Long Ascending Tracts Flashcards
The fasciculus gracilis is located ____
Medially
The fasciculus cuneatus is located ___
Laterally
Neurons located in dorsal root ganglion represent
First order neurons (neuron I)
Peripheral processes of First order neurons innervate
Pacinian corpuscle (sensing tactile and vibration stimuli) and Meisnner’s corpuscle (sensing touch) Also propioceptors involved in kinesthesia
How do the first order neurons central processes ascend
Ipsilaterally
Where do first order neurons end
They terminate at second order neurons in the ipsilateral nucleus gracilis in the medulla
How do axons of second order neurons travel
Ventromedially as internal arcuate fibers and cross midline to form medial lemniscus
Crossed tract that ascend through medulla, pons, and midbrain and terminates in third order neurons
Medial lemniscus
Location of third order neurons
Contralateral ventral posterolateral nucleus of the thalamus
Where does third order nucleus end
Terminates in medial aspect of sensorimotor cortex
Fasciculus gracilis is involved in mediating
Conscious proporception, kinesthesia, and discriminative touch
Where does fasciculus cuneatus appear
Thoracic segments above T6 (T1-T6)
Second order nucleus location (fasciculus cuneatus)
Ipsilateral Nucleus cuneatus of medulla
Different names for dorsal column pathways (gracilis and cuneatus)
Dorsal column or medial lemniscus
Damage to dorsal column/ medial lemniscus
Symptoms appear ipsilateral to affected dorsal column in dermatome so AT AND BELOW the level of spinal cord lesion
Symptoms of damage to dorsal column
Loss of tactile sense, kinesthetic sense,
Cervical lesion- can’t identify object placed in hand ipsilateral to lesion
Lumbar lesion- ipsilateral lower limbs, poorly coordinated movements (clumsy)
Innervates mainly muscle and tendon where central processes project to nucleus dorsalis of Clarke that ascend ipsilaterally, reach inferior cerebellar peduncle in medulla and terminate in cerebellar vermis of the anterior lobe.
(NON CONSCIOUS PROPIOCEPTION) LOWER LIMBS*
Dorsal spinocerebellar tract
Damage to dorsal spinocerebellar tract
Loss of non conscious proprioception and coordination ipsilateral to lesion
Absence of nucleus dorsalis of Clarke and is rostral to C8. Afferent fibers of this tact ascend ipsilateral in fasciculus cuneatus and project to neurons of accessory cuneate nucleus of the lower medulla. Related to UPPER LIMB non conscious proprioception and this tract ends in cerebellar cortex
Cuenocerebellar Tract
The axons of the second order neurons in this tract cross in the spinal cord and ascend through medulla to pons crossing again when it joins the superior cerebellar peduncle and termimates in the Vermal región of the anterior lobe of the cerebellum
Ventral (Anterior) Spinothalamic Tract
Conveys information about whole limb movements and postures to the cerebellum. Lesion causes loss of non conscious proprioception and coordination in lower limbs
Ventral spinothalamic tract
Similar course of ventral spinothalamic tract but afferents are from golgi tendon organs located in upper limb, tract is uncrossed, and it enters cerebellum via inferior cerebellar peduncle
Rostral spinothalamic tract
Damage to rostral spinothalamic tract causes
Loss of non conscious proprioception and coordination in the upper limb
Transmission of pain and temp sensations that ascend in ventrolateral quadrant of spinal cord located contralateral to the side where afferents carrying these sensations enter the spinal cord
Spinothalamic tract
Spinothalamic tract pathways
Direct pathway: neospinothalamic tract mediates pain and temp and simple tactile sensations
Indirect pathways: paleospinalthalamic, spinorecticular, and spinomesencefalic tracts that mediate effective and arousal components of these sensations
