Posture and Locomotion Flashcards
What is a decerebrate posture?
Upper and lower limbs extend
What are two postural signs of damage to the brainstem?
Decerebrate
Decorticate
What is a decorticate posture?
Upper limbs flex
Lower limbs extend
Which limbs does the rubrospinal tract contribute to in humans?
Upper limbs only
What limb movements does the reticular formation influence?
Extension of upper and lower limbs
Where is the reticular formation?
Pons and medulla
What limb movements does the red nucleus influence?
Flexion of upper limbs
Where is the red nucleus?
Midbrain
What is the role of higher cortical centres on the reticular formation and red nucleus in terms of limb movement control?
Inhibits their outputs
What position does a lesion above the midbrain cause, and why?
Decorticate
Remove inhibition to reticular formation and red nucleus
Lower limbs extend because of reticular formation influence
Upper limbs flex because
- Red nucleus has larger effect than reticular formation
- Flexors of upper limb stronger than extensors
What position does a lesion at the midbrain cause, and why?
Decerebrate
Remove inhibition to reticular formation
Cut red nucleus itself
Upper and lower limbs extend because of reticular formation influence
What is the Babinski sign?
Fanning of toes (upwards plantar flexion) rather than curling of toes in response to noxious stimulus on sole of foot
Up to what age is the Babinski sign normal?
12-24 months of life - until child gets good at walking
How are upper motor neuron lesions for cranial nerve lesions identified?
Pattern of loss, rather than LMN/UMN signs seen with spinal motor output
Which non-ocular lower motor neurons (cranial nerves) receive bilateral corticobulbar innervation?
All except those innervating lower face and tongue
Which motor neuron is affected if there is weakness in the inferior muscles of the face only on one side?
UMN on contralateral side
Which motor neuron is affected if there is weakness in all the muscles on one side of the face?
LMN on ipsilateral side
Why is only the lower half of the face affected when there is an upper motor neuron lesion?
Forehead receives bilateral input from cingulate motor area, and contralateral input from primary motor cortex
If UMN lesion on one side, input from cingulate motor area on contralateral side still present, so control of forehead remains
Rest of face receives only contralateral input from primary motor cortex, so if UMN lost > no input
What are the first movements that occur when you are going to abduct a leg?
Postural adjustments in anticipation of activity > move body weight to other leg
When pulling on a handle on a wall, what happens first?
In anticipation of change in position, calf muscles contract to stabilise body
When does locomotor activity become present?
Very early in life
Where is the pattern for locomotor activity?
Spine
Which muscle group bears weight?
Extensors - no weight bearing when you flex
When is useful work done?
During extension
How do decerebrate cats increase speed when treadmill speed is increased?
Only source of input from muscle sense
Spinal circuits tell muscles to speed up because of pattern of activation detected by muscle spindles
What are some abnormal gait patterns associated with CNS disorders?
Ataxic gait
Choreiform gait
Hemiparetic gait
Parkinsonian gait
What is an ataxic gait?
Unsteady, uncoordinated walk
Wide base
Feet thrown out
Come down first on heel then toes with double tap
What is a choreiform gait?
Irregular, jerky, involuntary movements in all extremeties
