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Neuro Block 4 > Motor Cortex > Flashcards

Motor Cortex Flashcards

0
Q

What are some characteristics of stellate cell?

A

Receive cortico information
Granular cortex is a bunch of these
A lot around sensory tissue
Look like sand in stain

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1
Q

What is motor cortex?

A

Anatomically: 6 layers, 4 cells, two types, stellate cells in the 4th layer, pyramidal cells everywhere else. Small layer 4 big layer 5
Physiologically:

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2
Q

Where are pyramidal cells projecting in layers 5 and 6?

A

Subcortically

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3
Q

What are Betz cells?

A

Large pyramidal cells
In the 5th layer
Only in layer 5

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4
Q

What is area 4?

A

Motor cortex

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5
Q

What is area 6?

A

Premotor cortex and supplementary motor cortex

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6
Q

Where is the frontal eye fields?

A

In front of area 8

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7
Q

What does the frontal eye fields do?

A

Gaze:
VOR
Fixation
Optokinetic response

Saccades
Smooth pursuit
Vengeance
Cancellation of VOR

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8
Q

Where is the horizontal gaze center?

A

Paramedian pontine reticular formation

PPRF

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9
Q

Where is the vertical gaze center?

A

Rostral interstitial nucleus of the medial longitudinal fasciculus

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10
Q

What does the PPRF project to?

A

Ipsilateral abducens

Contralateral CN III (via MLF)

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11
Q

What do the frontal eye fields do?

A

Select visual targets

Initiate Saccades and smooth pursuit

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12
Q

Where does the frontal eye field project?

A

The PPRF directly

And through the superior colliculus

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13
Q

Where is the PPRF?

A

The pons

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14
Q

What is the path of selecting eye targets?

A

Frontal eye field –> superior colliculus –> contralateral PPRF –>

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15
Q

What controls the rightward movement?

A

The left frontal eye field and the right PPRF

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16
Q

What happens when you get injury to the FEF?

A

Loss of voluntary Saccades to the contralateral side

Loss ability to move gaze away from a stimulus. Stuck involuntarily

Deviation of eyes to the side of the lesion

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17
Q

What are the three cortical motor areas?

A

SMA
Primary motor cortex
Premotor cortex

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18
Q

What does stimulus of an area of the motor cortex do?

A

Stimulates movement of a body part not a muscle

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19
Q

What does the M1 region do?

A

Direction, force among others

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20
Q

What are the inputs to M1?

A
  • Proprioception info: mostly contralateral via dorsal column and VP nucleus of the thalamus.
  • Tactile information from the hands
  • other cortical area: S1, premotor, cingulate, parietal lobe
  • cerebellum and basal ganglion
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21
Q

How is the premotor cortex functionally organized?

A

Dorsal - reaching

Ventral - grasping, cognitive control

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22
Q

Where does the premotor cortex receive input?

A 
SMA
Cingulate motor area
Prefrontal cortex (planning and learning)
Posterior parietal 
Cerebellum and basal ganglion
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23
Q

What does the premotor cortex do?

A

Gives complex multi joint movement
Eating

Sensorimotor transformation: transforming sensory cues into motor actions - externally driven

Way before the action, mirror neurons

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24
What are mirror neurons?
Responds if the monkey were doing an action but the monkey is actually just watching someone do something Signals intent Learning by watching Behavioral context - why we are doing what we do
25
What happens if there is a lesion in the premotor cortex?
Inability to properly respond to stimuli, plan movements based on circumstances, learn new sensory-motor associations, steer arm directly
26
What is the functional organization of the SMA?
Homunculus (leg, arm, face caudal to rostral)
27
What does SMA stimulation do?
Movement in multiple joints More than M1 but less than premotor Postural changes
28
Where does the SMA receive input?
M1 Prefrontal cortex Posterior parietal cortex Basal ganglion and cerebellum
29
What is the function of the SMA?
Internal generation of movement Activity is linked to learning sequences of movements, performing them, mental rehearsal Piano playing learning Suppresses premotor planning when inappropriate
30
What happens when a movement becomes a habit?
SMA becomes less and the M1 assumes control
31
What happens when there is a lesion in the SMA?
- Cannot learn new complex sequences - loss internal drive for movements - loss of suppression of motor programs triggered by visual stimuli: alien hand syndrome, utilization behavior - neglect of affected limb
32
What is alien hand syndrome?
Lesion in the SMA Contralateral semi-purposeful movements that are outside the patients volitional control
33
What is utilization behavior?
Caused by a lesion in the SMA Use of objects in an inappropriate setting
34
When is premotor and SMA active?
Premotor: when visual cue without prior learning, responds to external SMA: when there is prior learning, responds to internal Premotor is not active when the sequence has been learned SMA is not active when a sequence has not been learned
35
What are the paths of the corticospinal and corticobulbar tracts?
M1, premotor, SMA, somatosensory --> internal capsule --> cerebral peduncle (base of midbrain) --> through the pons --> pyramidal tracts on the ventral side of the medulla
36
Where does the corticobulbar tract projects and how?
Motor cranial nerves | Mostly bilateral
37
What is normal facial expressions controlled by?
Corticobulbar
38
What controls emotional facial expression?
The cingulate
39
What is the voluntary control of facial expression?
Contralateral of lower face | Bilateral of low face
40
Where does the corticospinal tract project?
Collateral to red nucleus and reticular formation
41
What is the function of the 10% of the corticospinal tract fibers that do not decussate?
Ventral corticospinal tract (medial) Collateral sac cross the midline Primarily innervates axial and proximal limb muscles (medial)
42
What does the corticospinal tract contact?
- Alpha-motor neurons | - Interneurons that are connected to alpha-motor neurons allowing for coordination
43
Where is most of the direct contact of the corticospinal tract and the alpha-motor neurons?
Forearm and hand areas
44
What is the rubrospinal tract associated with?
The red nucleus?
45
Where is the red nucleus?
The upper midbrain | By the superior colliculi
46
What are the two components of the red nucleus?
- Magnocellular | - Parvocellular
47
What is the input and output of the magnocellular part of the red nucleus?
Input: motor cortex Output: spinal cord
48
What is the input and output of the Parvocellular part of the red nucleus?
Input: cerebellum Output: inferior olive
49
Where does the axons of the red nucleus decussate?
Almost immediately
50
What is the function of the rubrospinal tract?
Primary motor pathway in lower vertebrates Terminates in upper half of spinal cord (cervical or thoracic) Controls arms
51
Where does the vestibulospinal tract receive input?
The cerebellum and vestibular organs
52
What is the function of the medial VN and where does it terminate?
Regulates head position Terminates bilaterally in the medial ventral horn of the spinal cord
53
What is the function of the lateral VN?
Activates physiological extensor muscles that work against gravity with deviations from posture
54
What are the two nuclei of the reticulospinal "nuclei"?
Pontine and medullary (rostral and caudal) Coordinate movements of the trunk and proximal limbs Really just continuous formation with little organization
55
What measures your intended output and readjusts?
Cerebellum
56
How is posture maintained?
By primary physiological extensors Through the tonic activity of alpha-motor neurons
57
How do you increase alpha-motorneuron activity thereby tone?
Directly - corticospinal neuron, vestibulospinal, reticulospinal (descending tracts) (gamma as well) Indirectly - stretch receptors (gamma motor activity) reflex.
58
How are adjustments are made on the fly?
Feedforward - anticipate, includes reticulospinal Feedback - includes vistibulospinal tract (random)
59
What does the vestibulospinal tract contact?
Alpha and gamma motorneurons
60
What do the vestibulocollic and vestibulospinal reflexes do respectively?
- act on neck muscles to adjust the head | - adjust limb
61
What are the three things that help you maintain balance?
Vision, proprioception, and the vestibular system
62
What provides central control of posture?
The corticospinal, rubrospinal, and reticulospinal tracts Adjust reflex sensitivity Enable Feedforward adjustments for self-generated movements (planning)
63
What allows for Feedforward (anticipatory) adjustments?
The corticoreticular and reticulospinal tracts
64
What is the pathway of Feedforward adjustments?
Cortex --> corticoreticular tract --> reticular formations --> reticulospinal tracts --> alpha and gamma motorneurons
65
What does the pontine reticular formation do?
Excites gamma-motorneurons | Is inhibited by the cortex Action
66
What does the medullary reticular formation do?
Inhibits gamma-motorneurons Excited by the cortex
67
How does the cortex affect gamma-motorneurons?
Dampens gamma-motorneurons activity Mechanism for modifying tone
68
What happens when there is a lesion of pyramids?
Well the pyramids becomes the corticospinal tract Loss of fine voluntary movements of the hands The other descending projects can compensate for this Hands are specifically innervating the hands, that is special, other things are compensated for
69
What happens when you have a spinal cord transection?
You take out all descending tracts No input to alpha or gamma neurons --> loss of muscle and reflexes However afterward 2months you get hypertonia (more tone and reflex)
70
Why do you get hypertonia and hypereflexia after a spinal cord cut?
Denervation sensitivity (increased) of receptors of motorneurons Local axons fill the synaptic void (more input) No longer inhibition of gamma-MN or excitation of the medullary reticular formation. So increased gamma-MN activity and increased tone.
71
What is characteristics of upper motor neuron syndrome (motor cortex or internal capsule)?
- initially, weakness (spinal shock) - a few days, babinski's reflex(spinal cortical tract), clonus, clasp-knife rigidity (hard, resistant, and them it collapses)
72
Where does the rubrospinal tract project?
The cervical spinal cord Flex ion of upper limbs From the red nucleus
73
How does the cortex affect the reticulospinal tract?
Generally inhibits gamma-MN activity Inhibits pontine reticular formation (less gamma-MN) Excites the medullary reticular formation (less gamma-MN)
74
How can you interrupt the cycle of UMN hypertonia and clonus?
By cutting the primary afferent, (dorsal root) Cures spasms
75
What is decorticate posture?
UMN lesion Upper extremities in flexion Lower in extension Brainstem centers intact, no input from cortex, above the red nucleus
76
What is decerebrate posture?
Progressive decorticate posture All limbs in extension, no longer have red nucleus doing flexion of upper extremities A lot of brain damage.
77
What happens when decerebrate posture progresses?
As it progresses further past the red nucleus it hits the vestibulo and reticulospinal tracts --> flaccidity (likely death)
78
What is the vermis?
The middle of the cerebellum
79
Where is the para vermis?
Lateral to the vermis
80
What are the divisions of the cerebellum?
Lobes, lobules, and folia
81
What is the function of the cerebellum?
Correcting or preventing motor mistakes Ensuring accurate and smooth movements Associative learning system
82
How does the cerebellum learn?
Receives a lot of sensory and motor input and associates sensory input with actual movements with intended motor output Modulates motor output to match expected sensory input Coordination Contributes to learn new motor skills specifically with respect to timing Automatic reactions
83
What are the other functions of the cerebellum besides motor?
Language and cognition
84
What is the function of the vermis?
``` Midline movements (structures that are on midline) -gait, speech, posture, stance, visceral function ```
85
What part of the cerebellum controls appendicular movements like reaching and grasping?
The paravermis
86
What do the lateral hemispheres of the cerebellum do?
Reciprocal connections with the cortex Spatially and temporally complex movements requiring synergistic coordination Cognition
87
What part of the cerebellum deal with cognition?
Lateral hemispheres
88
What makes up the spinocerebellum
The vermis and paravermis Output to the spinal cord
89
What composes the cestibularcerebellum
The floccularnodular region Coordinates vestibular function
90
What are the four nuclei of the deep cerebellum?
(Lateral to medial) Don't eat green frogs Dentate (largest) Emboliform (interposed) Globus (interposed) Fastigial
91
What does the vermis project to?
Fastigial
92
What does the paravermis project to?
The interposed nuclei (emboliform and globus)
93
What do the lateral hemispheres project to?
The Dentate nucleus
94
What is the main function of the cortex of the cerebellum?
Input Learning new complex stuff
95
What is the function of the deep cerebrallar nuclei?
Receive input from the cortex and direct input Provide output Provide ongoing monitoring of movements
96
What are the layers of the cerebellum from inner to outer?
White matter --> granular layer --> purkinje layer | --> molecular layer
97
What is significant of the purkinje cells?
Large cell bodies Large number of dendrites Broad one direction, thin in the other plane
98
What are the most numerous cell types in the brain?
Granule cells
99
Where do the granule cells project?
Into the molecular layer where they bifurcate
100
How do you get integration of information in the cerebellum?
Each parallel fiber contacts up to 200K purkinje cells Each purkinje cell receives contact from tens of thousands of parralell fibers
101
What does the purkinje cell project to?
Out of the cortex to the deep cerebellar nuclei
102
What are the two inputs to the deep nuclei?
Mossy fibers - nuclei and granule cells Climbing fibers - nuclei and purkinje cells
103
What are mossy fibers?
From the spinocerebellum Gets info from spinal cord, auditory, vestibular, visual And from the vestibulocerebellum - vestibular nerve and nuclei And from the cerebrocerebellum - cortex via the pontine nucleus Tons, input Excite the deep nuclei and granule cells
104
What takes in ipsilateral input from the dorsal and rostral spinocerebellar tracts and the cuneocerebellar tract?
The inferior cerebellar peduncle Mossy
105
What is the input front the middle cerebellar peduncle?
Massive contralateral input from the pontine nucleus Mossy
106
What is passing through the superior cerebellar peduncle?
Mostly output Input from the ventral spinocerebellar tract Mossy
107
Where do climbing fibers originate?
Contralateral inferior olive
108
Where does the inferior love receive input from?
Parvocellular red nucleus Reticular formation Spinal cord
109
Where do climbing fibers enter the cerebellum?
The inferior peduncle
110
What do climbing fibers contact?
Purkinje cells (1:1) | Climb then, wrap around
111
What are climbing fibers critical for?
Detecting error in motions Needed for motor learning
112
What is the function of the purkinje cells?
Inhibitory to the deep nuclei
113
What happens when purkinje cells are activated?
Stop movement just as you reach your target so you don't go too far
114
What is reafference?
Sensory from the periphery about motions actually occurring Enables the system to identify unexpected conditions
115
What enables the cerebellar system to identify unexpected conditions?
Reafference - sensory information about what is actually happening
116
What is efference copy (corollary discharge)?
Neural copy of motor commands
117
What do reafference and efference allow?
These inputs are compared and future motions are corrected
118
How is properioceptive info received into the cerebellum?
Ipsilateral from muscles Spinocerebellar mossy fibers 1. Dorsal spinocerebellar tract C8 and below via clerked column 2. Cuneocerebellar tract rostral to C8 via accessory cuneate nucleus 3. Mesencephalic nucleus, face
119
Where does the cerebellum receive motor information from?
Mossy fibers from: 1. Ventral spinocerebellar tract, crosses midline in spinal cord, enters through superior CP,macros see again in cerebellum 2. Rostral spinocerebellar tract, starts I'm cervical spinal cord, stays ipsilateral
120
What is the cerebellum in relation to the body?
Ipsilateral, same side lesion
121
What are the spinocerebellar outputs of the vermis?
Vermis --> fastigial nucleus --> 1a. Superior CP --> thalamus VL --> M1 --> ventral corticospinal tract 1b. Superior CP --> Superior colliculus --> tectospinal tract 2a. Inferior CP --> reticular nuclei --> reticulospinal tract 2b. Inferior CP --> vestibular nuclei --> vestibulospinal tracts Overall it does posture, orienting, and gait
122
Where does the paravermis project?
Interposed nuclei 1. --> VL thalamus --> M1 --> lateral corticospinal tract 2. --> magnocellular red nucleus --> rubrospinal tract Overall, reaching and grasping
123
Where are the Parvocellular and magnocellular parts of HHS red nucleus projecting?
Parvocellular - inferior olive Magnocellular - rubrospinal tract
124
What happens if you get a lesion in the vermis?
Gait ataxia ``` Spinocerebellar ataxia (SCA) Collection of genetic disorders ```
125
What happens with chronic alcohol abuse?
Deterioration of the anterior division of the cerebellum
126
What happens with a lesion in the paravermis?
Action tremor Timing disorders No longer adapt
127
What happens with damage to the lateral hemispheres?
Bad motor learning Cognition - language defects after PICA stroke - behavioral - developmental loss of purkinje cells in autism
128
What does the basal ganglia do?
``` Mutually exclusive movements - promote one and suppress another - can work at different levels - info contributing to choice - efference copy - associate memories and emotions Importance or urgency of possible action (bear) ```
129
What is the function of the corpus striatum?
Input zone of the basal ganglion Composed of putamen and caudate nucleus
130
What is the input some of the basal ganglion?
The corpus striatum | Caudate and putamen
131
What is the output of the basal ganglion?
The pallidum (globus pallidus and substantia Nigra pars reticulata (SNr))
132
What part of the BG receives striatal output?
The pallidum
133
Where is the input into the corpus striatum from?
1. Ipsilateral cortex (widespread and somatotopic) 2. SN pars compacta 3. Subcortical structures via intralaminar nuclei of the thalamus
134
What inputs into the BG besides the striatum?
Subthalamic nucleus Inputs outnumber outputs
135
What makes up 90% of the neurons in the BG?
Medium spiny neurons
136
What are medium spiny neurons?
GABAergic - inhibitory 1. Substance P 2. Enkephalins
137
What movement does the caudate nucleus do?
Eye movement
138
What does the putamen do?
Limb movement
139
What is the default of the BG?
To do nothing Active is inhibit
140
What are the three main pathways of the BG?
Direct - dis inhibits selected actions, allowing them to occur Indirect - inhibits actions selected against Hyperdirect - purely inhibits
141
What is topically active?
The globus pallidus NOT the striatum
142
What does he globus pallidus do?
Inhibits the thalamus --> prevents excitation of motor cortex
143
What does the striatum do?
Inhibits Gpi and Gpe
144
What excites the Gpi?
Subthalamic nucleus therefore inhibiting motion
145
What is the hyper direct pathway?
Suppresses motion by the cortex exciting the STN, therefore increases GPi and inhibiting the thalamus
146
What type of medium spiny neuron projects to the direct pathway?
GABA/substance P --> GPi and SNr Excitatory response to DA D1
147
What medium spiny neurons project to the indirect pathway?
GABA/enkephalin --> GPe D2 receptors Inhibitory response to DA
148
What is D1 and D2?
Excitatory and inhibitory respectively
149
What does the SNc do?
Is dopaminergic Projects to striatum
150
What is the firing of the SNc to the striatum?
Tonic Also in bursts to unexpected events
151
What happens of you get rid of STN?
Reduces inhibition | Get flailing
152
What causes Parkinson's?
Degeneration of the SNc No dopamine release
153
What are common symptoms of Parkinson's?
Hypokinesia/akinesia - placidity of movements - lack of facial expression Bradykinesia: slow movements Shuffling gait Rigidity (lead pipe or cogwheel) Postural instability Tremor at rest
154
What areas of the brain are stimulated for Parkinson's treatment?
GPi STN VIM (part of VL)
155
What is the pallidum composed of?
Globus pallidus (internal and external) SNr
156
What is the treatment of Parkinson's?
L-DOPA/carbidopa Deep brain stimulation Treatment of non motor symptoms
157
What degenerates in Huntington disease?
Caudate and putamen Also frontal temporal cortices
158
What is the inheritance pattern and cause of Huntington disease?
Autosomal dominant Expansion of CAG repeats in Huntington
159
What are symptoms of Huntington disease?
Rapid jerky movements (choreiform) Hypokinesia Later the pallidum and SN degenerate
160
What are the tracts?
Pic inserts
161
What is the treatment for Huntington?
Cannot change course of disease Treat early symptoms of hyperkinesia and psychiatric disturbances

Neuro Block 4 (13 decks)

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