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Spinal Cord, Chapter 18 Objectives, Chapter 11 objectives (Central…

- - - - can affect the decussating fibers of the spinothalamic tract
        
        what are decussating fibers
        
        nerve fibers that cross from one side of the central nervous system to the other, usually in an X shape
        
        what can occur from this
        
        these lesions can produce dissociated sensory abnormalities w loss of pain & temp in appropriate dermatomes
  - - - always pain & temp pathways; portion of adjacent tracts, adjacent grey mater, or both
    - - LMN weakness in the segment involved, with UMN dysfunction, and some cases loss of vibratory and position sense at levels below lesion
  - - - proprioceptive and vibratory sensations
    - - Isolated involvement of the dorsal columns occurs in tabes dorsalis, a form of tertiary (late phase; untreated) syphilis.
        
        what is tabes dorsalis
        
        rare, neurodegenerative disease that results from an untreated syphilis infection. It's characterized by a slow degeneration of the dorsal columns of the spinal cord
  - - - stab wound or compression of the spinal cord
    - - involves long pathways and gray matter; functions below the level of the lesion are abolished
  - - - Brown-Séquard syndrome :star:
        
        causes (5)
        
        bullet or stab wounds, spinal cord tumor, or hematomyelia
        
        syringomyelia
        
        what is this
        
        cerebrospinal fluid collects inside the spinal cord and forms a fluid-filled cyst; can affect the spinal cord
        
        what does it cause
        
        loss of pain and temperature bilaterally in the affected areas
        
        why does this happen
        
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        Effects
        
        what occurs at the spinal level of the injury
        
        loss of all sensation
        
        what occurs at the levels below, contralateral side (2)
        
        impaired pain and temp senses
        
        what occurs at the levels below, ipsilateral side (5)
        
        impaired proprioception, vibration, 2-point discrimination, and join and position sensation
  - - - the first order sensory neurons of a segment
    - - can produce pain as well as sensory loss
  - - - May compress the spinal cord against a vertebra, causing dysfunction of ascending and descending fiber systems
- - - - what are the dorsal and ventral roots called after L2
        
        cauda equina
        
        what is this space called
        
        Lumbar cistern
      - why does it end at L1-L2
        
        bc the vertebral column grows faster than the spinal cord
        
        when does the spinal cord and vertebral column stop growing at the same rate
        
        3rd month of fetal life
        
        when does the spinal cord stop growing
        
        few months after birth
  - - - called
        
        Skeletal (striated) muscles
    - - which ones are they (2)
        
        cardiac mm.
        
        Smooth (internal organs and glands) muscles
    - - Monoplegia
        
        paralysis of one upper or one lower limb
        
        Paraplegia
        
        both lower limbs
        
        Triplegia
        
        three limbs
        
        Quadriplegia
        
        all four limbs
        
        Hemiplegia
        
        upper and lower limbs on one side
    - - lesions below T10, pt can use AD to amb
      - lesions above T10, pt in w/c
  - - - 42-45cm
    - - 1cm
    - - 35 grams
  - - - during development the neural tube closes and adjacent mesoderm is segmented into somites that will in turn give rise to skin, muscle, and bone
  - - - anterior spinal artery
        
        what does it supply
        
        anterior two-thirds of the cord
      - posterior spinal aa.
        
        what does it supply
        
        posterior third of the cord
      - vertebral aa.
        
        what does it supply
        
        upper spinal cord
      - spinal aa. receive blood from which 2 aa.
        
        Vertebral aa.
        
        medullary aa.
        
        what is this
        
        branches of vertebral, cervical, thoracic, and lumbar aa.
- - - - refereed as what in the CNS
        
        nucleus
      - referred as what in the PNS
        
        ganglian
      - Nucleus dorsalis
        
        what does it do
        
        receives proprioceptive information, and its axons relay unconscious proprioceptive information to the cerebellum.
        
        also called
        
        Clark's column
        
        location
        
        extends vertically from T1-L3 in the medial gray matter anterior to the dorsal horn
      - Layers
        
        Lamina I
        
        also called
        
        the marginal zone
        
        what is it
        
        Thin layer of gray matter that covers the substantia gelatinosa.
        
        Lamina II
        
        what is it
        
        Is the substantia gelatinosa
        
        what does this do
        
        receives finely myelinated and unmyelinated sensory fibers that contain pain and temperature information.
        
        what is this
        
        Distinctive region of gray matter that caps the posterior horn.
        
        Lamina III - VI
        
        what is it
        
        Body of the posterior horn
        
        Lamina VII
        
        what is it
        
        Corresponds to the intermediate gray matter (including Clarke’s nucleus) but also large extensions into the anterior horn.
        
        Lamina VIII
        
        what is it
        
        Comprises some of the interneuronal zones of the anterior horn.
        
        Lamina IX
        
        what is it
        
        Consists of the clusters of motor neurons embedded in the anterior horn
        
        Lamina X
        
        what is it
        
        Zone of gray matter surrounding the central canal
        
        sensory areas
        
        what does Lamina I and II do
        
        Termination of pain and temperature
        afferents.
        
        what is Lamina III
        
        Tactile afferents from cutaneous nerves
        
        what is Lamina VI, VII, and IX
        
        Ia muscle spindle afferents
        
        definition
        
        primary afferent fibers that monitor the rate at which a muscle stretches
    - - refereed as what in the CNS (5)
        
        fasciculus, brachium, peduncle, column, and lemniscus
      - referred as white in the PNS (2)
        
        nerve or nerve root
        
        what are the 2 nerve roots
        
        Ventral root
        
        Location
        
        anterolateral sulcus of spinal cord
        
        what does it carry
        
        axons of motor neurons that originate in the spinal cord
        
        Dorsal root
        
        Location
        
        posterolateral sulcus of spinal cord
        
        what is the dorsal root ganglian
        
        cell bodies of primary sensory neurons that process sensory info
        
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        what does it do
        
        allow sensory info to enter spinal cord
        
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      - Columns
        
        Dorsal white column
        
        lateral white column
        
        anterior white column
        
        what is the area in the middle
        
        anterior white commissioner
  - - - how are they separated
        
        8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal.
  - - - inner layer of meninges; closely adheres to spinal cord surface
        
        what separates pia & arachnoid layer
        
        subarachnoid space
        
        this carries
        
        cerebrospinal fluid (CSF)
        
        also called
        
        intrathecal space
        
        what is it called when anesthetic is put in this area
        
        spinal anesthesia
        
        difference from epidural anesthetic (2)
        
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    - - between arachnoid and dura mater (outer layer)
    - - location
        
        between dura and vertebrae
  - - - 3 types of somatosensory tracts
        
        Conscious (discriminative) relay pathways
        
        2 types
        
        Dorsal column/ medial lemniscus
        
        function (2)
        
        conveys info about light touch and propioception
        
        first-order neuron synapse in the...
        
        Medulla
        
        2 tracts
        
        Fasiculus Gracilis
        
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        Fasciculus cuneatus
        
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        where does it originate
        
        peripheral receptors
        
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        Lesions along tract
        
        lesions in what area of the tract would result in contralateral loss of discrimitive touch & proprioceptive info (4)
        
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        lesions in what area of the tract would result in ipsilateral loss of discrimitive touch & proprioceptive info (3)
        
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        sterognosis
        
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        spinothalamic
        
        where does it originate
        
        dorsal horn of spinal cord (posterior grey mater)
        
        function (3)
        
        conveys discriminative info about nociception and temp, and non-discrimitive (crude) touch
        
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        what is its pathway (3 steps)
        
        the first-order neuron carries the information from the stimulus site, ascends or descends 1-2 spinal levels where it then synapses with the second-order neurons in the dorsal horn of grey mater
        
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        somatopic arrangement
        
        sacral most lateral, lumbar, thoracic, cervical most medial
        
        description
        
        Transmit information about location and type of stimulation to conscious awareness in the cerebral cortex
        
        Where is the info terminated
        
        in primary sensory are cerebral cortex
        
        Nonconscious relay pathways
        
        Posterior spinocerebellar & cuneocerebellar
        
        where does it originate
        
        High fidelity paths originate in peripheral receptors
        
        what are high fidelity paths
        
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        first-order neuron synapse in the... (2 possible places)
        
        nucleus dorsalis or medulla
        
        function
        
        convey unconscious proprioceptive info
        
        Anterior spinocerebellar & rostrospinocerebellar
        
        where does it originate
        
        internal feedback tracts originate in the dorsal horn of the spinal cord
        
        function
        
        convey info about activity in motor tract pathways and spinal interneurons
        
        description
        
        Transmit nonconscious proprioceptive information and other movement-related information to the Cerebellum
        
        where is the info terminated
        
        cerebellum
        
        Divergent pathways
        
        description
        
        Transmit information to many locations in the brain stem and cerebrum to be used both consciously and non-consciously
        
        what information is conveyed
        
        slow nociception
        
        what occurs if someone breaks a bone in their hand (6 things)
        
        divergent nociceptive pathways provide info to to automatically directing the eyes and head toward the injury, automatically moving the hand away from the cause of injury, becoming pale, and feeling faint, nauseous, and emotionally distressed.
        
        is this pathway localized
        
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        what is the medial nociception system
        
        divergent ascending group of neurons that responds to pain
        
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        what pathways does it use
        
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        3 types
        
        spinomesencephalic
        
        where is the info terminated
        
        midbrain
        
        spinoreticular
        
        where is the info terminated
        
        reticular formation
        
        spino-emotional
        
        where is the info terminated (3)
        
        amygdala, basal ganglia, many areas of the cerebral cortex
        
        where are the pathways located
        
        in the anterolateral columns, along with the axons of spinothalamic tract neurons
      - what information does it carry
        
        sensory
    - - Ceruleospinal
        
        where does it originate
        
        Locus coeruleus in brainstem
        
        function (2)
        
        Enhances the activity of interneurons and motor
        neurons in spinal cord
      - Raphespinal
        
        where does it originate
        
        Raphe nucleus in brainstem
        
        Enhances the activity of interneurons and motor
        neurons in spinal cord (same as ceruleospinal)
    - - Tracts in the lateral white column
        
        Lateral corticospinal
        
        function
        
        Contralateral fractionation of movement, particularly
        of hand movements
        
        where does it originate (3)
        
        Supplementary motor, premotor, and
        primary motor cerebral cortex
        
        somatotopic arrangement
        
        sacral most lateral, lumbar, thoracic, cervical most medial
        
        Rubrospinal
        
        where does it originate
        
        Red nucleus of midbrain
        
        function
        
        Facilitates contralateral upper limb extensors
      - Tracts in the medial white column
        
        Medial corticospinal
        
        where does it originate (3)
        
        Supplementary motor, premotor, and
        primary motor cerebral cortex
        
        function (3)
        
        Control of neck. shoulder, and trunk muscles
        
        Medial vestibulospinal
        
        where does it originate (2)
        
        Vestibular nuclei in medulla and pons
        
        function (2)
        
        Adjusts activity in neck and upper back muscles
        
        Lateral vestibulospinal
        
        where does it originate (2)
        
        Vestibular nuclei in medulla and pons
        
        function (2)
        
        Ipsilaterally facilitates motor neurons to extensors;
        inhibits motor neurons to flexors
        
        Reticulospinal
        
        function (2)
        
        Facilitates postural muscles and gross limb movements
        
        where does it originate (2)
        
        Reticular formation in medulla and pons
      - what information does it carry
        
        motor
      - what all do they have in common c their name
        
        all end in the word "spinal"
  - - - mainly of interneurons and projection neurons
        
        what are projection neurons
        
        ascending sensory pathways
    - - Grey matter
        
        2 parts
        
        substantia gelatinosa
        
        what is this
        
        distinctive region of grey matter that caps the posterior horn
        
        what does it receive
        
        finely myelinated and unmyelinated sensory fibers that contain pain and temperature information
        
        body of posterior horn
      - Lissauer's tract
        
        what is this
        
        White matter located between the substantia gelatinosa and the surface of the spinal cord.
        
        what does it contain
        
        finely myelinated and unmyelinated fibers with which the substantia gelatinosa receive.
  - - - cell bodies of the large motor neurons that innervate skeletal muscles
        
        2 other names that these neurons are called
        
        alpha motor neurons also referred to as lower motor neurons (LMNs)
        
        what happens if there is injury to LMNs
        
        causes paralysis of the m. that the motor neuron was innervating
        
        what is this type of paralysis called
        
        1 more item...
        
        how are they arranged
        
        arranged in clusters that are seperated by interneurons
        
        how are the clusters separated (2)
        
        2 more items...
        
        the neurons have what type of orientation and what does this mean
        
        longitudinal orientation, so each group innervates an individual muscle
- - - - what type of reflex does not have interneurons
        
        stretch reflex
        
        example
        
        hitting the patellar tendon
  - - - what occurs (2 steps)
        
        Ia (primary) afferent sensory fiber makes synapse w/in the spinal cord directly on the alpha motor neuron. That innervates the muscle containing the muscle spindle
        
        what is a muscle spindle
        
        mechanical stretch receptor that signal the length and changes in length of muscles
        
        what do gamma motor neurons do
        
        they activate during muscle contraction which maintains muscle spindle sensitivity
        
        m. spindle aka
        
        sensory organ or m.
        
        what happens right after the Ia afferent neuron fires
        
        the Golgi tendon organ (GTO) causes the Ib (secondary) afferent neuron to fire, which then innervates an interneuron to inhibit the alpha motor neuron
        
        why does this occur
        
        it is a protective mechanism to prevent excessive muscle tension
        
        what is this called
        
        autogenic inhibition
        
        what causes the rate of firing of the Ib afferent fibers to increase
        
        the fibers are compressed by collagen fibers which occurs when the GTO is stretched
    - - example
        
        flexor reflex
        
        definition
        
        a sensory signal like pain at the foot causes flexor mm. to contract from the associated spinal levels being innervated
    - - definition
        
        a sensory signal causes multiple types of mm. to contract from the associated spinal levels being innervated
- - - - affferent
        
        definition
        
        Fibers that convey sensory information from skin, joints, and mm. to the nervous system.
      - efferent
        
        definition
        
        Motor fibers that innervate the skeletal muscles.
  - - - efferent
        
        definition
        
        Motor autonomic (sympathetic or parasympathetic) fibers innervating viscera.
      - afferent
        
        definition
        
        Fibers that convey sensory information from the viscera
        
        what is the viscera
        
        The soft internal organs of the body,
        
        3 examples
        
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