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17 Cards in this Set
- Front
- Back
The Somatosensory System:
• The five modalities and where each originate • The morphology of neurons in the somatic sensory system • Where somatic sensory fibers and cell bodies are located |
Somatosensory system:
• The five modalities and their origin - touch, vibration, pain and temperature all originate in the skin - proprioception originates in the skeletal muscle system • They are all pseudo-unipolar • Fibers run in peripheral nerves, The cell bodies are located in either DRG (for spinal nerves) or Cranial nerve ganglia (for cranial nerves) |
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The Cutaneous Receptors:
• Touch - one basic type of receptor, two examples of these receptor types, their location in the skin and their fxn • Vibration - one basic type of receptor, two examples of these receptor types, their location in the skin and their fxn • Pain - two basic types of receptors, the part of the nerve that transduces them and its location in the skin • Temperature - two basic types of receptors, the part of the nerve that transduces them and its location in the skin |
The Cutaneous Receptors:
• Touch - Mechanoreceptor > Merkel's disks - discriminitive touch, located in the dermis > Ruffini's endings - skin stretching, located in the dermis • Vibration - Mechanoreceptors > Meissner's corpuscles - most sensitive to low frequency vibrations (~50Hz), located in the dermis > Pacinian - most sensitive to high frequency vibrations (~300 Hz), located in the dermis, but lower spatially than Meissner's • Pain - Mechano- and Thermo- receptors, transuced by free nerve endings, located in the epidermis • Temperature - Thermoreceptors, transduced by free nerve endings, located in the epidermis |
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The Muscle Receptors:
• Involves this receptor modality • The main somatic sensory receptors of the musculo-skeletal system (2) • Involved in forming two pathways to the cerebellum - Significant feature of the input carried by these tracts |
The Muscle Receptors:
• Proprioceptors • Muscle spindles and Golgi tendon organs - Dorsal and Spinal cerebellar tracts - the sensory info does not reach consciousness |
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Muscle Spindles:
• General location • Its type of primary receptor > the receptor contains this fiber > carries this sensory information > forms this limb of the of this reflex arc |
Muscle Spindles:
• Embedded in extrafusal fibers of muscle • Rapidly adapting receptor > Ia afferent > carries sensory information about muscle stretch > forms the afferent limb of the myotactic reflex arc |
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Golgi Tendon Organs:
• General location • Features about the receptor > Type of fiber it contains > Forms this limb of the of this reflex arc |
Golgi Tendon Organs:
• Located close to the border btwn muscle and tendon • Features about the receptor > contains Ib afferent fibers > Forms the afferent limb of the of reverse myotactic reflex arc |
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Name the four fiber types of somatic sensory receptors
• Which have the highest and lowest conduction velocities • How are they classified under the Lloyd system of skeletal muscle afferent fibers • How are they classified under the Erlanger & Gasser system of spinal nerves |
Large myelinated
Medium myelinated Small myelinated Unmyelinated • Large and Medium myelinated fibers have the highest conduction velocities • Unmyelinated fibers have the smallest conduction velocities Lloyd system of skeletal muscle afferent fibers - Large and medium myelinate muscle fibers are Type I a & b - Type II in muscle afferents correspond to Type II in Lloyd's - Small myelinated are Type III - Small unmyelinated are Type IV Erlanger & Gasser system of spinal nerves - Large and Medium myelinated nerves are Type A-alpha - Small myelinated are Type A-delta - Small unmyelinated are Type C |
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Large & Medium myelinated fibers:
• are found in these types of cutaneous receptors • carry these types of information |
Large & Medium myelinated fibers:
• found in mechano- and propio-receptors • carry touch, vibration and sensory information |
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Small myelinated and unmyelinated fibers carry this type of input
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pain and temp
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The largest drop of in conduction velocity occurs btwn these two sensory fibers
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Myelinated (4 - 36 m/s) and Unmyelinated (0.4 - 2 m/s) fibers
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Relative to which vertebrae(s) do the following spinal nerves emerge:
• C1 • C8 • T12 • L1 |
• C1 - Above C1 vertebrae
• C8 - Below the C7 vertebrae • T12 - Below the T12 vertebrae • L1 - Btwn the L1 and L2 vertebrae |
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Approximate locations for the following dermatomes:
• C2 • C6 • C7 • C8 • T4 • T10 • L1 • L5 • S1 |
Locations for the following dermatomes:
• C2 - Back of the head • C6 - Thumb • C7 - Middle finger • C8 - Pinky • T4 - Nipple live • T10 - Umbilicus • L1 - Inguinal ligament/groin • L5 - Big toe • S1 - Little toe |
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Two pathways in the spinal cord that carry different sensory modalities
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Dorsal Column/Medial Lemniscus System
Anterolateral System |
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Dorsal Column/Medial Lemniscus System:
• Carry these sensory modalities (3) • Trajectory - where the fibers enter - where they synapse • Topographical organization of the fibers originating from the leg trunk and arm - their location in the spinal cord in relation to one another |
Dorsal Column/Medial Lemniscus System:
• Carry touch, vibration and proprioception • Trajectory - fibers enter the dorsal column of the spinal cord - ascend up the white matter tract tract - where they synapse in the nuclei of the dorsal columns • Fibers originating from the leg are medial, the arm is lateral and the trunk is in between. |
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Anterolateral System:
• Carry these sensory modalities (2) • Trajectory - where the fibers enter - the location of 2nd order neurons on to which they synapse - the remaining pathway of the 2nd order neurons, include the commissure they use - Final destination of the tract • Topographical organization of the fibers originating from the leg trunk and arm - their location in the spinal cord in relation to one another |
Anterolateral System:
• Carry pain and temperature • Trajectory - fibers enter the dorsal column of the spinal cord - they synapse on 2nd order neurons in the dorsal horn - The 2nd order neurons cross to the contralateral side through the anterior commissure and ascend in the ALS fiber tract of the spinal cord - Thalamus • Fibers originating from the arm are medial, the leg is lateral and the trunk is in between. |
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Lissauer's Tract:
• another name • Carry these sensory modalities (2) • Trajectory - where the fibers enter - the location of 2nd order neurons on to which they synapse - the remaining pathway of the 2nd order neurons and the tract they join - Final destination of the tract |
Lissauer's tract:
• Dorsolateral fasciculus • Pain and temperature • Trajectory - fibers enter the dorsal column of the spinal cord - they synapse on 2nd order neurons in the dorsal horn, both above and below the level of entry - The 2nd order neurons cross to the contralateral side and ascend with the ALS tract, eventually synapsing at the VPLN of the Thalamus |
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Brown Sequard Syndrome:
• Cause and fibers involved • Tracts involved, Location of and presentation of sx - Discuss what happens at the level of and below the level of the lesion • Tract that can help recover some of the lost information and why |
Brown Sequard Syndrome:
• Hemisection of the spinal cord, ascending & descending fibers are interrupted on one side • Information -- At the level of the lesion: > The DC/ML system is affected and PTV are lost on the ipsilateral side (lesioned/injured side) > The ALS system is affected and Pain and Temp are lost on the contralateral side > The Corticospinal Tract is affected with LMNs in the anterior/ventral horn being damaged. Presentation of LMN syndrome at this level will include: flaccid paresis, fasciculations & fibrillations, and hypo- or a-reflexia -- Below the level of the lesion, > The DC/ML System is affected and TVP is lost ipsilaterally > The AL System is affected and Pain and Temp are contralaterally, starting 1-2 segments below the lesion > The Corticospinal Tract is affected and sx conducive to UMN syndrome are observed ipsilaterally: Hyperreflexia, clonus, Extensor Plantar reflex and spastic paralysis > Lissauer's tract, because it sends its input contralaterally to the ALS and has nociceptors that iNN not just at the level of axon entry but 1 - 2 segments above & below their level of entry. |
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Syringomyelia:
• Definition • Type of sensory information lost, include sidedness |
Syringomyelia:
• A pathological enlargement of the central canal of the spinal cord, interrupting fibers that cross through the white commissure • Pain and temperature lost bilaterally |