Test 2 (Lectures 8-16) Flashcards
1
Q
Definition of a reflex
A
A muscle contraction induced by an external stimulus that cannot be changed by pure thinking
2
Q
Are highly adaptable to changes in behavioral goals, but cannot be directly or voluntarily controlled
A
Reflexes
3
Q
Stereotyped responses to specific stimuli that are generated by simple neural circuits in the spinal cord or brain stem
A
Reflexes
4
Q
Consists of one central synapse
A
Monosynaptic reflex
5
Q
Consists of 2-3 central synapses
A
Oligosynaptic reflex
6
Q
Consists of many central synapses
A
Polysynaptic reflex
7
Q
Slow, steady-state, maintained
A
Tonic
8
Q
Fast, transient, in response to a change in the stimulus
A
Phasic
9
Q
No higher brain involvement is involved in
A
Reflexes
10
Q
Benefits of studying reflexes
A
It can assist in diagnosing certain conditions by localizing an injury or disease in the CNS.
11
Q
Often indicates a disorder in one or more components of the reflex arc
A
Absent or weak (hypoactive) reflexes
12
Q
Can cause both hyperactive and hypoactive reflexes
A
Lesions in the CNS
13
Q
Most common form of hyperactive reflex
A
Spasticity
14
Q
Spasticity results in
A
Increased muscle tone
15
Q
5 Components of the reflex arc
A
- Sensory element
- Afferent nerve
- Central processing unit
- Efferent nerve
- Effector
16
Q
3 components of reflex latency
A
- Afferent conduction delay
- Central processing delay
- Efferent conduction delay
17
Q
This type of reflex originates from Ia spindle afferents and induces responses in the same muscle or in muscles in the vicinity
A
Monosynaptic reflex
18
Q
Technique for examining monosynaptic reflexes developed in the 1950’s by P. Hoffman
A
H-reflex
19
Q
Commonly assessed by stimulating the tibial nerve and measuring the response of the soleus
A
H-reflex
20
Q
Electrical stimulation of the Ia afferents in a peripheral nerve and recording the motor response in the same muscle
A
H-reflex
21
Q
Stimulation is applied to both afferent and efferent fibers
A
H-reflex
22
Q
How the H-reflex and M-response work
A
Afferent fibers are the first to react to a slowly increasing electrical stimulus. They induce a reflex muscle contraction. Later, efferent fibers become excited and induce a direct muscle contraction.
23
Q
Further increase in the strength of the stimulation leads to an increase in the _____ and a suppression of the ______.
A
M-response, H-reflex
24
Q
How do sensory neurons conduct action potentials?
A
Antidromically
25
How do motor neurons conduct action potentials?
Orthrodromically
26
At high levels of stimulation, motor neurons also start generating action potentials
Antidromically
27
At high levels of stimulation, the antidromic motor neuron action potential cancels out the
antidromic sensory neuron action potential, thus suppressing the H-reflex.
28
The M-wave presents due to
the orthrodromic motor neuron action potential.
29
Successive stimuli at a high frequency induce
similar M-responses but progressively smaller H-reflexes
30
The refractory period for the ______ is much greater than the refractory period for the ________.
Central synapse; axon of the motor neuron
31
A ______ excites spindle endings a may induce a monosynaptic reflex contraction.
Tendon tap
32
The tendon tap is known as
the T-reflex
33
The T-reflex has the same pathway as the
H-reflex
34
Increases the amplitude of the H-reflex
Voluntary muscle activation
35
Voluntary activation of the antagonist muscle group
decreases the amplitude of the reflex due to Ia interneuron inhibition of the alpha motoneurons of the muscle being tested
36
How is the H-reflex amplitude increased?
Voluntary muscle activation excites the motoneuron pool of the activated muscle
37
Electrical stimulation of Ia afferents.
Excitation of alpha motoneurons through a central synapse.
Efferent command to the target muscle.
Twitch muscle contraction.
H-reflex
38
Fast stretch of a muscle, leading to activation of primary muscle spindle afferents.
Then same as H-reflex
T-reflex
39
Interneurons always send ____ signals.
Inhibitory
40
The simplest muscle reflexes acting in the human body
Monosynaptic reflexes
41
The functional importance of these reflexes are questionable
Monosynaptic reflexes
42
Induce brisk, brief, contractions that are poorly controlled voluntarily
Monosynaptic reflexes
43
Unlikely to be part of mechanism for voluntary control of movement
Monosynaptic reflexes
44
Examples of oligosynaptic reflexes
Ia-afferents and Ib afferents
45
Ia interneurons receive excitatory inputs from Ia afferents and make inhibitory synapses on motoneurons that innervate the antagonist muscle.
Reciprocal inhibition
46
Reciprocal inhibition is an example of what type of reflex?
Oligosynaptic inhibitory reflex
47
New thinking is that these receptors are used for fine motor control
Golgi Tendon Organs
48
Double inhibition is equivalent to
Disinhibition
49
Golgi tendon organs send Ib afferent axons to ____, which exert an inhibitory action on agonist alpha motoneurons
Ib interneurons
50
After inhibiting agonist alpha motoneurons, golgi tendon organs excite or _____ antagonist alpha motoneurons.
Disinhibit
51
Receive contributions from different receptors
Polysynaptic reflexes
52
Central pathway is unknown
Polysynaptic reflex
53
Flexor reflex is induced by a group of afferents called
Flexor reflex afferents
54
Includes muscle spindles, free nerve endings, cutaneous receptors, etc.
Flexor reflex afferents
55
Leads to an activation of flexor muscles within the limb
Flexor reflex
56
Emerge in response to a CHANGE in the level of a receptor specific stimulus
Phasic reflexes
57
Emerge in response to the level of a stimulus
Tonic reflexes
58
Typically a burst or brief depression of muscle activity leading to a twitchy or series of twitchy movements. All monosynaptic reflexes
Phasic reflexes
59
Typically lead to sustained muscle contractions and relatively smooth movements. Polysynaptic reflexes.
Tonic reflexes
60
Muscle spindles can lead to both
Phasic and tonic reflexes
61
The phasic reflexes disappear rapidly when
a muscle stays in its stretched state
62
Tonic changes may be observed after the stretch is completed if
the muscle was active before the stretch
63
6 steps of the tonic stretch reflex
1. A muscle is slowly stretched by an external force.
2. First resistance to stretching is provided by passive elastic properties.
3. At a certain length, a few alpha motoneurons are recruited autogenically.
4. This leads to active force development opposing the stretch.
5. The length at which this recruitment begins is the threshold of the tonic stretch reflex.
6. As the muscle continues to lengthen, more motoneurons and muscle force increases.
64
Reveals a relationship between muscle length and muscle force
Tonic stretch reflex
65
Autogenic recruitment means
Automatic recruitment
66
The major mechanism that defines the viscoelastic properties of muscles, joints, and limbs.
Tonic stretch reflex
67
The threshold is a control variable manipulated by the brain
Tonic stretch reflex threshold
68
Are not exclusively manipulated by the brain
Muscle activation levels, forces, changes in joint angles, etc.
69
Emerge with equal participation of central commands and external loads
Muscle activation levels, forces, changes in joint angle, etc.
70
Leads to a slow reflex increase in muscular force
High-frequency muscle vibration (Tonic vibration reflex)
71
Starts at a delay and lasts some time after the stimulus has ended
Tonic vibration reflex
72
Accompanied by a suppression of monosynaptic reflexes in the same muscle
Tonic vibration reflex
73
This suppresion is of a presynaptic origin
Suppression of monosynaptic reflexes (H-reflex, etc.) by tonic vibration reflex.
74
Receive mixed information from afferents originating from different receptors
Ia and Ib interneurons
75
Induces a reflex response in flexor muscles of the limb
Stimulation of the flexor reflexor afferents
76
Also induces a cross extensor reflex in extensor muscles of the contralateral limb
Stimulation of the flexor reflexor afferents
77
Reflex loop is unknown
Polysynaptic reflexes
78
Involve distant muscles
Polysynaptic reflexes
79
May show effects in other extremities
Polysynaptic reflexes
80
Longer latency, slow, steady-state character
Polysynaptic reflexes
81
Naturally occuring examples of polysynaptic reflexes
Flexor reflex
Crossed extensor reflex
Tonic stretch reflex
82
Artificial example of polysynatpic reflex
Tonic vibration reflex
83
Numerous reflex pathways exist for even
a single muscle
84
Controller
Brain
85
Variables the controller uses to formulate command signals
Control variables
86
Controller has the choice to ______ to peripheral information
React or not react
87
The controller uses independently controlled variables to formulate command signals to the "lower" (executive) structure.
Feedforward control
88
Examples of feedforward control
Soccer goalie, batter, etc.
89
Takes more time
Feedback
90
Commands are generated without regards to the consequences
Feedforward control
91
Open-loop command/control
Feedforward control
92
The sensorimotor loop is not completed by sensory feedback
Feedforward control
93
The speed of feedforward control
200 ms to respond to a visual stimulus
94
Is often used to start a movement, such as reaching
Open loop
95
Cannot correct for errors, and errors can compound
Feedforward control
96
Feedback control changes command signals based on their
outcome
97
Feedback control is done by a
Comparator
98
An example of a comparator in the body
Cerebellum
99
Changes in the output of the comparator so as to bring down any possible deviations of the output
Negative feedback
100
Amplifies any deviations of the output
Positive feedback
101
The sensorimotor loop is complete
Feedback control
102
Closed loop command/control
Feedback control
103
Uses sensory information to compare the intended action/movement to the actual action/movement
Feedback control
104
Can make adjustments
Feedback control
105
Takes time
Feedback control
106
Ratio of change in a control variable to change in a peripheral variable
(Change in control/change in peripheral)
Gain
107
Measure of time (seconds or ms)
Delay
108
A change in this can make an apparent negative feedback scheme function like a positive feedback scheme and vice versa
Delay
109
Uses both feedforward and feedback control
Nervous system
110
The longer the time delays in a servo,
the larger the errors that can accumulate before a corrective action
111
Feedback loop keeps the variable specified by the controller ____, despite possible changes in external conditions that may change the variable
constant
112
The servo is the same as
The feedback loop
113
Can shift the tonic stretch reflex to the left or decrease the delay
Gamma motoneurons
114
Merton's Servo Hypothesis believes that the CNS only sends signals to the muscles through
Gamma motoneurons
115
Considers the feedback loop to be a perfect servo
Merton's Servo Hypothesis
116
This reflex is an example of a negative feedback mechanism
Tonic stretch reflex
117
Suggests that the control of muscle spindles with the gamma system was part of a servo system controlling muscle length
Merton's Servo Hypothesis
118
When force or torque equals load
Equilibrium
119
How Merton's Servo Hypothesis works
If the load increases, the muscle lengthens.
Alpha motoneuron activity increases.
This increases muscular force
120
According to Merton's Servo Hypothesis, limb displacement due to load will
NEVER happen
121
1. Descending signal comes to the gamma motoneuron and changes sensitivity of muscle spindles to length.
2. Spindle endings activity changes via the TSR and alters alpha motoneuron activity
3. Level of muscle contraction changes, leading to changes in muscle length. Increase of contraction reulst in muscle shortening and a decrease in spindle activity.
4. Movement continues until muscle length reaches a new value, at which muscle spindle activity causes a contraction which exactly balances the external load
Merton's Servo hypothesis
122
The muscle will always reach a new equilibrium state
Merton's Servo Hypothesis
123
A large change in external force is assumed to be perfectly compensated by the tonic stretch reflex mechanism - the mechanism has infinite gain.
Merton's Servo Hypothesis
124
Merton's model was proven to be
false
125
All voluntary movements do not begin with activation of gamma-motoneurons, but
with gamma and alpha motoneuron coactivation.
126
The gain in the tonic stretch reflex is
small to moderate.
127
The tonic stretch reflex cannot function as a length-control servo because
the gain is only small to moderate.
128
Central command theory
Central commands directly specify the activity levels of alpha motoneurons pools and therefore specify the levels of muscle activation.
129
Reflexes play a minor role, contributing mostly to unexpected changes.
Central command theory
130
Central commands use muscle reflexes to change the levels of muscle activity and specify parameters of these reflexes.
Equilibrium-point hypothesis
131
1. Person tries to voluntarily activate the biceps brachii throughout the experiment.
2. Load is removed, EMG activity drops off, even when person is still trying to activate muscle.
3. Removing load greatly decreases the activity of the muscle spindles, so there is no reflexive recruitment of alpha motoneurons.
Unloading Reaction/Reflex
132
When a load is removed, a period of complete silence on the EMG follows even if the subject is trying to maintain activity
Unloading Reflex
133
According to the equilibrium point hypothesis, muscle reflexes specify a relation between muscle force and muscle length
An invariant characteristic
134
According to equilibrium-point hypothesis, the system is in equilibrium when
Muscular force is equal to external force.
135
In equilibrium point theory, if the external load changes,
muscular force and muscular length will change corresponding to a new equilibrium point
136
When muscle force is equal to external load in equilibrium point theory
Equilibrium point
137
A central command specifies the location of an invariant characteristic of the muscle (shifts the threshold of the tonic stretch reflex). A change in load can lead to a change in muscle length (isotonic), a change in muscle force (Isometric), and a change in both (elastic).
Equilibrium Point Hypothesis
138
What the subject is expected to do
Task parameters
139
What the subject actually does
Performance parameters
140
Triphasic EMG
Burst in agonist activity, followed by an antagonist burst, which is sometimes followed by a second agonist burst
141
Reasons for triphasic EMG pattern
A quick burst of activity in the agonist muscle group activates the muscle spindles of the antagonist, leading to activation of alpha motoneurons of the antagonist.
142
EMG peak amplitude, integrals over different time intervals
Magnitude
143
Delay of the antagonist burst, duration of EMG bursts
Timing
144
When load and distance are constant and velocity increases, 4 things happen
1. An increase in the rate of agonist EMG rise, peak value, and area
2. A decrease in the delay of the antagonist burst.
3. An increase in the antagonist burst amplitude and area
4. An increase in the level of final cocontraction.
145
When load and velocity are constant and distance increases, 3 things happen
1. Uniform rates of agonist EMG rise; higher and longer first agonist EMG burst
2. Longer delays before the antagonist burst
3. Inconsistent changes in the antagonist burst amplitude and duration.
146
Load increases. Distance and velocity are constant. (5 things happen)
1. Higher and longer agonist EMG bursts
2. No changes in the rate of EMG rise
3. Longer delay before the antagonist burst
4. No apparent changes in the antagonist burst characteristics
5. Increased final cocontraction
147
2 types of isometric contractions
Step contractions
| Pulse contractions
148
Step contraction
The participant increases joint torque to a certain level.
149
Pulse contraction
The participant increases joint torque to a certain level and then quickly relax.
150
Control over movement duration at different speeds
Speed-sensitive
151
No control over movement duration at the same speed
Speed-insensitive
152
CNS computes "excitation pulses" to motoneural pools.
Dual Strategy Hypothesis
153
EMGs are consequences of
both central commands and reflex loops
154
If a movement is perturbed, EMGs are expected to change at a short reflex delay; changes in commands are expected
to come later.
155
Early EMG changes are defined by
changes in muscle length
156
Are not always reliable indices of central control signals
EMG
157
Semi-automatic reactions to changes in muscle length, or other stimuli, that may be tentatively termed reflexes
Pre-programmed reactions
158
Bridge between reflexes and voluntary action
Pre-programmed reactions
159
Pre-programmed reactions are dependent on
Instructions
160
Also called triggered reactions, M2-M3, functional stretch reflex, transcortical reflex, long-loop reflex
Pre-programmed reactions
161
The latency of pre-programmed reactions
40-100 ms
162
Are involuntary in nature but can be modified by instruction
Pre-programmed reactions
163
Can be triggered by stimuli of virtually any modality
Pre-programmed reactions
164
Generate a quick, crude compensation for the perturbation and are followed by a voluntary correction
Pre-programmed reactions
165
Pre-programmed reactions can be stimulated by
proprioceptors, a flash of light, a loud tone, etc.
166
Perturbations during a fast voluntary movement, EMG changes for pre-programmed reactions will generally
increase the activity of the muscle acting against the perturbation and decrease the activity of the muscle acting with the perturbation.
167
3 things that can affect pre-programmed reactions
experience, instructions, and predictability
168
Pre-programmed reactions are triggered in response to
unexpected loading or unloading of effectors
169
The execution of any motor task is associated with
pre-programming of compensatory reactions to conceivable perturbations
170
5 examples of pre-programmed reactions
1. The "waiter's response:
2. Grasp adjustments
3. Two-hand object holding
4. Reactions to postural perturbations (ankle and hip strategies)
5. Corrective stumbling reaction
171
The amplitude of the pre-programmed response is determined
before the perturbation
172
Subjects can pre-program
any combinations of command functions to any muscle or muscle group
173
Pre-programmed reactions for posture
Corrective postural reactions
174
Pre-programmed postural corrections to a perturbation are dependent on
Context
175
A group of reactions to external stimuli that come at a longer latency than reflexes but shorter than voluntary reactions
Pre-programmed reactions
176
Can be modulated by prior instruction or experience or predictability
Pre-programmed reactions
177
Produce quick, crude corrective actions that counteract the mechanical effects of perturbation
Pre-programmed reactions
178
Can be seen in muscles whose length is increased, decreased, or unchanged by the perturbation
Pre-programmed reactions
179
Exact source of sensory information is not important as long as it carries sufficient information
Pre-programmed reactions
180
Are a very important component of postural control and locomotion
Pre-programmed reactions
181
Consists of the spinal cord and brain.
Central nervous system
182
Borders with the medulla
The spinal cord
183
Autonomic function
Medulla
184
Contains important nuclei (cardiac, vasomotor, and respiratory center)
Medulla
185
Located between the medulla and the midbrain
The pons
186
Contains both ascending and descending white fiber tracts and several nuclei including the cranial nerves V to VIII.
The pons
187
Lies behind the medulla and the pons. Consists of two hemispheres and a central area (vermis)
Cerebellum
188
Is supported by three peduncles
Cerebellum
189
Helps with timing of movements, balance, posture, coordination, and possibly assembling of motor synergies
Cerebellum
190
Contains four elevations called colliculi, which are divided into two superior colliculi (vision and occular reflexes) and two inferior colliculi (processing of auditory information)
The midbrain
191
A typical feature of cerebellar disorders
Dis-coordination or ataxia
192
The two major nuclei contained in the midbrain
The red nucleus
| The substantia nigra
193
Important for voluntary movement
The red nucleus
194
Motor control
Substantia nigra
195
Is almost completely surrounded by cerebral hemispheres
The diencephalon
196
Contains the thalamus, hypothalamus, the hypophysis, and the epiphysis
Diencephalon
197
Integration of sensory and motor information
Thalamus
198
aids in autonomic functions
Hypothalamus
199
The pineal gland
Epiphysis
200
Includes the hypothalamus, the fornix, the hippocampus, the amygdaloid nucleus, and the cingulate gyrus of the cerebral cortex
The limbic system
201
Short term memory and memory consolidation
Hippocampus
202
Connects the two hemispheres in the cerebrum
The corpus callosum and the anterior commissure
203
The five lobes of the cerebrum
```
Frontal lobe
Parietal lobe
Occipital lobe
Temporal lobe
Insula
```
204
Involved heavily in voluntary movements, coordination, and perception
The cerebrum
205
Consists of the globulus pallidus, putamen, caudate nucleus, subthalamic nucleus, and substantia nigra
Basal ganglia
206
Plays an important role in the initiation of voluntary movements
Basal Ganglia
207
Control of neck and face
Nuclei of the cranial nerves
208
Stimulation can induce locomotion
Reticular formation
209
Synergy formation, timing, memory, motor learning
Cerebellum
210
Source of a major descending pathway
Red nucleus
211
Sensorimotor integration
Thalamus
212
Emotions
Limbic circle
213
Motor control, movement initiation
Basal ganglia
214
"Higher" functions, motor control
Cortex of large hemispheres
215
Method to study the collective electrical activity of a large group of neurons
Electroencephalography (EEG)
216
EEG waves seen during consciousness
Alpha and Beta waves
217
EEG wave seen during rest or sleep
Delta and Theta waves
218
Allows for high temporal resolution (Changes in brain activity from millisecond to millisecond)
EEG
219
Very poor spatial resolution
EEG
220
Difficult to identify the exact source of the
electrical signal
221
Can be recorded from the back in response to an electrical stimulation of a peripheral nerve
Evoked potentials in the spinal cord
222
Identifies objects with different X-ray absorption
Radiography
223
Typically correlates with density
Radiography
224
High spatial resolution
Radiography
225
Detects changes in blood vessels (stroke, aneurysms)
Angiography
226
Creates a 3-D image based on radiography, short examination time
Computer Tomography (CT)
227
Relatively high resolution
CT
228
Can visualize white and gray matter
CT
229
Useful for looking at blood vessels in the brain
CT
230
Measures the concentration of radioactive tracers
Positron Emission Tomography (PET)
231
Selective sensitivity to different substances and processes
PET
232
Useful for detecting brain patterns that occur over longer periods of time
PET
233
Radio-frequency pulse perturbs protons, which release energy that can be analyzed
Magnetic Resonance Imaging (MRI)
234
Very high degree of contrast of different matter; no bone artifact
MRI
235
Requires high degree of cooperation from the patient
MRI
236
Has problems with metal objects
MRI
237
Superior ability to differentiate tissues
MRI
238
Good spatial, poor temporal resolution
MRI
239
Comparing MRI measurements obtained before and after performing a task
Functional MRI
240
Can show changes in the signal in different brain structures during natural tasks
Functional MRI
241
Very poor time resolution (need to wait several seconds or minutes between task)
Functional MRI
242
Questionable interpretation of the BOLD response
Functional MRI
243
Has a multilayer structure
Cerebral cortex
244
2 types of cells contained in the cerebral cortex
Pyramidal cells
| Stellate cells
245
Interprets sensory data
Cerebral Cortex
246
Provides perception of sensory data
Cerebral Cortex
247
Makes conscious decisions
Cerebral Cortex
248
Is active in voluntary movement
Cerebral cortex
249
Aids in the planning, execution, and accuracy of movements
Cerebral cortex
250
Most knowledge of the function of these structures comes from studies of individuals with brain injury
Cortex and cerebellum
251
This hemisphere of the brain is dominant in 96% of right handed people
Left hemisphere
252
This hemisphere of the brain is dominant in 70% of left handed people
Left hemisphere
253
This has been linked to the dominant hemisphere of the brain
Speech
254
First layer of the cerebral cortex
Molecular: Contains axons and dendrites
255
Second layer of the cerebral cortex
External granular: contains small pyramidal and stellate cells
256
Third layer of the cerebral cortex
The internal granular: contains stellate and pyramidal cells
257
Fourth layer of the cerebral cortex
Ganglionic: Large pyramidal cells
258
Fifth layer of the cerebral cortex
Multiform: Many different neurons which communicate within and leave the cortex
259
How many layers are in the cerebral cortex?
5
260
These cells in the cerebral cortex project to other neurons in the same cortical area and well as in other cortical areas
Pyramidal cells of layers II and III
261
Intracortical communication
When a pyramidal cell in one cortical area communicates with cells in another coritcal area
262
Most input from the cortex comes from the
Thalamus
263
Acts as a relay station, processing information from the peripheral afferents, the cerebellum, and the basal ganglia
Thalamus
264
Thalamic inputs make synapses in
Layer IV with the stellate cells
265
Stellate cells synapse with
Pyramidal cells
266
Pyramidal cells receive sensory information from
The thalamus and the cortex
267
Brodmann divided the cerebral cortex into over
50 areas
268
These cerebral cortex areas are important for the control of movements
Areas 4 and 6
269
Area 4 is also known as the
Primary motor area
270
This area of the cortex is active during movement
Primary motor area
271
This is an upper motor neuron syndrome
Amyotrophic lateral sclerosis (ALS), a.k.a.: Lou Gehrig's disease
272
Contains giant output cells, particularly in zones with projections to leg muscles
Primary motor area
273
Has a motor map of the body (somatotopic organization)
Primary motor area
274
Active during execution of voluntary movements
Primary motor area
275
Damage can cause paralysis and spasticity (upper motor neuron disorder)
Primary motor area
276
Area 6 of the cerebral cortex is also known as the
Premotor area
277
Is active during movement planning
Premotor area
278
More complex movements originate here
Premotor area
279
Hand and mouth movements start here
Premotor cortex
280
Goal directed actions such as grasping start here
Premotor cortex
281
Involved in the planning, generation, and control of sequential motor actions and contextual control
Premotor cortex
282
Impaired restraint of potential motor acts elicited by objects
Premotor cortex
283
Motor execution
Primary motor area
284
Motor preparation and planning
Supplementary motor area
285
Interprets clues or goal directed movements
Premotor area
286
Proprioceptive information, speech, verbal expression
Parietal lobes
287
Inputs to the motor cortex come from the
spinal cord, basal ganglia, and cerebellum
288
Inputs to the motor cortex are mediated by the
ventrobasal nuclei of the thalamus
289
Outputs of the motor cortex include projections to
basal ganglia, cerebellum (via pons), red nucleus, and reticular formation and spinal cord
290
Corticospinal tracts decussate at the level of the
Medulla
291
Stimulating different cortical cells may activate the same group of motor units and result in similar movements
Convergence
292
Stimulating one cortical cell can activate different groups of motor units and move different body parts
Divergence
293
Medial area of the cerebellum
Vermis
294
Has two hemispheres and a medial area
Cerebellum
295
The cerebellum is connected to other neural structures by
3 pairs of peduncles
296
Cerebellum makes up this much of brain volume
10%
297
How many neurons in the brain does the cerebellum contain?
More than half
298
Ratio of inputs to outputs in the cerebellum
40:1
299
Number of lobes of the cerebellum
3
300
Disorders of the cerebellum result in
Disruptions of normal movement
301
Is different than the paralysis caused by cerebral cortex damage
Cerebellum disorders
302
4 common symptoms of cerebellum disorders
Hypotonia
Astasia-abasia
Ataxia
Tremors
303
Hypotonia definition
Diminished resistance to passive limb displacements
304
Astasia-abasia
Inability to stand or walk
305
Abasia
Loss of the ability to maintain an upright stance against gravity
306
Astasia
Loss of the ability to maintain a steady limb or body posture across multiple joints
307
Ataxia
lack of coordination
308
When are tremors observed in cerebellum disorders?
Tremors are seen at the of movements or when attempting to stop (action or intention tremor)
309
How many types of neurons are in the cerebellum?
5 types
310
The 5 types of neurons in the cerebellum
```
Granule cells
Golgi cells
Stellate cells
Basket cells
Purkinje cells
```
311
Axons are called parallel fibers
| Excitatory to all cells below it
Granule cells
312
Excited by parallel fibers, inhibit granule cells
Golgi cells
313
Interneurons are within the cerebellum
Inhibits Purkinje cells
Controls the flow of output information
Stellate cells and basket cells
314
Only output of the cerebellum, inhibitory neurons
Purkinje cells
315
Timing, learning, memory, and modeling of motor actions happens in the
Cerebellar neurons
316
Excitatory inputs in the cerebellum are provided by
Mossy fibers and climbing fibers
317
make synapses on the Purkinje cells
Climbing fibers
318
Excites Granule cells
Mossy fibers
319
Granule cells (parallel fibers) send excitatory impulses to
Purkinje cells, basket cells, stellate cells, and golgi cells
320
Stelate cells make inhibitory synapses on
Purkinje cells
321
Basket cells inhibit
Purkinje cells
322
Golgi cells inhibit
Granular cells
323
Modulate the activity of the Purkinje cells
Stellate, basket, and Golgi cells
324
Purkinje fibers send output signal from the cerebellum. They innervate
the reticular formation, ventrolateral (cerebellar) thalmus, and the red nucleus.
325
Most information from the cerebellar thalamus projects to
areas 4 and 6 of the cerebral cortex
326
Removal of the cerebellum or lesions on the cerebellum can lead to major problems with
eye movements, balance, posture, and coordination
327
Helps with timing of actions
Cerebellum
328
Assembles motor synergies
Cerebellum
329
Compares intended action to actual action (acts as a comparator)
Cerebellum
330
Diseases of the basal ganglia
Parkinson's and Huntingdon's
331
5 Structures of the basal ganglia
```
Caudate nucleus
Putamen
Globulus pallidus
Subthalamic nucleus
Substantia nigra
```
332
Its importance for voluntary control has been inferred from clinical observations
Basal ganglia
333
Disorders can cause excessive involuntary movements, movement poverty, and slowness; all typically without paralysis
Disorders of the basal ganglia
334
Sites of almost all afferent inputs to the basal ganglia
Caudate nucleus and putamen (striatum)
335
Input to the basal ganglia comes from the
different areas of the cerebral cortex and nuclei of the thalamus
336
Projections from the cortex onto the internal globulus pallidus and substantia nigra. Project directly onto thalamus and back to cerebral cortex
Direct pathway
337
Projections from the cortex onto the external globulus pallidus, then to the subthalamic nuclei
Indirect pathway
338
Has a net excitatory effect on cortical neurons
Direct pathway
339
Has a net inhibitory effect on cortical neurons
Indirect pathway
340
Believed to play a major role in the control of limb movements
Direct pathway
341
Believed to play a role in oculomotor control
Indirect pathway
342
Disinhibits areas of the motor system and thus allows movement to occur (not well supported)
Basal Ganglia
343
Turns off postural activity and allows voluntary movement to occur (Not well supported)
Basal ganglia
344
Are involved in sequencing and initiating voluntary movements
Basal ganglia
345
Force control, controlling the antagonist muscle group
Basal ganglia
346
Helps prevent unwanted movements
Basal ganglia
347
Reciprocal inhibition is what type of reflex
Oligosynaptic
348
Typical latency o the H-reflex and T-reflex
35 ms
349
These receptors are involved in polysynaptic reflexes
Spindle endings, golgi tendon organs, articular receptors
