T2 L4 Motor learning

Question 1

Describe a simple motor pathway

Answer 1

Motor cortex of the brain –> upper motor neurone –> lower motor neurone –> muscle

Question 2

What are the descending motor pathways?

Answer 2

Rubrospinal
Corticospinal
Reticulospinal
Tectospinal
Vestibulospinal

Question 3

What descending pathways are ventromedial?

Answer 3

Reticulospinal
Tectospinal
Vestibulospinal

Question 4

What descending pathways are lateral?

Answer 4

Rubrospinal

Corticospinal

Question 5

Describe the reticulospinal pathway

Answer 5

From brainstem
Reticular formation just under cerebral aqueduct & 4th ventricle
Descends in 2 separate pathways: pontine (medial) & medullary (lateral)
Facilitates extension of limbs

Question 6

Describe the tectospinal pathway

Answer 6

Originates in superior colliculus in midbrain which receives direct input from retina & insula cortex
Used to construct map of world around us
Direct her & eye to move so appropriate point of space is imaged on fovea
Projections decussate immediately & lie close to midline into cervical regions to help control muscles of neck, upper trunk & shoulders

Question 7

Describe the vestibulospinal pathway

Answer 7

Originate in vestibular nuclei of medulla which relay sensory information from vestibular labyrinth in inner ear
Medial pathway projects down to spinal cord. Active spinal circuits that control neck & back muscles & guide head muscles
Lateral pathway projects ipsilaterally down to spinal cord to maintain upright & balanced posture by facilitating extensor muscles of the leg

Question 8

Describe rubrospinal pathway

Answer 8

From red nucleus
Innervate flexor muscles in upper limbs
Involuntary

Question 9

Describe corticospinal pathway

Answer 9

Only cortical tract to directly synapse with motor neurons
Predominantly derived from cells in layer V
90% fibres cross but individual variation may account for differences in deficits in stroke

Question 10

What stimuli can be used to induce posturing in coma?

Answer 10

Supraorbital pressure
Nail bed stimulation
Sternal rub

Question 11

What causes decorticate posturing?

Answer 11

Lesion above red nucleus
Rubrospinal pathways are disinhibited & therefore facilitate flexors in upper limbs
Flexion of arms, extension of legs

Question 12

What causes decerebrate posturing?

Answer 12

Lesion below red nucleus
Rubrospinal pathways are disrupted & therefore upper limbs are extended
Extension of all 4 limbs

Question 13

What happens if there is damage to the motor Cortex &. corticospinal tract?

Answer 13

Typical posture
Increased tone, brisk reflexxes
Extensor plantar

Question 14

What is the evidence of damage to motor neurons?

Answer 14

Reduced tone
Loss of reflexes
Muscle wasting

Question 15

Why does the babinski reflex occur in babies?

Answer 15

Corticospinal tracts aren’t fully developed which would inhibit spinal extensor response

Question 16

What are the symptoms of Bells palsy?

Answer 16

Weakness in entire half of face as damage is to lower motor neuron

Question 17

Describe innervation to lower 1/2 of the face

Answer 17

Contralaterally innervated

Question 18

Describe innervation to upper 1/2 of face

Answer 18

Bilaterally innervated

Question 19

Describe area 4

Answer 19

Primary motor cortex
Anterior to central sulcus in pre-frontal gyrus
Stimulating this area leads to simple movements on contralateral side

Question 20

Describe area 6

Answer 20

Complex movements on either side of the body

Question 21

Describe area 5 & 7

Answer 21

In posterior parietal cortex

Targets for inputs from primary somatosensory cortex

Question 22

What will a middle cerebral artery occlusion cause?

Answer 22

Proximal lesion affects internal capsule
Complete hemiparesis
Distal lesion may spare leg area of motor cortex but secondary swelling & ischaemia may compromise function
A more proximal blockage will take out all fibres from leg, hand & face

Question 23

What are the consequences of an anterior cerebral artery stroke?

Answer 23

ACA supplies medial part of frontal lobe including leg area of motor cortex
Crural paresis
Frontal signs e.g. aboulia

Question 24

What is a seizure ‘march’ (Jacksonian seizure)?

Answer 24

Partial onset simple motor seizure becoming secondarily generalised

Question 25

Describe the premotor area

Answer 25

Important in control of visually guided movements
Receives inputs from cerebellum
Lesions of PMA disrupt learns responses to visual cues

Question 26

What does simple finger flexion use?

Answer 26

M1

Question 27

What does a sequence of complex finger movements use?

Answer 27

M1 & SMA

Question 28

What does mental rehearsal of complex finger movements use?

Answer 28

SMA activation

Question 29

What is the bereitschaftspotential?

Answer 29

Activation of supplementary area precedes motor potential of primary motor area by 500-1000ms during self initiated movements

Question 30

What is apraxia?

Answer 30

Inability to carry out purposeful movements in absence of paralysis or paresis
Great difficulty in sequencing & execution of movements

Question 31

What is ideational apraxia?

Answer 31

Parietal

Unable to report sequence

Question 32

What is ideomotor apraxia?

Answer 32

Supplementary motor area

Unable to use tool

Question 33

What is dystonia?

Answer 33

Sustained muscle contractions, usually producing twisting or repetitive movements or abnormal postures or positions.