Peripheral Somatosensory System

Question 1

Loss of sensory function can result from ____ and ____ nervous system lesions

Answer 1

central; peripheral

Question 2

In the 3-neuron pathway what does the first order neuron do?

Answer 2

Brings information from sensory receptors into the spinal cord

Question 3

In the 3-neuron pathway what does the second-order neuron do?

Answer 3

Conveys information between the spinal cord or brainstem to the thalamus

Question 4

In a 3-neuron pathway what does the third-order neuron do?

Answer 4

Conveys information from the thalamus to the cerebral cortex

Question 5

True or False

The cerebellum uses sensory input to modify motor input but it does not percieve it

Answer 5

True

Question 6

What are the parts of the brain that can consciously percieve somatosensory information?

Answer 6

Thalamus and Cerebral Cortex

Question 7

What does the peripheral somatosensory information do?

Answer 7

Conveys information from the skin and musculoskeletal system to the spinal cord

Question 8

What does the peripheral nervous system convert mechanical, chemical, or thermal stimulation into?

Answer 8

Receptor potentials

Question 9

When is an axon potential produced in a peripheral axon?

Answer 9

When the receptor potential exceeds the threshold of the trigger zone

Question 10

List the pathway that the axon potential travels along in the Peripheral Somatosensory System.

Answer 10

• Axon potential travels along distal peripheral axon
• pas the T-junction that leads to the cellbody in the dorsal root ganglion
• Goes down proximal peripheral axon into spinal cord

Question 11

When does the axon potential reach the central nervous system?

Answer 11

When it reaches the spinal cord

Question 12

Which of the 3-neuron order’s is this?

Pseduounipolar neurons that have distal axons, cell bodies in the dorsal root ganglia and proximal axons

Answer 12

First-order somatosensory neurons

Question 13

What do the axons of the ventral ramus innervate?

Answer 13

Anterior and lateral trunk and limbs

Question 14

What do the axons of the dorsal ramus innervate?

Answer 14

Skin and deep muscles of the back

Question 15

What are sensory receptors?

Answer 15

Specialized end organs that communicate with peripheral nerves or are free nerve endings

Question 16

What is the following receptor called?

Have ion channels that are responsive to mechanical, thermal, chemical, or electromagnetic energy from environmental stimuli which converts into action potential transmitting the information to the CNS

Answer 16

Sensory Receptor

Question 17

What are sensory receptors classifed as?

Answer 17

• Chemoreceptors
• Mechanoreceptors
• Thermoreceptors

Question 18

What is the name of the following sensory receptor?

Consist of free nerve endings or specialized end-organs and respond to mechanical deformation of the receptor by touch, pressure, stretch of vibration

Answer 18

Mechanoreceptor

Question 19

What is the name of the following sensory receptor?

Free nerve endings and respond to exogenous chemicals or substances released by cells, including damaged cells following injury or infection

Answer 19

Chemoreceptors

Question 20

What is the name of the following sensory receptor?

Free nerve endings and respond to heating or cooling

Answer 20

Thermoreceptors

Question 21

Is the following a tonic or phasic sensory receptor?

Respond the entire time a stimulus is present providing constant input to the CNS

Answer 21

Tonic Receptor

Question 22

Is the following a tonic or phasic sensory receptor?

Adapt to a constant stimulus and stop responding while the stimulus is present

Answer 22

Phasic Receptor

Question 23

What is the role of a phasic receptor?

Answer 23

Alert the body about a change in a stimulus

Question 24

Which cutaneous sensory receptor is the following?

• axons myelinated by A(beta) fibers; respond to hair movement; phasic receptors; small receptive field diameter
• axons are lightly myelinated A(gamma): respond to hair movement; phasic receptors; small receptive field diameter

Answer 24

Hair Follicle Nerve Ending

Question 25

# Which cutaneous sensory receptor is the following? - Axons are myelinated A(beta) fibers: respond to dynamic movement across skin, slippage during grip; phasic receptors; small receptive field diameter

Answer 25

Meissner's Corpuscle

Question 26

# Which cutaneous sensory receptor is the following? - Axons are myelinated A(beta) fibers: respond to light pressure, curvature, edges; tonic receptors; small receptive field diameter

Answer 26

Merkel Cell

Question 27

# Which cutaneous sensory receptor is the following? - Reponds to nociceptive mechanical stimuli and cold stimuli; tonic receptors; medium receptive field diameter

Answer 27

Lightly Myelinated A(gamma)

Question 28

# Which cutaneous sensory receptor is the following? - Responds to nocieptive mechanical stimuli; pleasant mechanical stimuli; ticklish mechanical stimuli; pruritic stimuli; thermal stimuli; chemical stimuli; tonic receptors; medium field diameter

Answer 28

Unmyelinated C fibers

Question 29

# Which cutaneous sensory receptor is the following? - Axons are myelinated A(beta) fibers: respond to vibration; phasic receptors;large receptive field diameter

Answer 29

Pacinian Corpuscle

Question 30

# Which cutaneous sensory receptor is the following? - Axons are myelinated A(beta) fibers: respond to stretch of skin; tonic receptors; large receptive field diameter

Answer 30

Ruffini Corpuscle

Question 31

Why are larger diameter axons able to transmit information faster than smaller diameter axons?

Answer 31

Due to the low resistance to current flow in large-diameter axons and because they are myelinated allowing saltatory conduction of action potential to take place

Question 32

Large-diameter peripheral somatosensory axons only transmit action potential triggered by what?

Answer 32

Mechanical Stimuli

Question 33

Medium & small-diameter peripheral somatosensory axons are polymodal and transmit signals which sensory modalities

Answer 33

- mechanical - thermal - chemical

Question 34

When does the activity of polymodal neurons increase?

Answer 34

Following tissue injury

Question 35

20% of cutaneous and 50% of visceral nociceptors are ___

Answer 35

silent nociceptors

Question 36

What is a receptive field?

Answer 36

Area of skin innervated by a single peripheral somatosensory neuron

Question 37

Do distal regions of the body have greater or lesser density of sensory receptors than proximal regions?

Answer 37

Greater

Question 38

Information from cutaneous sensory receptors contribute to what?

Answer 38

Joint position and movement sense

Question 39

What do cutaneous receptors respond to?

Answer 39

Stretching or increasing pressure on the skin that occurs with movement

Question 40

Information from only a small amount of peripheral somatosensory neurons active at any given moment reach conscious awareness prevents what?

Answer 40

Sensory Overload

Question 41

Information used to make autonomic adjustments and is prevented from reaching consciousness is done via wha?

Answer 41

Descending and local inhibitory connections

Question 42

What is muscle spindle?

Answer 42

Sensory receptor in muscle that informs the CNS about limb position in space (moving or stationary & direction and rate of movement)

Question 43

What senses static position of a limb and limb movement by detecting changes in muscle length and velocity at which length of muscle is changing?

Answer 43

Muscle Spindle

Question 44

What is muscle spindle made of?

Answer 44

Muscle fibers, sensory endings, and motor endings

Question 45

What are muscle fibers in muscle spindles called?

Answer 45

Intrafusal fibers

Question 46

Where can the intrafusal contract and where can it not?

Answer 46

Contracts at ends Cannot contract in the central region

Question 47

What are the 2 types of intrafusal fibers?

Answer 47

- contains nuclear bag fiers which have a bundle of nuclei in central region - nuclear chain fibers which have nuclei arranged in a single file

Question 48

What are the 2 types of sensory afferents that innervate intrafusal fibers?

Answer 48

Type IA and II

Question 49

# Is the following Type IA or Type II afferent? Wraps around the central region of both nuclear bag and nuclear chain fibers phasic receptors that have maximal discharge during quick stretch of muscle

Answer 49

Type IA afferent

Question 50

# Is the following Type IA or Type II afferent? Mainly on nuclear chain fibers and some nuclear bag fibers tonic receptors that exhibit sustained firing proportional to the amount of stretch placed on muscle

Answer 50

Type II

Question 51

What innervates intrafusal muscle fibers to adjust stretch of the central region enabling the muscle spindle to be sensitive

Answer 51

Small-diameter gamma neurons

Question 52

Where do Gamma dynamic axons innervate the intrafusal fibers?

Answer 52

Contractile ends of nuclear bag fibers to adjust sensivity to velocity of muscle length changes

Question 53

Where to Gamma static axons innervated the intrafusal fibers?

Answer 53

Contractile ends of nuclear chains and some nuclear bags to tune their sensitivty to static muscle stretch

Question 54

Are there more muscle spindles in muscles that involve fine, skilled voluntary movement or in gross movements?

Answer 54

Fine, skilled voluntary movements

Question 55

When do muscle spindles respond to stretch?

Answer 55

During passive stretch

Question 56

What does passive stretching activate?

Answer 56

Spindle sensory receptors stimulating Type IA and II afferent fibers

Question 57

What does the excitation of alpha motor neuron via corticospinal neruon result in?

Answer 57

Contraction of extrafusal muscle fibers

Question 58

What is spindle sensivity to changes in length adjusted by?

Answer 58

Gamma Static Efferents

Question 59

What is velocity of change in muscle length signaled by?

Answer 59

Type IA afferents

Question 60

# What is the following a defintion of? Encapsulated nerve endings intertwined among the collagen strands of the tendon near the musculotendious junction

Answer 60

Golgi Tendon Organ

Question 61

What does Golgi Tendon Organs respond to?

Answer 61

Tension in tendons

Question 62

What causes the generation of action potential in Golgi tendon organ?

Answer 62

The contraction of a muscle pulls on collagen strand compressing the golgi tendon organ

Question 63

What responds to mechanical deformation of the capsule and ligaments?

Answer 63

Joint receptors

Question 64

What are Ruffini's endings?

Answer 64

In joint capsule and are tonic receptors innervated by type II afferent axons

Question 65

What do Ruffini's endings signal?

Answer 65

- Extremes of joint range - Responding more to passive versus active movement

Question 66

What are Paciniform corpuscles?

Answer 66

Phasic receptors innervated by type II afferents

Question 67

What do Paciniform corpuscles respond to?

Answer 67

Movement and are silent when joint position is constant

Question 68

What are ligament receptors innervated by and what does it signal?

Answer 68

Innervated by Type IB afferents and signals tension

Question 69

What are free nerve endings innervated by and what are they stimulated by?

Answer 69

Innervated by type III and IV afferents and stimulated by inflammation

Question 70

# What is the following Muscular Afferent Axon? - myelinated - innervaes nuclear bag and nuclear chian fibers; codes velocity of muscle stretch; phasic; found in intrafusal muscle fibers

Answer 70

Type IA

Question 72

# What is the following Muscular Afferent Axon? - Myelinated innervated golgi tendon organ; codes tension placed on muscle; tonic; found in tendons - innervated ligament receptors; codes tension place on ligaments

Answer 72

Type IB

Question 73

# What is the following Muscular Afferent Axon? - myelinated - innervated nuclear chain and some nuclear bag fibers; codes muscle length; tonic; found in intrafusal muscle fibers - innervated paciniform corpuscles; codes joint movement; phasic; found in the joint capsule - innervated Ruffini's endings; codes extreme joint stretch; tonic; found in the joint capsule

Answer 73

Type II

Question 74

# What is the following Muscular Afferent Axon? - lightly myelinated; unmyelinated - innervates free nerve endings; codes nociceptive stimuli; tonic; found in the muscle, joint capsule, and ligaments

Answer 74

Type III and IV

Question 75

# What is the superficial (tactile) sensation? - unpleasant feelings, resulting from a sensory stimulus that is sharp or pinpoint, especially when the stimulus has the potential to cause tissue damage - protective in nature, can also be referred to as sharp/dull discrimination - receptors: free nerve endings

Answer 75

Pain Sensibility

Question 76

# What is the superficial (tactile) sensation? - interprets the heat or cold state of an object or environment and plays protective role - Receptors: free nerve endings

Answer 76

Temperature Sensbility

Question 77

# What is the superficial (tactile) sensation? - sensation caused by mildest of tactile stimulation - Receptors: Merkel's cells, hair follicle nerve ending, Ruffini corpuscles, Meissner's corpuscles, free nerve endings

Answer 77

Light Touch

Question 78

# What is the superficial (tactile) sensation? - results from mechanical stimulation due to a greater magnitude of pressures with deeper skin deformation - conveys nondiscriminative tactile information allowing a person to sense a tactile stimulus without localizing it - important for general alertness - Receptors: Pacinian corpuscles, free nerve endings; Ruffini corpuscles

Answer 78

Pressure or Crude Touch

Question 79

# What is the following Proprioceptive Sensation? Conscious awareness of the relative static position of your body parts in space without the need for visual confirmation

Answer 79

Joint Position Sense

Question 80

# What is the following Proprioceptive Sensation? Awareness of the degree, velocity, and direction of movement at a single joint or body segment; sensory information about movement

Answer 80

Joint Movement Sense (Kinesthesia)

Question 81

# What is the following Proprioceptive Sensation? Sensation experienced from tactile contact with an object that is shaking or oscillating at a particular frequency

Answer 81

Vibration

Question 82

# What is the following Discriminative sensation? - awareness of the specific skin surface site to which stimulation was applied - Receptors: merkel cell, meissner's corpuscles

Answer 82

Tactile Localization

Question 83

# What is the following Discriminative sensation? - ability to distinguish two simultaneously applied blunt point as two discrete stimuli - smallest interpoint distance still perceived as two points - Receptors: Merkel Cell

Answer 83

Two-point discrimination

Question 84

# What is the following Discriminative sensation? - ability to recognize writing on the skin including shapes, numbers, or letters purely by the sensation of touch - Receptors: Meissner's corpuscles

Answer 84

Graphesthesia

Question 85

# What is the following Discriminative sensation? - ability to recognize by tactile manipulation only, the form and charactersitics of an object including size, shape, weight, consistency, and texture - Receptors: Meissner's corpuscles

Answer 85

Stereognosis

Question 86

Where does somatosensory information originate from?

Answer 86

Sensory receptors and musculoskeletal

Question 87

What is cutaneous somatosensory information referred to as?

Answer 87

Superficial or tactile sensation

Question 88

What is somatosensory information from the musculoskeletal system?

Answer 88

Deep sensation or proprioception

Question 89

What is combined cortical sensation?

Answer 89

Superficial and deep sensations and is referred to as discriminative sensations

Question 90

What is discriminative sensation?

Answer 90

Requires information from exteroreptive and proprioceptive sensory receptors and the articial sensory association areas of the brain