Spinal Cord: Ascending tracts & sensation Flashcards
List 5 types of receptors in the hand.
Meissner corpuscle
Pacinian corpuscle
Ruffini ending
Merkel discs
Free nerve endings
What do Meissner corpuscles detect?
Discriminative touch
What do Pacinian corpuscles detect?
Deep pressure & vibration
What do Ruffini endings detect?
Touch
Sheer stress / forces
What do Merkel discs detect?
Light, sustained touch
What do free nerve endings detect?
Pain & temperature
What is the function of the superior parietal lobe?
Integration of sensory inputs, sensory memory, perception of contralateral self/ world
What does the anterior limb of the internal capsule contain?
Descending fibres (frontopontine + frontothalamic)
What does the genu and posterior limb of the internal capsule contain?
Motor fibres to the head, arm, leg + sensory fibres
What does the retrolenticular part of the internal capsule contain?
Visual and auditory input
Describe the route of each neuron in the 3 neuron ascending sensory pathway.
1st order neuron – enters spinal cord via dorsal root, ascends ipsilaterally
2nd order neuron – decussates to ascend to the thalamus
3rd order neurons – leave thalamus to ascend to cortex via internal capsule
What are the 2 main nuclei in the thalamus for sensory input?
Ventral posterior lateral nucleus (VPL)
Ventral posterior medial nucleus (VPM)
The VPL nucleus in the thalamus receives sensory input from what?
Body
The VPM nucleus in the thalamus receives sensory input from what?
Face
What are the 3 sensory tracts?
Dorsal column pathway
Spinothalamic tract
Spinocerebellar tract
The dorsal column pathway receives sensory input from which 5 receptors?
Meissner’s, Merkel’s, Pacinian, Ruffini & joint proprioceptors
The dorsal column pathway receives which 2 kinds of sensory input?
Discriminative touch & vibration
Conscious proprioception
The spinothalamic tract receives sensory input from which receptors?
Free nerve endings
The spinothalamic tract receives which 3 kinds of sensory input?
Pain
Temperature
Simple touch
The spinocerebellar tract receives sensory input from which 2 receptors?
Muscle spindles
Golgi tendon organs
The spinocerebellar tract receives which kind of sensory input?
Unconscious proprioception
What are the 2 sections of the dorsal column pathway and from which vertebral levels do they receive fibres from?
Fasciculus Gracilis – from below T6
Fasciculus cuneatus – from above T6
Where do 2nd order neurons in the dorsal column pathway decussate?
Medulla
What are 2nd order neurons in the dorsal column pathway called after they decussate? Where do they ascend to?
Medial lemniscus – which ascends to VPL nucleus of the thalamus
Via what tract does sensory information from the face reach the brain?
Trigeminothalamic tract
Where do 1st order neurons of the trigeminothalamic tract enter the brainstem?
Pons
What are 2nd order neurons in the trigeminothalamic tract called after they decussate? Where do they ascend to?
Trigeminal lemniscus – which ascends to VPM nucleus of the thalamus
Describe the loss of sensation that would occur if the dorsal column pathway was damaged?
Ipsilateral loss of sensation below the level of the lesion
Which STD can damage the dorsal column pathway?
Tertiary syphilis
Which 2 conditions might result from dorsal column damage?
These are caused by the loss of which specific sensory input?
Pseudoathetosis – writhing of digits, hands, and feet
Sensory ataxia – leads to positive Romberg sign & stamping gait. Caused by a loss of proprioception
1st order neurons in the spinothalamic tract enter the spinal cord via what?
Tract of Lissauer
Where do 2nd order neurons in the spinothalamic tract decussate?
1-2 vertebral levels above the entry into the spinal cord
2nd order neurons in the spinothalamic tract decussate across what?
Anterior white commissure
The spinothalamic tract route can be damaged by which condition that typically occurs in the cervical vertebrae?
Syringomyelia – cavitation of the central canal which damages the anterior white commissure
Describe the somatotopic organization of the spinothalamic tract, beginning from the centre and going outwards.
Neck, arm/thorax, leg, sacral
Due to the direction it is likely to grow, a spinothalamic tract tumour can spare which region?
Sacrum – sacral sparing
Which part of the spinocerebellar tract receives input from muscle spindles?
Dorsal spinocerebellar tract
Which part of the spinocerebellar tract receives input from golgi tendon organs?
Ventral spinocerebellar tract
Does the spinocerebellar tract carry sensory to the ipsilateral or contralateral cerebellum?
Ipsilateral
Although it is rare for the spinocerebellar tract to be damaged in isolation, in which condition can this occur?
Friedreich’s ataxia – autosomal recessive condition
