piri chemical sensations

Question 1

what role do stem cells play in taste and olfaction

Question 2

compare the diameter of afferents with their function

Answer 2

large diameter projects to muscles, kinda small projects most sensory info, smallest project pain information

Question 3

how does receptor field size and density of afferent innervation relate

Answer 3

receptor fields with higher density innervation (ex. lips, fingers, toes) have smaller receptor fields

Question 4

fast adapting corpsucles

Answer 4

pacinian and meissner

Question 5

slow adapting corpsucles

Answer 5

merkel and ruffini

Question 6

what properties differentiates each parallel pathway of a sensory afferent

Answer 6

conduction velocity, receptive field size, dynamics, effective stimulus features

Question 7

pacinian afferents

Answer 7

rapidly adapting, deep in the dermis, very sensitive, detect vibrations, large receptive field

Question 8

ruffini afferents

Answer 8

slowly adapting fibers, elongated/spindle shaped, sensitive to cutaneous stretch, located deeper in the dermis

Question 9

meissner

Answer 9

rapidly adapting, on/off responses, close to skin surface, larger receptive fields but more sensitive (reduced spatial resolutions)

Question 10

merkel

Answer 10

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

Question 11

gracile tract

Answer 11

pathway conveying information from the lower limbs, lies medially

Question 12

cuneate tract

Answer 12

fibers conveying info about upper limbs, trunk, and neck, lateral bundle

Question 13

two subdivisions of the dorsal column nuclei

Answer 13

gracile nucleus and cuneate nucleus

Question 14

internal arcuate fibers

Answer 14

second order neurons which send projections to the contralateral part of the thalamus (form medial lemniscus tract)

Question 15

internal capsule neurons

Answer 15

third order neurons from the VPL thalamus to the postcentral gyrus (primary somatosensory cortex)

Question 16

the dorsal column medial lemniscal system

Answer 16

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)

Question 17

describe the trigeminothalamic system

Answer 17

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)

Question 18

principal nucleus

Answer 18

info from low threshold general cutaneous mechanoreceptors

Question 19

spinal nucleus

Answer 19

inputs from mechanoreceptor collaterals sensitive to pain, temp. and non-discriminative touch

Question 20

proprioceptive pathways (lower body)

Answer 20

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

Question 21

proprioceptive pathways (upper body)

Answer 21

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)

Question 22

proprioceptive pathways for the face

Answer 22

originate in the mesencephalic trigeminal nucleus in the CNS, pseudounipolar, has peripheral and central projections, eventually reaches the thalamus/somatosensory cortex