Somatosensation and motor pathways Flashcards
What type of axon for proprioception?
A alpha
myelinated
What type of axon for touch and pressure?
A beta
myelinated
What type of axon for fast pain?
A delta
myelinated
What type of axon for slow pain?
C
unmyelinated
What tract and what special features for fine touch (conscious)?
dorsal column-medial lemniscus (neck and below) trigeminothalamic tract (head)
2-point discrimination
Trigeminothalamic: 3 neurons, crosses ONCE in medulla
What tract and what special features for pain and temp?
lateral spinothalamic tract
Axons cross in anterior white commissure to contralateral white matter tract
What tract and what special features for crude touch?
anterior spinothalamic tract
non-noxious stimuli
What tract and what special features for unconscious proprioception from upper limbs?
dorsal spinocerebellar tract
UNCROSSED
Proprioception from lower limb muscle spindle
What tract and what special features for unconscious proprioception from whole body?
ventral spinocerebellar tract
Crosses TWICE (once in cord, once in midbrain)
What tract and what special features for motor control of face, tongue and pharynx/larynx?
corticospinal tract (+ corticobulbar)
(pyramidal tract) Mostly partly crossed Lateral crosses in medulla Anterior crosses in cord Upper and lower motor neurons
What tract and what special features for increasing extensor muscle tone
reflex muscle movements to maintain balance?
lateral vestibulospinal tract
extrapyramidal
ipsilateral
What tract and what special features for head position
reflex muscle movements to maintain balance?
medial vestibulospinal tract
extrapyramidal
bilateral
What tract and what special features for motor control, autonomic, pain reflex?
Reticulospinal tract (alpha motor neurons) (extrapyramidal)
Pontine (medial RST) UNCORSSED: facilitates extensors
Medullary (lateral RST) bilateral: inhibits extensors
Upper motor neuron lesions =
add or increase
Lower motor neuron lesions =
take away or decrease
4 stages in motor cortex stimulation loop?
Premotor cortex
basal nuclei
thalamus
(red nucleus) motor cortex
3 basal ganglia disorders
Parkinson’s- substantia nigra
Chorea & athetosis- striatum
Ballism- subthalamic nucleus
3 cerebellar disorders
Posterior lobe – intention tremor
Anterior lobe – gait ataxia
Flocculonodular lobe – truncal ataxia
8 stages of visual pathway
Retina optic nerve optic chiasm optic tract (info from contralateral visual field) LGD and superior colliculus optic radiations visual cortex visual association cortex
What is the light reflex?
brainstem reflex, direct (pupil in same eye constricts), consensual (pupil in opposite eye constricts)
What is the accommodation reflex?
controlled by ciliary muscle, sphincter pupillae contract (parasympathetic) and medial recti, like light reflex but goes to visual cortex first (conscious)
4 stages of the auditory pathway
ear to midbrain (IC, for reflexes) to thalamus (MGB) to cortex (conscious appreciation)
Three types of hearing damage and response
Unilateral destruction = hearing loss
Bilateral destruction = cortical deafness
Wernicke’s area damage = receptive aphasia
What is the vestibular pathway?
utricle, saccule & semicircular canals to vestibular nerve to lateral vestibular nucleus (control of posture) or medial vestibular nucleus (vestibuloocular reflexes)
