Motor Function Flashcards
(80 cards)
1
Q
three areas of motor cortex
A
primary motor cortex, premotor area, and supplementary motor area
2
Q
how much of the motor cortex is devoted to the hands and speech?
A
1/2
3
Q
what occurs in primary motor cortex damage if the caudate nucleus and adjacent premotor and supplementary areas remain intact?
A
- loss of voluntary control of discrete movements of the hand and finger
- can contract but loss of fine control
4
Q
Where does the intention to contract a muscle begin?
A
-motor assocaition (premotor) area of frontal lobes
5
Q
What occurs in premotor area of frontal lobes?
A
- plan our behavior
- neurons compile a program for degree and sequence of muscle contraction
- program transmitted to neurons of the precentral gyrus (primary motor area)
6
Q
What are the upper motor neurons?
A
pyramidal cells of the precentral gyrus
7
Q
What determines the onset and cessation of intentional movements?
A
basal nuclei
8
Q
What is the feedback circuit that the basal nuclei is invovled in?
A
cerebrum–> basal nuclei–> thalamus–> cerebrum
9
Q
what controls highly practiced, learned behaviors that one carries out with little thought?
A
basal nuclei
10
Q
Dyskinesias are movement disorders caused by what?
A
lesions in the basal nuclei
11
Q
cerebellum controls what factors of motro control?
A
Highly important in motor coordination Aids in learning motor skills Maintains muscle tone and posture Smooths muscle contraction Coordinates eye and body movements Coordinates the motions of different joints with each other
12
Q
What part of the brain is effected in ataxia and what are the symptoms?
A
cerebellum
clumsy, awkward gait
13
Q
What does the supplementary motor cortex do? What effect does excitation usually have?
A
- positions body and head for the fine motor control movements of the arms and hands
- excitation causes bilateral contraction
14
Q
What are the characteristics of the lateral corticospinal tract?
A
- crosses in the medulla
- terminates on interneurons in spinal cord
- gross motor movements
15
Q
What are the characteristics of the ventral corticospinal tract?
A
- cross in spinal cord throughout neck and upper thoracic
- bilat control of postural muscles
16
Q
What do the alpha motor neurons innervate?
A
large skeletal msucle fibers
17
Q
What is th emotor unit of the alpha motor neurons?
A
several to several hundred individual skeletal muscle fibers
18
Q
What do the gamma motor neurons innervate?
A
intrafusal fibers
maintain basic muscle tone
19
Q
What are interneurons responsible for?
A
intergration of information
-make up many different circuits within the spinal cord
20
Q
Dynamic vs, static neruons in the excitation of spinal cord motor neurons
A
dynamic: initial neuron excitation–> very high rate and intitiates a rapid development of force
static: fire much slower but maintain the force of contraction
21
Q
muscle spindles give information about…
A
muscle length and rate of change in length
22
Q
golgi tendon organs (GTOs) give information about…
A
tendon tension and rate of change in tension
23
Q
What are the two ways that the sensory fibers of the muscle spindle can be excited?
A
- lengthening the muscle will stretch the spindle
- contraction of the end portion of th emuscle spindle fiber
24
Q
What are the sensory fibers (group IA) of the muscle spindle?
A
primary ending- connects to both bag and chain fibers
secondary ending- excited only by chain fibers
25
Does the center of the muscle spindle have contractile proteins?
no
| thats why it sensory
26
What is the static response of the muscle spindle?
during slow stretch the number of impulses transmitted is directly proportional to the degree of stretch
27
What sensory fibers of the muscle spindle are activated in static response?
both primary and secondary
28
What is the dynamic response of the muscle spindle?
during rapid stretch the primary ending is stimulated powerfully, transmits a tremendous excess of impulses
29
What is the stretch (myotatic) reflex?
- when a msucle is stretched, it contracts and maintains increased tonus (stretch reflex)
- very sudden muscle stretch causes tendon reflex
- reciprocal inhibition prevents muscles from working against each other
30
When a muscle is stretched by tapping its tendon with a reflex hammer, that information is carried to where?
the spinal cord by a 1a afferent axon
31
Where does the 1a fibers synapse in deep tendon reflexes?
directly on alpha motor neurons that innervate the muscle
| the alpha motor neurons fire and muscle contracts
32
When does the golgi tendon reflex occur?
excessive tension on tendon inhibits motor neuron
| also functions when muscle contacts unevenly
33
what is the tendon reflex and an example?
reflexive contraction of a muscle when its tendon is tapped
| -knee-jerk reflex is a monosynaptic reflex
34
What is the reciprocal inhibition?
reflex phenomenon that prevents muscles from working against each other by inhibiting the antagonist
35
What are the 8 parts of the patellar tendon reflex arc?
1. extensor muscle stretched
2. muscle spindle stimulated
3. primary afferent neuron excited
4. primary afferent neuron stimulates alpha motor neuron to extensor muscle
5. alpha motor neuron stimulates extensor muscle to contract
6. primary afferent neuron stimulates inhibitory interneuron
7. interneuron inhibits alpha motor neuron to flexor muscle
8. flexor muscle (antagonist) relaxes
36
When does flexor withdrawal reflexes occur?
during withdrawl of foot from pain
37
What are the 6 steps of flexor withdrawl reflexes?
1. stepping on glass stimulates ppain receptors in right foot
2. sensory neuron activates multiple interneurons
3. Ipsilateral motor neurons to flexor excited
4. Ipsilateral flexor contracts
5. contralateral motor neurons to extensor excited
6. contralateral extensor contracts
38
How are movement patterns performed? What are some examples?
- performed by initiation in cortex and maintained with pattern generation centers within the spinal cord
- walking, scratching, posture
39
What do lesions of the pyramidal tract do?
abolishes fine grasping movement
40
Motor control pathways have a high level of convergence in order to provide high level of muscle control. What are the motor control pathways?
```
Propriospinal
Corticospinal
Rubrospinal
Reticulospinal
Tectospinal
Vestibulospinal
```
41
What special functions does the brainstem control?
```
Respiration
Cardiovascular
Partial GI
Stereotyped movements
Equilibrium
Eye movements
```
42
What does the pontine reticular nuclei of the brainstem control?
excite the axial muscles of the boyd
| vertebral column and extensor muscles of the limbs
43
What does the medullary reticular nuclei of the brainstem control?
counterbalance signals from the pontine reticular nuclei
44
What does the vestibular nuclei of the brainstem control?
function in association with the pontine reticular nuclei to control antigravity muscles
45
What are main functions of the cerebellum?
responsible for coordination of rapid movement activities, sequence motor activation, makes correctvie adjustments while activities are being executed
46
What portion of the cerebellum controls motor execution?
spinocerebellum
47
What portion of the cerebellum controls motor planning?
cerebrocerebellum
48
What portion of the cerebellum controls balance and eye movement?
vestibulocerebellum
49
What do the topographical sections of the cerebellum control?
vermis--> axial muscles
intermediate zone--> upper/lower limbs
lateral zone--> higher order planning/coordination
50
What connect the motor cortex with the lateral zones of the cerebellum?
corticopontocerebellar
51
What is the feedback system of the ventral spinocerebellar?
the ventral spinocerebellar is excited by motor signals arrivings in the sminal cord
the feedback systen tells the cerebellum what signals have arrived
used to compare what is happening with what is supposed to happen
52
Deep nuclei receive information from where?
cerebellar cortex & deep sensory afferent tracts to the cerebellum
53
What are the 2 efferent pathways from the cerebellum (beginning with vermis and intermediate zone)?
- vermis--> fastigial nucleus--> pontine brainstem(equilibrium)
- intermediate zone --> interposed nuclei--> thalamus--> cortex--> thalamus--> basal ganglia--> red nucleus and reticular formation (coordination of reciprocal contraction of agonist and antagonist muscles of the limbs)
54
What are the climbing fibers in the cerebellar cortex?
they are what always produces a single, prolonged AP in each purkinje cell they contact
55
What are the mossy fibers in the cerebellar cortex?
very weak synaptic connections with purkinje cells
| therefore requires a lot of mossy fibers to excite a purkinje cell
56
Damage to the vestibulocerebellum
equilibrium is disturbed during the performance of rapid motions and during change in direction
57
spinocerebellum is responsible for
coordination of the movement of the limbs
58
intermediate zone of the spinocerebellum
compares the intended sequential plan of movement with the actual movements
59
interposed nuclei of the spinocerebellum
send corrective signals to the cortex thru the thalamus
| send corrective signals to the red nucleus
60
how does the planning of sequential movement from the cerebrocerebellum work?
communicates with premotor and sensory cortices
| dentate nuclei coordinate this information
61
how does timing of sequential movements from the cerebrocerebellum work?
loss of dentate nuclei--> failure of smooth progression of movements
62
cerebellar disorder ataxia
uncoordinated, clumsy gait
63
cerebellar disorder dysmetria
abnormal overshoot or undershoot
64
cerebellar disorder dysrhythmia
abnormal rhythm and timing of movements
65
cerebellar disorder dysdiadochokinesia
patient cannot perform rapidly alternating movements
66
What is the basal nuclei?
masses of cerebral gray matter buried deep in the white matter, lateral to the thalamus
67
What are the functions of the basal nuclei?
- recevies input from the substantia nigra of the midbrain and the motor areas of the cortex
- sends signals back to both these locations
- involved in motor control
68
Basal ganglia
accessory motor system
| -receive most input from the cerebral cortex and return most output to the cerebral cortex
69
what are the components of the basal ganglia circuitry?
```
Caudate nucleus
Globus pallidus
Putamen
Substantia nigra
Subthalamic nucleus
```
70
Putamen circuit of the basal ganglia
- execution of learned patterns of movement
- inputs mainly from the premotor and supplemental motor cortex
- outputs back to the primary motor cortex
71
What 3 things can be caused by damage to the putamen circuit of the basal ganglia?
- athetosis--> spntaneous often continuous writhing movements
- hemiballismus--> flailing movements
- chorea--> flicking movements
72
Caudate circuit of the basal ganglia
cognitive control of motor acitvity
73
output from the caudate circuit of the basal ganglia
premotor and supplemental motor cortex
74
input from the caudate circuit of the basal ganglia
association areas of the cerebral cortex
75
What is responsible for planning which patterns of movement will accomplish the complex goal of fleeing from a lion?
caudate circuit of the basal ganglia-- puts together sequential patterns of activity lasting 5 or more seconds
76
What causes parkinsonism?
loss of dopamine which decreases thalamocortical excitation
77
what are 5 characteristics of parkinson's?
1. bradykinesis
2. rigidity
3. gait instability
4. resting tremor
5. masked face
78
Why is Parkinson's treated with L-dopa and not just dopamine?
L-dopa crosses the BBB
79
Loss of pigmentation in the substantia nigra is indicative of....
a loss of dopaminergic neurons (Parkinson's)
80
L-Deprenyl is also a treatment for Parkinson's; what does it do?
inhibtis MAO, dopamine remains in the synaptic cleft longer
