Overview of Ascending and Descending Tracts

Question 1

Between what spinal levels is there spinal cord?

Answer 1

foramen magnum –> L1/L2

Question 2

What runs in the subarachnoid space?

Answer 2

CSF and large named blood vessels

Question 3

What is the subdural space associated with?

Answer 3

venous bleeds

between dura and arachnoid

Question 4

Where is there the most white matter in the spinal cord ? What does this reflect?

Answer 4

more is rostral cord, little in caudal cord - reflects ascending and descending tracts joining / leaving cord

Question 5

What are the alternative names of the sensory and motor tracts?

Answer 5

Sensory = spinothalamic
Motor = corticospinal

Question 6

Describe the somatotopic organisation of the ventral horn (somatic motor)

Answer 6

North = flexor
South = extensor 
East = proximal 
West = distal

Question 7

Briefly describe the blood supply of the spinal cord

Answer 7

x1 anterior and x2 posterior spinal arteries

+ anastomoses

Question 8

What is the pre central and postcentral gyri?

Answer 8

pre central gyrus = primary motor cortex

post central gyrus = primary sensory cortex

Question 9

Where is the association motor cortex?

Answer 9

3 gyri in front of the pre central gyrus

- planning

Question 10

Describe the sensory homunculus from lateral to medial

Answer 10

intraabodminal
pharynx
tongue
teeth, gums, and jaw
lower lip
lips
upper lip
face
nose
eye
fingers (thumb --> little)
hand, wrist, forearm, elbow, arm, shoulder 
head, neck, trunk 
hip, leg, foot, toes
genitals

Question 11

What are the 4 fibres in white matter tracts?

Answer 11

short association fibres - between gyri
long association fibres - between lobes
commissure fibres - corpus callosum - between hemispheres
projection fibres - internal capsule –> midbrain, cross over –> SC

Question 12

What is the 3 neurone pathway of the ascending tracts/

Answer 12

primary - receptor to spinal cord (cell body in DRG)
secondary - decussates in grey matter, synapses in thalamus
tertiary - arises in thalamus, terminates in primary sensory cortex

Question 13

What sensory information is carried by the spinothalamic tract?

Answer 13

pain, temperature, crude touch

Question 14

Describe the pathway of the spinothalamic tract.

Answer 14

primary - receptor in spinal cord (cell body in DRG, synapses in dorsal horn
secondary - decussates in cord, synapses in thalamus
tertiary - terminates in primary sensory cortex

Question 15

What sensory information is carried by the trigeminothalamic tract?

Answer 15

pain, temperature, crude touch

Question 16

Describe the pathway of the trigeminothalamic tract

Answer 16

primary - receptor to spinal cord (cell body in CN V ganglion), synapses in brainstem
secondary - decussates in brainstem, synapses in thalamus
tertiary - terminates in primary sensory cortex

Question 17

What sensory information is carried by the dorsal column/medial lemniscus pathway?

Answer 17

fine touch and proprioception

Question 18

Describe the pathway of the dorsal column/medial lemniscus pathway

Answer 18

primary - receptor to spinal cord (cell body in DRG), synapses in brainstem
secondary - decussates in brainstem, synapses in thalamus
tertiary - terminates in primary sensory cortex
cuneate/gracilis = upper/lower limb

Question 19

What sensory information is carried by the spinocerebellar pathway?

Answer 19

unconscious proprioception

Question 20

Describe the pathway of the spinocerebellar tract

Answer 20

primary - receptor to spinal cord (cell body in DRG), synapses in SC
secondary - ipsilateral synapse in cerebellum

Question 21

Describe the 2 neurone descending motor pathway

Answer 21

UMN - primary motor cortex to SC, decussates, synapses on interneurone or LMN
LMN - SC to muscle/MEP, arises in vental horn, may be involved in plexi
- decussate at spinal level or pyramid

Question 22

Give examples of ischaemai, trauma and disease that can assault the CNS and PNS

Answer 22

CNS
- ischaemia = stroke/haemorrhage
- trauma = direct or indirect due to compression e.g. tumour or haematoma 
- disease = parkinson's/ alzheimers 
PNS
- ischaemia = little effect 
- trauma = direct e.g. knife, indirect e.g. compression 
- disease = MND, myasthenia gravis