Neurology lab#5
March 16-3-2011
This is the original version of the sheet, Dr.Aliya didn’t send the corrected sheet yet,
r7 nroud 2inazeil el sheet ma3 el 2ashya2 el zyadeih as soon as the dr. sends it 
Injuries of descending motor tract and cerebrum
Descending motor tract for example: corticospinal tract consist of :
-upper motor neuron: all neuron above alpha and gamma nucleus.
-lower motor neuron: all neuron below alpha and gamma nucleus.
….so the injury differ when it happen in upper or lower
*Upper motor neuron injury include the injury of cortical areas of
corticospinal tract like area 4, 6,3,2,1
*the neuron which start inside the cortex, it will descend and make
synapse with interneuron NOT directly to alpha and gamma neuron.
*interneuron **connect between upper and lower..
** do some integration..
**considered as a part of upper motor neuron..
**make activation for alpha and gamma neuron in
descending tract (e.g:corticospinal tract) ..For example if there is injury in
upper motor neuron <<the activation lost <<the inhibition occurs (e.g.: low
muscle tone instead of more muscle tone).
*Reflexes::::
* We knew the sensation transmitted through Afferent neuron and enter
inside dorsal root ganglia then to interneuron and there make some
integration then send the order to motor neuron (on the anterior horn of
the spinal cord) then reach the affecter (muscle) …….
*this is happen if there is reflex in the spinal cord and this reflex maybe
affected by higher center (motor area , brain stem)<<activation or
inhibition.
**simple reflex……
**Stretch reflex inside the spinal cord .
-the only monosynaptic reflex in the body >>one synapse between the
sensory and motor.
-most reflexes have interneuron except in stretch reflex.
-It is very important reflex related to its function.
-sensory information from muscle enter the dorsal root ganglia where the
cell body found there then to gray horn inside the spinal cord then make
synapse with motor cells(alpha, gamma) ,,,,NOTE::there is NO interneuron.
**the muscles like any organ in the body ,they receive motor and sensory
like a skin ……muscles have sensation through the receptors found inside
the muscle called (muscle spindle),,,there is two type of muscle fiber:
1)extrafusal….
2)intrafusal….
Inside the interspaces of extrafusal fibers there is a muscle spindle
,,function: transmit the sensation from muscle to spinal
cord,,,why??because spinal cord have to recognize the situation of the
muscle (stretch/contraction/relaxation)….
**muscle spindle: receptor organ inside the muscle between intrafusal
fibers …..
….so the sensation from muscle spindle to dorsal root ganglia to posterior
horn of gray matter (posterior root of spinal nerve)and then these afferent
neuron make synapse with alpha motor neuron….
**alpha motor neuron make synapse with:
1)afferent neuron.
2)gamma motor neuron.
3) descending fiber(tracts) from supraspinal center,,,these descending tract
if they make :activation/more contraction/more tone or inhibition/less
contraction/less tone <<through the gamma motor neuron….
**how we can examine the stretch reflex???
By Knee jerk (tendon jerk).
-knee jerk:::we stimulate (stretching) the quadriceps muscle by stretch its
tendon by a hammer then these sensation send to spinal cord via afferent
neuron then to alpha motor neuron to make rapid contraction,,, the
contraction here work as (protection) .
<<in normal cases the inhibition or the activation are balanced from
supraspinal center.
-stretch reflex responsible for muscle tone(partial contraction of the
muscle) …so all living bodies have muscle tone
**the importance of stretch reflex:
1)tendon jerk.
2)muscle tone.
<<Legion of upper and lower motor neuron>>
**what the effect of descending tract on stretch reflex???
Most of descending tract which originate from brain stem(like;tectospinal
,rubriospinal ,vestibulospinal tracts) increase the reflex
(facilitate)/hupertonia/hypereflexia…
-legion in lower motor neuron(alpha and gamma) :::hypotonia ,,why??
Bcoz the pathway of reflex CUT ,,the info’s does not reach the muscle
spindle to make muscle tone …..so legion in lower motor neuron will make
flaccid paralysis (‫(مرخية‬
--also atrophy happen in lower motor neuron legion,,,why??bcoz we cut the
alpha motor neuron so there is no contraction(atrophy).
-legion in upper motor neuron <<activation
**the effect of brain stem is activation and the cortex inhibit the brain stem
,,,so if the legion occur between cortex and brain stem <<the more
activation (hypertonia)<<spasm ….
--there is atrophy in upper motor neuron legion but this atrophy due to
disuse >>because the muscle still reach it (alpha and gamma)neuron<<still
have stretch reflex.
<<babinski sign>>
+ve (upper motor neuron legion)
-ve /absent (lower motor neuron legion)
**normal case:::scratching the lateral side of the sole <<planter flexion..but
patient with upper motor neuron legion <<+ve babinski sign <<dorsum
flexion (fanning all toes)
<<Fasciculation + fibrillation>>
--lower motor neuron legion
-twitches in the muscle and that twitches happen after death ,,,all muscle or
some fibers are contracted …
- absent in case of upper motor neuron legion.
<<Superficial (abdominal) reflex>>
-scratching the abdomen.
-in normal case:::reflex,,,abdominal contraction.
-upper motor neuron legion<< -ve absent….stretch reflex we notice if there
is legion in upper motor neuron no fibers descend from cortex(corticospinal
fibers) which control the abdominal muscle so no contraction <<absent
abdominal reflex….
-lower motor neuron legion<< +ve present.
<<Deep (tendon) reflex>>class knife phenomena
-upper motor neuron legion<< +ve
-lower motor neuron legion<< absent –ve
-examine the muscle contraction ,,,first he will find high resistance then the
relaxation occur suddenly….how??? upper motor neuron legion <<spasm
and rigidity that is why there is resistance at the beginning then what make
the resistance disappear and relaxation occur suddenly ???? the tendon
reflex send info’s through (alpha and gamma)motor neuron to extrafusal
fibers (relaxation)…..
**cerebrum injuries:
Cortical injury it is look like the injury of spinal tract bcoz it’s part of upper
motor neuron.
1) Primary and secondary motor areas <<like a upper motor neuron
legion.
2) Prefrontal cortex::responsible for judgment
Injury: schizophrenia (‫)انفصام الشخصية‬
Loss the ability to judge
Euphoria (‫ مزهزه‬,‫مبسوط‬
)
3) Speech area of broca : language center ,,program for movement of
the muscles of speech<<tongue, soft palate.
--dominant in left hemisphere and they found in right hemisphere but
in emotional domain(how to express).
--injury in broca’s area::: inability to talk ,,cant express but he can
write what he think ,,,he can understand the written language
,,,,,,,,,,,,,,,Expressive aphasia/ motor aphasia
4) wernicke’s area: association of association area
--great importance because it receive sensation from broca’s area, primary
sensory area , auditory area and visual area ….
--injury in wernicke’s area ::: patient can’t understand the written language
or speech ,,,he not suffer how to speech but how to understanding it ,,,cant
translate or express words to thoughts ,,,,,,,, sensory aphasia
4) Primary sensory cortex injury: patient can discriminate the touch but
he can’t make localization….because the discrimination of touch and
pressure related to the thalamus and the localization related to the
primary sensory area.
--cut in primary sensory area make contra lateral hemi anesthesia
(temporary)<<<loss of touch and pressure on the other side then
recovery after (10 hrs) ,,,why??? Because the thalamus will work but
he can’t make localization.
5) Posterior parietal area (association area): legion in this area <<contra
lateral hemi neglect, the patient neglect the other side of his body ,he
Denys the injured side.
6) Primary visual cortex:: legion <<blindness
7) Association visual cortex: he can see but he can’t discriminate what he
can see and send it to past experience.
8) Primary auditory area: inside temporal lobe
--injury in this area:: legion in right side <<partial deafness on both ears
but more in left ear …
9) Association auditory area :
Injury in this area ,,the patient can hear but he can’t discriminate what he
can hear ,,, and the injury here look like wernicke’s area injury ,,,why ???
Because these two areas are closed together in cerebrum.
Done by:
Amal Al-Qaisi
Neuro lab Wednesday
March 16th 2011