exam 2

Question 1

which of the following statements is incorrect?

a. spinothalamic fibers decussate in the ventral white commissure

b. internal arcuate fibers from gracile and cuneate nuclei decussate in the medulla

c. fibers from the nucleus dorsalis (of Clarke) decussate in the ventral white commissure

d. fibers forming the ventral trigeminothalamic tract cross diffusely throughout the medulla and pons

e. fibers forming the dorsal trigeminothalamic tract to not cross

Answer 1

C - the fibers of this tract never cross

• the nucleus dorsalis gets input from DRG that are covered with muscle spindles and GTO in the PNS
• nucleus dorsalis sends axons into the ipsilateral dorsal spinocerebellar tract which ascends enters the cerebellum via ipsilateral inferior cerebellar peduncle

Question 2

lesion to the gracilis fasciculus would compromise:

a. discriminative touch sensations from ipsilateral lower limb

b. discriminate touch from the ipsilateral upper limb

c. somatic pan and temp sensations from the ipsilateral lower limb

d. somatic pain and temp from the ipsilateral upper limb

e. somatic pain and temp from the contralateral upper limb

Answer 2

a.
discriminative touch sensation from ipsilateral lower limb

the fasciculus gracilis carries discriminative touch and sensation information in the DCML pathway

DCML - fasciculus gracilis + fasciculus cuneatus

DCML = ipsilateral discriminative touch

Question 3

tapping your patient’s chin with the jaw open elicits an exaggerated “jaw-jerk” reflex. what does this finding indicate?

a. lesion to the mesencephalic nucleus of CN 5

b. lesion to main sensory nucleus of CN 5

c. lesion to the motor nucleus of CN 5

d. lesion to the corticobulbar input to motor nucleus of CN 5

e. lesion to the spinal nucleus of CN 5

Answer 3

d. this indicates damage to the corticalbulbar system

exaggerated reflexes = upper motor neuron damage

• the corticobulbar system provides upper motor neurons with control of cranial nuclei

c. is wrong because the motor nucleus of 5 is a lower motor nucleus which is in charge of the muscles of mastication
- if lower motor neurons responsible for mastication were damaged, it would result in decreased reflexes
- the reflex would not be able to be elicited since the muscles can not contract

a. if mesencephalic nucleus was damaged, the sensory limb of the reflex arc would be damaged leading to decreased reflex

b. the main sensory nucleus is not involved in this reflex - it gets discriminative touch inputs from the face

e. the spinal nucleus is not involved in this reflex - it gets pain and temp inputs from the face

Question 4

a patient injured in a skateboarding accident presents to your clinic with
- loss of pain and temp sensations from left lower limb
- loss of 2 point discrimination from skin overlying his umbilicus down to toes on right side
- weak right leg
- exaggerated knee and ankle reflexes
- normal cranial nerve function
- normal speech, vision, alertness, and no difficulty following directions

a. R cerebral cortex
b. R brainstem
c. R cervical spinal cord
d. L cervical spinal cord
e. R thoracic spinal cord
f. L thoracic spinal cord
g. R lumbar spinal cord
h. L lumbar spinal cord
I. R sacral spinal cord
J. L sacral spinal cord

Answer 4

E. R thoracic spinal cord

impairments:
- left sided pain and temp loss (spinothalamic)
- diminished right sided tactile sensations (DCML)
- right leg weakness and exaggerated right leg reflexes (upper neuron motor signs = corticospinal)

Level of lesion:
- not cortex - normal cognitive and visual function
- not brainstem - normal cranial nerve function
- farther down brainstem - alternating signs on L and R side of body means this is below the upper midbrain
- has to be lower down where spinothalamic is on left and DCML is on right

Laterality:
spinothalamic - crosses right away so if the ascending tract is damaged, they will get signs on the opposite side of the body
DCML - does not cross until high up so we would see ipsilateral signs

Pathways:
start with the big 4
- DCML
- spinothalamic
- trigeminothalamic
- corticospinal

Question 5

which of the following nuclei is incorrectly matched with one of its target nuclei

a. dorsal cochlear nucleus and the inferior colliculus

b. ventral cochlear nucleus and the inferior colliculus

c. medial superior olive and the inferior colliculus

d. lateral superior olive and the inferior colliculus

e. periolivary nuclei and the inner hair cells

Answer 5

e. the periolivary nuclei and inner hair cells

• the periolivary nuclei projects to the outer hair cells via CN VIII (8) in the organ of corti
• it adjusts the length of the outer hair cells to modulate sensitivity of cochlear system
• inner hair cells do not change length and do not get periolivary projections
  — the changing length of the outer hair cells brings the tectorial membrane closer or further from the inner hair cilia which creates changes in spike frequency

wrong answers:
a. the dorsal cochlear nucleus sends all projections to the contralateral inferior colliculus via the lateral lemniscus

b. the ventral cochlear nucleus sends some projections to the contralateral inferior colliculus via the lateral lemniscus but also sends bilateral inputs to the superior olivary complex in the pons

c. medial superior olive projects to inferior colliculus via the lateral lemniscus

d. lateral superior olive projects to inferior colliculus via lateral lemniscus

Question 6

damage to the lateral lemniscus would lead to

a. total hearing loss from contralateral ear

b. diminished hearing loss from contralateral ear

c. upper motor neuron signs in the contralateral body

d. loss of vibration sense, pressure sense, and 2 point discrimination from contralateral body

e. loss of pain and temp from contralateral body

Answer 6

b. diminished hearing loss from contralateral ear

why: the lateral lemniscus carries binaural info with contralateral dominance
- unilateral lesions do not produce more than subtle hearing changes

wrong:
c. upper motor neuron signs are from damage to corticospinal
d. fine tactile signal info is carried by medial lemniscus
e. pain and temp info from contralateral body is from spinothalamic tract

Question 7

hair cells in semicircular duct ampullae:

a. project their cilia into the macula

b. are oriented in random directions

c. respond to linear accelerations experienced by moving the head

d. are arranged in ranks of stereocilia headed by a single tall kinocilium

e. all of the above

Answer 7

d. are arranged in ranks of stereocilia headed by a single tall kinocilium

• semicircular duct hair cells detect angular accelerations experienced by the head (pitch, yaw, and roll)

wrong:
- linear head movements are detected by the otolithic hair cells

• otolithic hair cells project to the macula which is the thing that holds the crystals
• hair cells in the semicircular duct are all oriented in the same direction
• auditory hair cells do not have a kinocilium

Question 8

the vestibular nuclei send output to

a. cerebellum

b. extraocular motor nuclei CN III, IV, and VI

c. lower motor neurons in the medial group of the spinal cord ventral horn

d. thalamus

e. all of the above

Answer 8

e. all of the above

vestibular system works to drive reflexes of eye, neck, limb, and body position

a. cerebellum - control over postural adjustments

b. extraocular motor nuclei - in the MLF which yokes together nuclei driving eye position and allowing the vestibular system to maintain stable retinal image during head rotation (VOR)

c. lower motor neuron groups - vestibular nuclei can initiate muscle contractions in axial and trunk muscles of the neck (VOR ) and the body (VSR)

Question 9

which of the following mechanisms maintains tautness of the muscle spindle organ during voluntary purposeful changes in muscle length

a. alpha motorneuron activation

b. alpha gamma coactivation

c. reflex activation of gamma motorneurons by vestibulo-spinal reflex

d. 1b afferent activation

e. none of these

Answer 9

b. alpha gamma co- activation

• making voluntary movements requires both alpha and gamma neurons via the supraspinal inputs ( upper motor neuron pathways involved in initiating the contraction like corticospinal inputs)
• when the CNS tells a muscle to contract, it sends signals to alpha totell it to contract but also tells gamma to get ready and to contract the intrafusal fibers appropriately
• gets rid of intrafusal fiber slack to keep spindle taut

gamma = desired position
alpha = current position

Question 10

when reaching for an object

a. premotor signals to primary motor with glutamate

b. premotor signals to striatum with glutamate

c. premotor signals to deep pontine nuclei with glutamate

d. all

e. none

Answer 10

d. all of the above

premotor is park of a network

a. corticospinal neurons in the premotor cortex are directly excited by premotor areas

b. basal ganglia networks become involved in initiating desired movement and suppressing non-synergistic movements (chunking elements into meaningful action sequences)

c. inputs to cerebellum convey the motor plan so that operations can keep the limb moving smoothly to the target

Question 11

which of the following locations contains neurons responsible l for organizing stereotypic, pattern generated movements of the jaw associated with chewing

a. pontine reticular formation

b. red nucleus

c. superior colliculus

d. spinal cord intermediate gray area

e. basis pontis

Answer 11

a. pontine reticular formation

local circuits of propriospinal interneurons yoke together proprioceptive and alpha/gamma motor neurons to form CPGs

for chewing movements, the main output is the trigeminal motor nucleus (SVE to mastication) located in pons with local propriospinal neurons found in the reticular core of the pontine tegmentum

Question 12

neurons located in the superior colliculus participate in which function

a. synthesizes dopamine for use in dorsal striatum

b. control of fractionated movements of individual muscles of the hand

c. orientation of head toward objects in the visual field

d. generation of error signal for use by cerebellum

e. jaw-jerk reflex

Answer 12

c. orientation of head to visual field

superior colliculus gets input from the retina, cerebral cortex, and inferior colliculus

certain axons leave the superior colliculus to form the tectospinal tract which extends around the periaqueductal grey and descends to mid thoracic levels where it synapses on axial lower motor neurons controlling neck muscles

when novel stimuli are detected within the visual field tectospinal reflexes turned the head toward the new stimulus (unless it is coming at you really fast then you turn away)

superior colliculus also drives pattern generated movements of the eyes!

Question 13

the burst neurons for horizontal saccades are located where?

a. paramedian pontine reticular formation

b. nucleus prepositus hypoglossi

c. interstitial nucleus of cajal

d. rostral interstitial nucleus of the medial longitudinal fasciculus

e. medial vestibular nucelsu

Answer 13

a. paramedian pontine reticular formation

wrong:
d. rostral interstitial nucleus of the medial longitudinal fasciculus is where vertical-torsional saccades are located

b and c . are important for generating a step signal to maintain eccentric gaze

e. medial vestibular nuclei - does not directly interface with the brainstem pattern generators for saccadic eye movements

Question 14

if the left abducens nucleus is damaged which of the following will happen

a. down and out appearance of right eye

b. lower quadrant palsy of the left facial muscles

c. patient corrected head tilt to the left when looking down at close objects

d. impairment of the left horizontal conjugate gaze

e. impairment of downward-directed vertical conjugate gaze

Answer 14

d. impairment of left horizontal conjugate gaze

• when abducens nucleus is lesioned it impacts
  1. neurons going out in ipsilateral abducens nerve to innervate lateral rectus
  2. interneurons that leave the nucleus and immediately cross to ascend in contralateral MLF to synapse in the ocular motor nucleus on the side opposite of the 6 lesion
• the person can not make horizontal gaze shift to the side of the lesion becuase ipsi abductor and contra adductor are out

Question 15

the basal system influences activity in the motor system mainly by directly controlling the

a. red nucleus

b. pontine, medullary, and spinal reticular formations

c. alpha and gamma motor neurons

d. ventral anterior thalamic nucleus

e. cerebellum

Answer 15

d. ventral anterior thalamic nuclei

• basal ganglia system suppresses movement by inhibiting the VA nucleus thereby suppressing activity in the premotor area and supplementary motor area
• basal ganglia system ends up disinhibing thalamus, allowing PMA and SMA to run slected motor plants to motor cortex

Question 16

which of the following statements is incorrect with respect to the action of DA in the basal ganglia system

a. dopamine faciliates activation of motor loops by binding to receptor on medium spiny neurons in the corpus striatum

b. dopamine from the substantia nigra pars compacta is excitatory to MSNs bearing D1 receptors for dopamine and inhibitory to MSNs bearing D2 receptors for dopamine

c. dopamine delivery to the striatum excites MSns in the direct pathway, fascilitating movemnt of desired motor loop

d. dopamine delivery to the striatum inhibits MSNs in the indirect pathway, facilitating movement of the desired motor loop

e. phasic release of dopamine to the striatum for a particular motor loop is activated by the substantia nigra pars reticulata

Answer 16

e. the phasic release of dopamine to the striatum is activated by the striatum’s patch neurons

• they project down to the substantia nigra pars compacta via the striato-nigral pathway
• causes dopamine to be delivered back to the striatum matrix where MSNs are located in the direct and indirect pathways of the loop
• DA is only sent to the chosen loop

NOTE: DA is only needed to inhibit the indirect pathway of the chosen loop you want to activate – all other loops are inhibited by corteical activation of indirect pathways

Question 17

to perform its operations, the cerebellum gets direct inputs from all of the following nuclei except:

a. nucleus dorsalis of clarke

b. vestibular nuclei

c. bipolar neurons in the vestibular ganglion

d. superior olivary complex

e. deep pontine nuclei

Answer 17

d. superior olivary complex - plays no role in cerebellar function, is part of the auditory pathway
- the inferior olivary pathway is super important in cerebellar function due to the climbing fibers

wrong:
a. nucleus dorsalis - supplies ipsilateral inputs from muscle spindles and GTOs in the lower limb and trunk via inferior cerebellar peduncle

b. vestibular nuclei and c. vestibular ganglion neurons enter the cerebellum via inferior cerebellar peduncle

e. deep pontine nuclei provide important crossed inputs via middle cerebellar peduncle

Question 18

each of the following statements about the cerebellum is correct except

a. functions to detect and correct errors in cortically-generated movements

b. climbing fibers provide excitatory inputs to the purkinje cells

c. purkinje cells send direct projections to the thalamus

d. blood supply is derived from the vertebrobasilar system

e. midline lesions are associated with truncal ataxia

Answer 18

c. perkinje cells send direct projections to thalamus

• purkinje cells inhibit firing of deep cerebellar nuclei (fastigial, interposed, and dentate nuclei)
• only the dentate nucleus projects back to the VL thalamus via the dentate rubro thalamic tract which goes through the red nucleus

Question 19

which of the following best describes symptoms expected to see with a unilateral lesion to the ventral area of a basis pontis brainstem slice

a. ipsilateral lateral rectus palsy and ipsilateral upper and lower facial palsy

b. ipsilateral lateral conjugate gaze palsy and contralateral lower facial palsy

c. ipsilateral lateral conjugate gaze palsy and ipsilateral upper and lower facial palsy

d. contralateral lateral conjugate gaze palsy and ipsilateral upper and lower facial palsy

e. internuclear ophthalmoplegia and contralateral lower facial palsy

Answer 19

c. ipsilateral lateral conjugate gaze palsy and ipsilateral upper and lower face palsy

lesion includes damage to:

facial nucleus and nerve = leading to ipsilateral upper and lower facial palsy

abducens nucleus = ipsilateral conjugate gaze palsy

wrong:

a. neglects abducens

b. neglects facial nerve and nucleus

d. contralateral

e. MLF is not affected

Question 20

a patient with a stroke to medullary level inferior cerebral peduncle would have all EXCPET:

a. vertigo
b. nausea
c. nystagmus
d. ataxia
e. diminished hearing from ipsilateral ear
f. contralateral loss of discriminative touch and conscious proprioception of the body
g. contralateral loss of pain and temp from body
h. ipsilateral loss of pain and temp from parts of face
i. uvula deviated to opposite side
j. dysphagia
k. dysarthria
l. droopy eyelid on same side otosis
M. constricted pupil on same side miosis
n. inability to sweat on same side anhidrosis
o. flushed skin of face on same side rubrosis
p. sunken eye on same side enophthalmos

Answer 20

f. contralateral loss of discriminative touch and conscious proprioception

a, b, c, d = vestibular signs with damage to vestibular nuclei

d = cerebellar sign ataxia with damage to inferior cerebellar peduncle

e = diminished hearing with damage to cochlear nuclei

g = spinothalamic tract - loss of pain and temp from body

h = spinal tract and nucleus - loss of pain and temp from ipsilateral face

I, J, K = damage to nucleus ambiguous explains vagal signs

L, M, N, O, P = damage to central tegmental tract explains sympathetic signs characteristic of Horner’s syndrome

Question 21

On a monthly check-up visit to a 81 year old woman, with a history of spinal osteoarthritis and now living in a nursing facility, a family physician was surprised to find the patient confined to a wheel chair as she was no longer able to stand unassisted and walking was difficult. On the previous visit, the patient had complained of numbness over the soles and outside edge of both her feet and that both her ankles felt “weak”.

Now, on examination, the patient has exaggerated ankle-jerk reflexes on both sides but normal patellar reflexes. Though the patient can dorsiflex her foot and extend her knee, her hamstring and calf muscles are now hypertonic.

Pinprick and thermal sensation is now absent from the gluteal region, posterior thigh, the leg below the knee and certain parts of the anterior thigh and lower abdomen bilaterally. Sensation to pinprick (pain), warm and cold, vibration, and position sense is intact bilaterally above the level of the umbilicus. The patient complains of tenderness over the lower thoracic and upper lumbar vertebral spines.

The lesion in this patient could best be described a

a. brown-sequard syndrome from a lesion at spinal cord T10

b. an intrinsic/central spinal cord lesion involving the lateral coricospinal tract and anterior white commissure at approximately level T10

c. an extrinsic spinal cord lesion involving the lateral coricospinal tract and anterior white commissure at approximately level T10

d. an intrinsic spinal cord lesion involving the anterior white commsirre at about T10

e. an extrinsic spinal cord lesion involving lateral corticospinal and spinothalamic tracts at about level T10

Answer 21

e.

exaggerated ankle-jerk reflexes, with hypertonic hamstring and calf muscles (upper motor neuron signs isolated to sacral levels of the lower extremities bilaterally

insensitive to pain/temperature bilaterally from the lower abdominal region down, but has intact somatosensory systems above the umbilicus (dermatome T10).

Question 22

Which of the following statements is INCORRECT regarding the area indicated by the tip of the red arrow? (head of the caudate nucleus)

a. located in the walls of third ventricle

b. contains MSNs that make GABA

c. degenerated in parkinsons disease

d. send inhibitory projections to the interanal segment of the globus pallidus

e. sends inhibitory projections to the external segment of the globus pallidus

f. sends striosomal projections to the sibstantia nigra pars compacta

Answer 22

c

The substantia nigra (in the midbrain, not shown) is degenerated in Parkinson’s disease. Degeneration of D2 medium spiny neurons in indirect pathways (the ones using enkephalin as a co-transmitter) in the caudate nucleus are the first neurons to be lost in Huntington’s chorea.

Question 23

Lesion to the area indicated by the tip of the red arrow would most likely cause (genu of the internal capsule on the right side )

a. upper motor neuron signs in the left lower extremity

b. upper motor neuron signs in right upper extremity

c. uvula deviation to left

d. tongue deviation to left

e. parkinsonism bradykinesia on right side

Answer 23

d

genu transmits upper motor neurons in the corticobulbar systems

the hypoglossal nucleus receives unilateral crossed corticobulbar inputs. If the XII nucleus/nerve is damaged, the tongue will point to the ipsilateral side

Question 24

DCML

To:
From:
Function:
1st order nuclei:
2nd order nuclei:
3rd order nuclei:
Lesions:
what one is lateral:
what one is medial:

Answer 24

To: VPL (ventral posterolateral) thalamus

From: DRG (dorsal root ganglion) 1a, 1b, Ab fibers

Function: send fine touch, vibration sense, pressure, proprioception, kinesthesia (movement awareness)

1st order nuclei: DRG ascends ipsilaterally after it enters the spinal cord and ascends as the fasciculus gracilis or fasciculus cuneatus

2nd order nuclei: synapses onto the gracilis or cuneatus tubercles in the medulla. becomes the internal arcuate fibers. cross midline and ascend contralaterally in the medial lemniscus

3rd order nuclei: VPL of thalamus sends axons to somatosensory cortex (S1)

Lesions:
- loss of DCML tract gives ipsilateral signs
- loss of medial lemniscus gives contralateral signs
- both give clumsy movements, ataxia

what one is lateral: cervical (upper limbs)
what one is medial: sacral (lower limbs)

Question 25

Spinothalamic / Anterolateral

To:
From:
Function:
1st order nuclei:
2nd order nuclei:
3rd order nuclei:
Lesions:
what one is lateral:
what one is medial:

Answer 25

To: VPL (ventral posterolateral) thalamus

From: DGR (Ad and c fibers)

Function: pain/temp and crude touch

1st order nuclei: dorsal root ganglion fibers enter into laminae 1 (postermarginal) and ascend ipsilaterally in Lissauer’s tract1-2 segments above where it entered

2nd order nuclei: 1st order neuron synapses onto neurons in the dorsal horn laminae I-IV, which cross via the ventral white commissure and ascend to the VPL contralaterally

3rd order nuclei: 2nd order neuron synapses onto neuron in the VPL thalamus which project to other nuclei

Lesions: loss of pain and temp to segments 1-2 levels below the lesion on the contralesional side
what one is lateral: sacral (pain/temp)
what one is medial: cervical (crude touch)

Question 26

cunneocerebellar tract (CCT)

To:
From:
Function:
1st order nuclei:
2nd order nuclei:
3rd order nuclei:
Lesions:

conscious or non-conscious

Answer 26

To: cerebellum

From: DRG Ia muscle spindle and Ib-Golgi tendon neurons from UPPER limbs

Function: conveys information from individual muscles in the upper limbs

1st order nuclei: Ia and Ib primary afferent neurons enters the fasciculus cuneatus and ascent to the medulla

2nd order nuclei: 1st order synapses onto the accessory cuneate nucleus located lateral to the cuneate tubercle in the medulla

3rd order nuclei: enters the ipsilateral cerebellum via the inferior cerebellar peduncle

Lesions: rarely lesioned alone, can have lateropulsion (walking towards ipsi side of lesion)

non-conscious - does not enter thalamus

Question 26

DSCT (dorsal spinocerebellar tract)

To:
From:
Function:
1st order nuclei:
2nd order nuclei:
3rd order nuclei:
Lesions:

conscious or non conscious?

Answer 26

To: cerebellum

From: muscle spindles and Golgi tendons

Function: conveys information from individual muscles in the lower limb

1st order nuclei: la and lb primary afferent neurons enter the dorsal white column and goes to the intermediate grey

2nd order nuclei: located in clarke’s nucleus and ascends ipsilaterally in the posterolateral white matter

3rd order nuclei: enters the ipsilateral cerebellum through the inferior cerebellar peduncle

Lesions: not really lesioned in isolation. can have lateropulsion where patient walks towards the side of the lesion

non-conscious - it does not enter the thalamus

Question 27

ventral spinocerebellar tract

To:
From:
Function:
1st order nuclei:
2nd order nuclei:
3rd order nuclei:
Lesions:

conscious or non-conscious

Answer 27

To: cerebellum

From: dorsal root ganglion (1b afferents)

Function: conveys non conscious proprioceptive movement and posture of whole lower limb

1st order nuclei: Ib enters the intermediate grey

2nd order nuclei: located at the base of the dorsal grey horn, decussates in the ventral white commissure, ascends in the anterolateral white matter to the upper pons and decussates again

3rd order nuclei: enters cerebellum via superior cerebellar peduncle

Lesions: rarely lesioned alone, can have lateropulsion (walking towards ipsilateral side of lesion)

non-conscious - does not enter thalamus . we do not need to know much about it. humans do not have it

Question 28

Trigeminothalamic system - spinal nucleus

To:
From:
Function:
1st order nuclei:
2nd order nuclei:
3rd order nuclei:
Lesions:

Answer 28

To: VPM of thalamus (ventral posteromedial)

From: trigeminal ganglion (Ad and C fibers) which are pseudo-unipolar

Function: pain, temp, and crude touch from face, head, neck, nasal, and oral cavities

1st order nuclei: Ad and C fibers go through the trigeminal ganglion and run down to terminate in the spinal nucleus of the medulla

2nd order nuclei: axons decussate and ascend as the ventral trigeminal tract (VTT) within the trigeminal lemniscus

3rd order nuclei: VPM of thalamus projects to the somatosensory cortex (s1)

Lesions:
- damage to tract = ipsilateral loss of pain and temp
- damage to VTT = contralateral loss of pain and temp

notes: division of CN V (ophthalmic, maxillary, and mandibular are somatotopically organized)

Question 29

Trigeminothalamic system - main (principle) nucleus of V

To:
From:
Function:
1st order nuclei:
2nd order nuclei:
3rd order nuclei:
Lesions:

Answer 29

To: VPM (ventro posteromedial thalamus)

From: trigeminal ganglion of head and face

Function: discriminative touch sensation from head and face (NO proprioception)

1st order nuclei: trigeminal ganglion in head/face to main nucleus of V in the pons

2nd order nuclei: neurons cross the midline and ascend in the VTT; few ascend ipsilaterally as the dorsal trigeminothalamic tract (DTT) but both are within the trigeminal lemniscus

3rd order nuclei: VMP of thalamus projects out to other areas

Lesions:
- damage to tract = loss of touch ipsilaterally
- damage to VTT = loss of touch contralaterally
- damage to DTT - loss of touch ipsilateral

Question 30

Trigeminothalamic system - mesencephalic nucleus of V

To:
From:
Function:
1st order nuclei:
2nd order nuclei:
3rd order nuclei:
Lesions:

Answer 30

To: VPM of thalamus

From: neurons from the head and face (mostly for mastication)

Function: processes non-conscious proprioception and some conscious

1st order nuclei: neurons from periodontal ligament for bite force control, facial muscles, tongue muscles to meV

2nd order nuclei: meV to midbrain and to supra-trigeminal nucleus

3rd order nuclei: supra-trigeminal nucleus to motor nucleus of V for jaw-jerk reflex

Lesions: only time to see a jaw-jerk reflex

note: only place (meV) where the CNS contains primary afferent cell bodies

Question 31

cochlear pathway

To:
From:
Function:
pathway
Lesions:

Answer 31

To: auditory cortex

From: spiral ganglion in the inner ear

Function: sound

Pathway: stereocilia release NT

1st order: inner hair cells send signal to spiral ganglion via CN VIII which goes to the cochlear nucleus in the pontomedullary junction

2nd order neurons can go 4 places:

1. cochlear root neurons descend to spinal cord for acoustic startle reflex
2. efferent fibers “olivocochlear bundle” to superior olivary complex to outer hair cells
3. Dorsal cochlear nucleus–> axons cross midline via dorsal acoustic striae –> lateral lemniscus (contralaterally) –> inferior colliculus –> Medial Geniculate Body –> Heschl’s gryus in A1

4.Ventral cochlear nucleus–> can go to two places:
a. Ipsilaterally to Superior Olivary Complex –> lateral lemniscus –> inferior colliculus –> Medial Geniculate Body –> Heschl’s gyrus in A1
b. crosses midline via trapezoid body –> contralateral Superior Olivary Complex –> lateral lemniscus –> inferior colliculus –> Medial Geniculate Body –> Heschl’s Gyrus

Lesions: lesion in the cochlea or VIII nerve can lead to sensorineural hearing loss
- lesion to lateral lemniscus is rare

notes: conductive hearing loss is in outer or middle ear (reversible/treatable usually)

Question 32

Medial Vestibulospinal tract

To:
From:
Function:
1st order neurons:
2nd order neurons:
3rd order neurons:
Lesions:

Answer 32

To: alpha motor neurons of the neck

From: medial vestibular nucleus

Function: stabilize the head during movement

1st order neurons: CN VIII (from vestibular system)

2nd order neurons: medial vestibular nuclei descends to neck bilaterally to intermediate zone

3rd order neurons: medial lower motor neurons to neck muscles

Lesions: no VCR reflex, issues with head stability

notes: this is the vestibulo-collic reflex (VCR) and it ends at T1

Question 33

Lateral vestibulospinal tract
To:
From:
Function:
1st order neurons:
2nd order neurons:
3rd order neurons:
Lesions:

Answer 33

To: lower motor neurons for limb and body

From: lateral vestibular nucleus

Function: acts to stabilize the limbs and body when perturbed. increase tone in trunk and proximal limb extenders

1st order neurons: CN VIII (from the vestibular system)

2nd order neurons: lateral vestibular nucleus descends the spinal cord, ipsilaterally, to the intermediate zone

3rd order neurons: lower motor neurons in the medial and lateral groups of the central horn (lateral horn?)

Lesions: ?

notes: activates axial extensor muscles and creates the vestibulo-spinal reflex (VSR)

Question 34

Medial Longitudinal fasciculus (MLF)

To:
From:
Function:
1st order neurons:
2nd order neurons:
3rd order neurons:
Lesions:

Answer 34

To: abducens nuclei (VI)

From: superior to medial vestibular nuclei

Function: yolks together nuclei to maintain stable vision during head movement (conjugate eye movement)

1st order neurons: CN VIII (from the semicircular canals)

2nd order neurons: superior vestibular nuclei to the medial vestibular nuclei then crosses and ascends as the MLF

3rd order neurons: synapses on abducens nuclei and sends ipsilateral excitation and contra excitation

Lesions:

notes: creates the vestibulo ocular reflec (VOR)

Question 35

Vestibulocerebellum

To:
From:
Function:
1st order neurons:
2nd order neurons:
3rd order neurons:
Lesions:

Answer 35

To: flocculonodular lobe of the cerebellum

From: lateral vestibular nuclei

Function: fine control over postural adjustment and eye movement

1st order neurons: CN VIII (vestibular system)
2nd order neurons: lateral vestibular system
3rd order neurons: axons through the inferior cerebellum
Lesions:
notes:

Question 36

Vestibular nuclei to VPi

To:
From:
Function:
1st order neurons:
2nd order neurons:
3rd order neurons:
Lesions:

Answer 36

To: VPI thalamus

From: medial vestibular nuclei

Function: conscious proprioception

1st order neurons: CN VIII (vestibular system)

2nd order neurons: medial vestibular nuclei

3rd order neurons: VPi of thalamus to parietal and temporal cortex

Lesions: ?

notes: from MVN fiber project bilaterally alongside MLF

Question 37

Corticopontine

To:
From:
Function:
1st order neurons:
2nd order neurons:
3rd order neurons:
Lesions:

Answer 37

To: pons (deep pontine nuclei)

From: fibers form all parts of the cerebral cortex

Function: conveys motor plans and integrated sensory data to the cerebellum

1st order neurons: frontopontine fibers travel in the anterior limb of the internal capsule

2nd order neurons: enter the pons and spread across the basis pontis. terminate ipsilaterally on deep pontine nuclei

3rd order neurons:
Lesions:
notes: largest descending motor control system in the CNS