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Neurology Lec 1

Terms in this set (38)

Neurons from higher centers that influence voluntary movement; Descending tracts
upper motor neurons
Upper motor neurons exert a largely _________ influence over lower motor neurons so when you lose UMN influence, you get ________
-inhibitory
-increased ton, excitation, and reflexes
Alpha motor neurons within the ventral horn of the spinal cord that innervate extrafusal muscle fibers of skeletal muscles
lower motor neurons
Excitation of LMNs leads to _________
muscle contraction
Descending tracts bring information from the ________ to the ______ and consist of UMNs
-brain, spinal cord
UMNs can be pyramidal or extrapyramidal. What's the difference?
-Pyramidal: from cerebral cortex
(lateral and ventral corticospinal tracts)
-Extrapyridimal: from non-cerebral cortex spinal tracts
(rubro-, tecto-, reticulo-, vestibulospinal tracts)
Ascending tracts bring information from the ________ to the ________. They bring information from LMNs
spinal cord, brain
An involuntary movement in response to a stimulus
reflex
Reflexes are mediated at the level of the _________
brainstem or spinal cord
(NOT the higher brain centers)
Considering both descending motor tracts and ascending sensory tracts, everything ________ to the lesion will be affected while everything ________ to the lesion will be normal
-caudal, cranial
Many ascending centers are located __________ in the spinal cord and many descending centers are located ________
-dorsally, ventrally
With dysfunction at C1-C5, you will have:
-lack of UMN influence to _______
-LNS disturbance of and lack of UMN influence over ______________ --> ventilatory failure/ventilatory disturbance
-all limbs
-phrenic nerve

(also lack of ascending sensory info from all limbs to the brain)
With dysfunction at C1-C5, describe what you will see in regards to posture/gait, proprioception, muscle tone, reflexes, and other
-Posture/gait: long-strided in all limbs (floating gait)
-Proprioception: delayed in all limbs
-Muscle tone: increased tone in all limbs
-Reflexes: Hyper reflective in all limbs
-Other: hypoventilation, UMN bladder, +/- vestibular signs
Describe the concept of UMN bladder
If there is a lack of UMN influence, then there is increased tone in the external urethral sphincter muscle and it is very difficult to get urine out! Difficult to express the bladder!

(Bladder may fill, be very firm and hard, and painful. The sphincter will be hypertonic, firm, tight, and closed)
Patients with dysfunction at C1-C5 are often described as hypermetric (hyperflexion of the joints while walking).. is this truly hypermetric?
NO it's a cerebellar phenomenon
What are the 7 major lower motor neurons (nerves) located in the C6-T2 region
suprascapular, subscapular, musculocutaneous, axillary, radial, median, ulnar
(SSMAR MU)
What 5 reflexes occur between C6-T2
biceps reflex, triceps reflex, extensor carpi radialis reflex, withdrawal reflex, cutaneous trunci reflex
The biceps reflex is mediated through which nerve?
musculocutaneous nerve (C6-C8)
The triceps reflex is mediated through which nerve?
radial nerve (C7, C8, T1)
The extensor carpi radialis reflex is mediated through which nerve?
radial nerve (C7, C8, T1)
The withdrawal reflex is mediated through which nerves?
axillary, musculocutaneous, median, and ulnar nerves (C7, C8, T1, T2)
The cutaneous trunci reflex is mediated through which nerve?
lateral thoracic nerve (C8, T1, T2)
What is Horner's syndrome and what clinical signs would you see?
-lack of sympathetic innervation to the eye
-ptosis, miosis, enopthalmos, 3rd eyelid elevation
If there is a lesion at C8-T1 and the lateral thoracic nerve is affected, what may you see?
absent cutaneous trunci reflex
With dysfunction at C6-T2, describe what you will see in regards to posture/gait, proprioception, muscle tone, reflexes, and other
-posture/gait: short-choppy gait in forelimbs, long-strides in hindlimbs
-Proprioception: delayed in all limbs
-Muscle tone: hypertonic in hindlimbs, hypotonic to flaccid in forelimbs
-Reflexes: hyperreflexive in hindlimbs, hyporeflexive in forelimbs
-Other signs: Horner's syndrome, absent cutaneous trunci, UMN bladder, root signature
What is root signature?
sign of nerve root pain, typically characterized by holding the limb up (flexed)
With dysfunction at T3-L3, describe what you will see in regards to posture/gait, proprioception, muscle tone, reflexes, and other
-posture/gait: normal in all forelimbs, long-strides in hindlimbs
-proprioception: normal in forelimbs, delayed to absent in hindlimbs
-Muscle tone: normal in forelimbs, hypertonic in hindlimbs
-Reflexes: normal in forelimbs, hyperreflexive in hindlimbs
-Other signs: cutaneous trunci cut-off, UMN bladder, Schiff-Sherrington
Schiff-Sherrington phenomenon: this occurs in _______ (species). They have a small population of border neurons, which are UMNs that send projections to the _________. If we have spinal cord lesion in the T3-L3 region, the border neurons may be affected
Dogs, thoracic limbs
If there is a T3-L3 lesion AND Schiff-Sherrington, what do you expect to see in regards to tone and reflexes?
increased tone and reflexes in ALL 4 limbs (increased ton in hindlimb from T30L3 lesion, increased ton in thoracic limbs from border neurons)
How can we tell a T3-L3 lesion AND Schiff-Sherrington apart from a C1-C5 lesion?
If you get this patient in a standing position, the front limbs should be much more normal- they should be able to move limbs and have normal proprioception
(If you only examine in lateral recumbency, you may mistake the lesion for C1-C5 becuase of increased tone in all 4 limbs)
What 6 reflexes occur between L4-S3?
patellar reflex, cranial tibial reflex, gastrocnemius reflex, sciatic/ischiatic reflex, withdrawal reflex, perineal reflex
Which nerve mediates the patellar reflex?
Femoral nerve (L4-L6)
Which nerve mediates cranial tibial reflex?
peroneal nerve (branch of sciatic)(L6-L7)
Which nerve mediates the grastrocnemius reflex?
tibial nerve (branch of sciatic)(L7, S1)
Which nerve mediates the sciatic/ischiatic reflex?
the sciatic nerve (before it branches a the level of the sciatic notch)
Which nerve mediates the withdrawal reflex
sciatic n
Which nerve mediates the perineal reflex?
pudendal nerve (S1-S3)
With dysfunction at L4-S3, describe what you will see in regards to posture/gait, proprioception, muscle tone, reflexes, and other
-posture/gait: normal in forelimbs, short-choppy gait in hindlimbs
-proprioception: normal in forelimbs, delayed to absent in hindlimbs
-Muscle tone: normal in forelimbs, hypotonic in hindlimbs
-Reflexes: normal in forelimbs, hyporeflexive in hindlimbs, decreased to absent perineal reflex, flaccid tail and anal tone
-Other signs: cutaneous trunci cut-off, LMN bladder (external urethral sphincter isn't functioning bladder is easily expressed), pain with tail extension, root signature
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