Posture and Locomotion

Question 1

What is a decerebrate posture?

Answer 1

Upper and lower limbs extend

Question 2

What are two postural signs of damage to the brainstem?

Answer 2

Decerebrate

Decorticate

Question 3

What is a decorticate posture?

Answer 3

Upper limbs flex

Lower limbs extend

Question 4

Which limbs does the rubrospinal tract contribute to in humans?

Answer 4

Upper limbs only

Question 5

What limb movements does the reticular formation influence?

Answer 5

Extension of upper and lower limbs

Question 6

Where is the reticular formation?

Answer 6

Pons and medulla

Question 7

What limb movements does the red nucleus influence?

Answer 7

Flexion of upper limbs

Question 8

Where is the red nucleus?

Answer 8

Midbrain

Question 9

What is the role of higher cortical centres on the reticular formation and red nucleus in terms of limb movement control?

Answer 9

Inhibits their outputs

Question 10

What position does a lesion above the midbrain cause, and why?

Answer 10

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

Question 11

What position does a lesion at the midbrain cause, and why?

Answer 11

Decerebrate
Remove inhibition to reticular formation
Cut red nucleus itself
Upper and lower limbs extend because of reticular formation influence

Question 12

What is the Babinski sign?

Answer 12

Fanning of toes (upwards plantar flexion) rather than curling of toes in response to noxious stimulus on sole of foot

Question 13

Up to what age is the Babinski sign normal?

Answer 13

12-24 months of life - until child gets good at walking

Question 14

How are upper motor neuron lesions for cranial nerve lesions identified?

Answer 14

Pattern of loss, rather than LMN/UMN signs seen with spinal motor output

Question 15

Which non-ocular lower motor neurons (cranial nerves) receive bilateral corticobulbar innervation?

Answer 15

All except those innervating lower face and tongue

Question 16

Which motor neuron is affected if there is weakness in the inferior muscles of the face only on one side?

Answer 16

UMN on contralateral side

Question 17

Which motor neuron is affected if there is weakness in all the muscles on one side of the face?

Answer 17

LMN on ipsilateral side

Question 18

Why is only the lower half of the face affected when there is an upper motor neuron lesion?

Answer 18

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

Question 19

What are the first movements that occur when you are going to abduct a leg?

Answer 19

Postural adjustments in anticipation of activity > move body weight to other leg

Question 20

When pulling on a handle on a wall, what happens first?

Answer 20

In anticipation of change in position, calf muscles contract to stabilise body

Question 21

When does locomotor activity become present?

Answer 21

Very early in life

Question 22

Where is the pattern for locomotor activity?

Answer 22

Spine

Question 23

Which muscle group bears weight?

Answer 23

Extensors - no weight bearing when you flex

Question 24

When is useful work done?

Answer 24

During extension

Question 25

How do decerebrate cats increase speed when treadmill speed is increased?

Answer 25

Only source of input from muscle sense

Spinal circuits tell muscles to speed up because of pattern of activation detected by muscle spindles

Question 26

What are some abnormal gait patterns associated with CNS disorders?

Answer 26

Ataxic gait
Choreiform gait
Hemiparetic gait
Parkinsonian gait

Question 27

What is an ataxic gait?

Answer 27

Unsteady, uncoordinated walk
Wide base
Feet thrown out
Come down first on heel then toes with double tap

Question 28

What is a choreiform gait?

Answer 28

Irregular, jerky, involuntary movements in all extremeties