2 Somatosensory System

Question 1

Dorsal root ganglian cell is located in the spinal cord

Answer 1

False. The dorsal root ganglian is a cluster of nerve cell bodies (a ganglion) in the posterior root of a spinal nerve. Their axons are afferents that relay sensory information into the central nervous system. The differ from majority of neurons in that an action potential in a posterior neuron may initiate in the distal axon, bypass the cell body, and continue to propagate along the proximal axon until reaching the synaptic terminal. Bare nerve ending in the distal end, possibly covered by meissner or pacinian corpuscle.

Question 2

What are the characteristics of a pacinian corpuscle? shallow/deep ? small/large receptive field? high/low frequency? transient/sustained?

Answer 2

A pacinian corpuscle (onion skin) is: deep large receptive field high frequency transient //sensitive to vibration and pressure //respond to sudden disturbances // ~250 Hz//unmylenated end of DRG is wrapped by skin cells like an onion

Question 3

What are the characteristics of a Meissner’s corpuscle?

Answer 3

shallowsmall receptive fieldlow frequencytransient//~10-50 Hz// gripping objects//epidermis with unmylinated end of DRG wrapped around it

Question 4

There is a higher density of Merkel disks on your finger than your arm

Answer 4

true

Question 5

What are the characteristics of Merkel disk cells?

Answer 5

shallow placementsmall, spotty fieldsustainedtwo point discrimination//sensitive to form, edges, texture

Question 6

What two types of mechanoreceptors are probably involved in reading Braille?

Answer 6

merkel disksmeissner’s corpuscles

Question 7

Where do we FIRST start to get direction selectivity from a single cell?a. S2b. S1c. VPNd. spinal corde. none of the above

Answer 7

S1

Question 8

S1 is located in the precentral gyrus

Answer 8

falseS1 is located in the (parietal lobe-somatosensory cortex) postcentral gyrus. It is the main sensory receptive area for TOUCH

Question 9

Signals from mechanoreceptors in your left hand end up in your right brain hemisphere

Answer 9

true!signals from mechanoreceptors in your right hand cross over to the left brain hemisphere too

Question 10

Weigert stain stains for a. somab. axonsc. whole neuronsd. whole gliae. none of the above

Answer 10

Weigert stain stains for AXONS

Question 11

What are the two primary types of DRG cells discussed in class?

Answer 11

(dorsal root ganglion)

Aa - proprioception - mylenated very fast

Ab - mechanoroception - mylenated pretty fast

Question 12

What are the three types of mechanoreceptors discssued in class?

Answer 12

merkel disk receptor

meissner’s corpuscle

pacinian corpuscle

Question 13

what are the different properties of response fields?

Answer 13

small vs. large

inhibititory vs. excitatory

complete vs. incomplete (surround)

whole vs. patchy

Question 14

which type of cell features an unmylenated end of DRG winding through a stack of flattened skin cells, placed shallow

Answer 14

meissner’s corpuscle

Question 15

which type of mechanoreceptor cell is response to light touch

Answer 15

meissner’s corpuscle sensitive to low frequency vibrations (10-50Hz) with a SMALL response field

Question 16

which cells help with grip control?

Answer 16

meissner’s corpuscle

Question 17

which mechanoreceptors feature unmylinated portions of DRG wrapped with multple layers of skin cells, placed deeply?

Answer 17

pacinian corpuscle

Question 19

which mechanoreceptor is rapidly adapting?

Answer 19

pacinian corpuscle

Question 20

which mechanoreceptors help to detect texture?

Answer 20

pacinian corpuscle and merkel disks

Question 21

which mechanoreceptor is sensitive to high frequency vibration?

Answer 21

pacinian corpuscle

Question 22

which mechanoreceptor features a single DRG cell contacting multiple cells embedded in the skin with shallow placement?

Answer 22

merkel disk

Question 23

which mechanoreceptor helps with multi-point discrimination?

Answer 23

merkel disks

Question 24

What are the components of the somatosensory cortex?

Answer 24

postcentral gyrus, posterior bank of central sulcus

composed of subregions: 3a, 3b, 1, 2

Question 25

What is topographic representation?

Answer 25

The way in which many neurons in the brain are anatomicall arranged in a systematic fashion such that neurons responding to similar features of a sensory modality are grouped in the same space

an example is the concept of barrel/whisker in the rat

Question 26

What do Goligi stains reveal?

Answer 26

these reveal cell bodies, axons and dendrites

Question 27

What do Nissl stains reveal?

Answer 27

these reveal cell bodies

Question 28

What do Weigert stains reveal?

Answer 28

these reveal axons

Question 29

at what level can we expect DRG to converge, maintaining directional sensitivity?

Answer 29

S2