Exam 1: Corticospinal and other descending pathways Flashcards Preview

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Flashcards in Exam 1: Corticospinal and other descending pathways Deck (32)
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1
Q

Identify the cortex or functional area represented by red line

A

Primary motor cortex

2
Q

Identify the cortex or functional area represented by red line

A

Somatosensory cortex

3
Q

Identify the cortex or functional area represented by red line

A

Premotor cortex

4
Q

Identify the cortex or functional area represented by red line

A

Supplementary motor cortex

5
Q

Identify the cortex or functional area represented by red line

A

posterior parietal cortex

6
Q

Pathway - Cortex:

• ___-___ neuron system that starts in the cortex and ends at various level of the spinal cord on _____ _____ neurons

A

Pathway - Cortex:

• 2-3 neuron system that starts in the cortex and ends at various level of the spinal cord on lower motor neurons

7
Q

Pathway - Cortex:

• Cell bodies of upper motor neurons are located in layer _____ if the cerebral cortex

A

Pathway - Cortex:

• Cell bodies of upper motor neurons are located in layer 5 of the cerebral cortex

8
Q

Pathway - Cortex:

  • Betz cells (_____ cells) – heavy _____ neurons that are _____ than other neurons from layer V of the cortex
  • Betz cells end directlyon _____ _____ neurons in the _____hornof thespinal cord
  • Other neurons from layer V synapse on _____ cells in the _____ horn of the spinal cord. Axons from the _____ cells end on _____ _____ neurons
A

Pathway - Cortex:

Betz cells (pyramidal cells) – heavy myelinated* neurons that are bigger* than other neurons from layer V of the cortex.

*Carries the signals faster and more powerfully!

  • Betz cells end directly on lower motor neurons in the ventral horn of the spinal cord
  • Other neurons from layer V synapse on intermediate cells in the central horn of the spinal cord. Axons from the intermediate cells end on lower motor neurons
9
Q

Upper Motor Neurons:

  • are found at what levels?
  • Dysfunction at these levels causes what?
A

Upper Motor Neurons:

  • Cortical, subcortical, or spinal levels
  • Dysfunction at these levels can cause weakness, increased or pathologic reflexes, and increased tone and spasticity
10
Q

Lower Motor Neurons:

  • are found at what levels?
  • Dysfunction at these levels causes what?
A

Lower Motor Neurons:

  • anterior horn cell, motor nerve root, plexus, peripheral nerve, or neuromuscular junction
  • Dysfunction at these levels can cause weakness, atrophy, fasciculations, decreased reflexes
11
Q

Pathway - Cortex:

Name the two corticospinal tracts and what they are involved in

A

Pathway - Cortex:

Both are descending corticospinal tracts!

  • Lateral corticospinal tract – involved in limb muscle contraction
  • Anterior corticospinal tract – involved in axial muscle contraction
12
Q

Pathway - Cortex:

The descending corticospinal tract gives off co-lateral fibers to:

  • Adjacent _____ cells
  • The _____ nuclei, _____ nucleus, _____ nuclei, and _____ nucleus
  • To the _____ formation
A

Pathway - Cortex:

The descending corticospinal tract gives off co-lateral fibers to:

  • Adjacent cortical cells
  • The basal nuclei, red nucleus, vestibular nuclei, and olivary nucleus
  • To the reticular formation
13
Q

Pathway - Cortex:

Contribution of cortical motor fibers from the cortex:

• ~___% of nerve fibers come from the primary motor cortex, ~___% come from the premotor and supplementary motor areas, ~___% come from the sensory cortex

A

Pathway - Cortex:

Contribution of cortical motor fibers from the cortex:

• ~30% of nerve fibers come from the primary motor cortex, ~30% come from the premotor and supplementary motor areas, ~40% come from the sensory* cortex

*sensory cortex fibers allow quick decisions (like if skin is burning, reflex to move it back)

14
Q

Cortex:

Understand the terms Homunculus and Somatotopic Arrangement

A

Cortex:

  • Homunculus: Scale model of human body illustrating physiological, psychological or other characteristics
  • Somatotopic Arrangement: Point to point correspondence of an area of the body to a specific point on the central nervous system
15
Q

Which tracks deal with voluntary limb movement?

A

Lateral corticospinal

Anterior corticospinal

Rubrospinal

16
Q

Which tracks deal with Reflex postural movement?

A

Tectospinal (sight)

Vestibulospinal (ear)

Reticulospinal

17
Q

Pathway - Cortex:

  • Descending axons pass through the _____ _____ and converge towards the posterior limb of the _____ capsule. The _____ capsule is located between the _____ and _____ nuclei
  • Due to the fact that all cortical motor nerve fibers are packed so close together, a small stroke in this area can paralyze _____ side of the body.
A

Pathway - Cortex:

  • Descending axons pass through the corona radiata** and converge towards the **posterior limb of the internal capsule. The internal capsule is located between the thalamic** and **basal nuclei
  • Due to the fact that all cortical motor nerve fibers are packed so close together, a small stroke in this area can paralyze** an **entire side of the body.
18
Q

Identify the marked landmark or structure

A

corona radiata

19
Q

Identify the marked landmark or structure

*** What artery supplies this area? ***

A

internal capsule

Note: i have read different things from different sources and I missed what branch he said during lecture so take these with a grain of salt…

*** It is supplied by the middle cerebral artery branches ***

lenticulostriate branches of middle cerebral artery (superior half of posterior internal capsule) and anterior choroidal artery branch of the internal carotid artery (inferior half of posterior internal capsule)

20
Q

Corticospinal Pathway - Midbrain:

  • At the midbrain level, the corticospinal fibers are located in the _____ _____. These cortical fibers form the _____ _____
  • The corticospinal fibers occupy the middle of the _____ _____ while the medial and lateral portion contain _____ fibers
  • Because there are many structures within close proximity to each other in the midbrain, strokes in this area are usually associated with other “_____ signs”
A

Corticospinal Pathway - Midbrain:

  • At the midbrain level, the corticospinal fibers are located in the cerebral peduncle. These cortical fibers form the crus cerebri
  • The corticospinal fibers occupy the middle of the crus cerebri while the medial and lateral portion contain corticobulbar (corticopontine) fibers
  • Because there are many structures within close proximity to each other in the midbrain, strokes in this area are usually associated with other “neighborhood signs
21
Q

Know what causes Weber’s syndrome and what happens due to the lesion.

A

Weber’s syndrome:

Midbrain infarction: Occlusion of paramedian branches of the posterior cerebral artery (PCA)

Unilateral lesion: Substantia nigra, Corticospinal, Corticobulbar, CN III Oculomotor

Corticospinal → contains UPM, damage leads to spastic hyper reflex

Corticobulbar → damage leads to contralateral lower face muscle weakness

CN III Oculomotor → damage leads to loss of all extraocular muscles (except superior oblique and lateral rectus) → droppy eyelids, down and out

22
Q

Tectospinal Tract - Midbrain:

  • Involved in _____ _____ movement in response to _____ stimuli
  • Originates form the _____ _____ located in the tectum of the midbrain
  • Descending nerve fibers then _____ _____ and form the _____ _____ _____ (MLF) which is located in the anterior white matter
A

Tectospinal Tract - Midbrain:

  • Involved in reflex postural movement in response to visual stimuli*
  • Originates form the _____ _____ located in the tectum of the midbrain
  • Descending nerve fibers then cross over and form the medial longitudinal fasciculus (MLF) which is located in the anterior white matter

*If you step on something and then look down you can react, example in class was a dead rat under your foot)

23
Q

corticospinal tract - Pons:

  • As the fibers from the cortex descend, they _____ _____
  • A lesion in this area of the corticospinal tract will?
A

corticospinal tract - Pons:

  • As the fibers from the cortex descend, they spread out
  • A lesion in this area of the corticospinal tract will likely not be as severe
24
Q

Corticobulbar Tract:

  • Comes from the _____ cortex and ends in the _____
  • Axons from these tracts go laterally and to the _____ (_____ tract)
  • The tract is composed of the _____ motor neurons of the cranial nerves
A

Corticobulbar Tract:** (AKA **corticopontine!)

  • Comes from the motor cortex and ends in the pons
  • Axons from these tracts go laterally and to the cerebellum** (**pontocerebellar tract)
  • The tract is composed of the upper motor neurons of the cranial nerves
25
Q

Corticobulbar Tract: KNOW THIS!!!

  • The muscles of the _____, _____, and _____ are controlled by this system
  • This system innervates cranial motor nuclei _____ except the _____ _____ nuclei and the _____, which are innervated _____ by the _____ cortex
A

Corticobulbar Tract:

  • The muscles of the face, head, and neck are controlled by this system
  • This system innervates cranial motor nuclei bilaterally except the lower facial (VII) nuclei and the hypoglossal (CN XII), which are innervated unilaterally** by the **contralateral cortex
26
Q

corticospinal tract - Medulla:

  • Corticospinal tractform two _____ on the ventral aspect of the medulla
  • Decussation of corticospinal nerve fibers takes place at the level of the _____ medulla
  • Approximately 90% of the nerve fibers decussate at this level to form the _____ corticospinal tract
  • The remaining ~10% form the _____ corticospinal tract
A

corticospinal tract - Medulla:

  • Corticospinal tractform two pyramids on the ventral aspect of the medulla
  • Decussation of corticospinal nerve fibers takes place at the level of the caudal medulla
  • Approximately 90% of the nerve fibers decussate at this level to form the lateral corticospinal tract
  • The remaining ~10% form the anterior corticospinal tract
27
Q

Spinal Cord Pathways:

Know the locations (and functions) represented in the

2 Pyramidal Tracts and 4 Extrapyramidal Tracts

A

2 Pyramidal Tracts:

  • Lateral* corticospinal tract (voluntary motor control of limbs)
  • Anterior corticospinal tract (voluntary motor control of axial and girdle)

4 Extrapyramidal Tracts

  • Rubrospinal (voluntary arm flexors, secondary to lateral corticospinal tract)
  • Reticulospinal (reflex postural)
  • Vestibulospinal (reflex postural)

*In the Lateral corticospinal tract the cervicle region is more medial since they will synapse first along the pathway!

28
Q

Rubrospinal Tract:

  • It starts from the _____ nucleus in the _____ _____
  • It ends on the ___lateral alpha and gamma motor neurons in the _____ horn of the spinal cord
  • After decussating in the _____ _____ the tract is located _____ brainstem and spinal cord
  • This tract influences _____ muscles of the _____
  • Its function is _____ _____ of the ___lateral muscles, however the level of control is _____ than the corticospinal tract
A

Rubrospinal Tract:

  • It starts from the red nucleus in the mid brain
  • It ends on the contralateral alpha and gamma motor neurons in the anterior horn of the spinal cord
  • After decussating in the mid brain the tract is located lateral brainstem and spinal cord
  • This tract influences flexor muscles of the limbs, (particularly arm flexors)
  • Its function is voluntary flexion of the contralateral muscles, however the level of control is far less** than the **corticospinal tract
29
Q

Rubrospinal Tract:

  • Its function is _____ _____ of the ___lateral muscles, however the level of control is _____ than the corticospinal tract
  • If their is a lesion disrupting the corticospinal tract the rubrospinal tract gives _____ _____, and the patient will appear _____ and _____
A

Rubrospinal Tract:

  • Its function is voluntary flexion of the contralateral muscles, however the level of control is far less** than the **corticospinal tract
  • If their is a lesion disrupting the corticospinal tract the rubrospinal tract gives backup movement, and the patient will appear clumsy and uncoordinated
30
Q

Reticulospinal Tract:

  • Starts from two reticular formations: _____ and _____
  • Regulation of _____ _____
  • If damaged, a harmless stimulus can elicit a _____ _____
  • 2 Reticulospinal Tracts: _____ and _____
A

Reticulospinal Tract:

  • Starts from two reticular formations: pontine and medullary
  • Regulation of voluntary movements
  • If damaged, a harmless stimulus can elicit a flexor reflex
  • 2 Reticulospinal Tracts: Lateral and Medial
31
Q

Name the 2 Reticulospinal Tracts and describe their basic functions

A

Lateral Reticulospinal Tract:

  • Receives input from both cortices and ascending sensory input from spino-reticular tract
  • Bilateral innervation of primary interneurons that in turn innervate alpha and gamma motor neurons to the limb muscles
  • Mainly excite flexors

Medial Reticulospinal Tract:

Mainly excite extensors

32
Q

Vestibulospinal Tract:

  • Receives excitatory input from vestibular organs and _____ _____ nuclei and some inhibitory input from the _____ _____ of the cerebellar cortex
  • Lateral: Causes _____ innervation of interneurons that excite alpha motor neurons to _____ limb and _____ muscles; Mainly to _______.
  • Medial: _____ to muscles of the _____ and _____ extremity; Helps to integrate information from the vestibule and cochlea to motor movements to regulate of _____ and _____
  • This tract normally keeps _____ level with the _____ and provides _____. A lesion to this tract may present with a _____ _____ as the healthy side overpowers the weak side.
A

Vestibulospinal Tract:

  • Receives excitatory input from vestibular organs and deep cerebellar nuclei and some inhibitory input from the Purkinje cells of the cerebellar cortex
  • Lateral: Causes ipsilateral innervation of interneurons that excite alpha motor neurons to lower limb and trunk muscles; Mainly to extensors.
  • Medial: Bilateral to muscles of the neck and upper extremity; Helps to integrate information from the vestibule and cochlea to motor movements to regulate of posture and balance
  • This tract normally keeps eyes level with the horizion and provides balance. A lesion to this tract may present with a positive Romberg as the healthy side overpowers the weak side.

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