1
Q
What is the primary function of the nervous system?
A
It is a communication and control network that allows an organism to interact with its environment.
2
Q
What are the three general functions of the nervous system mentioned?
A
- Sensory detection (by afferent division) 2. Information processing (by the brain/CNS) 3. Expression of behavior (by efferent/motor division)
3
Q
What are the two main sections of the nervous system?
A
- Central Nervous System (CNS) 2. Peripheral Nervous System (PNS)
4
Q
What structures make up the Central Nervous System (CNS)?
A
The brain and spinal cord.
5
Q
What is the primary role of the CNS?
A
It is the processing center for the entire nervous system.
6
Q
What structures make up the Peripheral Nervous System (PNS)?
A
Nerves and ganglia (groups of nerve cell bodies outside the brain and spinal cord).
7
Q
What are the two divisions of the PNS based on the direction of information flow?
A
- Afferent (sensory) division 2. Efferent (motor) division
8
Q
What is the function of the Afferent division?
A
To send sensory information (from external or internal environments) towards the CNS.
9
Q
What is the function of the Efferent division?
A
To send motor information from the CNS to the organs of the body to carry out responses.
10
Q
Which body parts does the PNS primarily serve?
A
The limbs (legs and arms) and internal organs.
11
Q
In the afferent division, what are examples of external environmental information?
A
Light and sound.
12
Q
In the afferent division, what is an example of internal environmental information mentioned?
A
Blood pressure.
13
Q
What are the three main sections of the brainstem in humans?
A
- Midbrain 2. Pons 3. Medulla oblongata
14
Q
Where is the brainstem located anatomically?
A
Between the deep structures of the cerebral hemispheres and the cervical spinal cord.
15
Q
What critical connection does the brainstem facilitate?
A
It connects the cerebrum (main brain) to the spinal cord and cerebellum.
16
Q
Why is the brainstem considered extremely important despite its small size?
A
Because all nerve connections between the main brain and the peripheral nervous system (motor and sensory) must pass through it.
17
Q
Name the two ascending sensory pathways that pass through the brainstem.
A
- Dorsal column-medial lemniscus pathway 2. Anterolateral (spinothalamic) pathway
18
Q
What types of sensation does the Dorsal column-medial lemniscus pathway carry?
A
Fine touch, vibration sensation, and proprioception.
19
Q
What types of sensation does the Anterolateral (spinothalamic) tract carry?
A
Pain, temperature, itch, and crude touch.
20
Q
Name the two descending motor pathways that pass through the brainstem.
A
- Corticospinal tract 2. Corticobulbar tract
21
Q
Which specific descending motor tract originates in the red nucleus of the brainstem?
A
The rubrospinal tract (a lateral pathway).
22
Q
Name the descending motor tracts that originate in the brainstem and are part of the medial pathways.
A
- Pontine and medullary reticulospinal tracts 2. Lateral and medial vestibulospinal tracts 3. Tectospinal tract
23
Q
Besides motor/sensory pathways, what other important physiological functions does the brainstem regulate?
A
Autonomic functions (e.g., cardiac and respiratory regulation) via autonomic centers like the vasomotor and respiratory centers.
24
Q
What are two important motor control functions of the brainstem mentioned in the context of this slide?
A
Postural reflexes and locomotion.
25
Define Posture.
The overall position of the body and limbs relative to one another and their orientation in space.
26
What are the two types of posture?
1. Static posture 2. Dynamic (phasic) posture
27
How you hold yourself when you are not moving (e.g., sitting, standing, sleeping).
28
Define Dynamic Posture
How you hold yourself when you are moving (e.g., walking, running, bending over).
29
What is the definition of a Postural Reflex?
Subconscious adjustments of muscle tone to maintain an upright and balanced position at rest or during displacement.
30
What are the two broad groups of postural reflexes?
1. Static reflexes 2. Phasic (or dynamic) reflexes
31
What elicits a Static Reflex, and what is its function?
Elicited by gravitational pull; involves sustained muscle contraction to maintain posture at rest.
32
What elicits a Phasic Reflex, and what is its function?
Elicited by acceleratory displacement or transient body movements; maintains stability for voluntary activity.
33
Which parts of the CNS are involved in integrating postural reflexes?
Various levels from the spinal cord to the cerebral cortex.
34
Which two descending motor tracts largely affect postural reflexes?
The corticospinal tract and the corticobulbar tract.
35
What are the three examples of postural reflexes involving the brainstem discussed?
1. Vestibular reflexes 2. Tonic neck reflexes 3. Righting reflexes
36
What elicits vestibular reflexes?
Head movement (specifically rotation).
37
Which sensory receptors are activated during vestibular reflexes?
Hair cells in the semicircular canals of the vestibular apparatus.
38
What are the two main outcomes of vestibular reflexes?
1. Generation of eye movement to maintain stable vision. 2. Postural adjustments to stabilize the body.
39
If the head rotates to the left, on which side is postural support increased?
On the left side (to prevent falling to the left).
40
What activates tonic neck reflexes?
Head movement (bending/flexing/extending) that activates stretch receptors in neck muscles.
41
Which specific receptors are responsible for detecting stretch in the neck muscles?
Muscle spindles.
42
In tonic neck reflexes, what happens when the neck is extended (bent backward)?
The forelimbs extend and the hind limbs flex.
43
What is the primary function of righting reflexes?
To restore an altered position of the head and body toward normal (maintaining upright head and standing position).
44
Which three receptor types contribute to righting reflexes?
1. Vestibular apparatus 2. Neck stretch receptors 3. Mechanoreceptors of the body wall.
45
Describe the "cat righting reflex" mentioned.
As a cat falls, it turns its head, rotates its spine, aligns its hindquarters, and arches its back to land on its feet.
46
What are the three main components of the reflex arc for postural reflexes?
1. Afferent pathways (Sensory input) 2. Integrating centers (CNS processing) 3. Efferent pathways (Motor output)
47
Which three sources provide afferent input for postural reflexes?
1. Eyes (visual receptors) 2. Vestibular apparatus 3. Proprioceptors (stretch receptors) in muscles (especially neck muscles).
48
Where are the integrating centers for postural reflexes primarily located?
In the brainstem and spinal cord.
49
Name two specific neuronal networks in the brainstem that act as integrating centers.
1. The vestibular nuclei 2. The reticular formation
50
What is the function of the vestibular nuclei in this context?
They are the cranial nuclei for the vestibular nerve located in the brainstem.
51
What is the reticular formation?
A set of interconnected nuclei located throughout the brainstem.
52
What is the role of these integrating centers in postural control?
To provide information to the spinal cord to maintain posture in response to environmental or self-induced disturbances.
53
What constitutes the efferent pathway for postural reflexes?
Alpha (alpha)-motoneurons supplying skeletal muscles.
54
Besides the brainstem and spinal cord, what other CNS structures are involved in postural reflexes?
The cerebral cortex and cerebellum.
55
What motor function does the brainstem control in addition to postural reflexes?
Locomotion (movement from one place to another).
56
Define Locomotion.
The voluntary movement of an organism from one place to another (e.g., walking, running, swimming).
57
What is the key difference between Locomotion and Movement as defined in the lecture?
Locomotion is always voluntary and involves moving away from the original position; Movement can be voluntary or involuntary and does not necessarily involve changing location.
58
What neural circuits in the spinal cord are responsible for generating rhythmic patterns for locomotion?
Central Pattern Generators (CPGs).
59
What kind of output do Central Pattern Generators (CPGs) produce?
Regular rhythmic output that controls stereotyped behavior (like walking).
60
Why might the stereotyped output of CPGs need modification?
To adapt to irregularities in the real-world environment (e.g., stepping over a hole).
61
Where does the voluntary control to activate, stop, or modify spinal CPGs originate?
In the cerebral cortex (motor cortex).
62
The cerebral cortex projects to which specific brainstem areas to control locomotion?
Locomotor regions (e.g., in the midbrain).
63
Which descending fibers project from the motor cortex to the midbrain locomotor region to trigger locomotion?
Corticobulbar fibers.
64
How are commands relayed from the brainstem locomotor regions to the spinal CPGs?
Via the reticulospinal tracts.
65
Summary: The brainstem is involved in which two types of movement?
1. Involuntary (postural reflexes) 2. Voluntary (locomotion)
66
How are voluntary movements initiated differently than reflexes?
They are frequently initiated by cognitive processes rather than in direct response to an external stimulus.
67
What are the three main areas of the motor cortex?
1. Primary motor cortex 2. Supplementary motor cortex (SMA) 3. Premotor cortex (PMA)
68
Where is the primary motor cortex located?
In the precentral gyrus.
69
Where is the premotor area located relative to the primary motor cortex?
Just rostral (anterior) to the primary motor cortex.
70
Where is the supplementary motor cortex located?
On the medial aspect of the hemisphere.
71
Which additional motor areas located in the frontal lobe are involved in voluntary movement?
Three cingulate motor areas.
72
What are the three steps of information processing for a voluntary movement?
1. Select an appropriate response. 2. Plan the movement. 3. Execute the movement.
73
Which cortical area provides the motivation and ideas for voluntary motor activity?
The posterior parietal cerebral cortex.
74
What sensory inputs does the posterior parietal cortex receive to localize the body and objects in space?
Visual, auditory, and somatosensory inputs.
75
After the posterior parietal cortex generates the idea for movement, where is this information sent for motor planning?
To the supplementary motor and premotor cortex.
76
What specific details does the "motor plan" identify?
Which muscles to contract, how much to contract, and in what sequence.
77
Which area is responsible for the actual execution of the movement after receiving the motor plan?
The primary motor cortex (via upper motoneurons).
78
What are the four primary sources of input to the motor areas of the cortex?
1. Other cortical motor areas (bidirectional connections). 2. Ascending sensory pathways via the thalamus. 3. The posterior parietal cortex (sensory information). 4. The cerebellum and basal ganglia (via the thalamus).
79
How do sensory pathways relay information directly to the motor cortex?
Via ascending pathways through the thalamus.
80
What specific types of sensory information are conveyed to motor areas from the posterior parietal cortex?
Somatosensory, visual, and auditory information.
81
Which two major subcortical brain regions project to the motor cortex through distinct parts of the thalamus?
The cerebellum and basal ganglia.
82
What are the two main types of descending motor pathways from the cortex mentioned?
1. Direct projections (Corticospinal and Corticobulbar tracts). 2. Indirect projections (via brainstem nuclei like the red nucleus).
83
What specific brainstem structure receives indirect projections from the motor cortex involved in motor control?
The red nucleus (and other interconnected nuclei in the reticular formation).
84
To which subcortical structure does the motor cortex project directly (part of a feedback loop)?
The striatum of the basal ganglia.
85
How does the motor cortex communicate with the cerebellum?
It projects to the cerebellum via the Pons (Pontine nuclei).
86
Why is the communication between the motor cortex and the cerebellum important?
For body balance and movement coordination.
87
How do motor cortical areas influence other cortical areas?
Directly (cortico-cortical connections) and indirectly through the thalamus (bi-directional pathways).
88
What is the primary function of the primary motor cortex?
It is responsible for the execution of movement.
89
What specific large upper motoneurons are found in the primary motor cortex?
Betz cells.
90
Where do the axons of Betz cells send their signals?
Down the spinal cord (via descending pathways).
91
Onto which two types of neurons do upper motoneurons synapse in the spinal cord?
1. Interneurons 2. Alpha motor neurons (directly).
92
What happens when upper motoneurons in the motor cortex are excited?
Activity is transmitted to the spinal cord, activating lower motoneurons to produce coordinated muscle contraction.
93
How is the primary motor cortex organized?
Topographically (represented as the motor homunculus).
94
Where are the face and upper limb represented on the motor homunculus?
On the lateral surface (face inferiorly, upper limb superior to face).
95
Where is the trunk represented on the motor homunculus?
Most superiorly on the lateral surface.
96
Where is the lower extremity represented on the motor homunculus?
Mostly on the medial aspect of the hemisphere.
97
The size of the cortical area assigned to a body part is proportional to what?
The complexity of the movements that body part can perform (not its physical size).
98
Which body parts have especially large areas in the motor homunculus due to their complex movements?
The hand and face.
99
What is the common nickname for the cerebellum?
"Little brain".
100
Where is the cerebellum located?
At the back of the brain, underlying the occipital and temporal lobes of the cerebral cortex.
101
What structure connects the two hemispheres of the cerebellum medially?
The cerebellar vermis.
102
How is the cerebellar vermis described in terms of lateralization?
It does not display any lateralization (unlike the hemispheres).
103
Name the three peduncles that connect the cerebellum to the brainstem.
1. Superior peduncle 2. Middle peduncle 3. Inferior peduncle
104
Through which peduncles do afferent (incoming) fibers mostly enter the cerebellum?
The inferior and middle peduncles.
105
Through which peduncle do efferent (outgoing) fibers mostly leave the cerebellum?
The superior peduncle.
106
Describe the internal organization of the cerebellum (layers).
Outer cortex (gray matter), deep white matter, and deep cerebellar nuclei buried within the white matter.
107
Name the four cerebellar nuclei from medial to lateral.
1. Fastigial 2. Globose 3. Emboliform 4. Dentate
108
What are the three lobes of the cerebellar cortex?
1. Anterior lobe 2. Posterior lobe 3. Flocculonodular lobe
109
What are the transverse folds of the cerebellar cortex called?
Folia.
110
Name the two major fissures separating the cerebellar lobes.
1. Primary fissure 2. Posterolateral fissure
111
With which nuclei outside of the cerebellum does it interact?
Red nucleus, Pontine nucleus, Vestibular nucleus, and Inferior olivary nucleus.
112
What are the three layers of the cerebellar cortex, from innermost to outermost?
1. Granular layer (innermost) 2. Purkinje cell layer (middle) 3. Molecular layer (outermost)
113
What are the output cells of the cerebellar cortex?
Purkinje cells.
114
Which cells are found in the granular layer?
Granule cells, Golgi II cells, Lugaro cells, and Unipolar brush cells.
115
What is a glomerulus in the cerebellar cortex?
A small, intertwined mass of nerve fiber terminals containing granule cell dendrites, Golgi cell axon terminals, and mossy fiber terminals.
116
Which neurons are the smallest and most numerous in the brain?
Cerebellar granule cells.
117
Which neurotransmitter do granule cells use, and what is their effect?
Glutamate (excitatory).
118
Describe the structure of a Purkinje cell.
It has an intricately elaborate dendritic arbor with a large number of dendritic spines.
119
What synaptic input does each Purkinje cell dendritic spine receive?
Input from a parallel fiber (axon of a granule cell).
120
Which neurotransmitter do Purkinje cells use, and what is their effect?
GABA (inhibitory).
121
What are the targets of Purkinje cell inhibition?
Cerebellar nuclei and vestibular nuclei.
122
Which cells constitute the sole output of all motor coordination in the cerebellar cortex?
Purkinje cells.
123
Which cells are found in the molecular layer?
Stellate cells, basket cells, dendrites of Purkinje and Golgi II cells, and parallel fibers (axons of granule cells).
124
Of the eight neuronal types in the cerebellar cortex, which two are excitatory?
Granule cells and unipolar brush cells.
125
What are the two major classes of afferent (input) systems to the cerebellar cortex?
1. Mossy fibers 2. Climbing fibers
126
Are mossy and climbing fiber inputs excitatory or inhibitory?
Both are glutamatergic excitatory inputs.
127
To which deep structures do both mossy and climbing fibers send excitatory collateral branches?
Directly to the deep cerebellar nuclei.
128
What distinctive structure do mossy fibers form within the granular layer?
Glomeruli (synaptic enlargements).
129
With which cells do mossy fibers form excitatory synapses within the glomeruli?
Granule cells and Golgi cells.
130
How does input from mossy fibers eventually reach Purkinje cells?
Via granule cell axons that ascend to become parallel fibers, which then synapse on Purkinje cell dendrites.
131
From where do mossy fibers originate?
Spinal cord, pontine nuclei, and vestibular nuclei.
132
From where do climbing fibers originate?
A single nucleus: the inferior olivary nucleus in the medulla.
133
Describe the unique synaptic arrangement of climbing fibers with Purkinje cells.
Each Purkinje cell receives input from only a single climbing fiber, which makes hundreds of excitatory synapses ("climbs" the dendrites).
134
What is the believed function of climbing fiber input on Purkinje cells?
To "condition" the Purkinje cells and modulate their responses to mossy fiber input (motor learning/error signal).
135
What provides the sole output from the cerebellar cortex?
Axons of Purkinje cells.
136
Is the output from Purkinje cells excitatory or inhibitory?
GABAergic inhibitory.
137
Where do Purkinje cell axons terminate
In the cerebellar nuclei (inhibiting them).
138
Among the cerebellar interneurons, which are the only excitatory types?
Granule cells and unipolar brush cells.
139
Which interneurons provide inhibitory input directly to Purkinje cells?
Basket cells and stellate cells.
140
What type of input excites granule cells in the cerebellar cortex?
Mossy fiber input.
141
What type of action potentials do Purkinje cells discharge in response to granule cell input (via parallel fibers)?
Simple spikes.
142
What is the typical spontaneous firing rate of simple spikes in a Purkinje cell?
Between 20 and 100 Hz.
143
What modulates the firing rate of simple spikes (from 0 to >200 Hz)?
The relative balance of excitation from parallel fiber input and inhibition from cerebellar cortex interneurons.
144
What type of input causes a Purkinje cell to discharge a "complex spike"?
Climbing fiber discharge.
145
Why does a climbing fiber cause a high-frequency burst of action potentials (complex spike)?
Because each climbing fiber makes hundreds of excitatory synapses along the dendrites of a single Purkinje cell
146
What is the average spontaneous firing rate of a complex spike?
Low, only about 1 Hz.
147
Do complex spikes substantially change the average firing rates of Purkinje cells?
No (because of their low frequency).
148
What is the proposed role of climbing fibers/complex spikes if not direct motor control?
To alter the responsiveness of Purkinje cells to parallel fiber input (motor learning/error signal).
149
What are the three groups of neuronal processes that attach the cerebellum to the brainstem?
The three cerebellar peduncles (inferior, middle, and superior).
150
What travels through the cerebellar peduncles?
All input to and output from the cerebellum.
151
Which peduncle connects the spinal cord and medulla with the cerebellum?
The inferior peduncle.
152
What type of fibers are primarily contained in the inferior peduncle?
Afferent fibers from the spinal cord (spinocerebellar/mossy fibers) and medulla (olivocerebellar/climbing fibers).
153
Which peduncle connects the pons with the cerebellum?
The middle peduncle.
154
What type of fibers are contained in the middle peduncle?
Only afferent fibers (mossy fibers) from the pontine nucleus.
155
From where does the middle peduncle convey input?
From the contralateral motor cortex via the pontine nuclei.
156
What is the function of the pontocerebellar tract (middle peduncle)?
It modulates skilled activities of the hands and fingers.
157
Which peduncle connects the cerebellum with the midbrain?
The superior peduncle.
158
What type of fibers are primarily contained in the superior peduncle?
Efferent projections (output) from the cerebellar nuclei to contralateral motor centers.
159
Where do the axons from the globose and emboliform nuclei synapse, and what is their function?
They synapse on neurons in brainstem motor centers (e.g., red nucleus) for motor execution.
160
Where do the axons from the dentate nucleus synapse, and what is their function?
They synapse on neurons in thalamic nuclei that project to the motor cerebral cortex for motor planning.
161
In the diagram, how are the fibers separated to aid understanding?
Afferent (Input) fibers are on the left; Efferent (Output) fibers are on the right.
162
What are the three sources of mossy fiber afferents mentioned?
1. Spinocerebellar axons 2. Pontine nuclei 3. Vestibular nuclei
163
What information do spinocerebellar axons convey, and via which peduncle?
Proprioceptive info (for muscle tone and body posture) via the Inferior peduncle
164
What information do pontine nuclei convey, and via which peduncle?
Information from the motor-related cerebral cortex via the Middle peduncle.
165
What is the functional role of the input from vestibular nuclei?
Maintaining equilibrium, posture, head position, and clear vision with movement.
166
What is the source of climbing fibers, and which peduncle do they use?
The Inferior Olivary Nucleus via the Inferior peduncle
167
Do cerebellar afferents (inputs) innervate only the cortex?
No, they innervate both the cerebellar cortex and the cerebellar nuclei.
168
Are cerebellar afferents generally excitatory or inhibitory?
Excitatory.
169
Through which peduncle do the Globose and Emboliform (Interposed) nuclei send output, and to which target?
Via the Superior peduncle to the Red Nucleus (brainstem motor center).
170
Through which peduncle does the Dentate nucleus send output, and to which target?
Via the Superior peduncle to the Thalamus (projecting to motor cerebral cortex)
171
Through which peduncle does the Fastigial nucleus send output, and to which targets?
Via the Inferior peduncle to the Reticular formation and Vestibular nuclei.
172
Contrast the primary functions of the Fastigial nucleus vs. the Dentate/Globose/Emboliform nuclei.
Fastigial: Balance and muscle tone. Dentate/Globose/Emboliform: Voluntary movement.
173
Why has the cerebellum historically been considered a motor structure?
Because cerebellar damage impairs motor control/posture, and most of its outputs are part of the motor system.
174
Does the cerebellum initiate motor commands?
No
175
What is the cerebellum's primary role in motor control?
To modify (fine-tune) motor commands from descending pathways, making movements adaptive and accurate.
176
What are the four specific functions of the cerebellum listed?
1. Maintenance of balance and posture. 2. Coordination of voluntary movements. 3. Motor learning. 4. Cognitive functions.
177
How does the cerebellum maintain balance and posture?
It uses input from vestibular receptors and proprioceptors to modulate motor commands, compensating for shifts in body position or load.
178
What aspect of voluntary movement does the cerebellum coordinate?
The timing and force of different muscle groups to produce fluid movements.
179
What is the role of the cerebellum in motor learning?
Adapting and fine-tuning motor programs through a trial-and-error process (e.g., learning a skill).
180
Besides motor control, what other functions is the cerebellum involved in?
Cognitive functions (language, attention, emotional control).
181
Which side of the body does a cerebellar hemisphere influence?
The ipsilateral (same) side.
182
What body part does the cerebellar vermis primarily control?
The trunk (coordination and muscle tone).
183
What is the general term for problems with maintaining balance and posture due to cerebellar damage?
Ataxia.
184
What are common symptoms of ataxia that mimic being drunk?
Slurred speech, stumbling, falling, and incoordination.
185
Define Dysmetria.
Errors in the direction and force of movement preventing a limb from reaching a desired position smoothly (overshooting or undershooting).
186
What is Dysdiadochokinesia?
The inability to perform rapid, alternating movements (e.g., flipping hand palm/back rapidly).
187
What is Decomposition of movement?
Breaking down complex movements into separate, discrete steps instead of a single smooth sequence.
188
Describe an Intention Tremor.
An involuntary tremor that increases in magnitude as a limb approaches its target (e.g., reaching for a cup).
189
What is Scanning Speech?
Slow and slurred speech.
190
What is Hypotonia?
Diminished muscle tone.
191
How can hypotonia be demonstrated clinically (reflex test)?
By the "pendular knee jerk" (the leg swings back and forth excessively after a patellar reflex test due to lack of damping).
192
How does cerebellar damage affect gait (walking)?
It causes a wide-based stance and a tendency to fall toward the affected side (gait ataxia).
193
What are the five main structures that make up the basal ganglia?
1. Caudate nucleus
2. Putamen
3. Globus pallidus (external and internal segments)
4. Subthalamic nucleus
5. Substantia nigra (pars reticulata and pars compacta)
194
Which two structures together form the Striatum?
Caudate nucleus and Putamen.
195
Which two segments make up the Globus Pallidus?
External segment (GPe) and Internal segment (GPi).
196
What are the two parts of the Substantia Nigra?
Pars reticulata and Pars compacta.
197
What is the primary function of the basal ganglia?
To influence motor control.
198
To which thalamic nuclei does the basal ganglia send its output?
Ventral Anterior (VA) and Ventral Lateral (VL) nuclei.
199
From where does the basal ganglia receive input?
The cerebral cortex (via the striatum).
200
What tract connects the thalamus back to the cerebral cortex?
The Thalamocortical tract.
201
In which part of the brain are the Caudate nucleus, Putamen, and Globus pallidus located?
In the cerebrum.
202
In which part of the brain is the Subthalamic nucleus located?
In the diencephalon.
203
In which part of the brain is the Substantia nigra located?
In the midbrain.
204
What neurotransmitter is produced by neurons in the Pars Reticulata (SNr)?
GABA (GABAergic neurons).
205
What neurotransmitter is produced by neurons in the Pars Compacta (SNc)?
Dopamine (Dopaminergic neurons).
206
Why do neurons in the pars compacta contain melanin?
It is a byproduct of dopamine synthesis.
207
The death of dopaminergic neurons in which specific part of the substantia nigra leads to Parkinson's disease?
The pars compacta (SNc).
208
What is the origin of the name "Striatum"?
It is derived from the striated appearance of the caudate nucleus and putamen.
209
After passing through the basal ganglia and thalamus, to which specific cortical area does the information return?
The Supplementary Motor Area (SMA).
210
Besides facilitating movement, what "filtering" function do the basal ganglia perform?
They act as a filter to block the execution of movements that are unsuited to the situation.
211
Which specific cortical areas do NOT project topographically to the basal ganglia through the striatum?
The primary visual and auditory cortices.
212
What is the excitatory neurotransmitter used by cortical neurons projecting to the striatum?
Glutamate.
213
Through which two main pathways does the striatum communicate with the thalamus (and back to the cortex)?
Direct and Indirect pathways.
214
In the indirect pathway, which structure does the striatum inhibit first?
The external segment of the Globus Pallidus (GPe).
215
In the indirect pathway, what is the effect of the subthalamic nuclei on the internal globus pallidus and substantia nigra pars reticulata?
Excitatory (input).
216
What is the overall output of the indirect pathway on the thalamus?
Inhibitory.
217
In the direct pathway, which structures does the striatum inhibit directly?
The internal segment of the Globus Pallidus (GPi) and the Substantia Nigra pars reticulata (SNr).
218
What is the overall output of the direct pathway on the thalamus?
Excitatory.
219
What is the main neurotransmitter used by the striatum to inhibit the globus pallidus and substantia nigra
GABA.
220
How do the outputs of the direct and indirect pathways balance each other?
They are opposite: Direct is Excitatory (facilitates movement), Indirect is Inhibitory (suppresses movement).
221
What is the functional consequence of an imbalance between these two pathways?
Motor disorders (either hypokinetic or hyperkinetic movements).
222
Why does the basal ganglia have an important influence on the lateral system of motor pathways?
Because the basal ganglia influence the cortical motor areas, which are the origin of the lateral system.
223
What are three types of motor deficits observed in basal ganglia diseases?
1. Abnormal movement (dyskinesia) 2. Increased muscle tone (cogwheel rigidity) 3. Slowness in initiating movement (bradykinesia)
224
What causes hypokinetic disorders?
Excessive output from the basal ganglia to the thalamus (excessive inhibition of the thalamus), limiting voluntary movement
225
What causes hyperkinetic disorders?
Insufficient output from the basal ganglia to the thalamus (insufficient inhibition), leading to uncontrolled involuntary movements.
226
Parkinson's disease is an example of which type of disorder (hypokinetic or hyperkinetic)?
Hypokinetic disorder.
227
What is the primary cause of Parkinson's disease?
Loss of dopaminergic neurons in the Pars Compacta of the Substantia Nigra.
228
In Parkinson's disease, how are the direct and indirect pathways affected?
Direct pathway activity is diminished; Indirect pathway activity is increased.
229
What is the net effect of the pathway imbalance in Parkinson's disease on the thalamus and motor cortex?
Greater inhibition of the thalamus and less activation of the motor cortical areas.
230
Huntington's disease is an example of which type of disorder?
Hyperkinetic movement disorder.
231
What causes Huntington's disease?
Neuronal death of GABAergic (and cholinergic) neurons in the striatum.
232
In Huntington's disease, loss of GABAergic projection to which structure initiates the imbalance?
To the GPe (external globus pallidus) as part of the indirect pathway.
233
What is the net effect of Huntington's disease on the thalamus and motor cortex?
Disinhibition of the thalamus, resulting in enhancement (excess) of activity in the motor cortex.
234
On which side of the body does motor dysfunction occur in basal ganglia disorders?
Contralateral to the diseased component.
235
Which specific cerebral association regions are crucial for the planning and formulation of motor activities?
The supplementary motor area (SMA), premotor cortex, and parietal association cortex.
236
What is Apraxia?
A deficit of higher-order motor planning and execution, despite normal muscle strength, caused by lesions in cerebral motor association regions.
237
Anatomically, where are the basal ganglia located and how do they project back to the cortex?
They are massive gray matter nuclei within each hemisphere, embedded in white matter, projecting back to the cortex through the thalamus.
238
What is the primary role of the basal ganglia regarding muscle tone?
They are involved with the subconscious control of skeletal muscle tone.
239
Do the basal ganglia initiate movement under normal conditions?
No, they do not initiate particular movements.
240
Once a movement has started, what specific contribution do the basal ganglia make?
They provide general pattern and rhythm, especially for the trunk and proximal limb muscles.
241
What are the two categories of diseases associated with the basal ganglia mentioned in the summary?
Hyperkinetic disorders (e.g., Huntington’s disease) and Hypokinetic disorders (e.g., Parkinson’s disease).
242
How do cerebellar feedback loops contribute to motor control?
They assist with programming and fine-tuning of movements controlled at both conscious and subconscious levels.
243
specifically, how does the cerebellum refine movement to ensure smoothness?
By comparing motor commands with proprioceptive information and performing necessary adjustments.
244
What clinical condition results from damage to the cerebellum preventing smooth movement?
Ataxia.
