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56 Cards in this Set
- Front
- Back
Each somatic sensory system contains what three neurons?
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1. Ganglion cell synapse
2. Projection cell synapse 3. Thalamic cell synapse |
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Briefly describe a ganglion cell synapse.
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Unipolar neuron with a receptor
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What happens with a projection cell synapse?
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Axon decussates
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Where does the thalamic cell synapse project to?
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Sensory cortex
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All neurons of the somatic sensory system contains what?
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Contains a receptive field
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Define Receptive Field.
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Area of a skin which when stimulated either increases or decreases the firing rate of that cell.
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All receptive field has what two things?
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Excitatory center
Inhibition surround |
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Define lateral inhibition.
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A mechanism by which neurons determine more specifically the origin of stimulus. A stimulated neuron will suppress the stimulation of neighboring neurons.
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Define Receptor.
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Sensory terminal whose membrane response to stimulus producing a local, graded, usually depolarizing potential (increased Na+ & K+ conductance)
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Define adequate stimulus.
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Unique for each type receptor,
it is the minimum stimulus needed to cause the receptor membrane to be depolarized. |
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What allows each type of receptor to make a unique contribution to somatic sensation.
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Adequate stimulus
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Define adaptation
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Decrease in receptor potential with continued stimulation.
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List all the slowly adapting receptors. x7
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Meckels Disk
Ruffini Ending Golgi Tendon Organ Muscle Spindle Warm & Cold Free nerve endings Pain |
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List all the rapidly adapting receptors.
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Meissner Corpuscle
Pacinian Corpuscle Peritrichial ending |
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List the Axonal categories including:
- AKA - Thickness - Speed - Myelination |
Type I: A alpha - Large, fastest, and myelinated
Type II: A beta - Medium, faster, and myelinated Type III: A delta - Small, fast, and myelinated Type IV: C - Small, slow, and UNmyelinated |
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Afferents to the spinal cord form what two divisions in the dorsal root?
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Medial division
Lateral division |
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The medial division contains what type of nerve fibers?
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Type I & II
Fast |
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The medial division mediates what type of sensory modalities?
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Discriminative touch
Pressure Proprioception |
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The lateral division mediates what type of sensory modalities?
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Pain
Temperature |
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The lateral division contains what type of nerve fibers?
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Type III & IV
Slow |
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Crude (light) touch is mediated by what nerve fibers?
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II & III
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Peripheral nerves carry which type of modalities and fibers?
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All sensory modalities + motor fibers
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During nerve fiber segregation in the medial and lateral divisions, the large fibers enter what?
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Dorsal Funiculus
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During nerve fiber segregation in the medial and lateral divisions, the small fibers enter what?
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Lissauer's Tract
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Nerve fibers entering either the Dorsal funiculus or Lissauer's Tract have what three functions?
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1. Reflexes
2. Muscle Coordination 3. Conscious sensation |
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Nerve fibers responsible for reflexes do what?
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Make reflex connections with motor neurons
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Nerve fibers responsible for muscle coordination provide input to where?
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Cerebellum
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Nerve fibers responsible for conscious sensation provide input to where?
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Cerebral Cortex
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Define protopathic.
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General, nondiscriminating, poorly-localized responsiveness to stimuli
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Define epicritic.
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Precise, well-localized responsiveness to stimuli
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Most protopathic senses are mostly conveyed where?
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Spinothalamic tract
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Most epicritic senses are mostly conveyed where?
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Dorsal Column Medial Lemniscus tract (DCML)
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Both the Spinothalamic tract and the DCML tract go where via where?
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Somatosensory cortex
via Thalamus |
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What are the categories of Thalamic nuclei?
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1. Specific Sensory Nuclei
2. Specific Motor Nuclei 3. Nonspecific Nuclei 4. Association Nuclei |
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What are the two functional states of the cerebral cortex due to the interplay of thalamocortical activity?
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Synchronized (Slow sleep wave)
Desynchronized (Awake or REM sleep) |
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The two functional states of the cerebral cortex is due to what?
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Interplay of the thalamocortical activity.
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The lateral surface of the thalamus, covered by GABA neurons comprise what?
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Reticular nucleus
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Axons of tertiary (thalamic) neurons terminate mainly in? which is where? in which gyrus?
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In layer IV
of the Primary Somatosensory Cortex (Area SI) in the Postcentral gyrus where sensations are perceived. |
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Name the Brodmann's cytoarchitectonic areas of the Primary Somatosensory cortex (Area SI)
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1
2 3a 3b |
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Which Brodmann's areas are responsible for Tactile sensory?
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1
3b |
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Which Brodmann's areas are responsible for Proprioceptive sensory?
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2
3a |
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Our subjective sensations result from the integration of what two areas?
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Area SI (primary somatosensory cortex)
Sensory Association areas |
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Unlike Protopathic, Epicritic is highly dependent on which area?
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Cerebral cortex
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Describe a dermatome's association with adjacent dermatomes.
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One will overlap the adjacent one by one-half.
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What does it mean for something to be somatotopically organizaed?
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Adjacent parts of the dermatome are represented in adjacent parts of the cortex. Neighborhood relationships are preserved.
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Neurons in DCML have receptive fields of what size and density?
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Small and high density
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What are the five epicritic sensations conveyed in the DCML?
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1. Discriminative Touch
2. Stereognosis 3. Graphesthesia 4. Vibratory sense 5. Proprioception |
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All epicritic sensations of the DCML require high degrees of what? x2
Which is made possible by what? x2 |
1. Spatial resolution
2. Temporal resolution Small receptive fields Large, rapidly-conducting axons |
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Dorsal column axons synapse where?
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Medullary dorsal column nuclei
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DCML senses from the upper body (T6 and above) ascend in where?
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Fasciculus Cuneatus
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DCML senses from the lower body (T7 and below) ascend in where?
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Fasciculus Gracilis
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What is the exception to the rule for a DCML sense that ascends in the spine?
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Some proprioception ascends in the dorsal part of the lateral funiculus
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Axons in the Nucleus Cuneatus and Nuclues Gracilis cross the midline in the what? and form the what?
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Sensory Decussation
Medial lemniscus |
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What type of orientation does the medial lemniscus have in the midline of the medulla?
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Vertical orientation
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Nerve fibers of the medial lemniscus terminate where?
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Ventral Posteriolateral (VPL) thalamic nucleus.
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In order to get to the postcentral gyrus, the axons of the VPL must project through what?
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Posterior limb of the Internal Capsule.
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