Peripheral Structures of the Somatosensory System N18

Question 1

Somatosensory function

Answer 1

receive, process, and relay sensory information from the skin, muscles, and joints to the cerebral cortex for CONSCIOUS appreciation of the information

Question 2

Some neural systems involve UNCONSCIOUS sensory processing

Answer 2

these involve the cerebellum

Question 3

Discriminative touch recognizes:

Answer 3

size, shape, and texture of objects and their movement across the skin

Question 4

Discriminative touch is greatest:

Answer 4

tactile sensitivity is greatest on hairless skin of fingers, palms, sole of feet, and lips

Question 5

Proprioception

Answer 5

Sense of static position and movement of the limbs and body

Question 6

Temperature sense

Answer 6

warmth and cold perception

Question 7

Nociception

Answer 7

perceived as pain or itch, tissue damage or chemical irritant, NOT overstimulation of generalized cutaneous receptors but stimulation of certain nociceptors

Question 8

Epicritic sensations involve

Answer 8

fine aspects of touch (highly localized and discriminative), mediated by encapsulated receptors (specialized function in the dermis and epidermis)

Question 9

Epicritic sensations include

Answer 9

detection and localization of gentle skin contact, vibration frequency and amplitude, touch spatial detail (texture, distance between two simultaneous stimuli), recognition of grasped object

Question 10

Protopathic sensations involve

Answer 10

pain, temperature, tickle, itch

Question 11

Protopathic sensations include

Answer 11

crude, more intense stimuli, poorly localized, non-discriminative; mediated by free nerve ending receptors

Question 12

Enteroceptors

Answer 12

conscious appreciation of sensations from external stimuli to our body

Question 13

Proprioceptors

Answer 13

receive information about the relative position of our body in space (kinesthesia: movement sense)

Question 14

Conscious proprioception is relayed to

Answer 14

cerebral cortex

Question 15

Unconscious proprioception is relayed to

Answer 15

cerebellum

Question 16

Interoceptors

Answer 16

processing of visceral information

Question 17

Mechanoreceptors function

Answer 17

respond to mechanical deformation

Question 18

Mechanoreceptors

Answer 18

Meissner’s Corpuscle (S), Merkel’s disc (S), Pacinian Corpuscle (D), Ruffini ending (D)

Question 19

Meissner’s Corpuscle

Answer 19

SUPERFICIAL - surrounds flattened epithelial cells and responds to FINE mechanical sensitivity

Question 20

Merkel Disc

Answer 20

SUPERFICIAL - center of papillary ridge surrounded by epithelial cells, signals PRESSURE and SHAPE of objects

Question 21

Pacinian Corpuscle

Answer 21

DEEP - CT lamellae surround nerve ending, responds to VIBRATORY stimuli

Question 22

Ruffini Ending

Answer 22

DEEP - links subcutaneous to folds in skin, senses LATERAL movement and STRETCH of skin, and perception of SHAPE of grasped objects

Question 23

Proprioreceptors

Answer 23

Change in position and movement

Question 24

Proprioreceptors include

Answer 24

cutaneous mechanoreceptors (Ruffini Endings), joint receptors, muscle spindles, golgi tendon organs

Question 25

Thermoreceptors

Answer 25

detect change in temperature and pain, only within a narrow temperature range (separate distinct receptors for warm and cold)

Question 26

Once outside of the narrow temperature range for thermoreceptors, what receptors detect temperature?

Answer 26

Thermal nociceptors

Question 27

Nociceptors

Answer 27

respond to stimuli that could damage tissue (3 classes)

Question 28

3 classes of nociceptors

Answer 28

Mechanical: intense pressure applied to skin Thermal: extreme temperatures Polymodal: respond to a wide range of stimuli

Question 29

Encapsulated receptors

Answer 29

surrounded by CT wrappings

Question 30

Nonencapsulated receptors

Answer 30

not associated with CT wrapping

Question 31

Examples of encapsulated receptors

Answer 31

Pacinian Corpuscle, Meissner's corpuscle, ruffini ending

Question 32

Examples of non encapsulated receptors

Answer 32

endings around hairs, Merkel endings, free nerve ending

Question 33

Receptive field

Answer 33

area of skin that when stimulated activates a particular neuron (can be small or large area)

Question 34

Fine touch receptive fields

Answer 34

small receptive fields, more axons/more neurons

Question 35

Crude touch receptive fields

Answer 35

large receptive fields, fewer neurons

Question 36

Acuity definition

Answer 36

precision with which we can locate the site of stimulus

Question 37

Acuity depends on 4 things:

Answer 37

size of receptive field, receptor density, receptor field overlap, convergence of neuronal input

Question 38

2-point discrimination definition

Answer 38

minimum distance by which two stimuli can be separated and still perceived as separate

Question 39

2-point discrimination depends on:

Answer 39

size of receptor field, density of receptors (fingertips 2mm, lips and tongue 5-8mm) [arms 50mm]

Question 40

Dermatome

Answer 40

area of the body innervated by one spinal nerve/segment

Question 41

Dermatome overlap

Answer 41

dermatomes overlap with the 2 adjacent dermatomes (each nerve innervates a portion of 3 dermatomes)

Question 42

Lesion to dorsal roots/nerves

Answer 42

3 consecutive nerves must be lesioned to observe sensory loss due to the overlap

Question 43

Peripheral nerve processes vary by

Answer 43

axonal size and degree of myelination

Question 44

The size principle states

Answer 44

larger axons conduct faster

Question 45

Degree of myelinization conforms to the Size principle

Answer 45

larger axons = more myelinization = fast conduction | small axons = less myelinization = slow conduction

Question 46

Ia

Answer 46

large, myelinated, fast conduction

Question 47

Ib

Answer 47

large, myelinated, fast conduction

Question 48

A-alpha

Answer 48

large, myelinated, fast conduction

Question 49

II (A-beta)

Answer 49

fairly large, myelinated, fairly fast conduction

Question 50

A-gamma

Answer 50

moderate size, moderate myelin, moderate conduction

Question 51

III (A-delta)

Answer 51

fairly small, fairly unmyelinated, fairly slow conduction

Question 52

B

Answer 52

slow, small, unmyelinated

Question 53

C

Answer 53

very slow, very small, no myelinization

Question 54

Mechanoreceptors use what type of receptors

Answer 54

A-beta (II)

Question 55

Thermal receptors

Answer 55

A-delta or C

Question 56

Nociceptors

Answer 56

A-delta or C

Question 57

Muscle Spindles

Answer 57

Ia or II

Question 58

Golgi Tendon Organs

Answer 58

Ib

Question 59

Lateral Dorsal Root Entry Zone

Answer 59

small, unmyelinated axons enter here; pain, temperature, crude touch, visceral afferents; ascend or descend 1-2 segments

Question 60

Medial Dorsal Root Entry Zone

Answer 60

Large, myelinated axons enter here; highly discriminative froms of touch and proprioception (skeletal muscles and joints)

Question 61

Lissauer's tract is associated with

Answer 61

small, unmyelinated fibers

Question 62

Substantia Gelatinosa is associated with

Answer 62

small, unmyelinated fibers

Question 63

Somatosensory pathways are typically ____ neurons

Answer 63

3

Question 64

Somatosensory pathways usually decussate at which neuron

Answer 64

2nd

Question 65

All ascending pathways except olfaction stop in the _____

Answer 65

thalamus

Question 66

Lemnisci

Answer 66

flat-bundle of ascending fibers

Question 67

Thalamic radiations

Answer 67

fibers leaving the thalamus radiate out to the cerebral cortex through the internal capsule

Question 68

Dorsal Column- Medial lemniscus

Answer 68

EPICRITIC sensations (localized, discriminative touch, conscious proprioception, vibration, 2-point discrimination)

Question 69

Anterolateral System is composed of 3 pathways

Answer 69

Spinothalamic, Spinoreticulothalamic, Spinotectal

Question 70

Anterolateral System

Answer 70

PROTOPATHIC sensations (crude touch, pain, temperature) and EPICRATIC sensations (pain and temperature)

Question 71

DC-ML decussates at the level of the

Answer 71

MEDULLA

Question 72

ALS decussates at the level of the

Answer 72

spinal segment 1-2 rostral