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Ascending and descending tracts (1)

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cajokefu's version from 2016-02-12 21:42

Section 1

Question Answer
Pathway responsible for touch, pressure, vibration, fine form and texture discrimination, sterognosis, proprioception, kinsthesiadorsal (posterior) column - medial lemniscus
recognition of 3D objectssterognosis
conscious awareness of body positionproprioception
limb movement in spacekinesthesia
input from which spinal levels forms fasciculus cuneatusC1-T5
input from which spinal levels form fasciculus gracilis T6-S5
first order neuron for dorsal column pathwaydorsal root ganglion
second order neurons for dorsal column pathwayneurons in cadual medulla in nuclei gracilis and cuneatus
where do axons in the dorsal column pathway cross the midlinecaudal medulla - as internal arcuate fibers to form medial lemniscus
3rd order neuron for dorsal column pathwayneuron in ventral posterior lateral nucleus of thalamus
where do axons arising from the ventral posterior lateral nucleus projectto the primary sensory cortex in the parietal lobe
in the medial lemniscus, which fibers are more ventral and which are more dorsal in the medulla?lower limbs more ventral, upper limbs more dorsal
tract related to vestibular system and control of eye movementsmedial longitudinal fasciculus
in the pons, which part of the medial lemniscus is more medial and which part is more lateral?upper limb is medial, lower limb is lateral
what axons join the medial lemniscus in the pons?axons from the main sensory and mesencephalic nucleus carrying touch information from face
where do the trigeminal axons that join the medial lemniscus terminate?ventral posterior medial nucleus of the thalamus
are the axons carrying sensory information from the face located medially or laterally in the medial lemniscus?medially
through what do axons arising from 3rd order neurons in VPL and VPM course through as they project to the parietal lobe?internal capsule
what cortex is located in the postcentral gyrus of the parietal lobe?primary sensory cortex
what sulcus separates the frontal lobe from the parietal lobe?the central sulcus
in the somatosensory cortex of the parietal lobe, which is more medial, upper limb or lower limblower limb
in the somatosensory cortex of the parietal lobe, which is more medial, face or upper limbupper limb
what is the somatotopic organization of upper limb, lower limb, and face in the somatosensory cortex of the parietal lobefrom medial to lateral - lower limb, upper limb, face
system containing multiple tracts that convey different aspects of pain, including location and intensity of painful stimulus, emotional response to pain, autonomic response to pain, increased attention to painful inputanterolateral system (spinothalamic tract is part of system)
tract responsible for conscious awareness of nature of a painful stimulus and where it is located; also conveys temperature informationspinothalamic tract
what kind of axons make up the spinothalamic tract?small diameter, lightly myelinated
first order neuron in spinothalamic tractdorsal root ganglia cells
second order neuron in spinothalamic tractneurons in dorsal horn of spinal cord
where do axons in spinothalamic tract cross the midlinein anterior commissure of spinal cord, at level of entry
third order neurons in spinothalamic tractneurons in ventral posterior lateral nucleus of thalamus
are tracts that add on to the spinothalamic tract from the upper body located more laterally or medially?medially - different from dorsal columns
why is the spinothalamic tract difficult to identify in the spinal column?not heavily myelinated - not darkly stained
where is the spinothalamic tract located in the mid and rostral medulla?just dorsal to the inferior olivary complex
which nucleus contains pain and temperature input from the face?spinal trigeminal nucleus
which nerves input pain and temp information to the spinal trigeminal nucleusV (majority), VII, IX, X
in the rostral pons, what is the ventral to dorsal organization of the spinothalamic tractface most ventral, then upper limb, lower limb most dorsal
activated by stimuli that make us feel comfortable or uncomfortable including pain, temperature, fatigue, or even watching someone in pain; also responds to vestibular changes insula
convey tactile, pressure, and proprioceptive information from muscle spindles and joint receptors in upper and lower limb to cerebellumposterior spinocerebellar and cuneocerebellar tracts
conveys more complex information from proprioceptors, spinal interneurons and variety of cutaneous receptors anterior spinocerebellar tract
what is the origin of the posterior spinocerebellar tract?Clarke's nucleus (T1-L2/3)
what is the origin of the anterior spinocerebellar tract?laminae V through VII, spinal border cells of ventral horn
what is the origin of the cuneocerebellar tract?lateral nuceate nucleus (medulla)
what part of the body is represented by the posterior spinocerebellar tract?trunk, lower extremity
what part of the body is represented by the anterior spinocerebellar tract?thorax, lower limbs
what part of the body is represented by the cuneocerebellar tract?trunk, upper extremity
what are the major inputs to the posterior spinocerebellar tract and the cuneocerebellar tract mechanoreceptors in muscles, joints, skin
what are the major inputs to the anterior spinocerebellar tract?mechanorecceptors, movement related interneurons
does the posterior spinocerebellar tract cross the midline?no
does the anterior spinocerebellar tract cross the midline?yes twice; once in the cord and again in the pons
does the cuneocerebellar tract cross the midline?no
what peduncle does the posterior spinocerebellar tract use to enter the cerebellum?inferior
what peduncle does the anterior spinocerebellar tract use to enter the cerebellumsuperior
what peduncle does the cuneocerebellar tract use to enter the cerebellum?inferior
are most of the tracts in the inferior cerebellar peduncle going in or out?in, some out
are most of the tracts in the middle cerebellar peduncle going in or out?all in (from basilar pons - axons cross midline in pons)
are most of the tracts in the superior cerebellar peduncle going in or out?out, some in (crosses midline as it exits - decussation of SCP)
what is one of the targets of the superior cerebellar axons?red nucleus
first order neurons for spinocerebellar and cuneocerebellar tractsdorsal root ganglia cells
second order neurons for spinocerebellar tractipsilateral Clarkes column loccated between T1 and L4
what is the target neuron for PSCT?neurons in the cerebellum
why can't axons from C1-C8 join the PSCT and how do they get to cerebellum?clarke's nucleus ends; instead join fasciculus cuneatus and ascend to the level of the caudal medulla, synapse in lateral cuneate nucleus in caudal medulla, enter cerebellum via ICP
second order neuron for cuneocerebellar tractipsilateral cuneate nucleus in caudal medulla
target neurons for CCTneurons in cerebellum
first order neuron for anterior spinocerebellar tractcells from T12-L5 (lower limb)
second order neuron for anterior spinocerebellar tractinterneuron in dorsal horn (integration of several systems - ascending, descending)
third order neuron for anterior spinocerebellar tractdiffuse collection of cells in ipsilateral intermediate spinal gray - axons cross midline to ascend to brainstem and cerebellum
target neuron for ASCTneurons in cerebellum
how do ASCT axons enter cerebellumsuperior cerebellar peduncle - most axons recross in cerebellum to return to ipsilateral side
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Section 2

Question Answer
what else makes up the cerebral peduncle, aside from CST?corticopontine and cortibulbar fibers
where do CST fibers move after they cross the midline to the contralateral side?dorsally and laterally to become the lateral corticospinal tract
what happens to the CST fibers that do not cross the midline in the medulla?remain on ipsilateral side in same ventral position to become anterior corticospinal tract
anterior CST axons terminate on motor neurons located _______ - primarily ______ muscles; terminate in cervical and thoracic segmentsmedially, axial
lateral CST axons terminate on motor neurons located ________ - primarily __________laterally; upper limb and digits
cells of origin in the rubrospinal tractred nucleus in the midbrain
descending tract that reveices input from cerebral cortex and cerebellum and modulates activity or motor neurons in the spinal cord; proximal limb muscles - flexorsrubrospinal tract
where are rubrospinal axons located in the spinal cord?just ventral to lateral corticospinal tract
what is located just ventral to the lateral corticospinal tractrubrospinal tract
which nuclei receive/contribute input from MLF?oculomotor (input and output); trochlear (input and output); abducens (input and output); vestibular (output)
what is the role of the ascending limb of MLF?link vestibular nuclei and nuclei that control eye movement
what is the role of the descending limb of MLF?links vestibular nuclei with interneurons and motor neurons in the cervical spinal cord
do most axons of the descending part of MLF (medial vestibulospinal tract) cross or do they stay ipsilateral?most stay ipsilateral, many cross
where do axons of the descending part of MLF (medial vestibulospinal tract) terminate?motor neurons that innervate axial musculature of the neck
is the medial vestibulospinal tract found below cervical levels?no
where is the medial vestibulospinal tract not found?below cervical levels
arises from neurons in another part of the vestibular nucleus and course ipsilaterally to all levels of the spinal cord to innervate motor neurons that innervate axial and proximal limb muscleslateral vestibulospinal tract
what structures does the lateral vestibulospinal tract innervate?motor neurons that innervate axial and proximal limb muscles
most ascending pathways from the spinal cord and head/neck region terminate _______ to the side on which they originatecontralateral
most pathways descending to the spinal cord are ________ to the side on which they arise; exception?contralateral; exception is anterior corticospinal, lateral vestibulospinal
exiting cranial nerves innervate _______ muscles/glands; exception?ipsilateral; trochlear is exception
origin of lateral corticospinal tractpyramidal cells in prefontal gyrus (motor related areas, especially those related to the limbs)
where does the lateral corticospinal tract cross?in caudal medulla
what is the target of the lateral corticospinal tract?alpha motor neurons, especially those related to hand and digits or interneurons
what is the function of the lateral corticospinal tract?initiation of movement
what is the origin of the anterior corticospinal tract?pyramidal cells in prefrontal gyrus (motor related areas; especially those related to trunk muscles)
where do does the anterior corticospinal tract cross?most of it is uncrossed, some cross in spinal cord
What is the origin of the rubrospinal tract?red nucleus
where does the rubrospinal tract cross?at level of origin in midbrain
what is the target of rubrospinal tract?alpha motor neurons related to proximal muscles, especially flexors
what is the function of the rubrospinal tract?supraspinal control of flexor motor neurons and proximal limb muscles
what is the origin of medial vestibulospinal tract (descending MLF)?medial vestibular nucleus
where does medial vestibulospinal tract (descending MLF) cross?bilateral from origin - does not extend beyond cervical region
What is the target of the medial vestibulospinal tract (descending MLF)?alpha and gamma motor nuerons, especially for extensor muscles
What is the function of the medial vestibulospinal tract (descending MLF)?supraspinal control of extensor muscles and muscle spindles
What is the origin of the MLF - ascending?vestibular nuclei, abducens, trochlear and oculomotor nuclei
Where does the MLF - ascending cross?bilateral
What is the target of the MLF - ascending?links vestibular and nuclei related to moving eye
What is the function of the MLF - ascending?coordinates head and eye movement
What is the origin of the lateral vestibulospinal tract?lateral vestibular nucleus
Where does the lateral vestibulospinal tract cross?doesn't cross - ipsilateral
What is the target of the lateral vestibulospinal tract?alpha and gamma motor neurons at all levels of the spinal cord
What is the function of the lateral vestibulospinal tract?supraspinal control of extensor muscles and muscle spindles
medial medullary syndrome is due to an occlusion of what artery?branch of vertebral - anterior spinal
Medial medullary syndrome due to occlusion of left branch of vertebral artery will lead to motor deficits on which side of the body, and paralysis of tongue muscles on which side?paralysis on right side of body (fibers haven't crossed yet) and left tongue due to loss of hypoglossal nucleus (ipsilateral)
dies medial medullary syndrome cause sensory deficits?yes because it involves medial lemniscus
what sensory deficits does medial medullary syndrome produce in the body?right side of body - axons crossed in caudal medulla
what sensory deficits does medial medullary syndrome produce in the face?none - general sensory information from V enters at mid-pons and synapses in the main nucleus of V (rostral to area affected by occlusion)
does medial medullary syndrome cause any pain or temperature loss?no, the spinothalamic tract is not involved - located laterally
does medial medullary syndrome cause any loss of taste?no, nucleus solitarious is not involved
hoarseness and difficulty swallowing confirm that an injury is at what level of the brainstem?medullary - because of involvement of nucleus ambiguus (CN X)
lateral medullary syndrome is also called Wallenberg's syndrome
lateral medullary (Wallenberg's syndrome) involves an occlusion of what artery posterior inferior cerebellar (PICA)
what would cause the contralateral loss of pain and temperature over right side of body as seen in lateral medullary (Wallenberg's) syndrome?damage of left spinothalamic tract
What could cause ipsilateral loss of pain and temperature to the left side of the face?damage of the left spinal V nucleus
what would cause the dizziness and loss of balance seen in lateral medullary (Wallenberg's) syndrome?involvement of vestibular nuclei - also loss of blood supply to caudal cerebellum
Weber's syndrome involves occlusion of what artery?perforating branch of posterior cerebral artery
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