-
Pyramidal cells are the origin of what pathways
Efferent
-
Granule cells receive information mainly from what structures
Thalamus and other regions of the cortex
-
How do the sizes of the granule cells and pyramidal cells compare in the cortex
- In motor regions, pyramidal cell layers are much greater in size then the granule cell layers.
- Opposite is true in the sensory regions
-
What are the Cerebral layers from top to bottom
- Molecular Layer
- External Granule Layer
- External Pyramidal Layer
- Internal Granule Layer
- Ganglionic Layer (Internal pyramidal)
- Multiform Layer
-
What is unique about the last layer of the cortex
The Multiform layer is the layer of polymorphic cells
-
What are the lateral descending motor spinal tracts
- Corticospinal tract
- Rubrospinal tract
-
What are the ventromedial descending motor tracts
- Tectospinal
- Vestibulospinal
- Pontine (medial) reticulospinal
- Medullary (lateral) reticulospinal
-
What is the alternate name for the corticospinal tract and what fibers does it carry
- Pyramidal tract
- Carries voluntary movement
-
How many descending tracts are there from the brain and brainstem respectively
-
What are the two motor pathways that descend from the cerebral cortex
- Corticospinal
- Corticobulbar
-
What other tract is functionally similar to the corticospinal tract
Rubrospinal tract
-
When can a lesion of the Coritcol spinal tract recover
- If the rubrospinal tract is intact
- Subsequent rubrospinal lesion would reverse the recovery
-
What is the trajectory of the Anterior Corticospinal tract
- Motor cortex
- Cervical/Thoracic spinal cord
- Bilateral for axial musculature (posture)
- Does not Cross pyramid of decussation
-
What is the pathway for the Lateral Corticospinal tract
- Primary motor cortex
- Internal capsule
- Cerebral peduncle
- Pons
- Pyramid of decussation (cross)
- Spinal cord
-
90% of the corticospinal tract crosses when
- In the pyramid of decussation (Lateral corticospinal tract)
- The other 10% are Anterior corticospinl tract (ACT) and Anterolateral corticospinal tract (ALCT) don't cross
-
What is the origin of the Corticospinal (Pyramidal) tract
- Primary motor cortex area 4 (30%)
- Primary somatosensory cortex areas 1, 2, 3 (40%)
- Supplemental motor & premotor cortex (30%)
-
In the corticocortical connections, what lobe does the posterior parietal cortex feed
Premotor and supplementary motor cortices
-
In the corticocortical connections what area does the supplemental and premotor cortices feed
Primary motor cortex
-
In the corticocortical connections what area of the brain does the primary somatosensory cortex feed into
Primary motor cortex
-
What are the effects of a lesion to the primary motor cortex, and what is often the cause
- Initial paralysis and weakness
- Often due to a stroke invloving the middle cerebral artery or anterior cerebral artery
-
What are the effects of a lesion to the supplementary motor cortex
- Reduced ability to coordinate actions on the two sides of the body
- Often akinesia - difficulty initiating movement
-
What are the effects of of a lesion to the premotor cortex
Apraxia - difficulty performing complex motor tasks such as tying shoelaces despite intact motor and sensory tracts
-
Symptoms of lower motor neuron (LMN) lesions occur where
Only at the level of the lesion on the ipsilateral side
-
What would be the effects of a lesion at the internal capsule of the corticospinal tract
- Contralateral hemiparesis, may also have other physical signs due to the involvement of corticobulbar fibers
- Lacunar strokes can cause this
-
What would a lesion just rostral to the Decussation of pyramids effect in a corticospinal tract
Contralateral hemiplegias with ipsilateral paralysis of the tongue, facial muscles, or lateral rectus muscle as well of most eye movements
-
What effects would a lesion to the decussation of pyramids have to the corticospinal tract innervations
Bilateral paresis of the upper limb if on the rostral end and lower limbs if on the caudal end
-
What tract makes contact either directly or indirectly with all of the cranial nerves nuclei
Corticobulbar (Corticonuclear) fibers
-
The corticonuclear (bulbar) innervate all of the cranial nerves motor nuclei bilaterally except which
- VII ventral cell group (Contralateral) Lower face
- XII (Contralateral) Tongue
- XI (Ipsilateral) Trapezius and Sternocleidomastoid
-
A lesion to the internal capsule would have what clinical features in the corticobulbar fibers
- Contralateral paralysis of lower face muscles, tongue muscle
- Ipsilateral deviation of the uvula, ipsilateral paralysis of trapezius and sternocleidomastoid
-
Supranuclear palsy
Unilateral lesion of the facial region of the primary motor cortex on the UMN, loss of contralateral lower face muscles
-
Lesion to the hypoglossal nerve (XII) UMN has what effect on the tongue
Deviation away from the lesioned side
-
A lesion to the UMN input to CN XI presents how
- Inability to rotate head to the contralateral side
- Inability to elevate shoulder on the ipsilateral side
-
What does a lesion to one hemisphere of the UMN of the trigeminal nerve cause
No deficit due to the bilateral innervation and compensation takes place
-
A lesion to the UMN of the Vagus nerve would have what effect on the uvula
Deviation towards the lesioned side
-
What are the functions of the Medial and Lateral reticulospinal tracts
- Medial - Excitatory to extensor motor neurons and axial musculature
- Lateral - Inhibitory to extensor motor neurons and neurons innervating muscles of neck and back
-
What is an example of the Tectospinal tract in action
An immediate turn of the head to a bright flash of light
-
What is the origin and decussation of the Tectospinal Tract
- Origin - Superior Colliculus
- Decussates - Dorsal tegmental decussation
-
What is the origin of the medial reticulospinal tract and where does it decussate
- Origin - Pons
- Doesn't decussate
-
What is the origination of the lateral reticulospinal tract and where does it decussate
- Origin - Medulla
- Decussation - Medulla
-
What fibers contribute to tonic extension of the arms and legs seen in decerebrate rigidity
Medial Reticulospinal and Lateral Vestibulospinal fibers
-
What is the function of the rubrospinal tract
- Innervate flexor muscles
- They are functionally parallel to the corticospinal tracts
-
What is the origin and decussation site of the rubrospinal tract
- Origin - Red nucleus
- Decussation - Midbrain
-
What is the functional difference beteween lateral and medial vestibulospinal tracts
- Lateral is used for extensor muscles that maintain posture
- Medial cause rotation and lifting of the head and shoulder blade as well as changes in posture and balance
-
What is origin and decussation of the lateral vestibulospinal tract
- Origin - Lateral vestibular nucleus of medulla
- No decussation
-
What is the origin and decussation of the medial vestibulospinal tract
- Origin - medial, lateral, and inferior vestibular nucleus
- Decussation - Medulla
-
Decerebrate Rigidity
- Damage to brain and midbrain where both medial reticularspinal and lateral vestibulospinal are intact
- All limbs are extended
- Jaw is clenched
- Neck is retracted
- Damage is done below red nucleus
-
Decorticate rigidity
- Damage to brain above the midbrain with the rubrospinal intact
- Arms flexed and adducted
- Legs and often trunk are extended
- Damage above red nucleus
|
|
