Postural Stability, Orientation, Praxis Flashcards
Define postural stability
Maintaining position
Define orienting movements
Movements that turn the body toward a sensory stimulus
Define voluntary actions AKA praxis
Includes speech, facial expressions, reaching, grabbing, holding, playing
Medial tracts function in
A) Orientation
B) Praxis
C) Posture
A and C (orientation and posture)
Lateral tracts function in
A) Orientation
B) Praxis
C) Posture
B (Praxis)
The lateral vestibulospinal tract, reticulospinal tract, and anterior corticospinal tract function in what?
They are parts of the medial tract that function in posture
The medial vestibulospinal tract and tectospinal tract function in what?
They are parts of the medial tract that function in orientation
The lateral corticospinal tract, corticobulbar spinal tract, and rubrospinal tract function in what?
They are parts of the lateral tracts that function in praxis
Which tracts function in complex movements?
Corticospinal and corticobulbar tracts
Complex movements require __________ projections while simple movements require ____________ projections
Direct; indirect
What are the direct projections involved in complex movements?
From motor control centers to motoneurons
What are the indirect projections involved in simple movements
From motor control centers through motor interneurons to motoneurons
Which tracts are involved with simple movements?
All descending tracts
What is the affect of a motoneuron lesion on volitional movement
Weak or none
What is the affect of a motoneuron lesion on reflexive movement
hyporeflexia or areflexia
What is the affect of a motoneuron lesion on muscle tone
Decreased or absent
What is the affect of a motoneuron lesion on muscle appearance
Moderate to severe atrophy from disuse
What is the affect of a motoneuron lesion on EMG findings suggestive of muscle denervation
Fibrillations, fasciculations
What is the effect of a lesion of descending tracts (corticospinal included) on volitional movement
None: paralyzed (if corticospinal tract is involved)
What is the effect of a lesion of descending tracts (corticospinal included) on reflexive movement
Hyper-reflexia
What is the effect of a lesion of descending tracts (corticospinal included) on muscle appearance
Mild atrophy from disuse mitigated by the hyper-reflexive use
What is the effect of a lesion of descending tracts (corticospinal included) on EMG findings suggestive of muscle denervation
Typically transient if present
Medial tracts correspond with ____________ and _________
posture and orientation
Lateral tracts correspond with _______
Praxis
Motoneuron death results in ___________
no movement, hypo/areflexia, atrophy
Motor tract lesions result in _______________
no volitional movements, hyperreflexia, no atrophy
Difficulty of holding a posture depends on what 2 things?
Center of mass and support surface
What is a “support surface”
Point at which the body touches the ground
Which of the following positions is easiest and why?
A) Lying prone
B) Sitting
C) Bipedal upright
A) lying prone because it has the maximum support surface
Which of the following positions is most difficult and why?
A) Lying prone
B) Sitting
C) Bipedal upright
C) Bipedal upright because there is limited support surface
Center of force must lie over ______________
support surface
What is the force equation?
Mass x acceleration = force
Feed forward reflexes are engaged in ______________
standing
Postural adjustments only occur when there is perturbation or a disturbance of equilibrium - true or false?
FALSE: Postural adjustments occur in the absence of any actual perturbation, precluding any disturbance of equilibrium before it happens
Somatosensory afferents detect and signal unexpected forces that impact the COM and elicit feedback corrections from _______________
Descending postural motor tracts
Give the pathway for the descending postural tract
Feedforward adjustments –> descending postural tract –> motor interneurons
LVST and RST terminate on _____________
Gamma motoneurons–> gamma loops –> alpha motoneurons
Which motoneuron elicits a contraction?
Alpha-motoneurons
How do descending postural tracts play a role in feedback?
By modifying corrective reflexes
Reversal of ___ reflex from inhibition to excitation happens in the feedback by descending postural tracts
lb
Increased sensitivity of ___ reflex during equilibrium instability happens in feedback by descending postural tracts
la
What are the postural descending tracts?
Lateral vestibulospinal tract (LVST), reticulospinal tract (RST), and anterior corticospinal tract (ACST)
What input does the superior colliculus receive?
Primarily visual, but also auditory and somatosensory
Define sensory-motor transformation
Transformation of sensory input by the superior colliculus into a motor map
Give the pathway for orienting movements
Sensory information –> superior colliculus –> tectospinal tract –> interneurons and central pattern generators in the brainstem and cervical spinal cord –> orienting movement of shoulders, neck, and eyes toward a stimulus on the opposite side
Define praxis
Physical actions that arise from cognitive processes, including internal thoughts and perceptions of external events
What is the function of the rubrospinal tract in praxis?
Fundamental gross movements
What is the function of the lateral corticospinal tract in praxis?
Volitional movements of skeletal muscles in the neck, body, and limbs
What is the function of the corticobulbar tract in praxis?
Volitional movement of the skeletal muscles in the oral cavity, larynx, and face
What is the origin of the rubrospinal tract?
Red nucleus
Where does the rubrospinal tract cross?
At the midline at the level of the red nucleus
What does the rubrospinal tract end in?
Spinal cord ventrolateral to the sorticospinal tract
What does the rubrospinal tract support?
Posture, locomotion, and reaching
Give the pathway of fine voluntary movements
Cortex (primary motor, somatosensory areas of parietal, premotor, and supplementary motor) –> corticospinal and corticobulbar tracts –> interneurons and motoneurons in the spinal cord and cranial nerve nuclei
Define somatotopy
Relative cortical area controlling different body parts related to the precision with which movements of the regulated muscles are controlled
Give the detailed pathway of fine voluntary movements
Cortex –> corticospinal and corticobulbar tracts –> internal capsule –> cerebral peduncle –> pons-pontine nuclei –> medulla-pyramid –> spinomedullary junction
Voluntary control of muscles on one side of the body depends on neurons in the motor cortex on which side?
Contralateral (opposite)
What is the function of the corticobulbar tract at the termination site of the motor trigeminal nucleus?
Muscles for chewing
What is the function of the corticobulbar tract at the termination site of facial nucleus
Muscles of facial expression
What is the function of the corticobulbar tract at the termination site of nucleus ambiguous
Laryngeal and upper airway muscles
What is the function of the corticobulbar tract at the termination site of the spinal accessory nucleus (spinal cord)
Muscles used for shrugging the shoulders and turning the head
What is the function of the corticobulbar tract at the termination site of the hypoglossal nucleus
Control tongue muscles
What are clinical signs of a unilateral dysfunction of the corticobulbar tract at the termination site of the motor trigeminal nucleus?
No discernible deficit, chewing muscles receive bilateral inputs
What are clinical signs of a unilateral dysfunction of the corticobulbar tract at the termination site of the facial nucleus
Loss of expressions in the contralateral lower face
What are clinical signs of a unilateral dysfunction of the corticobulbar tract at the termination site of the nucleus ambiguous
Deficits in swallowing or articulation
What are clinical signs of a unilateral dysfunction of the corticobulbar tract at the termination site of the spinal accessory nucleus (Spinal cord)
Weakness in shrugging the ipsilateral shoulder and rotating the head to look contralaterally
What are clinical signs of a unilateral dysfunction of the corticobulbar tract at the termination site of the hypoglossal nucleus
Contralateral loss, tongue sticks out toward the side fo the lesion
Corticobulbar tract ALWAYS controls motoneurons and movements contralateral to the side of origin - true or false?
FALSE; it does not always do this
Fine control of muscles in the bottom half of the face are important for which activities?
Eating and speech
Does the corticobulbar tract directly or indirectly innervate the motoneurons that control muscles of facial expression?
Directly
Is the top half of the human face primarily under direct or indirect motor control?
Indirect
Is corticobulbar tract innervation of facial motoneurons controlling the upper face muscles mostly unilateral or bilateral?
Bilateral
What is the advantage of direct projections of the corticobulbar tract from motor control centers to motoneurons?
Support of the ability to deliberately make fine movements
What is the advantage of indirect projections of the corticobulbar tract from motor control centers to motoneurons?
Support of simple bilateral movements; may support fine movements but requires practice to successfully engage this
Which is easier, fine control of the bottom half of the face or the top half?
Bottom half
Control of the top half of the face is dictated by what part of the brain?
Anterior cingulate gyrus
Control of the bottom half of the face is by what part of the brain?
Primary motor cortex
What is the outcome of a facial motoneuron lesion?
Cannot move the face on the side of the lesion
What is the outcome of a supranuclear (above the facial nucleus) lesion
Impacts the bottom half of the contralateral face musculature; can’t lift mouth on the side of the lesion to smile; can frown bilaterally
What is the effect on emotionally motivated movements by a corticobulbar lesion?
Can’t make facial expressions voluntarily, but CAN make reactions emotionally
What part of the brain controls volitional movement of the brain (mostly the contralateral bottom half)
Primary motor and premotor cortices
What is amimia
The ability to make voluntary facial expressions in response to a command, but not in association with an emotion
What part of the limbic system control emotional facial expressions of the top half of the face?
Anterior cingulate gyrus
Which part of the cortex is involved in communication being a reason for action (i.e., people reacting to verbal requests)?
Primary motor cortex
Which part of the cortex is involved in internal reasons for action (i.e., internal thoughts, emotions, motivations)
Supplementary motor area
Which part of the motor cortex is involved in external reasons for action (i.e., reactions to objects or stimuli in the environment)?
Premotor cortex
