Neuro: Somatosensory Sytem Flashcards
Friedreich’s ataxia:
-autosomal recessive neurodegenerative syndrome of spinal cord tracts
Friedreich’s ataxia presentation:
-impaired coordination of walking
-rombergs sign: unsteady standing with eyes closed
-sometimes additional brain degeneration
-kyphoscoliosis
Somatoensory nerve endings for fine/discriminative touch:
-hairs
-merkels touch domes
Somatosensory nerve endings for vibration:
Pacinian corpuscle
Somatosensory nerve endings for crude touch:
Meissner’s
Somatosensory nerve endings for proprioception
Ruffini
Somatosensory nerve endings for pain and temperature:
Free nerve endings
Fine/descriminative touch tests:
-sharp or dull?
-2-point discrimination
-stereogenosis (coin identification)
-graphesthesia (trace letters or numbers, pt identifies)
-vibration via tuning fork on bony prominences
Position sense or conscious proprioception in the limbs tests:
-“finger up or down?” After passive movement
-“flexed or straight?” After passive movements
Posterior dorsal column system pathway:
-Sensory fibers enter posterior funiculus (column) and ascend to brain
Sensory fibers do NOT enter __________ and do NOT synapse in _____________
Dorsal horn, spinal cord
A lesion to C5 dorsal root on the left side leads to:
-loss of fine touch and vibration sensation
-in the upper left arm
-segmental, localized in areas supplied by C5
Lesion to C5 dorsal column on left side would result in:
-loss of fine touch and vibration sensation
-in the area at and below the affected region on the left side
-level down pattern
Anterolateral neuron pathway:
-sensory neurons synapse in dorsal/posterior horn
-2nd neuron sends projection that crosses midline and enters anterolateral tract and ascends to brainstem, to synapse in thalamus
-3rd order neuron projects into somatosensory cortex
-sensation from right side of body is represented in left cortex (and vice versa)
Lesion to the dorsal root on the left side in the anterolateral system:
-loss of pain and temperature sensation in area corresponding to C5 nerve on the left side
Lesion to the dorsal horn of C5 on the left side in the anterolateral system:
Loss of pain and temperature sensation on the ipsilateral side in the neck and shoulder area
Lesion to the anterior white commissure of C5 on the left side in the anterolateral system:
-loss of pain and temperature sensation in the contralateral (right) side of the body
-level down
Lesion to the left anterolateral tract of C5 in the anterolateral system
-loss of pain and temperature sensation on the right side of body
Spinocerebellar pathway is involved in ______________
Proprioception
In Spinocerebellar pathway, proprioceptive info is sent to the cerebellum that leads to:
-activation of descending tracts to anterior/ventral horn LMNs
Spinocerebellar pathway is not usually used for diagnosing becasue it is…
Rarely the only damage
Pathway of visual system from retina to primary visual cortex:
-retinal ganglion neurons projected to thalamus
-thalamic neurons project via “optic radiations” to visual cortex in occipital lobe
LMNs for CN 3 and 4 are located in the ________ while. LMN for CN 6 is in the _______
Midbrain, pons
UMN for CN 3, 4, and 6 are located in the ______________
Cerebral cortex
Voluntary eye movements for CN 3, 4, and 6 can be disrupted at 4 different levels:
-cerebral
-midbrain
-pons
-PNS level
Pupil dilation deficits have many possible lesion sites and etiologies:
-lateral hypothalamus
-lateral brainstem
-lateral spinal cord (c1-T2)
-sympathetic chain
-carotid plexus
-cavernous sinus
-orbit and eye
Pupillary light reflex circuit in the midbrain:
-shine light into right eye activates sensory arc following optic tracts bilaterally to pretectal nucleus in midbrain
-send axon projections bilaterally to L and R EWN to activate pregang parasym neurons
-post gang parasym neurons in L and R ciliary gang activate pupillary constrictor in both eyes (direct and consensual response)
