Week Five - Pathways

Question 1

What do somatosensory pathways do?

Answer 1

Somatosensory pathways carry sensory information to the cerebral cortex

Question 2

What are the types of sensory information carried by the somatosensory pathways?

Answer 2

• nociception
• pain
• thermoreception
• pain
• mechanoreception
• touch
• pressure
• vibration
• proprioception

Question 3

What are the two major spinal cord pathways?

Answer 3

• Dorsal column pathway

- Spinothalamic tract

Question 4

What are the somatosensory pathways comprised of?

Answer 4

1. First- order neurons
2. Second-order neurons
3. Third-order neurons

Question 5

First-order neurons

Answer 5

• Start as peripheral nerve and enter the spinal cord

- Cell bodies in dorsal root ganglia

Question 6

Second-order neurons

Answer 6

• Axons cross the midline before ascending to the thalamus

- Cell bodies in grey matter of the brain stem/spinal cord

Question 7

Third-order neurons

Answer 7

• Start in the thalamus
• Via the internal capsule
• To primary somatosensory cortex

Question 8

What are the main differences between the two major somatosensory pathways?

Answer 8

• Function
• Cell body localisation 2nd order neuron
• Where pathway crosses the midline

Question 9

What is the function and assessment of the dorsal column pathway?

Answer 9

Function

• Localised touch
• Proprioception

Assessment

• Vibration sense
• Examiner extending or flexing joints
• Romberg’s sign

Question 10

What is the function and assessment of the spinothalamic pathway?

Answer 10

Function

• pain
• temperature

Assessment
-Examiner touches skin with sharp or blunt end of a pin

Question 11

Visual pathway

Answer 11

-leaves retina- optic nerve- optic chiasm - optic tract - lateral geniculate (thalamus) - optic radiations

Question 12

What are some synonyms for the primary motor pathways?

Answer 12

Pyramidal motor system

Pyramidal tract

Question 13

What are the two main primary motor pathways?

Answer 13

• corticospinal tract

- corticobular tract

Question 14

Corticospinal tract

Answer 14

• originates in the upper 2/3 of pre motor cortex
• projects to spinal cord
• most fibres decussate in medulla
• controls limb and trunk muscles

Question 15

Corticobulbar tract

Answer 15

• originates in lower 1/3 of pre motor cortex
• projects to brain stem
• terminates at cranial nerve motor nuclei
• lower jaw + chewing
• facial expression
• speech, swallowing and gag reflex
• not only contra- but also has many ipsilateral fibres
• most cranial nerve motor nuclei receive projection from both cerebral hemispheres
• exceptions- tongue and lower parts of the face

Question 16

Upper motor neurons

Answer 16

Corticospinal and corticobulbar tract neurons with cell bodies in motor cortex

Question 17

Lower motor neurons

Answer 17

=final common pathway

• motor neurons of the spinal tract and brain stem inervating skeletal muscles
• initiation of all movement

Question 18

Neuromuscular junction

Answer 18

Point of contact between LMN and skeletal muscle

Question 19

Possible causes of upper motor lesions

Answer 19

Stroke, trauma, tumours, infection, degenerative disease

Question 20

Upper motor neuron lesion characteristics

Answer 20

• hypertonicity
• hyperreflexia
• facial muscle
• speech and swallowing