Spinal Cord

Question 1

Clarke’s nucleus

Answer 1

•Clarke’s nucleus is a small section of grey matter located in lamina VII of the intermediate zone spinal cord which is found ventral to the gracile column and cuneate column and is involved in unconscious proprioception. It is found at the level of T1-L2 (lumbar vertebrae) on the spinal cord.

Question 2

Anterior funiculus

Answer 2

•area medial to the anterior horn

Question 3

Anterior horn

Answer 3

•anterior extension of the spinal cord grey matter •cell bodies of lower motor neurone •the motor neurone for a given muscle form a cigar heaped cluster of cells that extend longitudinally in the cord - both alpha and gamma •those cell bodies for axial muscles are located medial and those for distal muscles lie lateral (the anterior horns are enlarged in a lateral direction in the cervical and lumbosacral enlargements due to the motor needs of the arms and legs

Question 4

Anterior spinal artery

Answer 4

•two anterior vertebral arteries come off the vertebral arteries and fuse •supplies anterior 2/3 of the spinal cord, including the STTs and much of the LCSTs and the anterior horn of the grey matter where the LMNs live •a few radicular arteries and abdominal cavity, including the artery of Adamkiewicz, add to the blood supply of the anterior artery •occlusion can result in severe loss of spinal cord function —> loss of LMN at the affected level, loss of pain and temperature at that level and below, as well as loss of UMN connections to areas below the area of damage

Question 5

Cauda equina

Answer 5

•nerve heading caudally to exit the vertebral canal

Question 6

Cervical enlargement

Answer 6

•C5 to T1

Question 7

Conus medullaris

Answer 7

•end of spinal cord

Question 8

Intermediate grey

Answer 8

•area where posterior horn and anterior horn meet

Question 9

Interneurons

Answer 9

•found exclusively in CNS •enable communication between sensory or motor neurons

Question 10

Lateral Corticospinal Tract

Answer 10

•part of the lateral funiculus •principal pathway mediating voluntary movement - corticospinal fibers that start in the precentral gyrus of the frontal lobe

Question 11

Lateral funiculus

Answer 11

•area between anterior and posterior funiculi •damage to the lateral funiculus causes ipsilateral spastic weakness below the lesion - weakness of voluntary movement, increased tone, exaggerated reflexes and Babinski’s sign - because the lateral corticospinal tract runs through here!

Question 12

Lissauer’s Tract

Answer 12

•white matter at junction of posterior and lateral funiculi (stands out because it doesn’t stain as well for myelin as other white matter) •dorsal root fibers sort themselves just as they enter the cord - large, heavily myelinated fibers (touch, muscle and joint receptors) and small, thinly myelinated or unmyelinated fibers (pain, temperature, visceral and some touch); the small fibers enter Lissauer’s Tract and the large fibers enter more medially, towards the posterior funiculus

Question 13

Lower Motor Neurons

Answer 13

•motor neurons located in either the anterior grey column, anterior nerve roots or cranial nerve nuclei of the brainstem and cranial nerves with motor function

Question 14

Lumbar cistern

Answer 14

•Duran sac extends to vertebral level S2, even though the spinal cord ends at L1/L2 - the space after that is the lumbar cistern

Question 15

Lumbro -sacral enlargement

Answer 15

•L2 to S3

Question 16

Medial lemniscus

Answer 16

•primary afferents —> secondary neurons in medulla (nucleus gracilis or nucleus cuneatus) —> cross midline —> enter medial lemniscus t continue journey through brainstem to thalamus

Question 17

Nucleus cuneatus

Answer 17

•where primary afferents from fasciculus cuneatus synapse with second order neurons in the medulla •cross the midline here

Question 18

Nucleus gracilis

Answer 18

•where primary afferents from fasciculus gracilis (leg) synapse with second order neurons in the medulla •cross the midline here

Question 19

Post ganglionic neuron

Answer 19

•ganglion located outside the CNS •sympathetic post ganglionic are located close to the spinal cord •parasympathetic ganglionics are located near or in target tissue

Question 20

Posterior funiculus

Answer 20

•area medial to the posterior horn •further divides into funiculus cuneatus (lateral) - fibers from cervical and upper thoracic levels (arms) and funiculus gracilis (medial) - fibers from below the cervical enlargement (legs)

Question 21

Posterior horn

Answer 21

•posterior extension of the spinal cord grey matter •capped by substantia gelatinosa- pain and temperature information •rest of posterior horn is devoted to other aspects of sensory processing

Question 22

Posterior spinal arteries

Answer 22

•come off the vertebral arteries and form a plexiform network that runs along the lines of attachment of the dorsal roots, supplying the posterior columns, posterior horns and the dorsal part of the LCSTs

Question 23

Preganglionic neuron

Answer 23

•cell body located in the CNS •axon leaves the CNS in a ventral root or cranial nerve •sympathetic preganglionics are located in thoracic or upper lumbar segments, in thoracic segments they form a pointy lateral extension of the intermediate grey (intermediolateral cell column or lateral horn) •parasympathetic preganglionics originate in the medulla, but the ones for pelvic viscera come from sacral spinal segments, also in intermediate grey, but don’t form an obvious extension

Question 24

Precentral gyrus of the frontal lobe

Answer 24

•starting point for the collection of corticospinal neurons that mediate voluntary movement

Question 25

Primary afferents

Answer 25

•enter spinal cord through dorsal roots and end ipsilaterally on second order neurons (could be in the spinal cord, could be higher up!)

Question 26

Pyramidal decussation

Answer 26

•where the motor cortex fibers cross the midline at the spinomedullary junction, forming the lateral corticospinal tract (part of the lateral spinal funiculus) •damage to the lateral funiculus causes ipsilateral spastic weakness below the lesion - weakness of voluntary movement, increased tone, exaggerated reflexes and Babinski’s sign

Question 27

Spinothalmic Tract

Answer 27

•ascension tract for second order motor neurons on their way to the thalamus

Question 28

Substantia gelatinosa

Answer 28

•distinctive region of tightly packed small neurons in the posterior horn that play a role in the processing of pain and temperature •primary afferents for pain and temperature synapse with second order neurons before crossing the midline and travelling up the STT - the small neurons of the substantia gelatinous modulate the transmission of the information from the primary afferents to the secondary neurons

Question 29

Upper Motor Neurons

Answer 29

•found in cerebral cortex and brainstem and carry information down to activate inter neurons and LMN