Nervous System Pathways

Question 1

Which systems are not reversed?

decussation

Answer 1

The olfactory system not reversed at all

The visual system partly reversed

Question 2

If a tract name begins with “spinal-“, what type of tract is it?

Answer 2

Ascending sensory tract e.g. spinocerebellar

Question 3

If a tract name ends with “-spinal”, what type of tract is it?

Answer 3

Descending motor tract e.g. vestibulospinal

Question 4

What are the three white matter tracts of the brain?

Answer 4

Commissural tracts - between hemispheres
Association tracts - different areas of same hemisphere
Projection tracts - High brain regions to deep brain and spinal cord

Question 5

What are the three chains of neurons involved in sensory pathways?

Answer 5

First order; Sensation to CNS, cell body in dorsal or cranial root ganglion
Second order; Interneuron with cell body in spinal cord or brain
Third order - From thalamus to cerebral cortex

Question 6

How are sensory neurons organised in the spinal cord white matter?

Answer 6

• Separated by fine and crude touch
• Arranged according to site of origin (somatotropic)
• Low level neurons are more medial, high level more lateral

Question 7

What is carried in the posterior column tract?

Answer 7

Fine touch, vibration, pressure and proprioception

Question 8

Which order of axons are contained in the spinocerebellar tracts?

Answer 8

2nd order

Question 9

What are the three major sensory tracts through the spinal cord?

Answer 9

Posterior column tract
(Dorsal Column-Medial Lemniscus pathway)
Spinocerebellar tract
Spinothalamic (anterolateral) tract

Question 10

Which axons cross in the spinocerebellar tract?

Answer 10

Posterior axons do not cross

Some anterior axons do not cross

Question 11

What is transmitted in the spinothalamic tract?

Answer 11

Lateral - pain, temperature

Anterior - crude touch, firm pressure

Question 12

What is the difference between motor commands from the somatic and autonomic nervous systems?

Answer 12

SNS - skeletal muscle

ANS - glands, smooth muscle, cardiac muscle

Question 13

What are the two major descending tracts?

Answer 13

Corticospinal tract (conscious skeletal muscle control)
Subconscious tract - (balance, muscle tone, eye, hand,upper limb position)

Question 14

What are the three pairs of corticospinal tracts and their functions?

Answer 14

Corticobulbar tract - head and neck muscles

Lateral/Anterior - rest of body skeletal muscle

Question 15

What are the four subconscious motor tracts?

Answer 15

Vestibulospinal
Tectospinal
Reticulospinal
Rubrospinal