NERVE TRACTS

Question 1

WHERE IS THE PYRAMID FOUND

Answer 1

anterior surface of medulla

Question 2

PYRAMIDAL VS EXTRAPYRAMIDAL PATHWAY

Answer 2

pyramidal - voluntary actions , responsible for skeletal muscle contraction
extrapyramidal - involuntary , ensures fluid and stable movements wiht no delay

Question 3

CORTICOSPINAL TRACT

Answer 3

responsible for voluntary movement of trunk and limbs

Question 4

CORONA RADIATA

Answer 4

cerebral white matter

Question 5

LATERAL VS ANTERIOR CORTICOSPINAL TRACT

Answer 5

both begin in cerebral cortext and travel through corona radiata and internal capsule to reach brainstem
At the medulla , 85% of fibres cross to opposite side forming the lateral CST
15% of fibres remain on original side forming the anterior CST

Question 6

HOW MANY NEURONS ARE INVOLVED IN THE CORTICOSPINAL TRACT

Answer 6

2 (3) - an upper motor neuron and a lower motor neuron (may also be inter but this unimportant)
UMN synapse with LMN in ventral horn of spinal cord

Question 7

AT WHAT POINT DOES THE LATERAL CORTICOSPINAL TRACT CROSS TO THE CONTRALTERAL SIDE

Answer 7

level of the medulla

Question 8

CONSEQUENCE OF UPPER MOTOR NEURON DAMAGE IN CORTICOSPINAL TRACT

Answer 8

UMN damage sees an increase in (unwanted) activity of LMN due to them being unregulated
hyperflexia , hypertonia , spastic paralysis

Question 9

CONSEQUENCE OF LOWER MOTOR NEURON DAMAGE IN CORTICOSPINAL TRACT

Answer 9

LMN damage sees little to no movement of muscles
atrophy and floppyness

Question 10

SPINAL SHOCK

Answer 10

occurs after a spinal injury
initial loss of all muscle control
symptoms/ control will gradually re emerge

Question 11

CORTICOBULBAR (NUCLEAR) TRACT

Answer 11

voluntary movement of head and neck muscles

Question 12

LMN OF CORTICOBULBAR TRACT

Answer 12

LMNs are cranial nerves

Question 13

WHAT AREA OF THE INTERNAL CAPSULE DOES THE CORTICOBULBAR TRACT TRAVEL THROUGH

Answer 13

genu (turning point of capsule)

Question 14

WHAT AREA OF THE INTERNAL CAPSULE DOES THE CORTICOSPINAL TRACT TRAVEL THROUGH

Answer 14

posterior limb

Question 15

UMN IN CORTICOBULBAR TRACT

Answer 15

supranuclear fibre

Question 16

DESCRIBE THE PATHWAY OF UMN IN THE CORTICOBULBAR TRACT

Answer 16

UMN come from primary motor cortex and travel through corona radiata and genu of internal capsule towards brainstem
each UMN synapses bilaterally EXCEPT lower CN VII and CN XII

Question 17

DESCRIBE THE PATHWAY OF LMN IN THE CORTICOBULBAR TRACT

Answer 17

LMN i.e cranial nerves leave their nucleus and innervate ipsilaterally EXCEPT CN IV which innervates contralaterally

Question 18

EXCEPTIONS TO THE BILATERAL THEN IPSILATERAL RULE OF THE CORTICOBULBAR TRACT

Answer 18

Exceptions to bilateral innervation from UMN = lower facial nucleus and hypoglossal nucleus
exceptions to ipsilateral innervation from LMN = trochlear CN IV whose lower motor neurons innervate contralaterally

Question 19

PSEUDOBULBAR PALSY

Answer 19

bilateral innervation from UMN to corticobulbar nuclei in brainstem means that if damage to UMN , paralysis is not seen due to innervation still coming from other side
However a mild weakness of muscles is seen known as pseudobulbar palsy
(exceptions = lower CN VII and CN XII)

Question 20

NUCLEUS AMBIGUUS

Answer 20

shared motor nucleus between CN IX and CN X
Found in medulla

Question 21

WHY IS FOREHEAD SPARED DURING A STROKE

Answer 21

due to facial nerve motor nucleus being divided into upper and lower and corresponding to the upper and lower face
upper nucleus is supplied bilaterally by UMN whereas lower nucleus is only supplied contralaterally
therefore damage to an UMN will result in paralysis of the lower face and pseudobulbar palsy of the upper face on that side i.e forehead spared

Question 22

HOW WOULD YOU KNOW THERES BEEN DAMAGE TO AN UMN OF CN XII

Answer 22

deviation of tongue to contralteral side
muscles in tongue push against one another on each side to draw tongue out of mouth in centre position
due to the contralteral innervation of CN XII nucleus damage to an UMN would see the the tongue therefore deviate to the opposite side as no resistance is being offered