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71 Cards in this Set
- Front
- Back
Where are the cell bodies of afferent (sensory) fibers from peripheral nerves to the spinal cord located?
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In the spinal ganglia (dorsal root ganglia)
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Where are the cell bodies of afferent (sensory) fibers from cranial nerves to the brainstem located?
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In the gaglia close to the brainstem (e.g. semilunar ganglion of trigeminal nerve)
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Where do the two processes travel in primary afferent cells that are pseudo-unipolar?
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One process goes peripherally to a free ending or receptor, the other process travels to the spinal cord
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Where do the fibers with the thickest myelination (Ia, Ib, II) enter the spinal cord?
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On the medial aspect of the dorsal horn
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Where do the fibers with the thickest myelination (Ia, Ib, II) terminate?
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In lamina III-VI, VII and IX
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Where do A-delta fibers enter the spinal cord?
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On the lateral aspect of the dorsal horn
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Where do A-delta fibers terminate?
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In lamina I and V
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Where do C fibers enter the spinal cord?
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On the lateral aspect of the dorsal horn
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Where do C fibers terminate?
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In lamina II (substantia gelatinosa)
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What are three neurotransmitters associated with somatosensory pathways?
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Glutamate (excitatory), GABA (inhibitory), neuropeptides
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Where are neuropeptides found?
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In central and peripheral terminals
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What are three neuropeptides?
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Substance P (SP), cholecytokinin (CCK), somatostatin
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Do dermatomes overlap?
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Yes
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Every spot on the skin is innervated by sensory fibers from how many dorsal roots?
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At least two
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Is there more overlap of pain fibers or touch fibers in dermatomes?
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More overlap in touch fibers
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When a nerve root is irritated, what does the patient feel in the associated dermatome?
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A numb or pricking sensation is found in the territory of the dermatome
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Most somatosensory system pathways consist of a chain of how many neurons?
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Three
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Where are the cell bodies of primary sensory neurons located?
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In the dorsal root ganglion or cranial nerve ganglion
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Where do primary sensory neurons travel from and synapse to?
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They travel from peripheral receptors to synapse in the spinal cord or brainstem
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Where are the cell bodies of secondary sensory neurons located?
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In the gray matter (dorsal horn) of the spinal cord or in the brainstem
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Where do the axons of secondary sensory neurons ascend?
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In the spinal cord or brainstem
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Where do the axons of secondary sensory neurons terminate?
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In the thalamus
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Where are the cell bodies of third order sensory neurons located?
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In the thalamus
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Where do the axons of third order sensory neurons terminate?
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They terminate in the primary somatosensory cortex
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What are the two major divisions of somatosensory pathways?
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The dorsal column medial lemniscus (DCML) and the spinothalamic tract (ST)
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The DCML pathway carries impulses from what types of receptors?
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Low-threshold mechanoreceptors
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The spinothalamic tract carries impulses from what types of receptors?
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Pain and temperature receptors
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What are the three major subdivisions of the thalamus?
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Anterior, medial and lateral (dorsal and ventral)
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Intralaminal thalamic nuclei are important in the perception of what?
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Pain
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Where do fibers enter the spinal cord in the DCML pathway?
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On the medial aspect of the dorsal horn
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What is the gracile fasciculus?
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The medial portion of the dorsal column of the spinal cord
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The gracile fasciculus carries fibers with information from what part of the body?
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The lower trunk and lower extremities
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Where do fibers in the gracile fasciculus synapse?
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In the gracile nucleus in the medulla
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What is the cuneate fasciculus?
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The lateral portion of the dorsal column of the spinal cord
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The cuneate fasciculus carries fibers with information from what part of the body?
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The upper trunk and upper extremities
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Where do fibers in the cuneate fasciculus synapse?
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In the cuneate nucleus of the medulla
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The dorsal column nuclei of the medulla receives fibers from what two structures?
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The gracile fasciculus and the cuneate fasciculus
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What is the medial lemniscus?
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A fiber tract carrying second order neurons of the DCML
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Where do fibers from the medial lemniscus cross over
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The medulla
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Where are the cell bodies of second order neurons in the DCML pathway found?
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In the dorsal column nuclei
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Where do fibers of the medial lemniscus terminate?
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In the ventral posterior lateral (VPL) nucleus of the thalamus
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Fibers mediating information from the face terminate where?
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In the ventral posterior medial (VPM) nucleus of the thalamus
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Where are cell bodies of third order neurons in the DCML pathway located?
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In the VPM and VPL of the thalamus
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Where do third order neurons of the DCML pathway send axons?
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To the postcentral gyrus (Brodmann areas 1, 2 and 3)
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Where do third order neurons of the DCML pathway terminate?
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In the primary somatosensory cortex
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How are terminations in the primary somatosensory cortex organized?
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Somatotopically (sensory homunculus)
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What body parts have large areas of representation on the sensory homunculus?
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Lips, tongue and thumb
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Are fibers in the DCML pathway rapidly or slowly adapting?
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Rapidly adapting
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The DCML pathway is designed to mediate what type of information?
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Fast and precise information about stimulus type, exact site of stimulus and when the stimulus starts and stops
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Are fibers in the DCML pathway myelinated?
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Yes
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Lesions of the DCML pathway result in what kinds of deficits?
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The inability to discriminate spatial and temporal characteristics of a stimuli
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Are individuals with DCML pathway lesions able to perceive crude touch?
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Yes
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Can lesions of the DCML pathway result in motor deficits?
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Yes, due to the dependence of accurate voluntary movement on feedback regarding sensory information
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Syphilis can cause what condition affecting the dorsal column of the spinal cord?
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Tabes dorsalis-degeneration of the dorsal column
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Where do fibers from the spinothalamic tract enter the spinal cord?
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The lateral portion of the dorsal root
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The tract of Lissauer is made up of what fibers?
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Type C fibers
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Where is the tract of Lissauer located?
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Dorsal to the gray matter of the dorsal horn
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Where are cell bodies of second order neurons of the spinothalamic tract located?
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In the dorsal horn
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Where do fibers of the spinothalamic tract cross over?
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At the level of the second order neurons
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List the Six types of chemical agents.
blood, blister, nerve, what are the other three? |
Blood, Blister, Choking, Nerve, Incapacitating, Military Compound.
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Where is the spinothalamic tract situated in the pons?
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Lateral to the medial lemniscus
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Where is the spinothalamic tract situated in the midbrain?
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Dorsolateral and adjacent to the medial lemniscus
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Where do second order neurons of the spinothalamic tract synapse?
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With cells in the VPM, VPL, posterior complex and intralaminar nuclei of the thalamus
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Where do third order neurons of the spinothalamic tract send neurons?
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To the primary somatosensory cortex (areas 1, 2 and 3) and many parts of the ipsilateral cortex
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What is the function of the spinothalamic tract?
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It mediates perception of pain and temperature and a relatively crude sense of pressure and touch
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Lesions of the spinothalamic tract cause what sorts of deficits?
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Loss of pain and temperature sensation in the contralateral side of the body
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Where do deficits of the spinothalamic tract of the spinal cord begin to be seen?
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Two segments below the lesion
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How is the spinothalamic tract involved with referred pain?
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The spinothalamic tract receives input from nociceptors in the periphery and in the viscera. It is not possible for higher centers to determine where painful stimulus is coming from.
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What is reflex sympathetic dystrophy (CRPS) caused by?
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Spinal reflexes that trigger a release of neuropeptides from the sensory end organs in the skin
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Are the activation of nociceptors and the conscious experience of pain dependent on one another?
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No, pain can be perceived without activation of a nociceptor and vice versa
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What are two examples of pain without activation of a nociceptor?
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Phantom limb pain and thalamic pain caused by thalamic lesions
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