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56 Cards in this Set

  • Front
  • Back
Each somatic sensory system contains what three neurons?
1. Ganglion cell synapse
2. Projection cell synapse
3. Thalamic cell synapse
Briefly describe a ganglion cell synapse.
Unipolar neuron with a receptor
What happens with a projection cell synapse?
Axon decussates
Where does the thalamic cell synapse project to?
Sensory cortex
All neurons of the somatic sensory system contains what?
Contains a receptive field
Define Receptive Field.
Area of a skin which when stimulated either increases or decreases the firing rate of that cell.
All receptive field has what two things?
Excitatory center

Inhibition surround
Define lateral inhibition.
A mechanism by which neurons determine more specifically the origin of stimulus. A stimulated neuron will suppress the stimulation of neighboring neurons.
Define Receptor.
Sensory terminal whose membrane response to stimulus producing a local, graded, usually depolarizing potential (increased Na+ & K+ conductance)
Define adequate stimulus.
Unique for each type receptor,

it is the minimum stimulus needed to cause the receptor membrane to be depolarized.
What allows each type of receptor to make a unique contribution to somatic sensation.
Adequate stimulus
Define adaptation
Decrease in receptor potential with continued stimulation.
List all the slowly adapting receptors. x7
Meckels Disk
Ruffini Ending
Golgi Tendon Organ
Muscle Spindle
Warm & Cold
Free nerve endings
List all the rapidly adapting receptors.
Meissner Corpuscle
Pacinian Corpuscle
Peritrichial ending
List the Axonal categories including:
- 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
Afferents to the spinal cord form what two divisions in the dorsal root?
Medial division
Lateral division
The medial division contains what type of nerve fibers?
Type I & II

The medial division mediates what type of sensory modalities?
Discriminative touch
The lateral division mediates what type of sensory modalities?
The lateral division contains what type of nerve fibers?
Type III & IV

Crude (light) touch is mediated by what nerve fibers?
Peripheral nerves carry which type of modalities and fibers?
All sensory modalities + motor fibers
During nerve fiber segregation in the medial and lateral divisions, the large fibers enter what?
Dorsal Funiculus
During nerve fiber segregation in the medial and lateral divisions, the small fibers enter what?
Lissauer's Tract
Nerve fibers entering either the Dorsal funiculus or Lissauer's Tract have what three functions?
1. Reflexes
2. Muscle Coordination
3. Conscious sensation
Nerve fibers responsible for reflexes do what?
Make reflex connections with motor neurons
Nerve fibers responsible for muscle coordination provide input to where?
Nerve fibers responsible for conscious sensation provide input to where?
Cerebral Cortex
Define protopathic.
General, nondiscriminating, poorly-localized responsiveness to stimuli
Define epicritic.
Precise, well-localized responsiveness to stimuli
Most protopathic senses are mostly conveyed where?
Spinothalamic tract
Most epicritic senses are mostly conveyed where?
Dorsal Column Medial Lemniscus tract (DCML)
Both the Spinothalamic tract and the DCML tract go where via where?
Somatosensory cortex

via Thalamus
What are the categories of Thalamic nuclei?
1. Specific Sensory Nuclei
2. Specific Motor Nuclei
3. Nonspecific Nuclei
4. Association Nuclei
What are the two functional states of the cerebral cortex due to the interplay of thalamocortical activity?
Synchronized (Slow sleep wave)

Desynchronized (Awake or REM sleep)
The two functional states of the cerebral cortex is due to what?
Interplay of the thalamocortical activity.
The lateral surface of the thalamus, covered by GABA neurons comprise what?
Reticular nucleus
Axons of tertiary (thalamic) neurons terminate mainly in? which is where? in which gyrus?
In layer IV

of the Primary Somatosensory Cortex (Area SI)

in the Postcentral gyrus

where sensations are perceived.
Name the Brodmann's cytoarchitectonic areas of the Primary Somatosensory cortex (Area SI)
Which Brodmann's areas are responsible for Tactile sensory?
Which Brodmann's areas are responsible for Proprioceptive sensory?
Our subjective sensations result from the integration of what two areas?
Area SI (primary somatosensory cortex)

Sensory Association areas
Unlike Protopathic, Epicritic is highly dependent on which area?
Cerebral cortex
Describe a dermatome's association with adjacent dermatomes.
One will overlap the adjacent one by one-half.
What does it mean for something to be somatotopically organizaed?
Adjacent parts of the dermatome are represented in adjacent parts of the cortex. Neighborhood relationships are preserved.
Neurons in DCML have receptive fields of what size and density?
Small and high density
What are the five epicritic sensations conveyed in the DCML?
1. Discriminative Touch
2. Stereognosis
3. Graphesthesia
4. Vibratory sense
5. Proprioception
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
Dorsal column axons synapse where?
Medullary dorsal column nuclei
DCML senses from the upper body (T6 and above) ascend in where?
Fasciculus Cuneatus
DCML senses from the lower body (T7 and below) ascend in where?
Fasciculus Gracilis
What is the exception to the rule for a DCML sense that ascends in the spine?
Some proprioception ascends in the dorsal part of the lateral funiculus
Axons in the Nucleus Cuneatus and Nuclues Gracilis cross the midline in the what? and form the what?
Sensory Decussation

Medial lemniscus
What type of orientation does the medial lemniscus have in the midline of the medulla?
Vertical orientation
Nerve fibers of the medial lemniscus terminate where?
Ventral Posteriolateral (VPL) thalamic nucleus.
In order to get to the postcentral gyrus, the axons of the VPL must project through what?
Posterior limb of the Internal Capsule.