Sensory System & Lesions Flashcards
Somatosensory pathways carry this information and it can be divided into
- direct pathways
- indirect pathways
what pathway is somatotopically organized as a sensory discriminative function
direct pathways
which pathway projects to the somatosensory cortex on the contralateral side
direct pathways
which pathways is useful for diagnostically or localization of nervous system lesions
direct
___ pathway projects more diffusely with multiple synapses in the CNS
indirect pathways
___ pathway serves an affective arousal function (particularly pain) and project to the limbic cortices
indirect pathways
Cutaneous tactile receptors are located in glabrous and hairy skin are considered what
Sensory receptors
typically low-threshold ____ and may be encapsulated or unencapsulated
mechanoreceptors
example of a mechanoreceptors encapsulated
Meissner and Pacinian corpuscles
example of a mechanoreceptors unencapsulated
Merkel cell
what is located in the dermis, fascia around muscles and bone and in the periodontium
Deep tactile receptors
Ruffini endings and other specialized encapsulated receptors respond to what?
pressure, vibration, stretch, distension or tooth displacement
deep somatic tissues are innervated by
nociceptive afferents
Proprioceptive receptors include what
muscle spindles and golgi tendon organs
is formed by all of the receptors that can influence the activity of a single sensory (DRG) neuron
Receptor fields
fingers are considered what kind of receptor field?
Small fields
body surface is considered what kind of receptor field?
Larger fields
Primary pathways for conscious somatic sensation
Anterolateral system & Dorsal column-medial lemniscal system (DCML)
Crude touch, pain, and temperature
Anterolateral system
Carry these sensations into the lateral and anterior funiculi of the spinal cord
Anterolateral system
what is one of the reasons that some aspects of pain are well localized
somatotopically organized reaches primary somatosensory cortex in a highly organized and somatotopic fashion
Discriminative touch, vibration, and joint position sense
Dorsal column-medial lemniscal system (DCML)
Receptive field position and modality are segregated in the
dorsal column nuclei (topographically)
information carried in what tract is somatotopically organized
Medial Lemniscus
one way the brain can keep track of information for sensory origin/position is through what?
Medial Lemniscus
what pathway receives and processes all somatic sensory information destined for cerebral cortex
Medial Lemniscus to the thalamus
Medial Lemniscus to the thalamus processes almost all special sensory information except?
olfaction
what carries:
- proprioception (knowing where body parts are in space without looking)
- two point discriminative touch
- vibration sense
Dorsal columns
what are the 2 primary subdivision in the dorsal columns
medial fasciculus gracilis & lateral fasciculus cutaneou
axons of DRGs below T6 and carries information originating from the leg
medial fasciculus gracilis
axons from dermatomes above T6 and includes the arms and hands
lateral fasciculus cutaneou
sensory, but unconscious & motor related
spinocerebellar system
due yo sensory tract organization a lesions in cerebral cortex will produce sensory deficits on the….
opposite side of the body from the cerebral hemisphere
leg lateral, arm medial
Anterolateral system = ALS
arm lateral , leg medial
Dorsal columns = DC
Leg lateral, arm medial is controlled by what structute?
Thalamus
- Arm lateral, leg medial
- Sensory homunculus
- Disproportionate representation
Primary somatosensory cortex
thin sheet of neurons covering core thalamic nuclei anteriorly, dorsolaterally, and ventrolaterally
Reticular Nucleus
thin sheet of neurons covering core thalamic nuclei anteriorly, dorsolaterally, and ventrolaterally
Reticular Nucleus
whats important for sensory discrimination
primary somatosensory cortex
what contains a bilateral somatotopic body map
Secondary somatosensory cortex (SII)
what is important for tactile discrimination and transference of learned discrimination tasks from one hand to the other
Secondary somatosensory cortex (SII)
Parietal cortical regions also receive tactile inputs, including areas
5 & 7
areas 5 & 7 are associated with what
sensory-motor inter-relationships (primary projections to premotor cortex for motor planning)
an ipsilateral cranial nerve dysfunction & contralateral sensory and/or motor deficit of the body is a
Unilateral brainstem lesions
multiple sensory deficits in both systems since there is a convergence of sensory systems here is a lesion in the
thalamic nuclei or in close proximity to the thalamus
Sensory deficits is contralateral and usually incomplete with some return of sensation over time is a lesion where?
Thalamic
what lesion usually causes accompanying motor deficits
Posterior limb lesion
when you can’t identify objects
astereognosis
can result from a loss of the detection of sensation at a conscious level and/or the interpretation of sensory data received
astereognosis
loss of texture & shape discrimination will produce the inability to identify an object placed in the hand without looking at it is what?
astereognosis
