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martin chapter 10 Flashcards

1
Q

4 major components of the motor system

A
  1. descending cortical and brain stem pathways
  2. motor neurons and interneurons of the spinal cord
  3. basal ganglia
  4. cerebellum
    basal ganglia and cerebellum influence movements through connections to the cortical and brain stem motor pathways
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2
Q

spinal motor circuits are comprised by?

A

motor neurons and interneurons

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3
Q

where are motor neurons (that innervate limb muscles) and interneurons from which they receive inputs?

A

they are located in the lateral ventral horn and intermediate zone of the spinal cord

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4
Q

where are motor neurons that innervate axial and girdle muscles (ie neck and shoulder muscles) and their associated interneurons?

A

medial ventral horn and intermediate zone of spinal cord

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5
Q

the intermediate zone of the spinal cord corresponds to?

A

the spinal grey matter lateral to the central canal

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6
Q

where are motor neurons and interneurons that control muscles of the head (including facial muscles) located?

A

in the cranial nerve motor nuclei and the reticular formation

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7
Q

difference between a spinal motor circuit and descending motor pathway

A

spinal motor circuit=
Exists within the spinal cord itself.
Made up of local interneurons, motor neurons, and sometimes sensory neurons.
Responsible for basic movements like reflexes (e.g., knee-jerk reflex) and central pattern generators (for walking, swimming, etc.).
Can function independently of the brain — for example, you can still have a reflex even if the spinal cord is severed from the brain.

Descending Motor Pathway:
Comes from the brain (like from the motor cortex or brainstem) and travels down to the spinal cord.
Carries commands from the brain to the spinal motor circuits.
Modulates, initiates, or refines movement by influencing the activity of spinal motor circuits.

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8
Q

motor unit

A

a single motor neuron innervates a limited number of fibers within a muscle
each muscle fiber is innervated by exactly one motor neuron
NB: no muscle fiber receive input from more than one motor neuron

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9
Q

what is the upper motor neuron?

A

the cell of origin of the motor pathway
typically are neurons in the cerebral cortex that project directly to the spinal cord via the corticospinal tract

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10
Q

what are lower motor neurons?

A

-are the commonly named motor neurons
-neurons in the brain stem or spinal cord that innervate muscle fibers

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11
Q

the descending motor pathways, in addition to movement control regulate?

A

somatic sensory processing (our ability to feel touch, pressure, vibrations…) and the autonomic nervous system

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12
Q

3 motor control pathways that originate in layer V of the cerebral cortex (primarily in the frontal lobe) and terminate in motor centers of brain stem and spinal cord

A
  1. lateral corticospinal tract
  2. ventral (anterior) corticospinal tract
  3. corticobulbar tract (which terminates primary in cranial nerve motor nuclei in the pons and medulla and is the cranial equivalent of the corticospinal tracts)
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13
Q

4 motor control pathways that originate from brain stem nuclei and terminate in motor centers of brain stem and spinal cord

A

rubrospinal tract
reticulospinal tract
tectospinal tract
vestibulospinal tract

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14
Q

the cortical motor regions project to which brain stem nuclei?

A

the red nucleus
the superior colliculus
reticular formation
vestibular nuclei
NB: the cerebral cortex can also influence movements through indirect brain stem connections

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15
Q

which are the 2 lateral motor pathways?

A

lateral corticospinal tract
rubrospinal tract
they control muscles predominantly on the contralateral side of the body

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16
Q

which is the principal motor control pathway in humans?

A

lateral corticospinal tract

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17
Q

fractionation

A

loss of the ability to move one joint independent of others

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18
Q

what are the pre motor cortical regions?

A

supplementary motor area, cingulate motor area, pre motor cortex

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19
Q

what’s the major site of origin of the lateral corticospinal tract?

A

it is the primary motor cortex
axons also originate from the pre motor cortical regions and the somatic sensory cortical areas

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20
Q

where do descending axons from the primary motor cortex course within each cerebral hemisphere?

A

in the posterior limb of the internal capsule, lateral to the thalamus

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21
Q

where do descending axons from the primary motor cortex course in the midbrain?

A

in the basis pedunculi

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22
Q

the lateral corticospinal tract at a certain point disappear and reappear where?

A

on the ventral surface of the medulla as the pyramid

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23
Q

where do most of the axons in the lateral corticospinal tract decussate?

A

at the junction of the spinal cord and medulla
it is called pyramidal decussation

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24
Q

after decussating, the axons of the lateral corticospinal tract descend where?

A

in the dorsolateral portion of the lateral column of the spinal cord white matter
hence the name lateral corticospinal tract!

25
where does the lateral corticospinal pathway terminate?
in the lateral portion of the intermediate zone and in the lateral motor nuclei of the ventral horn of the cervical and lumbosacral cord (the locations of neurons that control arms and legs) some of these axons descend ipsilaterally, some others re-cross the midline within the grey matter in lamina 10 and descend controlaterally
26
where does the rubrospinal tract originate?
it originates from neurons in the red nucleus, primary from the caudal part. this portion is named magnocellular division because many rubrospinal tract neurons are large
27
where does the rubrospinal tract decussate and descend?
it decussate in the midbrain and descend in the dorsolateral portion of the brain stem.
28
where is the rubrospinal tract found in the spinal cord?
in the dorsal portion of the lateral column
29
where does the rubrospinal tract terminate?
into the lateral portions of the intermediate zone and ventral horn of the cervical cord. in humans this tract doesn't descend into the lumbosacral cord suggesting that it is involved in arms but not leg control
30
axial and girdle muscles are controlled by the 4 medially descending pathways:
ventral corticospinal tract reticulospinal tract tectospinal tract vestibulospinal tract
31
what are commissural interneurons?
interneurons whose axons decussate in the spinal cord
32
which type of control is exerted by the medial descending pathways?
bilateral control even though individual pathways may project unilaterally (either ipsilaterally or contra laterally) they synapse on commissural interneurons (whose axons decussate in the spinal cord)
33
origin of the ventral corticospinal tract
it originates from the primary motor cortex and the various pre motor areas
34
where does the ventral corticospinal tract descend?
it descends to the medulla along with the lateral corticospnal tract but it remains uncrossed and descends in the ipsilateral ventral column of the spinal cord
35
where does the ventral corticospinal tract terminate?
it terminates in the medial gray matter, synapsing on motor neurons in the medial ventral horn and on interneurons in the intermediate zone
36
the ventral corticospinal tract is preferentially involved in the control of?
neck, shoulders and upper trunk muscles because it projects only to the cervical and upper thoracic spinal cord
37
origin of the pontine reticulospinal tract and of the medullary reticulospinal tract
pontine one originates in the pontine reticular formation medullary one originates in the medullary reticular formation
38
where do the pontine and medullary reticulospinal tract descend in the spinal cord?
pontine: in the ventral column of the spinal cord medullary: ventrolateral quadrant of the lateral column they descend in the ipsilateral spinal cord but exert bilateral motor control effects
39
two vestibulospinal tracts
medial and lateral vestibulospinal tracts NB: the lateral vestibulospinal tract despite its name is a medial descending motor pathway they originate in the vestibular nuclei of the medulla and the pons and descend in the ventromedial spinal white matter
40
tectospinal tract
originates from neurons in the deeper layers of the superior colliculus (also named tectum) it projects only to the cervical spinal segments controls neck, shoulders and upper trunk muscles the tectum plays a key role in controlling eye movements and so the tectospinal tract plays a key role in controlling eye movements with head movements
41
4 separate motor areas have been identified in the frontal lobe
primary motor cortex 3 pre motor areas (supplementary motor area, pre motor cortex and cingulate motor area)
42
these frontal motor areas receive input from?
the motor thalamus that comprehends ventral lateral and ventral anterior thalamic nuclei
43
what's the principal thalamic relay nucleus for the cerebellum and for the basal ganglia?
for the cerebellum=ventral lateral nucleus for the basal ganglia= ventral anterior nucleus
44
the pre motor cortex has 2 distinct motor fields with separate sets of connections and distinctive functions:
dorsal and ventral pre motor cortices. each area is further functionally subdivided
45
which of the 2 subdivisions of the pre motor cortex contains mirror neurons?
the ventral subdivision these neurons fire when the animal performs a movement and when the animal watches someone else performing the same movements
46
the primary motor cortex receives inputs from 3 major sources
1. pre motor cortical regions 2. cortical somatic sensory areas (in parietal lobe) 3. motor thalamic nuclei
47
what is the corona radiata?
a portion of the subcortical white matter that contains descending cortical axons and ascending thalamocortical axons
48
where in the internal capsule the descending motor projection from the primary motor cortex to the spinal cord courses?
in the posterior part of the posterior limb
49
position of the descending projections from the pre motor areas within respect to those from the primary motor cortex
within the internal capsule ROSTRAL to those of the primary motor cortex
50
where are corticopontine axons and corticoreticular axons located?
in the internal capsule
51
what are the thalamic radiations?
are the ascending thalamocortical projections located in the internal capsule. the ascending projection from ventral anterior and ventral lateral nuclei of the thalamus course here.
52
main vessels that supply the internal capsule
posterior limb supplied by anterior choroidal artery anterior limb and genu supplied by branches of the anterior cerebral artery
53
the cerebral peduncle consists of
tegmentum and basis pedunculi
54
the substantia nigra is a nucleus that is part of?
the basal ganglia
55
3 kinds of spinal cord interneurons
segmental interneurons commissural interneurons propriospinal neurons
56
where are segmental interneurons primarily located
in the intermediate zone and in the ventral horn
57
how are the motor neurons that innervate a specific muscle positioned?
they are located within a column shaped nucleus that runs rosrocaudally over several spinal segments. these column shaped nuclei of motor neurons collectively form lamina IX
58

neuroanatomy (12 decks)

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