Sensation Flashcards
what are the modalities sensed by the spinothalamic system
pain, temperature and crude touch
what are the modalities sensed by the dorsal column
fine touch, 2 point discrimination, proprioception and vibration
where are the cell bodies for primary sensory neurones found
in the dorsal root ganglion
which sensory neurones decussate
secondary
where do sensory neurones decussate
spinothalamic = ventral white commissure
dorsal column = medulla
where are the cell bodies for the secondary sensory neurones
spinothalamic = dorsal horn
dorsal column = medulla
where are the cell bodies for the tertiary sensory neurones
thalamus
in the spinothalamic tract are fibres from higher regions added medially or laterally
medially
in the spinothalamic tract are the lower fibres more medial or lateral
lateral
in the dorsal column tract are fibres from higher regions added more medially or laterally
laterally
in the dorsal column tract are the lower fibres more medial or lateral
medial
where do the primary neurones of lower fibres in the dorsal column synapse
gracile nucleus
where do the primary neurones of the upper fibres in the dorsal column synapse
cungate nucleus
what is the name of the pathway of the secondary neurone in the dorsal column tract
medial lemniscus pathway
what are rapidly adapting receptors
receptors which initially give a higher frequency of action potentials but then slows down the rate of frequency
give an example of a rapidly adapting receptor
mechanoreceptors
what are slowly adapting receptors
where the frequency of action potentials given off by the receptor remains the same
give an example of a slowly adapting receptor
pain receptor
what happens to the acuity with a large receptive field
it decreases - therefore, there a less distinct outlines of dermatomes as theres no overlap
what is the receptive field
the regions containing receptors feeding back to one primary neurone
describe the homunculus
lower regions of the body are projected medially on the cortex but the upper regions are projected laterally onto the cortex
what happens if there is a lesion to the dorsal roots
you will lose all modalities at that level
when does brown-sequard syndrome occur
when there is damage to one half of the spinal cord only
describe the effect of brown-sequard syndrome
- anaesthesia across the single dermatome
- ipsilateral loss of dorsal column modalities at that level and below
- contralateral loss of spinothalamic modalities at that level and below
what are the name of the primary neurones involved in the sensation of pain
C fibres
how can the sensation of pain be inhibited
- mechanoreceptors
- heat
- opiates
- descending projections from the brain
describe how mechanoreceptors inhibit pain
activating the mechanoreceptors by rubbing them excites inhibitory enkephalinergic interneurones which inhibit pain through activating A fibres
