration
    • role is to monitor the degree of belly contraction and to initiate contraction when the muscle belly is suddenly and unexpectedly stretched
  121. neurotendinous spindles
    • (Golgi tendon organs) also relatively complex structures associated with skeletal muscles.
    • activated by stretching, and under extreme circumstances initiate spinal reflexes that inhibit contraction of their parent skeletal muscle.
    • role is a protective one designed to prevent a muscle from contracting with more force than it can structurally withstand
  122. Rods
    • activated only by dim light and actually become nonfunctional in bright light
    • black and white vision ONLY
    • photoreceptor
  123. cones
    • more concentrated in the central region of the retina
    • responsible for color vision (including black and white)
    • result in sharper visual images that those produced by rods
    • photoreceptor
  124. hair cells of the spiral organ
    • ("organ of Corti") - in the internal ear, have hair-like projections that are moved when the fluid in the internal ear is set in motion by sound vibrations
    • initiates impulses that are conveyed to bipolar neurons, result in audition
  125. hair cells
    • similar to hair cells of the spiral organ
    • also found in the internal ear
    • those in the ducts are stimulated by relative movement of the fluid which occurs during turning, twisting, and bending movements of the head/neck
    • those in the macula and saccule of the internal ear are embedded in a gel and respond to gravitational forces as well as straight-line increased and decreases in body motion (linear acceleration)
  126. gustatory cells
    located in the taste buds that are embedded in the fungiform and vallate papillae of the tongue
  127. taste bud
    microscopic structure consisting of several gustatory cells surrounded by supporting cells
  128. Four basic modalities of taste
    • salt, sour, sweet, bitter
    • detection is concentrated over certain areas of tongue surface:
    • Pure salty is sensed over most of tongue w/ lateral and ant. aspects most sensitive
    • sour receptors concentrated on later aspects of tongue
    • sweet receptors concentrated on ant. aspect of tongue
    • bitter sensations on posterodorsal aspect of the tongue
  129. olfactory cells
    • bipolar neurons whose dendritic endings are located in the olfactoy mucosa of the nasal cavity
    • when stimulated, these cells generate impulses which are coveyed to the brain in their axons (olfactory nerves)
  130. dermatome
    • a specific area of skin surface whose sensory neurons are carried by a particular spinal nerves
    • dermatome maps are helpful in evaluating nerve injuries
  131. facial nerve paralysis
    produces ipsilateral immobility of the facial musculature on the affected side resulting in facial distortion, inability to purse the lips or close the ipsilateral eye, and xerophthalmia
  132. xerophthalmia
    dry eye
  133. bell's palsy
    if the cause of facial nerve paralysis cannot be traced to traumatic incident
  134. trigeminal neuralgia
    condition characterized by severe pain when a sensory branch of the 5th cranial nerve is stimulated. cause is unknown
  135. disynaptic reflexes
    spinal reflexes with two synapses btwn the three neurons
  136. monosynaptic reflex
    • the sensory information generated by neuromuscular spindles is carried by pseudounipolar neurons to the spinal cord
    • Ex: knee jerk
  137. interneurons
    • additional neurons within the spinal cord that join the sensory neurons to the motor neurons
    • these reflexes are called disynaptic (since two synapses occur within the CNS
  138. phantom pain
    • pain amputees sometimes experience in body parts they no longer have
    • occurs because sensory neurons that supplied amputated portions sometimes continue to send impulses
  139. referred pain
    • pain that is perceived in certain areas or organs but is actually caused in another location
    • usually, the area of referred pain is supplied by the same spinal nerve component as the actual site of the pain
  140. nerve that is responsible for the "funny bone"
    ulnar nerve
  141. anosmia
    • loss of sense of smell
    • may be caused by fractures of the ethmoid bone or neoplasia
  142. When a nerve is severed, some function can often be restored by suturing the severed ends back together. However, several months are required for recovery and recovery is typically only partial. Why?
    Regeneration of the severed nerve processes is very slow.  In addition, fore regeneration to occur, the severed processes must grow into the myelin sheaths of the severed distal parts of the fibers. Many regenerating fibers may fail to "find" a myelin sheath or bet blocked by ingrowth of fibrous conn. (scar) tissue
  143. If a patellar reflex ("knee jerk reflex") is normal, what can a medical practitioner conclude?
    The sensory pathway (within the femoral nerve) is intact, the spinal cord segments involving the femoral nerve are functional, and the motor pathway within the femoral nerve is normal
  144. What cranial nerves are involved in eating a pizza?
    • Looking at it involves CN 2 for vision and CN 3,4 and 6 for eye movement
    • Smelling and tasting involves CN's 1,7,9 (perhaps 10)
    • Chewing and savoring involves CN 5 for muscles that close the mouth, CN's 5&7 for opening the mouth, and CN12 for tongue movements
    • CN7 involved in manipulations of lips required during prehension and both CN's 7&9 required for salivation
  145. The 4 taste modalities (sweet, sour, bitter, and salty) do not explain the large variations in the tastes of different foods. What does?
    A significant portion of what we call taste is actually olfaction. This is supported by the fact that individuals with severe nasal congestion usually experience significant anosmia (reduction in their ability to taste
  146. what are the differences in sensory impulses involved in the hearing pathway, a visual pathway, or any other kind of sensory information?
    • The impulses are all the same.
    • In fact, motor impulses are identical to them as well. The differences in sensations are determined by where the impulses go in the brain
  147. Why is it that most spinal nerves carry fibers of all four functional modalities but the majority of cranial nerves carry only one, two, or three functional neuronal types?
    Spinal nerves are distributed to regional segments of neck/trunk/limbs. These areas contain skeletal m.t.(SE), smooth m. in vessel walls and gl. epithelium in sweat glands (VE), all have cutaneous receptors and sensory neurons from bones, muscles and joints (SA) and all have sensory receptor in vessel walls (VA). Many cranial nerves are much more limited in the distribution
  148. How can a physician use a combination of loss of muscle function and loss of sensation to dermatomes to assess nerve damage?
    • Skeletal muscles have definitive nerves that supply them with motor impulses and loss of nerve supply is accompanied by paralysis of those muscles.
    • Likewise, named nerves carry sensory impulses form certain areas of skin. Loss of sensation can be mapped and will indicate dysfunction of certain nerves
  149. Two men suffered complete severance of the radial nerve. One could still extend his elbow joint afer the injury, but the other could not. Explain
    The location (level) of the injury was significant. The one who could still extend his elbow joint (contract his triceps brachii muscle) must have had his radial nerve transected distal to the origin of the radial nerve branches to the triceps brachii m.  The other individual, the radial nerve was transected above the origin of these muscular branches
  150. Which named branches of the brachial plexus are the most significant in carrying impulses to and from superior limb structures?
    most of the muscles in the free part of the superior limb are supplied by the radial, ulnar, median, and musculocutaneous nerves
  151. Which named branches of the lumbosacral plexus are the most significant in carrying impulses to and from the inferior limb structures?
    Most of the muscles in the free part of the inferior limb are supplied by the sciatic nerve and it's two terminal branches (tibial and common fibular nn), obturator nerve and femoral nerve
  152. A named appendicular nerve carries fibers from several segments of the spinal cord. How does this occur?
    The numbers spinal nerves exchange fibers at the brachial and lumbosacral plexuses such that the named nerves continuing distally from the plexuses contain fibers from several numbered spinal nerves
  153. Severance of left spinal nerve C7 is much more debilitating than severance of left spinal nerve T7. Why?
    • The 7th cervical spinal nerves supply fibers to the brachial plexus and thence to the superior limb. Disruption will leave parts of the limb dysfunctional.
    • the 7th thoracic spinal nerves supply motor fibers to a regional segment of the thoracic wall. Loss of this innervation is much less debilitation
  154. Loss of function of a certain spinal nerve will not necessarily deprive the pt. of all sensation from it's dermotome because...
    There is considerable overlap in the cutaneous distribution of sensory pathways
  155. Which of the five groups of sensory receptors (based on the type of stimulus which incites an impulse) has the most specific receptor types?
  156. Why do all sensory receptors have in common?
    An ability to generate a nervous impulse if supplied with the right type of stimulus (and sometimes even when supplied with the wrong type of stimulus)
  157. Severance of the spinal cord at a fairly high level can cause quadriplegia but may not interfere with respiration. Why?
    The impulses controlling respiration (via the phrenic nerves to the diaphragm) leave the spinal cord within cervical spinal nerves C4 and C5. Transection of the spinal cord above C4/C5 segments results in death by asphyxiation. Transection just below that level results in a quadriplegic individual (who can still respire)
  158. Why are sensory nerve, motor nerve and mixed nerve misleading terms?
    Essentially all nerves are mixed (contain both motor and sensory fibers) only a few of the cranial nerves are sensory onl (CN 1,2,8) no nerves are motor only
  159. Which two cranial nerve (pairs) have the most extensive areas of fiber distribution?
    The vagus and accessory nerves (CN 10 & 11)
  160. Which cranial nerve (pair) is the shortest?
    The olfactory nerves.
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