Term
| What is the role of the Dorsal column system - medial lemniscal system? |
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Definition
| perception and appreciation of mechanical stimuli |
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Term
| What information is carried by the dorsal lemniscal system? |
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Definition
a. conscious appreciation of cutaneous
(1) discriminative touch
(a) fine form and texture discrimination, recognition of three dimensional shape (stereognosis)
(2) vibration
b. conscious appreciation of proprioception
(1) position sense - position of limb or body part in space
(2) awareness of movement at joints and degree of muscle contraction (kinesthesia) |
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Term
| What information is carried by the dorsal column system? |
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Definition
a. conscious appreciation of cutaneous
(1) discriminative touch
(a) fine form and texture discrimination, recognition of three dimensional shape (stereognosis)
(2) vibration
b. conscious appreciation of proprioception
(1) position sense - position of limb or body part in space
(2) awareness of movement at joints and degree of muscle contraction (kinesthesia) |
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Term
| What information from peripheral mechanoreceptors is brought into the dorsal column system? |
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Definition
| 1. Information is brought into the spinal cord from peripheral mechanoreceptors which include those for discriminative touch, vibration sense and proprioception such as joint receptors for awareness of movement and position of body parts), muscle stretch receptors (muscle spindles) and Golgi tendon organs for detecting muscle tension |
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Term
| What does the collateral branch of the central process of axons exiting the dorsal root ganglia do? |
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Definition
| each axon ascends within the ipsilateral dorsal column |
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Term
| What is the fasciculus gracilis? |
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Definition
| carries information principally from lower limb and lower portions of the body (~T6 and below) |
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Term
| What is fasciculus cuneatus? |
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Definition
| (a) carries information principally from upper limb and upper portions of the body (above T6) |
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Term
| How does somatotopic organization work? |
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Definition
(1) the lower portions of the body are mapped medially and progressively more rostral portions are mapped more laterally within the dorsal column
(2) this somatotopic mapping continues throughout the dorsal column - medial lemniscal system |
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Term
| What fibers synapse on the dorsal column nuclei (nucleus gracilis and cuneatus) |
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Definition
| Fibers of the fasciculus gracilis and cuneatus |
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Term
| Where are internal arcuate fibers located? |
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Definition
| above the gracile and cuneate nuclei-->curve toward midline and cross to the other side of the medulla to form the contralateral medial lemiscus |
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Term
| What is the ventral posterolateral (VLP) nucleus of the thalamus? |
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Definition
| a. fibers of the medial lemniscus carrying touch, vibration and proprioceptive information synapse |
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Term
| Where do ascending fibers leaving the VPL go? |
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Definition
| via the posterior limb of the internal capsule to the cortex and synapse in a wide region including a very strong projection to the postcentral gyrus (primary sensory cortex, somatosensory cortex (SI), Brodmann areas 3,1,2) |
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Term
| What are the signs of dorsal column damage? |
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Definition
1. impaired vibration sense
2. inability to determine limb position
3. impaired stereognosis (astereognosis)
4. impaired 'two-point tactile discrimination'
5. motor deficit characterized by a shuffling, uncoordinated gait
a. loss of sensory input, particularly proprioceptive input, severely impairs motor behavior
6. Romberg's sign
a. when patient stands erect with eyes closed and feet together, they tend to sway and fall toward the side of the lesion
b. be aware that a Romberg’s sign is also seen with cerebellar damage |
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Term
| What type of info is carried by the spinothalamic tract? |
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Definition
a. primary pathway for pain (mechanical, chemical and thermal)
b. Thermal (non-painful warm or cold)
c. Nondiscriminative touch - crude or poorly localized touch |
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Term
| What happens when the spinothalamic tract is damaged? |
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Definition
| ranging from reduced sensibility (hypesthesia), to numbness, tingling and prickling (paresthesia), to a complete loss of sensibility (anesthesia) |
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Term
| Fibers of the spinothalamic tract exit the dorsal root ganglia and enter what? |
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Definition
| posterolateral fasciculus (Lissauer’s tract) and bifurcate into ascending and descending branches |
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Term
| Collaterals of the spinothalamic tract do what? |
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Definition
| synapse on interneurons in the dorsal horn gray matter and participate in the circuits that mediate spinal reflexes such as the flexor withdrawal reflex |
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Term
| What is the clinical significance of the Lissauer's tract? |
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Definition
| unilateral lesion at a particular level of the cord will lead to a loss of pain and temperature sensitivity at dermatomal levels beginning about one or two segments below the injured segment |
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Term
| Where is the spinothalamic decussation? |
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Definition
| a. axons of interneurons of the posterior horn cross the midline via the anterior white commissure to form the contralateral spinothalamic tract (anterolateral system |
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Term
| Where to the contralateral spinothalamics tracts go? |
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Definition
| a. axons ascend as the contralateral spinothalamic tract to reach brainstem reticular formation and thalamus |
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Term
| What is the importance of the brainstem reticular formation (spinoreticular tract)? |
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Definition
| changes in level of attention in response to pain |
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Term
| Where do some of the axons of the spinothalamic tract go after leaving the spinoreticular tract? |
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Definition
| ventral posterolateral (VPL) nucleus of the thalamus. Thus pathway is responsible for the conscious awareness of pain and temperature. |
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