spinal cord

Question 1

Spinal Cord - what? where? enlargements? cover? canal?

Answer 1

• cylindrical cable of pathways to and from brain and rest of body
• extends from base of skull (medulla) to L1-2
• has cervical (brachial plexus) and lumar (lumbosacral plexus) enlargements
• meninges cover it like the brain
• central canal continuous with ventricles of the brain

Question 2

Spinal cord - organization? horns?

Answer 2

• organized into inner grey and outer white matter
• gray matter: posterior dorsoal sensory and anterior ventral motor horns
• dorsal and ventral horns lead to dorsal and ventral roots, which join up to form spinal nerve

Question 3

Pathway nomenclature - 2 types?

Answer 3

• named according to site of origin and destination
• spinothalamic: spinal cord to thalamus
• corticospinal: cerebral cortex to spinal cord

Question 4

3 major somatic snesory pathways

Answer 4

1. dorsal column( spinal cord)/medial lemniscal (brain stem) pathway
2. spinothalamic (antolateral pathway)
3. spinocerebellar pathway

Question 5

dorsal column/medial lemniscal pathway?

Answer 5

• join position, vibration sense (poprioception), discriminative touch (3D and fine touch)

Question 6

Spinothalamic (anterolateral) pathway

Answer 6

• pain, temperature and crude touch = deep touch = pressure

Question 7

spinocerebellar pathway

Answer 7

unconscious proprioception

Question 8

Dorsal columns - function? 1/2/3order neurons?

Answer 8

• conveys joint position and discriminative touch and sterognosis )3D recognition of objects w/o vision)
• 1: skin/joing receptor to medulla same side (fasciculus gracilis (LL + trunk) and fasciculus cuneatus (UL + trunk)
• 2: medulla - crosses to opposite side = ascents as medial lemniscus - to thalamus
• 3 thalamus to primary sensory cortex (thalamocrotical proejctions)

Question 9

Spinothalamic pathway - conveys? 1/2/3/ order neurons?

Answer 9

• pain and temperature and crude (non-discriminative touch - itch, tickle, pressure)
• 1: skin receptors to dorsal horn spinal grey
• 2: dorsal horn - crosses over - ascends on opposite side of spinal cord - to thalamus (lateral = pain and temp, anterior = crude)
• 3: thalamus to sensory cortex

Question 10

Spinocerebellar - carries? 1/2?

Answer 10

• unconscious proprioception (joint position and vibration sense) from trunk and extremities to cerebellum
• 1: receptors in joint capsules/tendons/muscle spindles to dorsal horn spinal grey
• 2nd order: dorsal horn to cerebellum via spinocerebellar tracts

Question 11

Motor Systems - somatic

Answer 11

• contraction of skeletal muscle
• at least 2 motor neurons: upper UMN - cell body in CNS processing centres, lower LMN - cell body in ventral horn of spinal cord or motor cranial nerve nucleus in brainstem

Question 12

upper motor neuron lesion?

Answer 12

• bath is broken - signal can’t get down to synapse
• dis-inhibition leads to spastic paralysis
• contraction to the max

Question 13

lower motor neuron lesion?

Answer 13

• no response leads to flaccid paralysis - no tone in muscle

Question 14

Common Final Pathway for muscle contraction

Answer 14

• only axon of LMN extends to skeletal msucle

Question 15

Motor Systems - two pathways

Answer 15

1. corticospinal / pyramidal pathway
2. corticonuclear / corticobulbar pathway

Question 16

Corticospinal/ pyrmaidal pathway?

Answer 16

• upper motor neurons extend from cerebral cortex to spinal cord
• regulate distal musculature in limbs and trunk

Question 17

corticonucleaur/corticobulbar pathway?

Answer 17

• upper motor neurons extend from cerebral cortex to motor cranial nerve nucli in brain stem
• regulate muscles of head and neck

Question 18

Motor systems - extrapyramidal pathways

Answer 18

• subsidiary descending pathways important as back up systems

Question 19

motor systems - basal nuclei and cerebellum

Answer 19

• modulate and modify activity in corticospinal tract to ensure smooth, coordinated purposeful movement

Question 20

Voluntary Movements

Answer 20

• central motor program:

1. identification, localization of targets in space - posterior parietal cortex
2. formulation of plan of action - premotor cortex, supplementary motor cortex

• esecution of mocemtn: primary motor cortex

Question 21

Corticospinal Pathway

Answer 21

• massive bundle of fibres (~1m) forming direct pathway from cerebral cortex to spinal cord
• originates from pyramidal neurson in cortex: primary motor cortex, premotor and supplementary motor cortex, primary sensory cortex
• regulate distal limb muscles: important for precise, skilled, learned movements (fingers)