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Neuroanatomy (OCCU 6140) > Midterm 5 > Flashcards

Midterm 5 Flashcards

Neuroanatomy of motor systems Motor and premotor cortex

1
Q

The pyramidal decussation is considered the dividing point between the _________ and the _______________.

A

The pyramidal decussation is considered the dividing point between the medulla and the spinal cord.

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2
Q

Axons of upper motor neurons form white matter that descend, ultimately becoming the __________________. Before entering the spinal cord, most fibers (~85%) cross at the _____________________.

A

Pyramids of the medulla
Pyramidal decussation

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3
Q

Below the pyramidal decussation, the fibers descend to the appropriate level of the spinal cord, enter gray matter and synapse onto dendrites of _______________________ in the anterior (ventral) horn.

A

Lower motor neurons

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4
Q

Axons of lower motor neurons (somatic motor) form anterior (ventral) roots and join spinal nerves to innervate ____________________.

A

Skeletal muscle of the body

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5
Q

In the corticospinal pathway, white matter containing the axons of upper motor neurons exits the cerebrum (to enter the brainstem) via the ________________________________.

A

Posterior limb of the internal capsule

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6
Q

What are the three anatomical positions that the internal capsule is divided into?

A

Anterior limb
Genu
Posterior limb

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7
Q

The anterior limb of the internal capsule contains the descending axons of upper motor neurons, true or false?

A

False, the posterior limb contains the descending axons of the upper motor neurons

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8
Q

The internal capsule is surrounded by regions of _____________ deep to the cerebral cortex.

A

gray matter

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9
Q

At the base of the cerebrum, the corticospinal fibers in the internal capsule travel through the upper part of the brainstem (at the level of the midbrain) via the _____________________. These then connect with the __________________ (clusters of corticospinal fibers within the anterior pons) and then the ___________________.

A

Crus cerebri
Basis pontis
Pyramids of the medulla

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10
Q

Corticospinal fibers have a characteristic position as they travel through the brainstem.

Corticospinal fibers are in the most _______________ part of the brainstem.

A

Anterior

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11
Q

The tract in the spinal cord carrying the crossed corticospinal fibers from the pyramidal decussation is called the _____________________ tract.

A

Lateral corticospinal tract

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12
Q

The lateral corticospinal tract is located within the posterior portion of the _______________________ of spinal cord white matter.

A

lateral funiculus

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13
Q

The 15% of corticospinal fibers that do not cross at the pyramidal decussation descend in the __________________________ tract (within the ______________________funiculus).

A

Anterior corticospinal tract (sometimes referred to as medial, it is anterior and medial)

Anterior (ventral) funiculus

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14
Q

In the spinal cord gray matter, anterior horn:
Lateral motor nuclei receive ___________ (what type?) innervation from fibers in the lateral corticospinal tract and innervate muscles of the _______________.

A

Lateral motor nuclei receive IPSILATERAL (same side) innervation from fibers in the lateral corticospinal tract and innervate muscles of the limbs.

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15
Q

In the spinal cord gray matter, anterior horn:
Medial (anterior) motor nuclei receive mostly ____________(what type?) innervation from the fibers in the anterior corticospinal tract and innervate muscles of the _______________.

A

Medial (anterior) motor nuclei receive mostly CONTRALATERAL (opposite side) innervation from fibers in the anterior corticospinal tract and innervate muscles of the trunk.

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16
Q

The crossed projections (fibers in the anterior corticospinal tract) travel from one side of the spinal cord to the other (to innervate medial/anterior motor nuclei of the contralateral side) via the _______________________.

A

Anterior white commissure

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17
Q

The primary motor cortex (pre-central gyrus) show somatotopic organization, the upper motor neurons responsible for motor function of specific body regions are organized systematically along the length of the precentral gyrus, explain where the lower limb, upper limb, neck and head are located.

A

Lower limb: Medial and superior surface
Upper limb: Lateral and superior surface
Neck and head: Lateral and inferior surface

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18
Q

How do upper motor neurons reach the lower motor neurons that innervate the muscles of the head and neck?

A

There are projections from upper motor neurons associated with head and neck contained within the corticobulbar tract.

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19
Q

Initially (cerebral white matter) the corticobulbar fibers travel with corticospinal fibers, true or false?

A

True

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20
Q

The corticobulbar fibers travel through the internal capsule via which section?

A

The genu of the internal capsule

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21
Q

The corticobulbar fibers travel with corticospinal fibers through the crus cerebri, basis pontis and pyramids of the medulla, true or false?

A

True

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22
Q

Lower motor neurons innervated by the corticobulbar pathway are motor nuclei associated with certain ______________ nerves.

A

Cranial nerves

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23
Q

The trigeminal motor nucleus for muscles of mastication is located where?

A

Midpons

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24
Q

The facial motor nucleus for muscles of facial expression is located where?

A

Lower pons

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25
The nucleus ambiguus for muscles of the pharynx and larynx is located where?
Medulla
26
The spinal accessory nucleus is located in the __________________,the corticobulbar fibers that innervate these lower motor neurons descend via the __________________.
Cervical spinal cord, anterior horn Lateral corticospinal tract
27
The hypoglossal nucleus for muscles of the tongue is located where?
Medulla
28
The innervation of cranial nerve motor nuclei( lower motor neurons) by corticobulbar fibers is _______________. What is the exception?
Bilateral Innervation of neurons in CN VII (facial) motor nuclei
29
What are the pyramidal tracts?
Corticospinal tract Corticobulbar tract
30
What are the extrapyramidal tracts?
Vestibulospinal tract Reticulospinal tract Tectospinal tract Rubrospinal tract
31
What is an important difference between the pyramidal and extrapyramidal systems (tracts)?
The pyramidal system sub-serves volitional movements, whereas the extrapyramidal systems are automatic (i.e., reflexive), concerned with maintaining balance, posture and some coordination of movement
32
What is the function of the rubrospinal tract?
Crawling in babies, arm swing while walking in adults
33
What is the function of the vestibulospinal tract?
Promotes stabilization of the head, maintenance of upright and balanced posture (antigravity muscles in the legs)
34
What is the function of the reticulospinal tract?
Automatic posture and gait control
35
What is the function of the tectospinal tract?
Visually-guided head movements
36
The lateral motor system including the lateral funiculus and muscles of the limbs is associated with which pyramidal and extrapyramidal tracts?
Pyramidal = Lateral corticospinal tract Extrapyramidal = Rubrospinal tract
37
The medial motor system including the medial funiculus and muscles of the trunk is associated with which pyramidal and extrapyramidal tracts?
Pyramidal = anterior/medial corticospinal tract Extrapyramidal = Vestibulospinal tract, recticulospinal tract, tectospinal tract
38
There are three cranial nerves (and corresponding nuclei) involved with eye movements, these nuclei do not receive innervation from the corticobulbar tract, what are they and where are they located?
CN III occulomotor nerve = upper midbrain CN IV trochlear nerve = lower midbrain CN VI abducens nerve = lower pons
39
The neurons of the oculomotor, trochlear, and abducens nuclei are innervated by neurons in the primary motor cortex, true or false?
False, the neurons of the oculomotor, trochlear and abducens nuclei are NOT innervated by neurons in the primary motor cortex
40
Cortical areas (the frontal eye field and the parieto-occipito-temporal area) are cortical regions associated with ______________________.
Volitional eye movements
41
The cortical areas (frontal eye fields, parieto-occipital-temporal area) associated with volitional eye movements do not directly project to the eye movement nuclei (i.e., CN III, IV and VI) but to subcortical regions that are involved in eye movement control. The subcortical regions involved depend on the direction of _________________.
eye movement
42
The ___________________________ is the horizontal gaze center with neurons projecting to the _______________________nucleus.
The paramedian pontine reticular formation is the horizontal gaze center with neurons projecting to the abducens (CN VI) nucleus.
43
In addition to providing innervation of the lateral rectus (abductor) muscle, neurons in the abducens nucleus cross and project (via a tract called the ___________________________) to the oculomotor (CN III) nucleus, the neurons of which innervate the medial rectus (adductor).
medial longitudinal fasciculus
44
The rostral interstitial nucleus of the medial longitudinal fasciculus and interstitial nucleus of Cajal, both in the midbrain, are __________________ gaze centers.
vertical
45
The primary motor cortex is not the actual start of volitional motor control, "motor association" areas lie just anterior to the primary motor cortex, what are these areas?
Supplementary motor area Premotor cortex
46
The supplementary motor area and premotor cortex are involved in __________________ motor planning and make reciprocal connections with the primary motor cortex.
higher-order motor planning
47
The output of the motor system is modulated extensively by the ________________ and ________________.
Cerebellum and basal nuclei (ganglia)
48
The motor cortex can be divided into: 1) _____________ 2) _____________ 3) _____________
1) Primary motor cortex 2) Premotor cortex 3) Supplementary motor area
49
More recent research suggests that the motor cortex encodes movement, not individual muscles, true or false?
True
50
Which area of the motor cortex is involved in the execution of voluntary movements?
Primary motor cortex
51
Neural activity in the primary motor cortex produces movements of ___________________ body parts.
contralateral
52
The ___________________cortex encodes the force, direction, and speed of movement
Primary motor cortex
53
Alien hand syndrome is characterized as involuntary movement of the upper extremity, and is caused by...
The isolation of the contralateral primary motor cortex (only the contralateral primary motor cortex is activated)
54
The premotor cortex is located where?
In the frontal lobe anterior to the primary motor cortex
55
The __________________ cortex is involved in motor planning, integrating information from cortical regions (parietal, frontal lobes) to select the appropriate movement to perform.
Premotor cortex
56
The ________________ cortex signals preparation for movement.
Premotor cortex
57
Mirror neurons are active in the _____________ when watching someone complete an activity/movements.
premotor cortex
58
The premotor cortex influences motor behavior primarily via... and less commonly via...
Primarily via connections with the primary motor cortex Less commonly via axons projecting through the pyramidal tracts (influencing interneurons and lower motor neurons in the spinal cord)
59
Impaired speed and automaticity of reaching/grasping, sequential movements, gait and posture is related to a lesion in the _______________cortex.
Premotor cortex
60
What is the function of the supplementary motor area?
Programming complex sequences of movements and coordinating bilateral movements. Selects movements based on previous experience.
61
Which area of the motor cortex is involved in programming complex sequences of movements and coordinating bilateral movements and selecting movements based on previous experience.
The supplementary motor area
62
Which part of the motor cortex is active during motor imagery practice?
The supplementary motor area
63
The supplementary motor area helps to translate kinematic information into _____________ information
dynamic
64
A unilateral lesion of the supplementary motor area causes...
Complete lack of contralateral movement and impaired ipsilateral movement. Antiphase movements can be affected (both limbs moving together but not completing the same task).
65
The inputs to the motor cortex involve: 1. Intention 2. Planning (target behavior and how it can be achieved) 3. Programming and execution (timing and sequence of muscle contractions using feedback and feedforward information) Which area(s) of the brain are involved in each of the stages of input?
1. Intention = Prefrontal cortex 2. Planning = Premotor cortex, supplementary motor area, basal ganglia, parietal cortex, cerebellum 3. Primary motor cortex, supplementary motor cortex, premotor cortex, basal ganglia cerebellum
66
Lower motor neurons receive instructions from 3 sources:
- Upper motor neurons (descending pathways) - Local circuit neurons/interneurons - Sensory inputs
67
Explain the somatotopic organization of the anterior horn
The medial part of the anterior horn corresponds to the proximal muscles The lateral part of the anterior horn corresponds to the distal muscles
68
What are interneurons?
A neuron that branches locally to innervate other neurons
69
Interneurons/local circuit neurons are primarily ______________________(excitatory or inhibitory?)
Inhibitory
70
Interneurons project contralaterally or ipsilaterally, true or false?
True
71
What are local circuit neurons?
A cluster of interneuron networks that can innervate lower motor neurons (common final output)
72
What is this statement helpful for remembering? "Local circuit neurons are short and long distance runners"
There are two types of local circuit neurons: 1) Short distance 2) Long distance
73
Local circuit neurons can be acted on by: -______________________ -______________________ -______________________
- Direct sensory inputs (i.e., reflexes) - Descending pathways - Central pattern generators
74
Interneuron networks (local circuit neurons) also link to somatotopic organization of the spinal cord in the anterior horn, explain this organization:
Long distance interneurons: are found more medially and therefore innervate (indirectly) proximal musculature for balance and postural control Short distance interneurons: are found more lateral and therefore innervate (indirectly) distal musculature for fine motor control
75
Name some characteristics of long distance local circuit neuron networks.
- Span multiple levels - Can cross sides (bilateral) - Activate medial aspect of anterior horn (proximal muscles)
76
Long distance local circuit neurons act in the ______________________ (ipsilateral or bilateral?) control of proximal muscles.
Bilateral
77
___________(long or short?) distance local circuit neurons involve multiple segment control for anticipatory postural adjustments (balance)
Long distance
78
Long distance local circuit neurons are modified by descending tracts, what are these tracts?
Anterior corticospinal tract Extrapyramidal tracts: tecto, vestibulo, reticulo
79
_____________(short or long?) distance local circuit neurons span few spinal levels (2-3 spinal levels).
Short distance
80
Short distance neurons are almost exclusively ___________________(ipsilateral or bilateral?)
Ipsilateral
81
Short distance local circuit neurons activate the ______________ aspect of the anterior horn.
Lateral aspect of anterior horn (distal muscles)
82
Short distance local circuit neurons are required for ________________(what type of movement?)
Fine motor movements
83
Short distance local circuit neurons are modified by descending tracts, what are these tract(s)?
Pyramidal: Lateral corticospinal tract
84
Both long and short distance local circuit neurons are modified by descending tracts, what are these tract(s)?
Long distance: anterior/medial corticospinal tract, tectospinal tract, vestibulospinal tract, reticulospinal tract Short distance: lateral corticospinal tract
85
The descending motor pathways can be divided into two tracts:
Pyramidal Extrapyramidal
86
Pyramidal tracts originate in the _____________________ and are responsible for _________________________.
Pyramidal tracts originate in the cerebral cortex and are responsible for skilled, voluntary movements of the limbs.
87
Extrapyramidal tracts originate in the ___________________________ and are responsible for ________________________.
Extrapyramidal tracts originate in the brainstem and are responsible for posture, balance and gait.
88
When thinking of the terms specialists and generalists and relating them to the two type of descending motor pathways, which term relates to which pathway?
Pyramidal = Specialists Extrapyramidal = Generalists
89
There are two types of corticospinal tracts, what are they called?
Anterior (medial) corticospinal tract Lateral corticospinal tract
90
The lateral corticospinal tract originates in the ____________________, then travels through...
The lateral corticospinal tract originates in the primary motor cortex, then travels through the internal capsule, 85% of the lateral corticospinal tract crosses to the other side of the spinal cord at the pyramidal decussation (medulla) and arrives at lower motor neurons in the lateral part of the spinal cord.
91
The lateral corticospinal tract corresponds to which type of local interneuron networks?
Short distance local circuit neurons (distal muscles)
92
Is the lateral corticospinal tract or the anterior corticospinal tract considered the main voluntary motor pathway?
The lateral corticospinal tract (distal musculature, limbs, fine motor, skilled, voluntary)
93
If there is a lesion to the lateral corticospinal tract, above the pyarmids of the medulla, there is expected to be impairments on the __________________ (contralateral or ipsilateral side?)
Contralateral side
94
The anterior corticospinal tract originates in the ____________________, then travels through...
The anterior corticospinal tract originates in the primary motor cortex, then travels through the internal capsule, the fibers travel through the medulla WITHOUT CROSSING and arrives at the lower motor neurons in the medial part of the spinal cord bilaterally via long distance interneuron networks.
95
Does the anterior corticospinal tract cross in the medulla?
No
96
The anterior corticospinal tract corresponds to which type of local interneuron networks?
Long distance interneuron networks (proximal musculature, posture, balance, gross control)
97
If there is a lesion to the anterior corticospinal tract, what do you expect to see clinically?
There is minimal clinical effect, it is unlikely that a lesion would affect the anterior corticospinal tract in an isolated manner (would present in addition to a lesion affecting other structures)
98
Most corticospinal fibers do not synapse directly with lower motor neurons, they synapse with _____________________.
Most corticospinal fibers do not synapse directly with lower motor neurons, they synapse with spinal interneurons that in turn synapse with lower motor neurons.
99
Most corticospinal fibers do not synapse directly with lower motor neurons, they synapse with spinal interneurons that in turn synapse with lower motor neurons. Those that synapse directly on lower motor neurons are involved in _________________.
Fine motor control (e.g., innervating the intrinsic muscles of the hand or fingers)
100
The corticobulbar tract originates in the _______________________, then travels...
The corticobulbar tract originates in the motor cortex, then travels through the internal capsule (genu) and terminates bilaterally on local circuit neurons in the brainstem to eventually connect with the lower motor neuron nuclei of cranial nerves
101
The corticobulbar tract terminates _________________(ipsilaterally or bilaterally?) in the brainstem
The corticobulbar tract terminates bilaterally in the brainstem
102
What is the general function of the corticobulbar tract?
Controls the efferent (motor) activation of cranial nerves (trigeminal, facial, glossopharyngeal, vagus, accessory, and hypoglossal)
103
Explain the difference between an upper motor neuron and lower motor neuron injury resulting in varying degrees of facial muscles weakness:
An upper motor neuron injury (corticobulbar tract) would involve weakness of lower facial muscles (excluding upper facial muscles) on the contralateral side. A lower motor neuron injury would involve weakness of lower and upper facial muscles on on the contralateral side. The primary motor cortex is responsible for the lower face (contralaterally). The part of the facial motor nucleus that innervates the upper face is supplied more equally by the corticobulbar inputs from the two sides (bilateral) (cingulate motor area).
104
The origin of the extrapyramidal tracts is generally...
Various nuclei in the brainstem
105
Extrapyramidal tracts can be modified by many inputs, name some:
- Sensory areas of the cortex - Basal ganglia - Pyramidal system - The cerebellum - Other cortical inputs
106
Generally, what is the destination of the extrapyramidal tracts?
Send projections to the spinal cord to innervate bilateral local long interneuron circuits (proximal musculature, posture, balance)
107
When there is damage to the pyramidal tracts, the extrapyramidal tracts attempt to "step-in", true or false?
True, may be the reasoning for less-skilled movement
108
What is the general function of the extrapyramidal tracts?
- Proximal musculature - Gait - Postural stability - Recruits lower motor neurons for sophisticated reflexes - Largely automatic control of movement - Can maintain some function if pyramidal pathways are damaged
109
What is the general function of the reticulospinal tract?
Influences voluntary movements, gait, posture, reflexes, and excites/inhibits muscle tone, sympathetic nervous system functions
110
Which extrapyramidal tract influences voluntary movements, gait, posture, reflexes, and excites/inhibits muscle tone?
Reticulospinal tract
111
Which extrapyramidal tract is involved in the modulation of flexor muscle tone and arm swinging?
Rubrospinal tract
112
Which extrapyramidal tract is involved in tone of extensor muscles and maintenance of posture and balance?
Vestibulospinal tract
113
Which extrapyramidal tract is involved in eye/head motion primarily?
Tectospinal tract
114
Parkinson's disease, Huntington's disease, multiple system atrophy, and progressive supranuclear palsy are examples of ________________disorders/syndromes.
Extrapyramidal
115
What is the general clinical presentation of extrapyramidal disorders?
Slowing or loss of voluntary (walking, writing, speaking) and automatic movements (arm swing during walking, facial expressions), postural instability, abnormal movements (termors hypertonicity, choreic and athetotic movements), commonly deficits are bilateral
116
Pyramidal deficits are commonly ____________, whereas extrapyramidal deficits are __________________.
Pyramidal deficits are commonly unilateral, whereas extrapyramidal deficits are bilateral.
117
Name the motor system associated with these characteristics: - Volitional control - Mostly short distance local circuit neurons
Pyramidal system
118
Name the motor system associated with these characteristics: - Automatic control - Mostly long distance local circuit neurons
Extrapyramidal system
119
The pyramidal system involves mostly short distance local circuit neuron networks except...
The anterior corticospinal tract involves long distance local circuit neuron networks
120
The ___________ cortex is integrating information from various cortical regions to select appropriate movements.
premotor cortex
121
The _____________________ is responsible for programming complex movements.
supplemental motor area

Neuroanatomy (OCCU 6140) (20 decks)

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