Spinal cord: ascending tracts Flashcards
What type of sensation is detected by Meissner Corpuscle receptors?
Discriminative touch
What receptors detect deep pressure and vibrations?
Pacinian Corpuscle receptors
What types of sensation do free nerve endings detect?
Pain
Temperature
What receptors detect light touch?
Merkel cells
What do Ruffini endings detect?
Touch
What are the 3 types of interconnection fibres in the cortex?
Projection fibres
Association fibres
Commissural fibres
What type of interconnection fibres makes up the corpus callosum?
Commissural fibres
What types of dysfunction would be caused by damage to the internal capsule?
Contralateral motor and sensory symptoms
What makes up the internal capsule?
Anterior limb
Genu (bend/ angle)
Posterior limb
Retrolenticular
Where does the retrolenticular of the internal capsule sit?
Behind the lentiform nucleus
What are the 2 main nuclei of the thalami?
Ventral posterior medial nucleus (VPM)
Ventral posterior lateral nucleus (VPL)
Where do the VPM and VPL receive their input from?
VPM = head and face VPL = limbs and trunk
What are the identifying features of a cervical or a lumbar spinal cross section?
Large grey horns (due to large population of neurons required to innervate upper limbs)
What are the identifying features of a thoracic spinal cross section?
Small grey horns
What are the identifying features of a sacral spinal cross section?
Small white matter tracts
What is the fasciculus cuneatus?
Section of dorsal column that receives input from above T6 (e.g. arms)
What section of the dorsal column receives input from below T6 (e.g. legs)?
Fasciculus Gracilis
What does the dorsal columns pathway detect?
Discriminative touch
Vibrations
Conscious proprioception
What is the route of the dorsal columns pathway (from the trunks and limbs)?
- 1st order neurons pass into dorsal cord and ascend ipsilaterally to the lower medulla
- 1st order neurons synapse with 2nd order neurons in the lower medulla
- 2nd order neurons dessucate and ascend to VPL of the thalamus
- 2nd order neurons synapse with 3rd order neurons at the thalamus
- 3rd order neurons travel to the primary sensory cortex
What is the route of the dorsal columns pathway (from the face)?
- 1st order (trigeminal nerve sensory) neurons enter the Pons and synapse in the CN V nucleus
- 2nd order neurons ascend in the trigeminal leminscus to the VPM of the thalamus
- 3rd order neurons pass to the primary sensory cortex
What can cause damage to the spinal column?
Infarction
Infection
Compression (e.g. tumour, trauma)
B12 deficiency
What is psuedoathetosis?
Writhing of the digits, hands and feet (due to loss of conscious proprioception)
What would damage to the dorsal columns result in?
Loss of discriminative touch, vibration and conscious proprioception below the level of lesion
What information does the spinothalamic tract relay?
Pain
Temperature
Simple touch
What is the route of the spinothalamic tract?
- 1st order neurons from the body ascend ipsilaterally for 1-2 vertebral levels in the Tract of Lissaeur
- Synpase with 2nd order neuron
- Decussates across the anterior white commissure
- Ascends in the spinothalamic tract to the ventral posterior lateral nucleus of thalamus
- Synapses with 3rd order neuron in VPL thalamic nucleus
- Travels to primary sensory cortex
What is syringomyelia?
Cavitation/ expansion of central spinal canal in cervical region
Damages neurons decussating at expansion site
Causes loss of pain, temperature and simple touch sensations in arms, upper back and upper thorax
How is the spinothalamic tract organised?
Somatotopically
Dorsal to ventral: sacral, leg, arm/thorax, head/neck
What is sacral sparing?
Expanding ventral grey matter tumour can knock out contralateral pain and temperature sensations but may not affect sacral region
What information do the spinocerebellar tracts relay?
Unconscious proprioception
Monitors muscle length, speed of contraction and tension
What route does the dorsal spinocerebellar tract take from the lower limbs?
- Lower limb muscle spindle information enters cord
- Synapses in Clarke’s Dorsal Nucleus (in the white matter)
- Ascends ipsilaterally in the DSCT
- Ends in cerebellum
What is Freidrich’s ataxia?
Inherited disorder causing degeneration of the DSCT
Causes loss of sensation/ coordination in arms and legs, speech impairments, muscle wasting
What route does the dorsal spinocerebellar tract take from the upper limbs?
- Upper limb muscle spindle information runs with the Fasciculus Cuneatus (dorsal column)
- Synapses in Pons
- Proceeds with cuneocerebellar to the cerebellum
What route does the ventral spinocerebellar tract take from the lower limbs?
- LMN enters spinal cord and synapses with UMN
- Decussates at level of synapse
- Ascends spinal cord and decussates at Cerebellum
What route does the ventral spinocerebellar tract take from the upper limbs?
- Upper limb golgi tendon information passes through the Rostral spinocerebellar tract
- LMN synapses with UMN at level of entry to spinal cord
- Ends in cerebellum
How does information from dorsal and ventral spinocerebellar tracts differ?
Information in DSCT mainly from muscle spindles
Information in VSCT mainly from golgi tendon organs
