somesthesis

Question 1

what are the 2 major groups of tactile receptors?

Answer 1

slowly adapting mechanoeceptors and rapidly adapting mechanoreceptors ( pg. 541)

Question 2

what do slowly adapting mechanoreceptors respond to?

Answer 2

an enduring stimulus

Question 3

when do rapidly adapting mechanoreceptors respond?

Answer 3

only at the onset and sometimes the termination of a long stimulus.

Question 4

name two rapidly adapting mechanoreceptors

Answer 4

meissner’s corpuscle and pacinian corpuscle

Question 5

name two slowly adapting mechanoreceptors

Answer 5

merkel receptors and ruffini’s corpuscle

Question 6

every hair on the body is a __________

Answer 6

mechanoreceptor

Question 7

what areas of the body have the smallest receptor field sizes?

Answer 7

sensitive areas with lots of receptors e.g. lips and finger tips

Question 8

which areas of the body have the greatest capacity for fine spatial discrimination?

Answer 8

the highly sensitive areas like lips and finger tips

Question 9

what are 2 major ascending systems that carry somatosensory information to the cerebral cortex?

Answer 9

the dorsal column-lemniscal system and the anterolateral system

Question 10

what does the dorsal column-lemniscal system mediate?

Answer 10

tactile sensations including vibration and proprioception ( the sense of the relative position of neighbouring parts of the body and strength of effort being employed in movement)

Question 11

what does the anterolateral system mediate?

Answer 11

it carries mainly information about pain and temperature

Question 12

what are the peripheral mechanoreceptors innervated by and where do their cell bodies lie?

Answer 12

the sensory ( afferent) axons whose cell bodies lie in the dorsal root ganglia.

Question 13

where does crossing of the sensory fibers occur?

Answer 13

in the caudal medulla oblongata

Question 14

where do the sensory fibers synapse?

Answer 14

in the cuneate and gracile nuclei= the dorsal column nuclei

Question 15

what happens at the level of the dorsal column nuclei receptor?

Answer 15

neurons coverage onto single 2nd order neurons:

their receptive fields enlarge due to convergence of input from many 1˚ neurons

and they become more complex b/c 2nd order neurons have BOTH excitatory and inhibitory regions while 1st order only have excitatory receptive fields

Question 16

what does lateral inhibition w/ a punctate stimulus show ( point source deformation of the skin for e.g. )?

Answer 16

this demonstrates how the primary units of a point source ( like a pin for example) stimulates or influences it’s own 2˚ units and the neighboring 2˚ units. ( pg. 553)

Question 17

what is two point discrimination and what s the basis for it?

Answer 17

the ability to discern that two nearby objects touching the skin are truly two distinct points, not one.

this occurs because the two 1˚ units that share a neighbor in the middle will have a negative effect on the common neighbor at the 2˚ unit while each of the 2˚ units of the point sources will be stimulated.

Question 18

what is the medial lemniscus?

Answer 18

the fiber bundle in which the the sensory fibers travel to the brain once the decussate at the dorsal column nuclei.

Question 19

the right side of the brain receives sensory input from _________ side of the body?

Answer 19

the left

Question 20

where do the medial lemniscus fibers synapse?

Answer 20

on the ventral posterior nucleus of the thalamus

Question 21

what is on the lateral division of the ventral posterior nucleus?

Answer 21

trunk and limbs terminating cells

Question 22

what is on the medial division of the ventral posterior nucleus?

Answer 22

the input from the face

Question 23

what is the part of the cortex that receives somatosensory input from the ventral posterior nucleus?

Answer 23

the post central gyrus

Question 24

how are projections from the medial division of the ventral posterior nucleus directed in the post central gyrus?

Answer 24

the medial division ( face) of the ventral posterior nucleus projects to the lateral portion of the post central gyrus. (see pgs 563-564)

Question 25

how are projections from the lateral division of the ventral posterior nucleus directed in the post central gyrus?

Answer 25

the lateral division ( trunk and limbs) of the ventral posterior nucleus projects to the medial and superior portion of the post central gyrus. ( the foot is most medial in the post central gyrus) ( see pgs 563-564)

Question 26

what are the broadman areas of sensory information?

Answer 26

3a, 3b, 1, and 2

Question 27

what does broadman area 3a respond to?

Answer 27

deep tissue input

Question 28

what does broadman area 3b respond to?

Answer 28

activation of rapidly or slowly adapting cutaneous receptors

Question 29

what does broadman area 1 respond to?

Answer 29

activation of rapidly adapting cutaneous receptors

Question 30

what does broadman area 2 respond to?

Answer 30

deep pressure

Question 31

where are the cells that respond only to a stimulus when it moves across the skin in a particular direction located?

Answer 31

in the most posterior portion of the sensory information section mostly in area 2 but also in 1 but not in areas 3a and 3b.

Question 32

what occurs in broadman areas 5 and 7 (located posteriorly in the posterior parietal complex)?

Answer 32

processing of sensory information becomes even more complex

Question 33

how did the hand rotation experiment with the monkeys demonstrate that plasticity can occur in adulthood?

Answer 33

since the monkeys were encouraged to use their three fingers and not use the pinky or thumb to get a reward, more cortex became devoted to the middle fingers was increased so that after the experiment was done they still used those 3 fingers more.