Ascending and Descending Pathways ☺️ Flashcards
Spinothalamic tract
- functions
- pathway
Lateral - pain, temperature
Anterior - crude touch, pressure
Sensory neurone synapses in DH of SC Decussates ventrally in SC Ascends via STT 2ndary neurone synapses in VPL nucleus of thalamus 3ary neurone ascends via TCT Synapses in somatosensory cortex
Effects of lesions in spinal cord affecting the
- STT
- MLT
STT - Contralateral sensory loss
MLT - Ipsilateral sensory loss
Medial leminiscal tract
- functions
- pathway
Proprioceptive
Fine touch
Vibration
Upper limb (T6 upwards) => fasciculus cuneatus (lateral dorsal column)
Lower limb (T6 downwards) => fasciculus gracilis (medial dorsal column)
Synapse with nucleus cuneatus of medulla oblongata
Decussates ventrally in MO
2ndary neurone synapses in VPL nucleus of thalamus
3ary neurone ascends via TCT
Synapses in somatosensory cortex
Corticospinal tract
- functions
- pathway
Motor function of body from
- primary motor cortex
- premotor cortex
- supplementary motor area
- somatosensory area
Cortex => internal capsule => medulla
DIVIDES INTO 2
Lateral decussates in medulla => ventral horn in SC => supply muscles of the body
Anterior descends into SC => decussates => ventral horn in cervical, upper thoracic SC
Corticobulbar tract
- functions
- pathway
Same inputs as CST
Cortex => internal capsule => brainstem => motor nuclei of CN
-bilateral innervation of UMN
EXCEPT
-contralateral for UMN VII
(LMN that supplies upper face gets innervation from both sides)
(LMN that supplies lower face gets innervation from contralateral side only)
Effects of lesions in the SC affecting the
- CST
- CBT
- EPT
Lateral => ipsilateral motor loss
Anterior above lesion => contralateral motor loss
Increased muscle tone
Increased reflexes, +ve Babinski
Increased fasciculations
Muscle weakness
CNVII => spastic paralysis of contralateral lower face
Often in encephalitis, tumours, degenerative conditions
-dyskinesias
Extrapyramidal tracts
Brainstem - involuntary, automatic control of muscle
IPSILATERAL - vestibulospinal, reticulospinal
CONTRALATERAL - rubrospinal, tectospinal
Vestibulospinal - inputs from balance nuclei
- innervate arm flexors, leg extensors
- balance and posture
Reticulospinal
- MRS from pons => voluntary mv, increased tone
- LRS from medulla => inhibits voluntary mv, reduced tone
Rubrospinal - inputs from red nucleus in midbrain
-decussate in midbrain => SC => fine hand mv control
Tectospinal - inputs from sup colliculus (visual inputs)
-decussate in midbrain => cervical SC => head mv in response to visual stimuli