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33 Cards in this Set
- Front
- Back
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What 4 things are sensed by the somatosensory systems?
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-Touch (crude & discriminative)
-Movement (Proprioception) -Temp -Pain |
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What are the 2 somatosensory pathways?
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-Dorsal columns (medial lemniscus pathways)
-Anterolateral pathways |
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What 5 modalities does the dorsal column pathway carry?
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-Fine touch
-Pressure -2-point Discriminative touch -Vibration -Proprioception |
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What type of nerve fibers carry dorsal column pathway info?
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A-beta (type II)
-Myelinated/med diameter -Med conduction |
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Where is the cell body of the primary neurons in the dorsal column pathway?
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In the DRG (unipolar)
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Where does the first synapse occur in the dorsal column pathway?
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In the nucleus cuneatus or gracilus on the same side of the spinal cord at the medulla level
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Where do 2nd order neurons in the dorsal column pathway project?
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-Decussate
-Project to CONTRAlateral VPL of thalamus |
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Where do 3rd order neurons from the VPL of the thalamus project?
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To the posterior limb of the internal capsule, then primary somatosensory cortex in the postcentral gyrus
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What 3 modalities does the anterolateral pathway carry?
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-Pain
-Temp -Crude touch |
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What type of nerve fibers carry anterolateral pathway info?
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A-gamma and C fibers (Type III/IV)
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Where is the cell body of the primary neurons in the anterolateral column pathway?
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In the DRG
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Where does the first synapse occur in the anterolateral pathway?
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In the dorsal horn of the spinal cord gray matter at the same level of the DRG
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Where do 2nd order neurons in the anterolateral column pathway project?
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-Decussate just ventral to the central commissure
-Ascend in the CONTRAlateral anterolateral white matter to the VPL of the thalamus |
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Where do 3rd order neurons from the VPL of the thalamus project?
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To the somatosensory cortex
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What type of peripheral receptors detect touch and pressure?
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Mechanoreceptors in the skin
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What are the 4 types of mechanoreceptors that detect touch and pressure?
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-Pacinian corpuscles
-Meissner's corpuscles -Ruffini's corpuscles -Merkels disks |
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Where are Pacinian corpuscles located and what do they look like?
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-Subcutaneous skin
-Oniony structures |
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Pacinian corpuscles:
-Sensation encoded -Adaptation |
Sense = vibration/tapping
Rapidly adapting |
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Where are Meissner's corpuscles located?
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In non-hairy skin
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Meissner's corpuscles:
-Sensation encoded -Adaptation |
Sense = Velocity
Rapidly adapting |
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Ruffini's corpuscles
-Description -Sensation encoded -Adaptation |
-Encapsulated
Sense = Pressure Slowly adapting |
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Merkel's disks:
-Location -Sensation encoded -Adaptation |
-On epithelial cells
Sense = location (propriocept) Slowly adapting |
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How is somatosensory info arranged in the thalamus?
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Somatotopically
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What happens to somatosensation if the thalamic nuclei are destroyed?
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Loss of sensation from the contralateral side of the body
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How is the somatosensory cortex in the postcentral gyrus organized?
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As a homunculus
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What are the major somatosensory areas?
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SI and SII
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What are the largest areas of the body represented by the homunculus?
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The face hands and fingers
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What is another term for Pain?
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Nociception
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What are the receptors for pain?
What are 3 locations of them? |
Free nerve endings
-In skin/muscle/viscera |
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What is a special neurotransmitter for pain?
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Substance P
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What drug inhibits the release of substance P resulting in pain relief?
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Opioids
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What are the 2 fiber types that carry pain info?
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Group III (A-delta) - fast pain
C fibers - slow pain |
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How are fast pain and slow pain different?
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Fast = rapid onset/localized
Slow = vague; ache/burn/throb |
