Somatosensory Tracts

Question 1

what sensors do proprioception?

Answer 1

receptors in joint capsules- position and speed of movement

receptors in muscles detect tension and stretch- muscle spindle and golgi tendon organs

Question 2

what does each peripheral nerve fiber type do?

Answer 2

A-a- largest- muscle spindles
A-b- touch, pressure, and joint proprioception
A-g motor and muscle spindles
A-d- pain

B- sympathetic preganglionic

C- pain, thermo

Question 3

first, second, third order neurons

Answer 3

first- peripheral axon, cell body in DRG

second- CNS tract ends in thalamus

third- thalamocortical

Question 4

what are the two pathways do tactile and proprioceptive info?

Answer 4

dorsal column/medial lemniscus

trigemninal mechanosensory system

Question 5

what are the two pathways that do pain and crude touch

Answer 5

anterolateral (spinothalamic)

spinal trigeminal

Question 6

what two pathways do unconscious proprioception

Answer 6

dorsal spinocerebellar

cunceocerebellar

Question 7

are ALT receptors encapsulated or no? what do they sense?

Answer 7

not encapsulated- free nerves- Ad and C fibers

pain/crude touch

Question 8

heat/cold receptor range

Answer 8

heat- 29-45 C
cold 5-40 C

TRP receptors

Question 9

fast v slow pain

Answer 9

fast A-d- sharp pain

slow- C- dull, aching, burning

Question 10

sensitization of nociceptos

Answer 10

when excited, become more sensitized via prostaglandins/bradykinins

Question 11

substance P

Answer 11

released by activated nocioceptors, cause dilation, swelling and histamine

Question 12

allodynia

Answer 12

benign stimuli percieved as dangerous

Question 13

hyperalgesia

Answer 13

painful stimuli perceived as more painful

Question 14

where do ALT fibers dessucate

Answer 14

spinal cord, w/in a few segments of entering

dessucate through the anterior commissure

Question 15

how are the fibers in the ALT organized?

Answer 15

legs lateral, arms medial, trunk in between

Question 16

where do ALT neurons synapse in thalamus?

Answer 16

VPL nucleus- travel to primary somatosensory cortex in postcentral gyrus

Question 17

periaqueductal gray

Answer 17

pain modulating pathways that project to substantia gelatinosa

Question 18

gate control theory of pain

Answer 18

descending inputs synapse on interneurons that release inhibitor NTs on nocioceptor synapses

Question 19

what mechanoceptors do fine touch?

Answer 19

meissner corpuscle- fine touch
pacininan corpuscle- pressure
ruffini ending- stretch

Question 20

where do first order fibers synapse in the dorsal columns?

Answer 20

the gracile and cuneate nucleus to internal arcuate fibers

Question 21

second order neurons in DC-ML

Answer 21

from gracile/cuneate nucleus, thru internal arcuate fibers, and up to VPL

Question 22

organization with medial lemniscus

Answer 22

legs is most anterior, arms most posterior. slowly legs swing laterally while arms stay medially

Question 23

the only sensory ganglion cells inside the CNS

Answer 23

proprioceptive sensory fibers of trigeminal. the rest of the trigeminal sensory cell bodies are in the trigeminal ganglion

Question 24

difference between the 3 sensory trigeminal ganglia

Answer 24

principle nucleus (chief) - well localized touch/pressure

mesencephalic- proprioceptive

spinal nucleus- pain/temp

Question 25

second order trigeminal touch neurons

Answer 25

anterior/ventral trigeminothalamic tract some ipsilateral fibers

Question 26

where do second order neurons for trigeminal touch terminate

Answer 26

VPM

Question 27

spinal tract of the trigeminal nerve

Answer 27

enter w/ trigeminal nerve in pons, run caudally conveys pain/temp ipsilateral sensation

Question 28

second order neurons of spinal nucleus of trigeminal

Answer 28

anterior trigeminothalamic contralateral, runs near medial lemniscus synapses at VPM

Question 29

reflexs of trigeminal

Answer 29

``` corneal reflexes (motor 7) tearing (motor 7) cough and sneeze oculocardiac (motor 10) jaw jerk (motor 5) ```

Question 30

spinal reticular fibers

Answer 30

collateral spinothalamic

Question 31

dorsal spinocerebellar pathway

Answer 31

ipsilateral- arising from muscle spindles, golgi tendon unconscious proprioception to cerebellum only lower body

Question 32

nucleus dorsalis

Answer 32

where the dorsal spinocerebellar first order neurons synapse with second order neurons in the spinal cord

Question 33

cunceocerebellar

Answer 33

upper limb equivalent of dorsal spinocerebellar tract ascends w/ fasiculus cuneatus second order neurons arise from cuneate nucleus ispilateral