somatosensory system Flashcards
what does the somatosensory system do for us?
touch , pressure, vibration, joint and muscle position sense
temperature
pain
itch
what are the sensory receptive properties of primary afferent (sensory) neurones?
- modality
- threshold
- adaption rate
- conduction velocity
- site and extent of peripheral termination
describe the threshold units?
low threshold units respond to low intensity/non damaging stimuli
high threshold units respond to high intensity/ damaging and painful stimuli
what is adaption?
this determines whether they change their firing rate only in response to a stimulus of changing intensity or do they fire continuously throughout a constant stimulus
what does conduction velocity depend on?
the diameter of the neurone
what are the 2 somatic sensory pathways?
dorsal column medial leminscal pathway
spinothalamic tract
in dorsal colum medial leminscal pathway where do the first and second neurones synapse?
brain stem
in the spinothalamic tract where do the 1st and 2nd order neurones synapse?
in spinal cord
2nd to 3rd order neurones in both sensory pathway shappens where?
thalamus
medial fasiculus gracilis and lateral fasciculus are part of what?
dorsal colums
sensory input to T6 and below travels in..?
fasciculus gracilis
sensory input above T6 travels in ..?
fasciculus cuneatus
major route for touch and proprioception?
dorsal column medial lemniscal pathway
explain how the dorsal column medial lemniscal pathway work?
first order neurone enters dorsal horn and forms synapses in the horn and forms an immediate ascending component.
axons from the second order neurones cross collectively in the great sensory decussation and ascend in the medial leminscus to the ventral posteriolateral nucleus of the thalamus
3rd order thalamic neurones project to the primary somatosensory coretx via the posterior internal capsule
what system does sensory for the anterior head?
trigeminal system
