Lecture 4a-ascending pathways 2 Flashcards Preview

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Flashcards in Lecture 4a-ascending pathways 2 Deck (20)
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what are the 3 kinds of connections that afferent info makes?

1. local reflex connections
2. connections destined for the cerebral cortex (perception)
3. connections destined for the cerebellum (position of joints, etc)


what is the spinocerebellar circuitry involved in

pathways for fine coordination of posture, movement of limbs, muscle tone


proprioceptive inputs to the cerebellum are ____
-inputs to the cerebellum are usually ______
-enter cerebellum via _____ or _____

inf cerebellar peduncle or inf olive


the dorsal spinocerebellar tract has unconscious proprioception and tells the ______ cerebellum ONly about what?

lower body position


the pathway "unconscious proprioception from the lower extremities" is a 2-neuron system. what is the main tract and what is the other tract called

main tract is the dorsal spinocerebellar tract
cuneocerebellar tract


do somatosensory pathways from the periphery to the cerebellum pass through the thalamus? how many neurons does it involve



where does the dorsal spinocerebellar tract start

at clarke's nucleus located only in T1-L3 (prominent at lower thoracic/upper lumbar lvls)


when propeioceptive leg info enters T1-L3, what happens

unconscious proprioceptive info from the legs enters and synapses right away on clarke's
-fibers leaving clarke's find the dorsolatreal funiculus of white in the cord and rise as the DSCT


what happens if you have proprioceptive leg info entering below L3?

you have to rise to find a clarke's to synapse on.
-hitch a ride on the dorsal columns (only fasc gracilis down there) until it sees a clarke's nucleus
-then those fibers can happily leave FG and synpase on clarke's
-then rise as the dorsal spinocerebellar tract


the dorsal columns below L3 (FG below L3) carry what

both types of proprioceptive info-conscious and unconscious


why is clarke's so prominent at low thoracic levels

all the lower lumbar info wa waiting for it first chance to synapse


what does the spinocerebellar tract enter the cerebellum via?

inferior cerebellar peduncle


when proprioceptive info comes into the cord from the lower extremeities, it can:

1. participate in local reflexes
2. send info up fasc. gracilis to thalamus and then to somatosensory cortex (conscious)
3. send info to clarke's nucleus to eventually get to cerebellum (unconscious)


what is ataxia

lesions resulting in uncoordinated movement

clinically tested by heel to shin test for lower extremeites and finger to nose for upper w/ pt eyes closed


where is the lesion located in ataxia

since the pathway is uncrossed, the ataxia is ipsilateral to the lesion


-a lesion in the SCBT reults in....
-a lesion in the dorsal spinocerebellar tract below L3 (dorsal columns) affects what


-loss of unconscous proprioception giving ipsilateral postural incoordination
-both conscious and unconscious proprioception, ipsilaterally from below that level on down

-lesions of this tract dont occur in isolation and are instead often masked by the effects of its neighbor, the coricospinal tract


what is the cuneocerebellar tract

why does this pathway excist

unconscious proprioception from the upper extremity (C5-T1) from the UPPER extremities via fasciculus cuneatus

-this pathway exists bc clarke's nucleus doesnt exist above T1


the accessory cuneate nucleus doesn't appear until waht

the medulla

-it is the homologue to clarke's nucleus


what happens in the cuneocerebellar tract (C5-T1)

1. proprioceptive info from the upper extremities coming into the cord has to hitch a ride w/ fasci. cuneatus
2. proprioceptive info rises here int he dorsal columns until finding the accessory cuneate nucleus to synapse on
(nucleus located right next to nucleus cuneuatus of the DCML pathway)
3. rises as the cuneocerebellar tract
4. enters the cerebellum through the inf cerebellar peduncle alongise the DSCT


fasc. cuneatus from C5-T1 contains both kinds of proprioceptive info, what are they

1. destined for conscious perception (travels to thalamus and then cortex via DCML pathway)
2. unconscious cerebellar cirucuits