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NS9 - Sensory Rs + Pathways (iii) (Spinothalamic Pathway/Anterolat system,…
NS9 - Sensory Rs + Pathways (iii)
All pathways pass through thal before cortex EXCEPT...
olfactory pathway: nose->cortex
equilibrium pathway: to cerebellum (with brain to cortex via the thal)
Spinothalamic Pathway/Anterolat system
for pain + temp
1st order neurons: axons from R to cord via dorsal root, synapse in doral horn
2nd order neurons: axons decussate in ant. commissure (connects 2 temporal lobes) + ascend in spinothalamic tract, synapse in thal
3rd order neurons from thal to cortex
3 neuron system
causes convergence + divergence of input
convergence: 1 postsynaptic neuron receives multiple inputs from different presynaptic neurons
divergence: 1 presynaptic neuron communicates with many postsynaptic neurons
influences quality of sensation in CNS (conscious/subconsious)
non-specific pathways transmit information from multiple R types to the brainstem reticular formation + regions of thal not part of specific ascending pathways
Dorsal column med/lemniscal system
for proprioception in arms, vibration, discriminative touch
1st order neurons from R to cord via dorsal root, ascend in doral columns + synapse in gracile + cuneate nuclei of medulla
2nd order neutrons decussate in lower medulla + form med. lemniscus synapse in thal
3rd order neutrons from thal to cortex
3 neuron system
Spinocerebellar pathway
lower limb unconscious proprioception
provides information to cerebellum
ascends in dorsal column to thoracic/upper lumbar region
synapses in Clarke's column/nucleus dorsalis, the projects to medulla in doral spinocerebellar tract
rejoins med lemniscal system, from thal to cortex
Cortical sensory homunculus
model of human body reflecting how much each body part occupies on SS cortex (reflects R density)
big hands + lips
SS strip = inverted
Perception
conscious
special senses
vision, hearing, taste, smell, balance
somatic senses
touch, pain, pressure, temp, proprioception
subconscious
somatic stimuli
muscle length + tension
visceral stimuli
BP, pH, pO2, osmolarity, temp, blood glucose, GIT distension, lung inflation