Anatomy of the spinal cord

Question 1

ANATOMY

i) what level does the spinal start and end?
ii) what does it become when it narrows and ends?
iii) what does the cauda equina contain? where is it found?
iv) what is the name of the pia extension that attaches to the coccyx?

Answer 1

i) starts at the atlas and extends to L1
ii) narrows at L1 to form conus medullaris

iii) cauda equina contains lumbar and sacral dorsal and ventral roots
- found in the lumbar cistern

iv) pia extension that attaches to the coccyx = terminal filum

Question 2

ANATOMY CONT

i) what is the spinal cord protected by? what does it sit in?
ii) what roots/ganglia do the meninges surround?
iii) what two structures is the neural arch made of?
iv) what are structures A, B and C?

Answer 2

i) protected by the vertebral column and sits in the vertebral canal
ii) meninges surround both dorsal and ventral roots as well as DRG
iii) neural arch = spinous and TV process

iv) A = dura
B = arachnoid
C = pia

Question 3

REGIONS OF THE SPINAL CORD

i) how many nerves are found in
a) cervical
b) thoracic
c) lumbar
d) sacral regions?

ii) why is the cervical region enlarged? what area of the body does this innervate?
iii) what other region is enlarged and what does it innervate?
iv) what is the space below L1 called and what does it contain?
v) what are regions labelled A,B and C?

Answer 3

i) cervical = 8 spinal nerves
thoracic = 12 spinal nerves
lumbar = 5 spinal nerves
sacral = 5 nerves

ii) cervical region is enlarged due to lots of grey matter
- innervates the upper limb

iii) lumbosacral region is also enlarged and innervates the lower limb
iv) space between L1 is called the lumbar cistern and it contains the cauda equina

v) A = conus medullaris
B = internal part of terminal filum (pia)
C = external part of terminal filum (dura)

Question 4

SPINAL NERVES

i) what two areas do they connect?
ii) how many pairs are there? what two things are the formed by
iii) what do dorsal root ganglia contain?
iv) what type of nerve fibres make up the dorsal and ventral roots? what type of information does each carry?
v) what are labels A, B and C?

Answer 4

i) connect the periphery to the spinal cord
ii) there are 31 pairs that are formed by a dorsal and ventral root
iii) DRG contains cell bodies of primary sensory neurons

iv) dorsal root = afferent (fibres carry sensory info to the spinal cord)
ventral root = efferent (motor axons/sympathetic autonomic)

v) A = Dorsal root ganglia
B = dorsal root
C = ventral root

Question 5

INTERNAL ANATOMY OF SPINAL CORD

i) what is the inner core made from? name three things it contains
ii) name the three horns that make up the inner core - label diagram A,B,C
iii) what is the outer layer made from? what does it contain? label 1,2,3
iv) what do levels that have expanded grey matter supply? give two examples of these levels

Answer 5

i) inner core = grey matter
contains neuronal cell bodies, synapses, dendrites

ii) inner core made from dorsal, lateral and ventral horn
- A = dorsal horn, B = lateral horn and C = ventral horn

iii) outer layer is made from white matter and contains myelinated axons
1 = dorsal column, 2 = lateral column, 3 = ventral column

iv) levels with expanded grey matter supply the limbs eg C5 (upper limb) and L2 (lower limbs)

Question 6

GREY MATTER ORGANISATION

i) what type of information does each horn recieve?
ii) give an example of the type of neurons present in each horn
ii) at what level are interneurons found? what are they important in?

Answer 6

i) dorsal = sensory
lateral = autonomic
ventral = motor

ii) dorsal = sensory neurons
lateral = pre ganglionic sympathetic neurons
ventral = motor neuron cell bodies

iii) inter neurons are found between/within all levels
- important in reflexes

Question 7

WHITE MATTER ORGANISATION

i) what does it principally contain? what are these made from?
ii) what type of information do ascending tracts carry? where is it taken to?
iii) what type of information do descending tracts carry?
iv) what happens to tracts from ceb hemis in relation to their position? which side of the body does the left hemisphere therefore control?
v) what tracts does the a) dorsal b) lateral and c) ventral column contain?
vi) in the picture which type of tracts do the blue and red represent?

Answer 7

i) contains tracts which are made from long myelinated axons
ii) ascending tracts carry afferent information to the brain
iii) descending tracts carry efferent information from the brain

iv) tracts cross the midline after leaving the ceb hemis
- left hemi controls right side of the body

v) a) dorsal cont ascending tracts
b) lateral cont desc and asc tracts
c) ventral cont descending tracts

vI) blue = ascending
red = descending

Question 8

ASCENDING TRACTS

i) what type of information do ascending tracts contain?
ii) what are the two subtypes of this information? and where does information originate in each?

Answer 8

i) ascending tracts contain sensory information

ii) two types of sensory information = proprioceptive and exteroceptive
- proprioceptive = info originating from inside the body (muscle spindles, joints and tendons)
- exteroceptive = info originating from outside the body (pain, temperature, touch)

Question 9

ASCENDING TRACT NEURON ORGANISATION

i) how many neurons are in the circuit?
ii) which neurons are found outside the spinal cord? where do they oconsequently enter the spinal cord?
iii) which neurons are found in the spinal cord?
iv) which neurons project into the cerebral cortex?

Answer 9

i) three

ii) outside spinal cord = first order neurons
enter the spinal cord via the dorsal root

iii) second order are found in the spinal cord
iv) third order neurons project into the cerebral cortex

Question 10

DORSAL COLUMN MEDIAL LEMNISCUS PATHWAY

i) what type of information does it carry (2)
ii) which structures does each type of information come from?
iii) what is tactile discrimination? what type of information is this
ii) what type of information does it provide to the brain? what does this allow?

Answer 10

i) carries both extraceptive (fine touch) and proprioceptive information

ii) fine touch = from cutaneous mechanoreceptors
proprioception = from muscle spindles (muscle length) and golgi tendon organs (muscle force)

iii) tactile discrimination is discrimination between sharp and blunt pressure = extraceptive info
iv) provides brain with positional information (we know different parts of the body are doing and where they are positioned)

Question 11

DC-ML pathway - FIRST ORDER NEURONS

i) where do they enter the spinal cord?
ii) do they ascend the dorsal column on the same or opposite side?
iii) what is the name of the two columns that information ascends up? which one is lateral and which one is medial?
iv) do the fibres ascend the dorsal column to the brainstem crossed or uncrossed?
v) it contains some of the longest neurons in the body - true or false?

Answer 11

i) enter the spinal cord through the dorsal roots
ii) ascend the dorsal column on the same side

iii) ascend the dorsal column within the
1) fasciculus gracilis (medial)
2) fasciculus cuneatus (lateral)

iv) fibres ascend the dorsal column uncrossed
v) true

Question 12

DCML PATHWAY ORGANISATION

i) where do first order neurons synapse on second order neurons?
ii) what nucleus does the fasciculus gracilis terminate in? which area does it carry information from?
iii) which nucleus does the fasciculus cuneatus terminate in? which area does it carry information from?
iv) what nuclei are labelled A & B?

Answer 12

i) first order synapse to second order in the medulla

ii) F.gracilis terminates in the gracile nucleus
- carries information from the lower limb

iii) F.cuneatus terminates in the cuneate nucleus
- carries information from the upper limb

iv) A = gracile nucleus
B = cuneate nucleus

Question 13

DCML PATHWAY - SECOND/THIRD ORDER NEURONS

i) where do 2nd order cross? where do they then ascend to?
ii) what is the name of the ribbon like structure 2nd order form?
iii) where do 2nd order synapse to 3rd order?
iv) where do 3rd order project from and to?

Answer 13

i) second order neurons cross in the medulla and ascend to the thalamus
ii) ribbon like structure = medial lemniscus (this passes to the thalamus)
iii) second order synapse onto third order in the thalamus
iv) third order project from the thalamus to the somatosensory cortex in the post central gyrus

Question 14

DAMAGE TO THE DORSAL COLUMN

i) a lesion on one side of the spinal cord leads to loss of what? does this happen on the same or opposite side to the lesion?
ii) what condition may this be seen in?
iii) name a symptom and explain
iv) what is the clinical test? what is seen if there is a lesion?

Answer 14

i) a lesion leads to loss of tactile discrimination and proprioception on the same side (as axons have not yet crossed)
ii) may be seen in multiple sclerosis
iii) sensory ataxia - loss of co-ord and balance without visual cues (ie without positional info such as looking at feet)
iv) Rombergs sign - see severe swaying on standing with eyes closed and feet together (no visual cues going to the brain on the bodys position)

Question 15

SPINOTHALAMIC TRACT

i) what type of information does it convey? give three examples
ii) how many neurons form the basic circuitry?
iii) when first order neurons enter the dorsal horn, what tract do they form?
iv) how many spinal segments do they collateral branches run up or down?
v) where do collateral branches of this tract synapse to second order neurons?

Answer 15

i) conveys extraceptive information such as pain, temperature and crude touch
ii) three neurons in basic circuitry
iii) first order enter dorsal horn and form the tract of lissauer
iv) collat branches run up/down one or two spinal segments
v) collateral branches of tract of liss synapse to second order neurons in the dorsal horn

Question 16

SPINOTHALAMIC TRACT 2ND & 3RD ORDER NEURONS

i) at what level do second order neurons decussate? what column do they then ascend in?
ii) what aspect of the tract do fibres from a) lower limb and b) upper limb run in? (opposite of DCML)
iii) where do second order synapse onto third order neurons?
iv) where do third order neurons project to?

Answer 16

i) decussate at the dorsal horn and ascend in the anterolateral column

ii) lower limb = lateral in tract
upper limb = medial in tract

iii) second order synapse to third order in the thalamus
iv) third order project to the somatosensory cortex via the internal capsule

Question 17

DAMAGE TO ANTEROLATERAL COLUMN

i) what type of sensation is lost? (3)
ii) are sensations lost on the same or opposite side of the lesion?
iii) give an example of an outer tract injury? which limbs lose pain first? why?
iii) give an example of an inner tract injury? which limbs lose pain first? why?

Answer 17

i) loss of pain, temperature and crude touch
ii) loss of sensation on the opposite side to the lesion

iii) outer tract injury = cord compression due to herniated disk
- loss of lower limb pain first as fibres run laterally

iv) inner tract injury = grey matter tumour
- loss of upper limb pain first as fibres run medially

Question 18

SPINOCEREBELLAR TRACTS

i) is this an ascending or descending pathway?
ii) what is it responsible for?
iii) where do axons of this tract terminate?

Answer 18

i) ascending
ii) responsible for unconcious muscle proprioception and smooth motor co-ordination
iii) axons terminate in the cerebellum (dont go to the cerebrum)

Question 19

SPINOCEREBELLAR TRACT ANATOMY

i) how many neurons are in the pathway?
ii) how many main tracts are there?
iii) what type of info do the ant and post SC tracts carry? where from?
iv) where do the tracts terminate? on the same or opposite side that they enter the spinal cord?
v) what side of the body does the left cerebellum control?

Answer 19

i) two (first and second order)
ii) three main tracts
iii) ant and post SC tracts carry proprioceptive information from trunk and lower limb
iv) tracts terminate in the cerebellum on the same side
v) left cerebellum control the left side of the body

Question 20

POSTERIOR SPINOCEREBELLAR TRACT

i) where does it carry sensory information from?
ii) where do first order neurons synapse to second order?
iii) which column do second order neurons then ascend in? where do they terminate?
iv) what speed is information passed up the axons? (fast or slow)
v) a lesion on one side of the spinal cord will cause problems on which side? what will be seen?

Answer 20

i) carries sensory info from the lower limb
ii) first order synapse to second order in the dorsal horn
iii) second order then ascend in the lateral column and terminate in the cerebellum
iv) info passes along axons very fast
v) lesion on one side will cause problems in the same side = unco-ord lower limb muscular activity

Question 21

DESCENDING TRACTS

i) what do they control?
ii) what two groups can they be classified into?
iii) which tract is known as the ‘great vountary motor pathway’

Answer 21

i) control muscular activity
ii) classified into pyramidal or extrapyramidal
iii) the corticospinal tract

Question 22

CORTICOSPINAL TRACT

i) what does it innervate?
ii) what type of tract is it?
iii) how many neurons are in the circuit?
iv) what are the neurons in the circuit and where do they go to/from?
v) where do they neurons synapse?

Answer 22

i) innervates all skeletal muscles
ii) pyramidal tract (axons pass through the medullary pyramids)
iii) there are two neurons in the circuit
iv) upper and lower motor neurons

• UMN from cerebral cortex to ventral horn of spinal cord
• LMN from ventral horn to skeletal muscle

v) UMN synapse to LMN in the ventral horn

Question 23

PYRAMIDAL TRACT

i) which type of neurons pass through the pyramids of the medulla?
ii) where do the cell bodies of UMNs sit?
iii) which three structures do they then pass through before they reach the medullary pyramids?
iv) which two tracts can the axons then enter after the pyramids?
v) which tract do most axons pass through

Answer 23

i) UMNs
ii) cell bodies of UMNs sit in the primary motor cortex
iii) PMC > internal capsule > cerebral peduncle > pons
iv) after the pyramids the axons can either enter the lateral or anterior CS tract
v) most axons enter the lateral CS tract

Question 24

PYRAMIDS OF DECUSSATION

i) what % of CS tract fibres cross the midline? which tract do they enter?
ii) what % of CS tract fibres stay on the same side? which tract do they enter?
iii) label A-C

Answer 24

i) 80% cross the midline and enter the lateral tract
ii) 20% say on same side and enter the anterior tract

iii) A = lateral CS trac
B = pyramid
C = pyramids of decussation

Question 25

LMN organisation

i) where do UMN synapse to LMNs?

ii) what areas are innervated by neurons in the
a) medial
b) anterolateral
c) posterolateral areas of the ventral horn?

iii) what body areas are innervated by axons from A-C

Answer 25

i) in the ventral horn

ii) a) medial VH - trunk
b) anterolat VH - proximal limbs
c) posterolat VH - distal limbs

iii) A - postlat (distal limbs)
B - antlat (proximal limbs)
C - medial (trunk)

Question 26

UPPER MOTOR NEURON DISEASE

i) caused by disruption to which tract?
ii) what happens to UMNs in this disease?
iii) give three characteristic clinical signs
iv) what event may this occur after?

v) if the lesion is a) above and b) below the pyramids
- which side of the body will be affected?

Answer 26

i) disruption to the corticospinal tract
ii) degeneration of UMNs

iii) characteristic clinical signs are
1) spastic paralysis (increased muscle tone as still have LMN function)
2) overactive tendon reflexes
3) no significant muscle atrophy (as LMN are still in tact and can supply muscles with trophic factors)

iv) may occur after a stroke

v) a) above pyramids = affects opposite side
b) below pyramids = affects same side

Question 27

LOWER MOTOR NEURON DISEASE

i) where are LMNs affected?
ii) name three clinical signs
iii) give two examples of LMN disease
iv) which conditions are implicated in damage in area A and B

Answer 27

i) degeneration of LMNs in ventral horn or in the periphery

ii) 1) flacid paralysis (no muscle tone due to no innervation to skeletal muscles)
2) no tendon reflexes
3) muscle atrophy (as muscles arent supplied with trophic factors)

iii) spinal muscular atrophy (degen of LMN in ventral horn) and Guillian-Barre syndrome (demyelination of LMNs)

iv) A = spinal muscular atrophy
B = Guillain Barre syndrome

Question 28

AMYTROPHIC LATERAL SCLEROSIS

i) which motor neurons does it affect?
ii) what happens?
iii) which symptoms are seen initially? (2)
iv) which cranial nerves are affected in the medulla? (4)
v) which motor neurons are affected when spasticity is seen?
vi) what eventually happens?
vii) what is the prevalence?

Answer 28

i) affects both upper and lower motor neurons
ii) progressive muscle weakness and atrophy but the mind is still in tact
iii) initially see symptoms in limbs or bulbar signs (speech and swallowing difficulty)
iv) CNs IX - XII
v) spasticity = UMNs affected
vi) short life span ( 5 years post diagnosis) > respiratory failure
vii) affected 4-5 in 100,000

Question 29

EXTRA PYRAMIDAL TRACTS

i) are these ascending or descending?
ii) do they pass through the pyramids?
iii) what two things are they important for?
iv) name three tracts and where they run from
v) what do lesions in these tracts cause?

Answer 29

i) descending
ii) no they dont pass through the pyramids
iii) important for maintaining posture and regulating involuntary movement

iv) rubrospinal (from red nuc in midbrain)
reticulospinal (from reticular format in pons)
vestibulospinal (from vestibular nuclei in medulla)

v) lesions cause movement disorders such as dyskinesia and dystonia (invol movement and contractions)