Somatosensation beyond the DC/ML

Question 1

what are 5 primary somatosense modalities

Answer 1

1. nociception
2. temp
3. vibration
4. light touch
5. proprioception

Question 2

what are 4 cortical sensory modalities

Answer 2

1. graphesthesia
2. stereognosis
3. 2 point discrim
4. double simultaneous stims

Question 3

what are 3 main classes of receptors and what they respond to

Answer 3

1. exteroceptors - light, sounds, tissue damage, temp, touch, pressure
2. proprioceptors - monitor muscle, tendons and joints
3. enteroceptors - monitor visceral stim

Question 4

what do chemoreceptor sense

Answer 4

taste and smells

Question 5

what do mechanoreceptors snese

Answer 5

deformation in cell membrane

Question 6

what do nociceptors sense

Answer 6

tissue damage in reposnse to mech, thermal, chem damage

Question 7

what is the receptor threshold

Answer 7

stim intensity needed for AP 50% of the time

Question 8

what are low and high threshold receptors senses for

Answer 8

low - tactile

high - nociception

Question 9

what are rapidly adapting receptors

Answer 9

only fire during changes in stim - good for high freq vibration and movement of objects across skin

Question 10

what are slow adapting receptors

Answer 10

report continuously on the stim - good for pressure, shape

Question 11

what are nerve fiber classes from largest diameter to smallest

Answer 11

Aa, 
Ab
Ag
Ad
B
C

Question 12

which are not mylenated

Answer 12

C

Question 13

what are sensations and location of Aa

Answer 13

limb position, motion - extrafusal muscle cell

Question 14

what are sensations and location of Ab

Answer 14

skin - conscious proprio, touch, pressure, vibraiton

Question 15

what are sensations and location of Ag

Answer 15

intrafusal muscle fibers

Question 16

what are sensations and location of Ad

Answer 16

fast pain, cold, hair follicles

Question 17

what are sensations and location of B

Answer 17

preganlionic autonomic: white rami

Question 18

what are sensations and location of C

Answer 18

slow pain, warmth: autonomic post-ganglionic

Question 19

how is stim intensity coded

Answer 19

frequency of AP

Question 20

how is locaiton coded

Answer 20

receptor field

Question 21

how is modality coded

Answer 21

based on the type of axon firing

Question 22

how is total quality coded

Answer 22

by the population of axons firing

Question 23

what is adv. to 3 neuron system

Answer 23

can relay to places other than the cortex as well

Question 24

what are 3 other areas of projection and for what

Answer 24

1. to neuron in dorsal horn to supress pain pathway
2. to medullary and pontine reticular formations for alter response and modifying reflexes
3. to sup. colliculus to drive orienting reflexes

Question 25

what are 3 integrations that happen at first synapse

Answer 25

1. cortical descending inhibition refines attention
2. lateral inhibition sharpens localization (review)
3. modalities remain segregated

Question 26

what are Funct. of 4 areas of primary somatosensory area

Answer 26

1. responds to input from cut. mechanoreceptors
2. responds to input from propriot
   3 and 4 - integrate these modalities to diff. shape, size and texture

Question 27

what is secondary somatosensory area

Answer 27

receives from S1 and thalmus for tactile memory

Question 28

what is sensory association area

Answer 28

integration of vision and somatosense