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Medsci 142 Test 1 > The Motor Systems of the Brain L4 > Flashcards

The Motor Systems of the Brain L4 Flashcards

1
Q

What is a homunculus?

A

representation of the body on cortices

Cant be either a Motor Homonculus or Sensory Homunculus

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2
Q

What is the Motor homunculus?

A

Motor map of the body
Representation is proportional to the Complexity of control over those muscles, Dexterity of those muscles, or Degree of Activity.
Somatotopical map in the Motor Cortex
Different muscles are represented unequally in the 1 Primary Motor area
Large representation= thumb, fingers, lips and tongue
Small representation = toes, trunk/abdomen
More cortical area is devoted muscles involved in Movement which is Skilled, Complex and or Delicate

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3
Q

What areas of the body have a large representation on the Motor homunculus?

A 
Thumb
Fingers
Face
tongue
Lips
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4
Q

What ares of the body have a small representation on the Motor Homunculus?

A

Toes
Trunk
Abdomen

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5
Q

What is the reason behind more cortical motor area devoted to particular parts of the body over others?

A

More cortical area is devoted to muscles involved in Movement which is Skilled, Complex and Delicate

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6
Q

What is the representation on the motor homunculus proportional to?

A

Complexity of control
Dexterity of the muscles
Degree of activity

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7
Q

What is the sensory homunculus?

A

Sensory map of the body
Representation is proportional to the number of specialised sensory receptors within the corresponding body part
A larger representation means the body part has a more highly specialised sensory function (has more cortical area devoted to it)
Large representation= Lips(bigger than motor) and Fingertips
Smaller representation = trunk and abdomen
More sensitive, able to Localise specifically (discriminative)
Large number of receptors = larger representation on homunculus =/= does not equal larger size of the body part (lips and finger tips are small yet they are largely represented on the primary somatosensory cortex)

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8
Q

What areas of the body have a large representation on the Sensory homunculus?

A

Lips (bigger than on motor homunculus)

Finger tips

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9
Q

What areas of the body have a small representation on the Sensory homunculus?

A

Trunk

Abdomen

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10
Q

What is the reason behind more cortical sensory area devoted to particular parts of the body over others?

A

Representation is proportional to the number of specialised sensory receptors within the corresponding body part
Large number of receptors = larger representation on homunculus =/= does not equal larger size of the body part (lips and finger tips are small yet they are largely represented on the primary somatosensory cortex)

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11
Q

What is the reason behind more cortical sensory area devoted to particular parts of the body over others?

A

A larger representation on the sensory cortex means the body part has a More Highly Specialised Sensory Function (more cortical area devoted to it)
-More Sensitive
-More able to localise sensation specifically (Discriminative)
-Greater discrimination and precision
-More receptors
Large number of receptors = larger representation on homunculus =/= does not equal larger size of the body part (lips and finger tips are small yet they are largely represented on the primary somatosensory cortex)

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12
Q

How many neurons do the Sensory neuron pathways consist of?

A

3
1st order neuron
2nd order neuron
3rd order neuron

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13
Q

How many neurons do the Motor neuron pathways consist of?

A

2 mainly - UMN + LMN

3 sometimes - UMN + interneuron + LMN

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14
Q

What does the Primary Motor Cortex do?

A 
Primary motor cortex controls the movement of muscles CONTRALATERALLY (on the opposite side of the body to the brain)
Highly Organised and Intricate system
Organised via homunculus
Controls VOLUNTARY movements
Contains Upper Motor Neurons (UMNs)
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15
Q

What does the Cerebellum do?

A

Cerebellum controls the Co-ordination of movements, as you do them, at every point in time, IPSILATERALLY (on the same side of the body to the brain(cerebellum))

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16
Q

What does Contralaterally mean?

A

Control on the OPPOSITE side of the body to certain area
-Majority of brain control is contralateral
Esp:
- 1 motor cortex
- 1 somatosensory cortex
NOT cerebellum

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17
Q

What does Ipsilaterally mean?

A

Control on the SAME side of the body to the certain area

  • ONLY ONE region in the brain has Ipsilateral control (all the rest contralateral control)
  • is the CEREBELLUM
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18
Q

What are Upper Motor Neurons (UMNs)?

A

UMN’s cell Bodies are located in the 1 Primary motor area and Premotor area
Axons extend down through brain (pyramidal/corticospinal tract) and spinal cord(lateral or ventral corticospinal tract)
UMNs extending down through Lateral Corticospinal Tract =70-90%
UMNs extending down through Ventral Corticospinal Tract =10-30%
Extend to the specific area of the body which is required to move
Terminate in Ventral gray horn, either directly onto LMN or onto Inter Neuron
Are LARGE PYRAMIDAL cells
LArge cell bodies
Long and Myelinated axons
Oligodendrocytes - as in CNS Central NS - increased Insulation and Conduction
50ms-1 –> 100ms-1
Organised in the Primary Motor Cortex via the Motor Homunculus
Controls voluntary Movements
Tells LMN when to Fire, to give Smooth movements
CNS –> effector muscles
Pathway: 1 Primary Motor cortex –> Internal capsule (big fat fibre tract) –> Crus Cerebri of Midbrain (big fat fibre tract still) –>(Pyramidal/Corticospinal Tract)–> Pons (in separate fasicles) –> Pyramid of Medulla (in ventral bulges called pyramids) –> Spinal Cord –> a. pyramidal decussation and then Lateral Corticospinal Tract (70-90%) b. no decussation and instead down Ventral Corticospinal tract (10-30%)

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19
Q

What does the internal capsule directly translate to?

A

Capsule = Fibre bundle

is a Big Fat fibre bundle Tract

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20
Q

What does Capsule mean?

A

Fibres bundle

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21
Q

What is another name for pyramidal cells?

A

Upper Motor Neurons (UMNs)

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22
Q

What is another name for the Pyramidal Tract?

A

Corticospinal Tract

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23
Q

What is another name for the Corticospinal Tract

A

Pyramidal Tract

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24
Q

What is the Pyramidal/Corticospinal Tract?

A

1000 or so fibres
Highly organised
Compact motorway
AXONS of UPPER MOTOR neurons (UMNs) come together to form a Nerve Bundle
In the Brain and brainstem (following is ventral and lateral corticospinal tract in spinal cord)

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25
What is the Upper Motor UMN Axon pathway like in the Crus if Cerebri of Midbrain?
Within the Internal Capsule So Big and Fat Thick pathway In the Crus of Cerebri of the Midbrain
26
What is the Upper Motor UMN Axon pathway like in the Pons?
broken up into fasicles
27
What is the Upper Motor UMN Axon pathway like in the Medulla?
Recollected after Pons Begins its pyramidal shape formation Form VENTRAL BULDGES called Pyramids Pyramid of Medulla Oblongata
28
What is the uppermost decussation of UMN's called?
Pyramidal decussation
29
What do neurons C5-C7 control?
arms forearms fingers
30
What is the Lateral Corticospinal Tract?
70-90% of all UMNs undergo pyramidal decussation and go down the Lateral Corticospinal tract Decussation at the Medulla, to the Opposite side of the body - at the pyramids -Massive decussation, involved Millions of fibres Towards Spinal cord Pathway is the biggest at the top, as neurons peel to terminate off to their respective effector muscle under dermatomes as the spinal cord goes down Precise, Agile and highly skilled movements - (hands and finger tip's movements) Towards muscle in the Distal parts of limbs
31
Where is the Lateral Corticospinal Tract the thickest?
Pathway is the biggest/(containing the most UMN axons) at the top, as neurons peel to terminate off to their respective effector muscle under dermatomes as the spinal cord goes down
32
What is the trend of termination for UMNs?
Terminate in Ventral gray horn Either directly onto LMN or onto Inter Neuron The majority of UMNs terminate directly on LMNs, but also a significant number terminate onto interneurons UMNs extending down through Lateral Corticospinal Tract =70-90% UMNs extending down through Ventral Corticospinal Tract =10-30%
33
Where does every UMN terminate?
Ventral gray horn of the spinal cord
34
What is the pathway of muscle innervation beginning at cortex?
1 Primary Motor Cortex --> UMN --> (interneuron) --> LMN --> Synaptic Junction --> Motor End Plate --> Effector Muscle/Organ/Cell
35
What is a Lower Motor Neuron LMN?
PNS Large Cell bodies in Ventral Gray horn Myelinated -conduction and insulation Schwann Cells 50ms-1 Grouped according to the muscles groups they supply undergo a Synapse with UMN at the Ventral gray horn Lower Motor LMNs are critical for PROVIDING the OUTput from the CNS --> skeletal muscle fibres
36
What nervous system is the UMN part of?
Central CNS | -therefore myelinated by Oligodendrocytes
37
What nervous system is the LMN part of?
Peripheral PNS | -therefore myelinated by Scwhann cells
38
Are Lower Motor Neurons LMNs grouped?
Yes | Lower Motor Neurons LMNs are grouped according to the muscle groups that they supply
39
What are Upper Motor Neurons critical for?
Highly specialised movments
40
Where to UMNs axons extend to?
specific area of the body which is required to move | via Co-ordinated Specific muscle contractions
41
What must Upper Motor Neurons UMNs receive in order to produce smooth, co-ordinated muscle movements?
From the THALAMUS, must receive very Refined, Complex information about When, How Many, How Often to send impulses out, in order to produce, Smooth, Co-ordinated muscle movements
42
What forms the Pyramidal/corticospinal tract?
UMNS | they for the corticospinal/pyramidal tracts via the Pyramidal pathway, via the Internal Capsule (DEEP) of the cerebrum
43
Where is the Internal capsule located?
cerebrum
44
What is the pathway of Upper Motor N?
1 Primary motor cortex --> Internal capsule (big fat fibre tract) --> Crus cerebri of Midbrain (big fat fibre tract still) -->(Pyramidal/Corticospinal Tract)--> Pons (in separate fasicles)--> Pyramid of Medulla (in ventral bulges called pyramids) --> Spinal Cord --> a. pyramidal decussation and Lateral Corticospinal tract.(70-90%) b. no decussation and then down Ventral corticospinal tract (10-30%)
45
What is the Ventral Corticospinal Tract?
10-30% of all UMNs DONT pyramidal decussate and Instead go Straight down the Lateral Corticospinal tract Decussation is at the Level of the Spinal Cord, via the AWC Anterior White Commissure Fibres REMAIN Ipsilateral (same side of the body) Until muscle responsible for Co-ordinating movements of the Axial skeleton Goes to the muscles in the Trunk and Proximal parts of the limbs
46
What is thicker: Ventral or Lateral Spinothalamic Tract?
Lateral
47
What is the role of the Lateral Spinothalamic Tract?
Responsible for movements which are: Precise, Agile and Highly skilled e.g. hand or fingertip movemnts
48
What is the role of the Ventral Spinothalamic Tract?
Responsible for Co-ordinating movements in the Axial skeleton goes to the muscles in the Trunk and the Proximal parts of limbs
49
What co-ordinates the movements of the Axial skeleton?
Ventral Spinothalamic Tract UMN neurons (10-30% which don't decussate at the medullary pyramidal decussation)
50
Does the Trunk or Leg have a larger representation on the Motor homunculus?
LEG has a greater representation | Leg>trunk (tiny)
51
Why are Upper Motor Neurons UMNs critical?
UMNs are critical at transferring the highly important and specific information from the cortex to the LMN
52
Why are Lower Motor Neurons LMNs critical?
LMNs are critical for PROVIDING the OUTput from the CNS --> to skeletal muscle fibres
53
What does the Thalamus talk to?
1 cortexes
54
What is the VP nuclei of the Thalamus involved in?
Sensory INput information 2nd order Sensory neuron termination Ventro Posterior Nucleus of the Thalamus On the inner part of the thalamus (closer to midline)
55
What is the VAVL nuclei of the Thalamus involved in?
its neuron Controls/Tells that UMN the Motor OUTput information for effector muscles/co-ordinated movement VAVL itself (before UMN) is affected by Basal Ganglia and Cerebellum Ventro Anterior Ventro Lateral Nucleus of the Thalamus Outer part of the thalamus
56
What input does the VAVL get?
2x Thalamic inputs from the Basal Ganglia (GPi) from the Cerebellum (cerebellar cortex) N
57
What is the Cerebellar cortex?
Cerebellum's (little brain's) cortex
58
What is the Cerebral cortex?
5-7mm thick gray matter covering the brain (cerebrum)
59
What is a Spastic Paralysis?
Pyramidal Tract lesion in the UPPER Motor UMN -still hasn't decussated by the brain stem Results in: 1. Increased Reflexes (heightened involuntary movements) 2. Decreased Precision of Voluntary movements (more crude) 3. Increased Tone and Increased Rigidity (muscles are continually contacting causing increased stiffness and tightness) -patients may or may not know or feel the continuous contractions Becomes HypERsensitive and Spasms occur Lost input into the Lower Motor Neurons, so the LMN is very sensitive to input from other areas such as the brainstem and other reflexes (no interference from other motor pathways (non-voluntary inputs)) Lesions occur in association with spinal cord injuries (brain trauma)
60
What is Flaccid Paralysis?
can be caused by the Polio Virus (disease of LMN) Lesion in the LOWER motor Neuron LMN There are NO Neural Pathways to the Effector Muscle!! therefore: Results in: 1. No reflexes (voluntary or involuntary) 2. No Movement (muscles flop) 3. Decreased Tone of muscles (wasted away) (characterised by wasted muscles, weakness, paralysis) (DISUSE ATROPHY) disuse atrophy is the waste/degeneration of muscles/cells/organs, and therefore these muscles are no longer used (NO TONE and NO NEURAL INPUT) Overall there is NO NERVE IMPULSES (neural input) AT ALL as the path to the LOWER MN (LMN) is now Impaired
61
What is the Polio Virus?
Disease of the Lower Motor Neuron LMN Leads to Flaccid paralysis causes Disuse Atrophy
62
What is Atrophy?
Waste/Degeneration of body tissue/cells/organ DISUSE atrophy occurs in Flaccid Paralysis characterised by: 1. waster muscles 2. weakness 3. paralysis (flaccid)
63
What 3 things does Flaccid paralysis result in?
1. No reflexes 2. No movement 3. Decreased Tone -Wasting away of muscles -- Disuse Atrophy
64
What 3 things does Spastic paralysis result in?
1. Increased reflexes (hypersensitive an spasms) 2. Decreased Precision (more crude) of Voluntary movements (More Crude movements) 3. Increased Tone, + increased rigidity (more stiff and tight as the muscles are continually contracting/in a more partially contracted state)
65
What is an Ataxia?
damage to the Cerebellum, Spinal Cord and Peripheral Nerves Results in: 1. Un-co-ordinated movements 2. Loss of balance Disorder in Muscle co-ordination due to Damage to the cerebellum such as Trauma or Disease
66
What is spastic paralysis caused by?
Lesion in Upper Motor Neurons
67
What is flaccid paralysis caused by?
Lesion in the Lower Motor Neuron | could be Polio Virus
68
What is Ataxia caused by?
Damage to either 3 things | Damage to the Cerebellum, or Spinal cord or Peripheral Nerves
69
What is Paraplegia caused by?
Spinal cord injury
70
What does ataxia result in?
2x: 1. Unco-ordinated movements 2. Loss of Balance
71
What sort of Ataxia does the cerebellum result in?
IPSIlateral ataxia Affects the same side of the body as the brain - as the Cerebellum is the only part of the brain which controls activity on the same side of the body
72
What sort of Ataxia does the Spinal cord or Peripheral nerve result in?
CONTRAlateral ataxia | loss of movement co-ordination and balance on the opposite side of the body to side of damage
73
What is Paraplegia?
``` Damage to the spinal cord Results in: 1. Paralysis 2. Loss of sensation Causes an impairment of BOTH Sensory AND Motor function In the LOWER extremities ```
74
What causes Paraplegia?
Damage to the spinal cord
75
What does Paraplegia result in?
``` Results in: 1. Paralysis 2. Loss of sensation Causes an impairment of BOTH Sensory AND Motor function In the LOWER extremities ```
76
What can you deduce the paralysis to be if the lesion is in the Same side?
Spastic Paralysis: UMN - 1 motor cortex - brainstem = brain - still hasn't decussated therefore still opposite
77
What can you deduce the paralysis to be if the lesion in on the Opposite side?
EITHER 1. Spastic Paralysis : UMN - Spinal Cord - some UMN some LMN 2. Flaccid Paralysis - LMN - Spinal Nerve - EFFECTOR
78
Is a Spastic Paralysis always on the opposite side?
No Same side if the lesion is in the Brain stem/brain, as hasn't decussated to opposite side OR Opposite side if lesion is in the Spinal Cord - Some UMN some LMN
79
Is a Flaccid Paralysis always on the opposite side?
Yes Flaccid Paralysis: LMN spinal NERVE lesion affects the Effector
80
What are the 3x motor-neuron systems of the brain?
1. Pyramidal System 2. Basal Ganglia System 3. Cerebellar System
81
What is the role of the 3x Motorneuron systems of the brain
The INput the a LOWER Motor LMN RECEIVES involves the 3x motorneuron systems to CO-ORDINATE and CONTROL movements -when and how to fire -when and how to do movements
82
What does the Basal Ganglia Motor Neuron System consist of?
``` 4x groups of Nuclei 1. Striatum (caudate nucleus + putamen) + 2. Globus Pallidus (GPinterna + GPexterna) + 3. Subthalamic Nucleus (SUT) + 4. Substantia Nigra (Snc + Snr) ```
83
What does the Striatum consist of?
Caudate Nucleus Putamen is divided into two parts bt the internal capsule -is one of the two main nuclei of the Basal Ganglia
84
What does the Globus Pallidus consist of?
GPi GPe -is one of the two main nuclei of the Basal Ganglia
85
What does the Sub-thalamic nucleus consist of?
SUT
86
What does the Substantia Nigra consist of?
``` Snc = pars compacta Snr = pars reticulata ```
87
Where is the Substantia Nigra located?
in the Midbrian
88
What isn't seen on the cross section/is in the Midbrain?
Substantia nigra
89
What are some features of the Snc?
``` Substantia Nigra pars Compacta In the Midbrain Contains all the pigmented cells More Compact cells Makes the Substantia Nigra Black ```
90
What are some features of the Snr?
Substantia Nigra pars Reticulata In the Mid brain No pigmented cells (doesn't contribute to colour) More Dispersed cells
91
What is the Pyramidal system?
Directly gives information from the UMN --> to the LMNs responsible for Precise Voluntary movements Lesion in the UMN would result in Spastic Paralysis
92
What is the Pyramidal system responsible for?
Voluntary movements that are Precise
93
What is the Basal Ganglia System?
2 main nuclei are the Striatum and the Globus Pallidus Controls how the UMN works and functions Receives input from the cerebral cortex Output is to --> Prefrontal premotor and motor cortices, VIA the Thalamus Involuntary movements --> Huntington's disease Releases Inhibitory Neurotransmitter GABA (-) via the Thalamus
94
What are some features of the Substantia Nigra?
``` Located in the Midbrain Black More distinct "black Substance" Is affected in Parkinson's disease ```
95
What is the Cerebellar system?
Controlled by the Cerebellum (little brain) at the Base of the brain contains Billions of Neurons Cerebellum controls the Same side of the body (exclusively the only part of the body which has ipsilateral control) Releases Excitatory neurotransmitter Glutamate
96
What is the combination which produces perfect co-ordinated smooth movements?
combination of the relase of Basal Ganglia's/Gpi's GABA inhibitory neurotransmitter and Cerebellum's/Cerebellar systems Glutamate excitatory neurotransmitter release
97
What are some features of the striatum?
divided into 2 x parts by the Internal capsule(the big white matter tract which allows the passage of axons from the cortex to the thalamus) Gets input from the substantia nigra No direct input/output between the spinal cord and basal ganglia -Striatum is largely controlled by motor areas of the frontal cortex
98
What is the striatum largely controlled by?
Motor areas of the frontal cortex
99
What is the pathway of the corticospinal tract?
UMN from the cerebral cortex --> via the LMN to/down the spine
100
What are some features of the Thalamus?
Divided into the VP(for sensory Input) and VAVL(for motor Output) Complex Relay system an Intermediate between the brain's target organ's/ structures Processes information Relays information on sensory information form the periphery of the brain
101
What 4x things does the Basal Ganglia system do?
1. Initiate and Terminate Movements (GABA release) 2. Muscle Tone (readiness of movement so not flying everywhere) 3. Memory and Planning of movement (initiation of impulses) 4. Mood and Movements (muscle emotional expression -espec. Face, and some hands)(integrates with projections from other areas
102
What is the characteristic symptom of Huntington's disease?
INvoluntary movements | Basal Ganglia is affected
103
What are the 3x characteristic symptoms of a lesion in the Basal Ganglia?
1. Rigidity 2. Tremor at rest 3. HypOkinesia (decreased movement)
104
What neurotransmitter does the Basal Ganglia release?
GABA inhibitory from the GPi
105
What 3x things does the Cerebellar system do?
Cerebellum (little brain) contributes to: 1. Posture 2. Balance 3. Co-ordinates movement (as you do them - at every point in time) (avoids over or undershooting)
106
What are some features of the cerebellum(little brain)/Cerebellar system?
90% of the cells in the brain are located in the cerebellum, as the are packed Very tightly and are Very small contain Purkinje fibres If an athlete is working, she is training her cerebellum in particular , as well as basal ganglia, to retain movement which is co-ordinated
107
What does an athlete do in training?
If an athlete is working, she is training her cerebellum in particular , as well as basal ganglia, to retain movement which is co-ordinated
108
Where is the major of the brain's' cells?
90% of brain cells are in the Cerebellum (little brain) | as the cells are SMALL and VERY TIGHTLY PACKED
109
What are the 3x characteristic symptoms of a lesion in the Cerebellum?
1. Ataxia (loss of co-ordinated muscle movement) 2. Loss of Balance 3. Intention tremor (loss of co-ordinated muscle movement) - Looks to be drunk
110
What neurotransmitter does the Cerebellum release?
Glutamate Excitatory (Cerebellar system)
111
What could someone have if they were characteristically acting as if they were drunk?
Lesion in the Cerebellum which controls balance and coordination of movement (avoids ataxia and intention tremor)
112
Involving the motor neuron systems, where do the excitatory and inhibitory neurons get released?
VAVL nucleus of the Thalamus | which then effects the Cerebral cortex with the UMN

Medsci 142 Test 1 (20 decks)

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