Postural Control & Locomotion pp Flashcards
Ventromedial P/W’s
Both lateral vestibulospinal tract & reticulospinal tract
extend length of spinal cord. Facilitate motor neurons of extensor muscle.
Extensor drive cause of decerebrate posturing
Medial Vestibulospinal Tract
Only descends as far as upper thoracic cord
FX: is mediation of reflex head movements in response to vestibular stimuli.
Reticulospinal System
Role in anticipatory postural adjustmants to prepare cortical controlled movements
Activating locomotion & controlling its speed
Colliculospinal Tract
aka TECTOSPINAL Tract
Origin in superior colliculus & projects to the cervical S.C.
Major output to S.C via reticular formation
Posture
Overall position of the body & limbs relative to each other & orientation of body & limbs in space
FX of Postural Adjustments
Support head & body against gravity & external forces
Keep center of gravity & balance over base of support
Sensory influences on postural control
Vision
Vestibular
Somatosensation
Visual Kinesthesis
Dependent on internal sensors & external stimuli
Normal sway but increases in swinging room
Feeling of visual kinesthesis
Compelling feeling of body movement when large part of a persons visual field is moving
ex. IMAX
Vection
Is the perception of self motion induce by visual stimuli
Vestibular system is to suppress the sense of self generated movement
Postural Reflexes
Head position Visual input Vestibular input via vestibulocollic Neck reflexes acting on muscles Proprioceptive input from neck muscle spindles
Decerebrate posture problem
Upper pontine damage
Decorticate postures problem
Upper midbrain damage
Decerebrate posturing
Lesions caudal to red nucleus but rostral to the lateral vestibular nucleus.
Patient extensions of both arms & legs w/ arching of back & dorsiflexion of head & feet plantar flexed
Decorticate rigidity
Lesion is in a supratentorial, causes central herniation the patient will switch to decerebrate posturing
Postural Stability in Humans
Maintained by continuously monitoring posture & making appropriate adjustment
Increasing or decreasing the strength of reflexes
Control of locomotion
Spinal cord contains stepping pattern generators for each limb
Oscillatory - alternating flexion & extension during locomotion
Gamma Rigidity
gMN are excited enough will cause contraction of intrafusal fibers which stimulates 1a afferents from the muscle spindle loop to aMN cause contraction of muscle
Decerebrate rigidity
Through gamma loop
Posterior roots cut loses its hypertonus
Interferes w/ 1a activates extensor aMN
Dorsal Rhizotomy
Child w/ cerebral palsy
Excessive spasticity in his legs, can be decreased by cutting some rootlets
Decreasing effect of gamma loop
