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Flashcards in Sensation Deck (65)
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Where is the primary sensory cortex

Post-central gyrus


Where is the primary motor cortex

Pre-central gyrus


How much of the cortical mantle is occupied by representation of the face?

1/3 of cortical mantle within S1


Does cerebellar (proprioceptive) info come from ipsi- or contra- inputs?



Does input to S1 come from contra- or ipsi- input?



What are the three neurons involved in general somatasensation?

1) Primary sensory neuron outside CNS (except CN V) enter SC and travel to caudal medulla in medial-lemniscal columns ipsilaterally
2) Secondary sensory neuron in caudal medulla (or brainstem) --- DECUSSATE --- and go to thalamus
3) Tertiary neuron in the VPL (body) or VPM (face) thalamus goes to S1 via the internal capsule


Where do second order neurons eminate from prior to decussation in the caudal medulla?

1) Gracile nucleus (lower limb, most medial)
2) Cuneate nucleus (upper limb, most lateral)


What is the name of the pain/temp system

Anterolateral system/spinothalamic tract


Which 4 pathways are involved in nonconcious prorpioception

1) Cuneocerebellar (upper limb)
2) Posterior spinocerebellar (lower limb)
3) Anterior spinocerebellar (trunk + lower limb)
4) Rostral spinocerebellar (trunk + upper limb)


Which 2 pathways are involved in concsious prorprioception

1) Discriminative touch pathway (upper limb)
2) Collaterals of the PSCT (lower limb)


Where is the end point for CONCIOUS proprioception

S1 (via VPL)


What is the external cuneate?

Site of first synpase for non-conscious proprioception of the upper limb


Describe the neurons involved in nonconcious proprioception of the upper limb (above C8) via the cuneocerebellar tract

1; Fibres from skeletal muscle and skin receptors above C8 enter the dorsal horn and travel to rostral medulla via fasciculus cuneatus
2; Synapse in external cuneate nucleus -- 2nd order neurons tracel from ECN to cerbellum via Inferior Cerebllar Peduncle


Describe the neurons involved in nonconscious proprioception of the lower limb (below C8) via the posterior spinocerebellar tract

1a) Below L3; fibres enter in the dorsal horn and travel in the fasciculus gracilis until they reach L3, where they synpase at Clark Nucleus
1b) L3 to C8; fibres enter the dorsal horn and synpase at Clark Nucleus
2) Second order neurons travel in the POSTERIOR spinocerebellar tract (PSCT) and into the ICP to reach the cerebellum


Where do the first synapses occur for nonconcious proprioception of the upper and lower limb, respectively

1) upper limb; rostral medulla in the external cuneate nucleus
2) lower limb; Clark's nucleus in the spinal cord (L3 to C8)


Which lamina is Clarke's nucleus in?

Lamina VII


What are three inputs to spinal border cells?

Muscle spindles and golgi tendon organs, descending modulating tracts to LMNs, flexor reflex arcs in the SC


what are the outputs of SBCs?

1) Anterior spinocerebellar tract (ASCT)
2) Rostral spinocerebellar tract (RSCT)


Synapses in ASCT

1) proprioceptive afferents enter dorsal horn and synapse with SBCs (which can also receive descending modulatory inputs)
2) SPCs cross the midline and travel to the pons in the ASCT
3)Enter the cerebellum via SCP and then cross midline again to arrive at the ipsilateral cerebellar hemisphere


Synapses in RSCT

1) proprioceptive afferents ABOVE T8 enter dorsal horn and synapse with SBCs (which can also receive descending modulatory inputs)
2)SBC fibres travel uncrossed to the ipsilateral cerebellum as the RSCT


Sensory information from the head and face is carried by which cranial nerve

Trigeminal (V)


Which nerve has the largest sensory ganglion in the skull?

Trigeminal (V)


How many cranial nerve nuclei does CN V have?

4: Chief sensory nucleus (touch); Spinal nucleus of V (pain/temp in face); motor nucleus of V (motor); mesencephalic nucleus (proprioception)


Which neurons (2) are involved in discriminative touch in the face?

1) 1st order neuron enters through ganglion of V (midpons) and synpases w/i chief sensory nucleus
2) 2nd order neuron crosses midline and ascends through the trigeminal lemniscus to VPM thalamus


Which neurons (2) are involved in pain transmission from the face?

1) 1st order neuron (c-fibres, A-delta) enter through ganglion of V (mid-pons) and DESCEND through spinal tract of V to the spinal nucleus of V (synpase here)
2) 2nd order neurons cross the midline and join the trigeminal lemniscus to the VPM thalamus


What are the three regions of the spinal tract of V

Most rostral to most caudal: oralis, interpolaris, caudal


What is carried in the spinal tract of V

Pain fibres from the face (descending to the appropriate level of the medulla)


Which cranial nuclei mediate jaw and bite reflexes

1) Mesencephalic nucleus of V; 2) Motor nucleus of V


What neurons are involved in proprioception of the face (e.g., jaw and bite reflexes)

1) A-alpha sensory neuron (cell body in the mesencephalic nucleus in the midbrain) synpases at motor nucleus of V
2) 2nd order neuron (motor efferent) goes back to face via trigeminal root


Where is the ganglion for A-alpha fibres carrying proprioceptive info from the face

In the midbrain (unlike all other primary sensory neurons, whose cell bodies are outside the CNS)