piri chemical sensations Flashcards
what role do stem cells play in taste and olfaction
compare the diameter of afferents with their function
large diameter projects to muscles, kinda small projects most sensory info, smallest project pain information
how does receptor field size and density of afferent innervation relate
receptor fields with higher density innervation (ex. lips, fingers, toes) have smaller receptor fields
fast adapting corpsucles
pacinian and meissner
slow adapting corpsucles
merkel and ruffini
what properties differentiates each parallel pathway of a sensory afferent
conduction velocity, receptive field size, dynamics, effective stimulus features
pacinian afferents
rapidly adapting, deep in the dermis, very sensitive, detect vibrations, large receptive field
ruffini afferents
slowly adapting fibers, elongated/spindle shaped, sensitive to cutaneous stretch, located deeper in the dermis
meissner
rapidly adapting, on/off responses, close to skin surface, larger receptive fields but more sensitive (reduced spatial resolutions)
merkel
express Piezo 2 (helps with sustained and static firing), signal about grip control and motion, slow adaptation, tip of epidermal sweat ridges, shape/texture, low overall sensitivity but very high resolution
gracile tract
pathway conveying information from the lower limbs, lies medially
cuneate tract
fibers conveying info about upper limbs, trunk, and neck, lateral bundle
two subdivisions of the dorsal column nuclei
gracile nucleus and cuneate nucleus
internal arcuate fibers
second order neurons which send projections to the contralateral part of the thalamus (form medial lemniscus tract)
internal capsule neurons
third order neurons from the VPL thalamus to the postcentral gyrus (primary somatosensory cortex)
the dorsal column medial lemniscal system
allows for mechanosensory signals in the cutaneous surfaces to travel contralaterally to the somatosensory cortex via dorsal column nuclei (internal arcuate fibers) and the VPL thalamus (medial lemniscus)
describe the trigeminothalamic system
first order neurons from the trigeminal ganglion enter the brainstem at the pons in the trigeminal brainstem complex (spinal or principal nucleus). These nuclei project to the ventral posterior medial nucleus of the thalamus via trigeminal lemniscus the the S1 and
S2(overall ipsilateral)
principal nucleus
info from low threshold general cutaneous mechanoreceptors
spinal nucleus
inputs from mechanoreceptor collaterals sensitive to pain, temp. and non-discriminative touch
proprioceptive pathways (lower body)
ascending pathway-carry cutaneous info via the dorsal column, synapse at the dorsal nucleus of clarke(first order) then travel to the ipsilateral posterior lateral column of the spinal cord via dorsal spinocerebellar tract (second order) then to the cerebellum, a collateral branch of the dorsal column nuclei upwards and synapse in the VPL thalamus via medial lemniscus to eventually project to the cerebellum
proprioceptive pathways (upper body)
travel up dorsal column, synapse on lateral dorsal column nuclei called the cuneate nucleus (first order), then they project to the ipsilateral cerebellum or join the contralateral medial lemniscus (second order)
proprioceptive pathways for the face
originate in the mesencephalic trigeminal nucleus in the CNS, pseudounipolar, has peripheral and central projections, eventually reaches the thalamus/somatosensory cortex
