martin chapter 4

Question 1

spinal somatic sensory system

Answer 1

conveys info from the body (limbs, neck, trunk..) to the brain

Question 2

trigeminal somatic sensory system

Answer 2

conveys info from the face, scalp, head to the brain

Question 3

what is proprioreception?

Answer 3

our sense of limb position and limb movement

Question 4

each somatic sensation (modality) has multiple?

Answer 4

submodalities

Question 5

what is a dorsal root ganglion?

Answer 5

cluster of neuronal cell bodies located in the dorsal root of a spinal nerve, just outside the spinal cord

Question 6

dorsal root ganglion neurons are which type of neurons?

Answer 6

pseudounipolar neurons

Question 7

the cell bodies of dorsal root ganglion neurons are in?

Answer 7

the dorsal root ganglia

Question 8

dorsal root ganglion neurons are pseudo unipolar. a single axon arises from the cell body and it branches in?

Answer 8

one axonal branch is directed towards the periphery (where it innervates the skin or other tissues)
one axonal branch is directed towards the CNS, to synapse with CNS neurons

Question 9

the peripheral or central axon branches of dorsal root ganglion neurons are called?

Answer 9

primary (afferent) sensory fibers

Question 10

the receptive portion of the dorsal root ganglion neuron is?

Answer 10

the peripheral axon terminal

Question 11

the receptive field of the neuron corresponds to?

Answer 11

the area of the skin where stimulation activate the neuron

Question 12

where are mechanoreceptors located?

Answer 12

at the terminal end of the peripheral axon branch of a dorsal root ganglion neuron

Question 13

which types of channels are present in the membrane of mechanoreceptors?

Answer 13

stretch activated channels

Question 14

rapidly adapting receptors

Answer 14

receptors that respond quickly to the onset of the stimulus or when the stimulus changes (such as the end of the stimulus)

Question 15

slowly adapting receptors

Answer 15

respond for the duration of the stimulus

Question 16

rapidly adapting receptors (2)

Answer 16

Meissner corpuscles and pacinian corpuscles

Question 17

slowly adapting receptors (2)

Answer 17

Merkel’s receptor and Ruffini corpuscles

Question 18

5 major types of encapsulated sensory receptors that mediate mechanosensation

Answer 18

-Meissner corpuscles
-Pacinian corpuscles
-Merkel’s receptor
-Ruffini corpuscles
-hair receptors

Question 19

location of Merkel’s receptor and Meissner corpuscles

Answer 19

at the epidermis-dermis border
small receptive field
high spacial resolution
(High spatial resolution means you can feel the difference between two separate points of pressure, even if they are very close together)
receptors important in fine tactile discrimination

Question 20

location of Ruffini and pacinian corpuscles

Answer 20

in the dermis
Ruffini corpuscles are sensitive to skin stretch and are important in discriminating the shape of grasped objects
pacinian are the most sensitive, can respond to slight skin displacments.

Question 21

each peripheral axon of each dorsal root ganglion neuron has multiple branches, so….

Answer 21

multiple terminal ends->multiple mechanoreceptors

Question 22

where is the muscle spindle positioned?

Answer 22

within the muscle belly

Question 23

what does the muscle spindle contain?

Answer 23

intrafusal fibers (tiny muscle fibers) that detect changes in muscle length.
intrafusal fibers are controlled by the CNS

Question 24

muscle spindle provides info to the brain about?

Answer 24

limb proprioception
the ability to know the position of our limbs in space without seeing them

Question 25

Golgi tendon receptor, where is it? is sensitive to what?

Answer 25

it is within the collagen fibers of tendons it is sensitive to the force generated by the contracting muscle it may have a role on the individual perception of the effort it takes to perform a specific motor action

Question 26

Does the Merkel cell accomplish mechanosensory transduction?

Answer 26

yes. it forms a synapse-like apposition with the axon terminal of the sensory fiber mechanosensory transduction is performed by the merkel cell, which synaptically activates the sensory fiber

Question 27

morphology of nociceptors, pruritic receptors, thermoreceptors

Answer 27

bare nerve endings

Question 28

Each spinal cord segment is associated with a specific somite during development. As a consequence, each spinal cord segment innervates what?

Answer 28

each spinal cord segment innervates the muscle and skin of the body parts deriving from its associated somite

Question 29

what is a dermatome?

Answer 29

The area of the skin innervated by the axons of a single dorsal root. Dermatomes overlap->if damage occurs to a single dorsal root no anesthetic area is observed (usually damage to a single dorsal root causes radicular pain to the dermatome associated with that dorsal root).

Question 30

the dorsal horn of the grey matter of the spinal cord mediates?

Answer 30

sensory functions

Question 31

the ventral horn of the grey matter of the spinal cord mediates?

Answer 31

motor functions

Question 32

what is the Lissauer's tract?

Answer 32

a region in the spinal cord made of unmyelinated and thinly myelinated fibers for pain and temperature.

Question 33

which branch of the axon of a dorsal root ganglion neuron is the main one for perception?

Answer 33

ascending branch

Question 34

each dorsal column transmits info from....to....?

Answer 34

from the ipsilateral side of the body to the ipsilateral medulla

Question 35

where in the dorsal column axons coming from the lower limbs ascend?

Answer 35

in the most medial portion of the dorsal column, termed the gracile fascicle

Question 36

where in the dorsal column axons coming from the lower trunk ascend?

Answer 36

within the gracile fascicle, lateral to those coming from the lower limbs

Question 37

where in the dorsal column axons coming from the upper trunk, upper limbs, neck and occiput ascend?

Answer 37

within the cuneate fascicle

Question 38

at which thoracic segment does the cuneate fascicle begins?

Answer 38

at the level of the 6th thoracic segment

Question 39

what separates the gracile and the cuneate fascicles?

Answer 39

the dorsal intermediate septum

Question 40

the dorsal columns at the two halves of the spinal cord are separated by?

Answer 40

the dorsal median septum

Question 41

where do dorsal column axons synapse?

Answer 41

in dorsal column nuclei ->the first major relay in the ascending pathway for touch and limb position senses.

Question 42

where do axons of the gracile fascicle synapse?

Answer 42

into the gracile nucleus located close to the midline

Question 43

where do axons of the cuneate fascicle synapse?

Answer 43

in the cuneate nucleus

Question 44

what does the somatotopic organization ensure?

Answer 44

that adjacent structures in the periphery are represented at adjacent sites in the CNS.

Question 45

in the Dorsal Column-Medial Lemniscus Pathway, what are the second order neurons?

Answer 45

neurons in the gracile and cuneate nucleus

Question 46

name of axons of second order neurons

Answer 46

internal arcuate fibers

Question 47

where do internal arcuate fibers decussate?

Answer 47

in the caudal medulla (they cross the midline)

Question 48

which one between gracile and cunate fibers decussate more ventrally?

Answer 48

gracile fibers decussate more ventrally

Question 49

internal arcuate fibers decussate and converge to form?

Answer 49

the medial lemniscus

Question 50

axons in the medial lemnisucs ascend to synapse where?

Answer 50

in the thalamus

Question 51

the ventral posterior nucleus in the thalamus has a lateral and medial division

Answer 51

ventral posterior lateral nucleus and ventral medial lateral nucleus

Question 52

neurons receiving inputs from leg and arms are located in which division of the ventral posterior nucleus?

Answer 52

in the lateral division of the nucleus

Question 53

neurons receiving inputs from the face are located in which division of the ventral posterior nucleus?

Answer 53

medial division

Question 54

where do axon in the ventral posterior nucleus ascend?

Answer 54

to the primary somatic sensory cortex in the posterior limb of the internal capsule

Question 55

mechanoreceptive informations are processed in 3 main cortical areas

Answer 55

primary somatic sensory cortex secondary somatic sensory cortex posterior parietal cortex

Question 56

where is the primary somatic sensory cortex located?

Answer 56

in the post central gyrus of the parietal lobe

Question 57

what is the sensory homunculus?

Answer 57

The sensory homunculus is a visual representation of the human body mapped onto the primary somatosensory cortex

Question 58

in which layer of the cerebral cortex does the thalamus primarily project?

Answer 58

layer IV (and the adjoining portion of layer III)

Question 59

neurons within a cortical column in the primary sensory cortex receive informations from?

Answer 59

the same peripheral location on the body and from the same class of mechanoreceptors

Question 60

how many layers does the cortex comprise in the post central gyrus?

Answer 60

6

Question 61

in the postcentral gyrus neurons whose cell bodies are located in layer II and III project to?

Answer 61

other cortical areas

Question 62

in the postcentral gyrus neurons whose cell bodies are located in layer V project?

Answer 62

to subcortical regions

Question 63

in the postcentral gyrus neurons whose cell bodies are located in layer VI project?

Answer 63

to the thalamus

Question 64

what do neurons in layer IV of the postcentral gyrus do?

Answer 64

receive infos from the thalamus and transmit infos to other cortical layers

Question 65

the primary somatic sensory cortex consists of 4 cytoarchitectonic divisions (brodmann's areas)

Answer 65

1,2,3a,3b

Question 66

association areas

Answer 66

-regions of the cerebral cortex that integrate and process information from multiple sensory and motor areas. -are involved in higher order functions