control of posture and locomotion

Question 1

Lateral vistibulospinal tract

Answer 1

• Origin = lateral vestibular nucleus
• Descends to ALL spinal cord levels
• Function: facilitates alpha and gamma motor neurons of extensors muscles
• -> provides way for vestibular input to affect posture

Question 2

Medial vestibulospinal tract

Answer 2

• Origin = medial and inferior vestibular nucleus
• descends to upper thoracic cord
• FUNCTION: reflex head movements in response to vestibular stimuli
• -> adjust the position of the head in response to postural change

Question 3

Pontine reticulospinal tract

Answer 3

• ORIGIN = pontine reticular formation
• Descends to all levels of SC
• FUNCTION; adjustment of posture and body balance by facilitating alpha and gamma motoneurons to extensor muscles

Question 4

Medullary reticulospinal tract

Answer 4

• ORIGIN = medullary reticular formation
• FUNCTION: inhibit voluntary and cortically induced movement
• -> activation of this pathway DECREASES MUSCLE TONE
• -> inhibitory effect ons pinal reflexes and cortically induced movement (lesion to this tract leads to disinhibition contributing to spasticity)

Question 5

Reticulospinal system

Answer 5

• Function: modulate reflex action during movement
• -> integrates vestibular and other sensory input with motor commands from cerebral cortex
• -> role of making anticipatory postural adjustments to prepare for cortically controlled movements
• activating locomtion and controlling its speed

Question 6

tectospinal tract (colliculospinal tract)

Answer 6

• ORIGIN = superior colliculus
• projects to cervical spinal cord
• FUNCTION: important in coordinating head and eye movements
• -> can cause movement of the head in response to visual, auditory and somatic stimuli

Question 7

Sensory input for Vestibulocollic reflex

Answer 7

• Proprioceptive input fro neck muscle spindles and joint receptors in the NECK

Question 8

Sensory input for vestibulospinal reflex

Answer 8

• turning of head activates postural change in opposing side limb muscles
• ACTS ON THE LIMBS

Question 9

sensory input for cervicocollic reflex

Answer 9

• neck reflexes reacting on neck muscles contract stretched neck muslces: act synergistically with vestibulocollic reflexes
• Acts on the neck

Question 10

sensory input for Tonic neck reflexes

Answer 10

• In children AKA asymmetrical tonic neck reflex; head turned to one side, limbs on that side extend and other limbs flex; seen in adults when posture requires accurate control or upon vestibular damage
• acts on the neck and limbs

Question 11

describe asymmetrical tonic neck reflex

Answer 11

• AKA obligatory tonic neck reflexes
• seen in young infants
• head turned to one side, limbs on that side extend while opposite limbs flex
• almost identical to adult tonic neck reflex

Question 12

• Describe FEED-FORWARD mechanisms for controlling posture

Answer 12

• ANTICIPATE or PREDICT the effect of environmental distrubances (or mtoor command) wil have on variable to be controlled
• apply corrective action before there is error (postural adjustment

Question 13

describe feedback (aka compensatory) mechanisms for controlling posture

Answer 13

• Appropriate correct is applied AFTER ERROR id detected (loss of balance)
• automatic adjustments can be very rapid and improve with practice and learning
• Anticipatory mechanisms can sometimes predict postural disturbances and preprogram what stabilizing response will occur

Question 14

describe swinging room experiment in relationship to the role of vision in postural stability

Answer 14

• SWINGING ROOM EXPERIEMENT: when the room approaches, the subject sways back to avoid falling forward
• -> when the room moves away from the subject, the subject sways forward to avoid falling back
• toddlers can have difficulty standing with their eyes close and can fall easily during test since their posture is dependent upon vision
• adults just increase their body sway

Question 15

what sensory system involved in control of posture

Answer 15

• vestibular system = senses body sway through head motion
• Proprioceptive (muscle spindles, GTO, joint receptors)
• cutaneous receptors (touch and pressure)
• visual

Question 16

Define posture

Answer 16

• overall position of the body and limbs relative to each other and orientation of body and limbs in space

Question 17

what are the behavior functions of postural adjustment

Answer 17

• support head and body vs gravity and external forces
• keep center of gravity of body aligned and balanced over base of support on ground (maintain steady state)
• stabilize supporting parts of the body during movement of other parts (especially anticipatory movements)
• SYSTEM MUST BE ADAPTABLE

Question 18

Decerebrate posture

Answer 18

• Extension of all four limbs and neck
• can be intermittent or seen in response to noxious peripheral stimuli
• humans show this posturing after lesion of the UPPER PONS
• -> lesion below red nucleus but above the vestibular nuclei, the lateral vestibulospinal tracts increase their facilitation of extensor motor neurons, which is responsible for decerebrate posturing

Question 19

Decorticate posture

Answer 19

• arms are flexed and legs are extended when patient is lying on their back with head facing straight forward
• posture RESULTS from LESIONS of internal capsule that release both vestibulospinal and tonic neck reflexes from cortical control
• IF head is turned, you will see obligatory neck reflexes