Brain and Behavior
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Upper motor neurons are located in the cerebral cortex and the ___ nuclei (3) in the brainstem.
- red nucleus in the midbrain
- vestibular nuclei in the caudal pons/ medulla
- reticular nuclei in the medulla and pons
maintenance of the body’s center of gravity (CG) over its base of support
overall position of limbs & body in space & relative to one another
position in which lower limbs support the rest of the vertically-oriented body
position of body parts for balance in the bipedal position against gravity
adjustment of position of some parts of the body (especially trunk & proximal limbs) in anticipation of purposeful movements of other parts.
state of contraction of any muscle of the body when it is not working against gravity or in a purposeful movement
resting muscle tone
The __ are primitive, powerful and rapid motor centers for maintaining whole-body balance in space. They work primarily on a reflex basis, responding to peripheral receptors that sense shifts in ones center of gravity.
Major input to vestibular nuclei:
a) peripheral receptors:
- ____ receptors (for head position sense)
- ____ (body position sense)
- _____receptors (indirect path via cerebellum)
Major outputs of vestibular nuclei:
- bilateral spinal lower motor neurons for trunk and proximal limbs via ___ tracts
- bilateral brainstem extraocular lower motor neurons via the ____
- ____ neurons for resting muscle tone.
- gamma motor
True or False:
The vestibular nuclei rely on cortical input for balance adjustment.
- Vestibular nuclei
- Vestibular fibers -> MLF and vestibulospinal tracts
The brainstem ___ ___ are groups of cells in the pontine and medullary reticular formation
that process motor information.
When the motor cortex sends orders for voluntary movements, it notifies the _____ to “take care of” proximal body posture in advance of movements of distal body parts.
The reticular nuclei receive input from:
1) _____ cortex
- motor cortex (positional changes )
- receptors (current position )
- cerebellum -postural adjustments based on previously stored “motor memories” of postural set in the cerebellum.
The ____ sends fibers bilaterally to lower motor neurons via multiple reticulospinal tracts, for preparatory postural adjustments based on previously stored “motor memories” of postural set.
The red nucleus of the midbrain is mainly
involved in ____of the proximal upper limb, as a part of the postural set to position the hand for
use as a tool (rather than use the upper limb as a body support). Its axons cross the midline in the
___ midbrain and descend in the _____ and lateral white matter of the spinal cord as
the rubrospinal tract.
- reticular formation
The red nucleus has major input from:
___cortex, ___, and __.
Output: _____ fibers that decussate at the level of the red nucleus and that supply contralateral ___ __ __, mainly of the proximal flexors of the upper limb.
- lower motor neurons
Which nucleus has the following function:
Postural adjustments of the upper limb during reach, retrieval, and stable positioning of objects in the hand.
The red nucleus in the midbrain
The ___ ___ may be able to initiate voluntary flexion at the shoulder, elbow, and wrist after cortical upper motor neuron lesions.
Fibers of the rubrospinal tract descend in the spinal cord adjacent to the ___ ____ ___(the path for voluntary movements of the distal hand and foot).
lateral corticospinal tract
The vestibulospinal and reticulospinal tracts travel in the ____ white matter of the spinal cord. The rubrospinal tracts travels in the ___ ___ near the lateral corticospinal tract.
From vestibular & reticular nuclei:
- axons descend _____ (uni or bilaterally ?) through the ___ ____ of brainstem and ventral white matter of
- axons from each group send terminals to LMN ___(uni or bilaterall?)
-crossing/partial crossing near __ __ __
- lower motor neurons
From red nucleus, axons:
-cross the midline at the level of the ____
-descend through __ ___ of brainstem & ___ ___in spinal cord as the rubrospinal tract
-supply LMN __ (uni or bilaterally?)
- nucleus in the midbrain
- reticular formation
- lateral columns
movements at joints or digits of one hand that are independent of other
digits during a single action. Example: movements of different fingers while playing the piano.
cortical upper motor neurons; located in the precentral gyrus + anterior paracentral lobule
primary motor cortex (M-1):
can be looked at as a type of primary motor cortex for voluntary saccades; located in the lateral frontal cortex, anterior to the premotor area
- frontal eye field:
located anterior to the lateral primary motor cortex
motor planning cortex; anterior to the upper lateral and medial parts of the primary motor cortex
- supplementary motor area (SMA):
motor planning cortex for movement sequences that produce language symbols; located on one side only (usually the left)
Broca’s motor speech area
What area of the cortex specializes in selection of the anticipatory postural set of proximal muscles for voluntary movements?
Premotor Area (PMA):
What area of the cortex specializes in planning complex movement sequences, such as those that require fractionated (independent) movements of the digits and those that require simultaneous, independent movement of the two hands (bimanual movements) - used in visually-guided movement imagery?
Supplementary motor cortex
The premotor cortex and supplemental cortex receive input from the:
- lateral prefrontal cortex (decision)
- sensory association cortex (body position)
- basal ganglia (circuits for selection of motor sequences)
What is the main blood supply to the precentral gyrus and frontal eye field?
middle cerebral artery
What is the blood supply to the paracentral lobule?
The anterior cerebral artery
A lesion of the anterior cerebral artery will most likely display as motor defecits to what part of the body?
knee and below
A lesion of the middle cerebral artery will show motor deficits in what area of the body?
above the knee and frontal eye field
The corticospinal tract travels through the internal capsule in the forebrain, the ___ of the brainstem, and the ____ matter of the spinal cord. The ventral part of the tract contains fibers to the ___,__,__ and the lateral part fibers to the ___ ___.
- proximal parts ie: shoulder hip and trunk
- distal limbs
The corticobulbar fibers travel through the ___ in the forebrain. These fibers descend and supply most brainstem LMN __ (uni or bilaterally?) Fibers of this tract also go to brainstem motor centers such as __ and __ nuclei.
- Red and reticular
Corticospinal tracts pass from cerebral cortex through deep white matter & _____.
Corticospinal tracts in the internal capsule:
corticobulbar fibers (head muscles):___
corticospinal fibers (trunk & limb muscles): ___
fibers from frontal eyefield: ___
- posterior limb
- anterior limb
Blood supply to deep white matter & internal capsule: lateral & anterior _____
- striate arteries
- choroidal artery
Corticospinal fibers in the midbrain pass through the middle of the ___ ___. The corticobulbar fibers will be ___. The corticospinal fibers of the ____ will be intermediate and ____ will be lateral.
- basis pedunculi/cerebral peduncles
- upper body
- lower body
Cortical fibers pass through the ___ ___ of the midbrain but do not supply fibers to the oculomotor nucleus.
Some corticospinal fibers in the pons send terminals to the ___ nuclei and ___ nuclei bilaterally. Some terminals are also sent to the ___ nucleus at this level.
- Trigeminal and reticular
The corticospinal tracts regroup to form the ___ in the medulla. Other fibers peel away to send terminals to the ___ nucleus, the nucleus ambiguous, and the ___ nuclei bilaterally.
Unilateral lesions of the UMN coticobulbar system cause paralysis of the___ (contralateral or ipsilateral?) lower facial muscles; while a unilateral lesion of the LMN facial motor nucleus/nerve root often causes paralysis __ (contralateral or ipsilateral?) of all facial muscles.
At caudal end of medulla all remaining fibers are corticospinal. 90% cross at decussation of pyramids to form ___ ___ __. The remaining 10% continue ipsilaterally into spinal cord as __ ___ __.
- lateral corticospinal tract
- Ventral corticospinal tract
In the spinal cord the lateral corticospinal tract: travels in the lateral white matter on the same side as it’s targets (GSE motor nuclei to muscles of the distal upper and lower limbs, especially digits, hands, wrist, toes, feet, ankle) and terminates at/near __ __ __of the anterior horn in only the cervical & lumbosacral enlargements.
lateral motor nuclei
The ventral corticospinal tract travels in the ventral white matter and terminates at __ __ __bilaterally at all levels of spinal cord and directs voluntary control of coarse, proximal (trunk, girdle) movements.
medial motor nuclei
What has exclusive control of fine, manipulative movements of distal limbs, especially digits
The lateral corticospinal tract and lateral motor nuclei
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