Sensorimotor systems Flashcards
What is the spinal organisation of a reflex arc?
Muscle spindle - type 1a proprioceptor - cell body in DRG - axonal projection to the dorsal horn -
1) - synapse with inhibitory internueron - synpase with antagonist muscles alpha motor neuron in ventral horn - project to muscle - relaxation
2) syanpse directly with agaonist muscle alpha maotor neuron in ventral horn - project to muscle - contraction.
Where do proprioceptors project to?
Includes type Ia, Ib and type 2
Project to different layers of the ventral horn.
Or project up the spinal cord via the dorsal columns or the spinocerebellar tracts
Where do primary sensory neurons project to?
Different layers of the dorsal horn
What do primary mechanoreceptors neurons project to?
Are sensory neurons
Project to the dorsal horn locally as well as up the dorsal columns in the spinal cord.
What are some different mechanoreceptors linked to the function of A-beta fibres?
Pacinian corpuscles - vibration
Meissners corpuscles - fine touch, dscriminative touch
Ruffini endings - twisting
Alpha-beta is responsible for pressure and vibration
What is the role of C-fibres?
Type of sensory neuron
Project to dorsal horn
Responds to nociceptors - chronic, dull, poorly localised pain or delayed pain
What is the role of A-delta fibres?
Type of sensory neuron
Project to the dorsal horn
Responds to nociceptors - fast pain and cold
What is the difference between a funiculus and a fasiculus?
Funiculus = big chunk of white matter
Fasiculus = particular axon tract
For example cuneate fasiculus is in the dorsal white funiculus.
What is the dorsal intermediate sulcus?
Groove separating gracile fasiculus and cuneate fasiculus - appears at T6 level.
What are the two axon tracts for the DCML (touch signalling) pathway in the spinal cord?
The cuneate fasiculus - (the lateral one) appears at T6 above level, for upper limbs
The gracile fasiculus - (the medial one), present throughout the spinal cord, for lower limbs.
Label the following cross section of the spinal cord.
What are the dark green tracts?
The dorsal and ventral spinocerebellar tracts
What is the orange tract?
The spinothalamic and spinoreticular tracts
What are the blue tracts?
The ventral and lateral corticospinal tracts
What is the brown tract?
The vestibulospinal tract
What is the purple tract?
The recticulospinal fibres
What tract is responsible for the mechanosensory circuitry of touch for the body?
The DCML pathway
Describe the mechanosensory circuitry pathway underpinning touch in the body?
The DCML pathway
Mechanosensory receptors active primary sensory neurons from lower/upper body have cell bodies in the DRG
Then travel up the the gracile tract and cuneate tract respectively.
Synapse with a secondary neuron in the gracile and cuneate nucleus respectively in the medulla
Internal arcuate fibres desicate to the contralteral side
Contineu as the medial lemnisuc axons projecting the the ventral posterior lateral nucleus of the thalamus
Synapse with a tertiary neuron which projects to S1.
Describe the mechanosensory circuitry responsible for pain/touch in the head.
Primary somatosensory neurons has cell bodies in the trigeminal ganglion
Axonal projections to the trigeminal sensory nucleus in the pons - synapse with secondary neuron
Thse trigeminal leminscus axons desicate to the contralateral side and project to the ventral posterior Medial nucleus of the thalamus.
Synapse with tertiary neuron
Ventral posterior medial nucleus axons project to S1.
What is the embryological origin (secondary vesicle) from which the thalamus develops from?
The diencephalon.
What nucleus in the thalamus does the limbic system use?
The anterior nuclear group