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Pyramidal tract exam 5
Exam 5 pyramidal tract
57
Anatomy
Graduate
09/05/2010

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Term
lesion to basal ganglia causes:
Definition
- abnormal movements
Term
lesion to cerebellum causes:
Definition
- loss of coordination
Term
cerebralcortical lesions cause:
Definition
- paresis or paralysis
Term
with the pyramidal system, upper motor neurons have both their cell bodies and axons in the ___. The cell bodies are in the ___ ___. The axons descend to the ___ level or to the __ ___ and synapse on ___ ___ ___ in either ___ __ ___ ___ in the brainstem, or on ___ ___ ___ at the cord level.
Definition
- CNS
- cerebral cortex
- brainstem
- spinal cord
- lower motor neurons
- cranial nerve motor nucleus
- spinal motor neurons
Term
Upper motor neurons synapse where and with what?
Definition
- brainstem level with cranial nerve motor nuclei (lower motor neuron)
- spinal cord level with spinal motor neurons (lower motor neuron)
Term
Lower motor neurons have their cell bodies in the ___, but their axons in the ___.
Definition
- CNS
- PNS
Term
The cell bodies of lower motor neurons are specifically located where?
Definition
- brainstem in the cranial nerve motor nuclei
- ventral motor horn of spinal cord
Term
The axons of lower motor neurons form what?
Definition
- motor component of cranial/spinal nerves
Term
where do lower motor neurons synapse?
Definition
- on the skeletal muscle
- also called "final common path" neurons
Term
Upper motor neuron lesion manifestations:
Definition
- if lesion before decussation of pyramids (where axons cross over), then the manifestations are exhibited on the contralateral side of the lesion
- if lesion is after decussation of pyramids, then the manifestations are on the ipsilateral side as the lesion
Term
Where are possible sites of damage on a lower motor neuron?
Definition
- cranial nerve motor nuclei and/or their axons
- ventral horn spinal motor neurons and/or their axons
Term
Lower motor neurons manifestations are always ___.
Definition
IPSILATERAL to the lesion
Term
Upper motor neuron lesion manifestations:
Definition
- spastic paralysis
- hyperactive deep tendon reflexes
- Babinski sign present
Term
Lower motor neuron manifestations:
Definition
- flaccid paralysis
- atrophy
- hypoactive or absent deep tendon reflexes
- fasciculations
-
Term
if you seen Babinksi sign, what kind of lesion?
Definition
- UMN
Term
If you see pronounce atrophy, what kind of lesion are you looking at?
Definition
- LMN
Term
If you note hyperactive reflexes, what kind of lesion is it?
Definition
- UMN
Term
If you note hypoactive or absent reflexes what kind of lesion are you seeing?
Definition
- LMN
Term
If you note flaccid paralysis what kind of lesion is it?
Definition
- LMN
Term
If you note spastic paralysis, what kind of lesion is it?
Definition
- UMN
Term
If you note fasciculations (small localized muscle twitches), what kind of lesion is it?
Definition
- LMN
Term
what two tracts make up the pyramidal system?
Definition
- Corticobulbar tract
- Corticospinal tract: lateral and ventral corticospinal tracts
Term
what does the pyramidal system originate from?
Definition
- cerebral cortex pyramidal cells of Betz in layers 3 and 5 of cerebral cortex
Term
describe the pyarmidal cells of betz:
Definition
- large multipolar neurons with pyramid shaped cell bodies
- located in layers 3 and 5 of cerebral cortex and in other coritical and subcortical regions
- about 1 million of these axons descend from the 6th layer of the cerebral cortex to form the corticobulbar and corticospinal tracts of the pyramidal system
Term
The axons of what cells form the corticospinal and corticobulbar tracts?
Definition
- pyramidal cells of Betz
Term
describe the internal capsule:

TEST QUESTION ON THIS
Definition
- organized compact bundle of ascending and descending myelinated fibers passing between the thalamus and the basal ganglia
Term
what two structures do the myelinated fibers of the internal capsule pass between?
Definition
- thalamus and basal ganglia
Term
the anterior limb of the internal capsule has what?
Definition
- anterior thalamic radiations
- frontopontine fibers
Term
the genu of the internal capsule has what?
Definition
- corticobulbar fibers
Term
the posterior limb of the internal capsule has what?
Definition
- major motor and sensory pathways
Term
where does the optic tract terminate?
Definition
- lateral cuneate nucleus of thalamus, then you have optic radiations back to occipital area of brain
Term
the corona radiata is:
Definition
- diverging fibers of internal capsule that radiate in all directions to the cerebral cortex
- converging fibers of internal capsule that come from all directions of the cerebral cortex and go to lower brain structures and the spinal cord
Term
what three sets of fibers pass through the cerebral peduncles from medial to lateral?
Definition
- corticopontine fibers from frontal lobe
- corticobulbar and coritcospinal fibers
- corticopontine fibers from parietal temporal, and occipital lobes
Term
if someone injures their cerebral peduncles, what will you see?
Definition
- paralysis on contralateral side of lesion
Term
what is inside of pons?
Definition
- CN V motor nucleus
- corticopontine fibers from fronal lobe
- corticobulbar and corticospinal fibers
- corticopontine fiber from parietal, occipital, and temporal lobes
Term
the lateral corticospinal tract is in ___ ___ of the spinal cord. the ventral corticospinal tract is the ___ ___ and ___ levels of the spinal cord.
Definition
- all levels
- cervical
- upper thoracic
Term
The corticobulbar tract starts in the primary motor cortex then goes to the corona radiata and then the genu of the internal capsule. What three places does it go to from there?
Definition
- trigeminal motor nucleus on both sides> muscles of mastication
- facial motor nucleus on both sides> muscles of facial expression
- middle 1/3 of cerebral peduncle
Term
from the middle 1/3 of the cerebral peduncle, where does the corticobulbar tract go?
Definition
- pons
- medulla
From the medulla the corticobulbar tract goes two places:
- hypoglossal nucleus on both sides> tongue muscles
- nucleus ambiguus (motor nuclues of IX, X, XI cranial nerves on both sides)> muscles of pharynx, larynx, sternocledomastoid, and trapezius
Term
so ultimately what muscles does the corticobulbar tract control?
Definition
- muscles of facial expression (CN VII)
- muscles of mastication (CN V3)
- tongue muscles except for palatoglossus (CN XII)
- pharynx muscles (CN IX and X)
- larynx muscles (CN IX and X)
- sternocleidomastoid (CN XI)
- trapezius (CN XI)
Term
so what cranial nerves is the corticobulbar tract associated with?
Definition
- CN VII (facial expression)
- CN V3 (mastication)
- CN IX and X (larynx and pharynx)
- CN XI (sternocleidomastoid and trapezius)
- CN XII (tongue muscles)
Term
the motor nucleus for the trigeminal nerve is in the ___.
Definition
pons
Term
the hypoglossal nucleus and nuclues ambiguus is in the
Definition
medulla
Term
what motor nuclei do NOT receive direct innervation from the primary motor cortex?
Definition
- oculomotor nucleus
- trochlear nucleus
- abducens nucleus
Term
the nuclei that do not receive direct innervation by the primary motor cortex, are instead innervated by what?
Definition
- oculomotor, trochlear, and abducens nuclei
- bilaterally innervated from gaze centers in the midbrain and pons, which in turn receive innervation from gaze centers in the frontal lobe
Term
gaze centers in the frontal lobe innervate gaze centers in the __ and ___. These gaze centers then innervate the __, __ and ___ nuclei.
Definition
- pons
- medulla
- oculomotor, trochlear, and abducens
Term
The motor nucleus of cranial nerve VII that innervates the lower half of the face, receives projections from ____ cerebral hemisphere only.
Definition
- contralateral
Term
Since the lower facial muscles of facial expression are only innervated by the contralateral cerebral hemisphere, and upper motor neuron lesion would only knock out the ___ facial muscles on the ___ side of the lesion b/c the upper face would be innervated by neurons from the ipsilateral hemisphere. But a lower motor neuron lesion that occurs after the the facial motor nucleus would not out ___ and ___ facial muscles on the ___ side.
Definition
- lower
- contralateral
- upper and lower
- ipsilateral side
Term
an upper motor neuron lesion to the facial nerve would cause:
Definition
- paralysis on contralateral side, lower face muscles only
Term
a lower motor neuron lesion to the facial nerve would cause:
Definition
- complete facial paralysis on the ipsilateral side
Term
an example of a lower motor neuron lesion in the facial nerve is called:
Definition
Bell's palsy, complete paralysis on ipsilateral side of face
Term
the corticobulbar tract goes through the __ of the internal capsule, while the corticospinal tract goes through the ___ __ of the internal capsule.
Definition
- corticobulbar> genu
- corticospinal> posterior limb
Term
After going through the posterior limb of the internal capsule, the corticospinal tract goes where?
Definition
- middle 1/3 of crus cerebri of midbrain
Term
10-15% of corticospinal tract fibers do not cross at the pyramids in medulla. What tract do these become and what path do they take?
Definition
- ventral corticospinal tract fibers
- become the lateral faniculus of spinal cord in the upper thoracic and cervical regions
- cross midline at the anterior white commissure> motor neurons in the ventral horn> muscles of the neck and upper limbs
Term
muscles of the neck and upper limb are mostly innervated by:
Definition
- motor neurons in the ventral corticospinal tract in the lateral fasciculus in the upper thoracic and cervical regions
Term
Most corticospinal tract fibers DO cross over. These become what tract and what is their path?
Definition
- lateral corticospinal tract in the lateral funiculus of all spinal cord regions
- motor neurons in ventral horn> muscle of neck, trunk and limbs
Term
so the ventral corticospinal trunk only innervates ___ and ___ muscles, while the lateral corticospinal tract innervates ___, ___, and ___ muscles.
Definition
- neck and arm
- neck, trunk, and limb
Term
the reason you don't see the corticobulbar tract in a cross section of spinal cord is b/c the CNV nucleus is in the internal ___, CNVII is at junction of pons and medulla, and the hypoglossal nucleus and nucleus ambiguus are in the ___ ___.
Definition
- pons
- upper medulla
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