06: Overview Of The Sensory Systems; Somatosensory 1

Question 1

True or false: Specific types of sensory information are carried along specific afferent pathways and processed by specific brain regions.

Answer 1

True

Question 2

Converting mechanical energy into a neural signal is an example of which of the following?

A. Absolute threshold
B. Sensory transduction
C. Signal detection theory

Answer 2

B

• Absolute threshold is the minimum amount of stimulus energy that must be present for the stimulus to be detected 50% of the time.
• Signal detection theory states that the detection of a sensory signal depends on the stimulus intensity and the physical/psychological state of the individual.

Question 3

True or false: The type of stimulus that a sensory receptor is adapted to respond to is considered the adequate stimulus for that receptor.

Answer 3

True

Question 4

True or false: The minimum amount by which stimulus intensity must be changed in order to produce a noticeable variation in sensory experience is called the absolute threshold for that stimulus.

Answer 4

False

This is known as the just noticeable difference.

Question 5

Receptive field properties of neurons and the topographical organization in the central nervous system allows the sensory system to encode which of the following?

A. Stimulus modality
B. Stimulus location
C. Stimulus duration

Answer 5

B

• Stimulus modality refers to how receptors are differential responsible to specific forms of energy and those afferent signals are transmitted over dedicated systems.
• Stimulus duration states that receptors have different adaptive properties that allow the encoding of the timing of a stimulus.

Question 6

True or false: An increasing number of action potentials being fired by a single sensory receptor as stimulus intensity increases is an example of population coding.

Answer 6

False

Question 7

Which of the following receptors detects stimuli from muscles, tendons, and joints?

A. Exteroceptors
B. Proprioceptors
C. Special sensory receptors

Answer 7

B

• Exteroceptors detect stimuli from the external world; allows us to use our sense of touch, pressure, vibration, pain, and temperature.
• Special sensory receptors are located in the head and detect various types of stimuli; allow us to use our senses of taste, smell, hearing, balance, and vision

Question 8

What does the sensory system do?

Answer 8

Transduces, encodes, and perceives information from in- or outside the body.

Question 9

The conversion of various forms of energy into neural signals that convey information by specialized receptors is called…

A. Adequate stimulus
B. Signal detection theory
C. Sensory transduction
D. Modality

Answer 9

C

Question 10

What is the difference between the absolute threshold and just noticeable threshold?

Answer 10

Absolute threshold: minimum amount of stimulus energy that must be present for the stimulus to be detected 50% of the time.

Just noticeable threshold: minimum amount by which stimulus intensity must be changed in order to produce a noticeable variation in sensory experience.

Question 11

A interoceptor detects…

A. Stimuli from the outside world
B. Stimuli from viscera
C. Stimuli from muscles, tendons, and joint capsules

Answer 11

B

Question 12

A proprioceptor detects…

A. Stimuli from the outside world
B. Stimuli from viscera
C. Stimuli from muscles, tendons, and joint capsules

Answer 12

C

Question 13

An exteroceptor detects…

A. Stimuli from the outside world
B. Stimuli from viscera
C. Stimuli from muscles, tendons, and joint capsules

Answer 13

A

Question 14

How does the sensory system encode location of a stimuli?

Answer 14

Topographic arrangements in the CNS, such that excitation receptors in a specific location results in activity within a specific area of the CNS (receptive fields)

Question 15

What is the difference between perception and sensation?

Answer 15

Sensation is the signal from the stimuli, whereas perception is the “response” to (integration of) the signal.

Question 16

What is meant by bottom-up processing in perception?

Answer 16

Perceptions are built from sensory input

Question 17

What is meant by top-down processing in perception?

Answer 17

Interpretation of sensations is influenced by thought about the sensation, knowledge, or previous experience.

Question 18

True or false: The somatosensory system can be divided int 3 subsystems: one that processes touch, pressure, and vibration; one that processes proprioception; and one that processes pain and temperature information.

Answer 18

True

Question 19

True or false: The primary afferents of the somatosensory system are pseudo-unipolar neurons.

Answer 19

True

Question 20

Which of the following fiber types conducts action potentials at the highest speed?

A. Group Ia
B. Group II
C. Group III
D. Group IV

Answer 20

A

Question 21

True or false: The majority of the mechanoreceptors in the somatosensory system contain stress-gated ion channels selective for anions.

Answer 21

False

The majority of the mechanoreceptors contain stress-gated ion channels selective for CATIONS.

Question 22

Which of the following statements best reflects the density of receptors, receptive field size, and cortical representations in somatosensory cortex?

A. As receptor density decreases, receptive field size decreases, and cortical representation decreases.
B. As receptor density increases, receptive field size increases, and cortical representation increases.
C. As receptor density decreases, receptive field size increases, and cortical representation decreases.
D. As receptor density increases, receptive field size increases, and cortical representation decreases.

Answer 22

C

Question 23

Which of the following cutaneous mechanoreceptors is rapidly adapting and important for sensing tapping or movement in non-hairy skin?

A. Meissener’s corpuscle
B. Pacinian corpuscle
C. Ruffini corpuscle

Answer 23

A

• Pacinian corpuscle: a deep receptor; rapidly adapting; important for sensing deep pressure and vibration.
• Ruffini corpuscle: a deep receptor; rapidly adapting; important for sensing skin stretch.

Question 24

Which of the following cutaneous mechanoreceptors is located deep in the dermis or subcutaneous tissue? Select all that apply.

• Pacinian corpuscle
• Meissner’s corpuscle
• Merkle cell
• Ruffini corpuscle
• Hair follicle

Answer 24

• Pacinian corpuscle
• Ruffini corpuscle
• Hair follicle

Question 25

True or false: Merkel cells allow us to have discriminative touch.

Answer 25

True

Question 26

Which proprioceptor is important for monitoring muscle length and transmits information about the velocity of limb movements to the CNS? A. Golgi tendon organ B. Hair follicle C. Muscle spindle

Answer 26

**C** * *Golgi tendon organ*: In fibers located in muscle tendons; important for monitoring muscle tension * *Hair follicles*: deep cutaneous mechanoreceptor; rapidly adapting; important for sensing movement.

Question 27

Which of the following central pathways relays touch, pressure, vibration and proprioceptive sensations to primary somatosensory cortex? Select all that apply. * Posterior Columns-Medial Lemniscal System * Anterior spine cerebellar tract * Cuneocerebellar tract * Trigeminal system

Answer 27

* Posterior Columns-Medial Lemniscal System * Trigeminal system

Question 28

True or false: The lower limb representation in primary somatosensory cortex is located in the posterior paracentral gyrus.

Answer 28

True

Question 29

True or false: The primary proprioceptive afferents of the trigeminal system are located in the principal sensory nucleius.

Answer 29

**False** The primary proprioceptive afferents are located in the *mesencephalic nucleus* and the second order neurons of the trigeminal system are located in the principal sensory nucleius.

Question 30

What sensations are processed by Meissner’s corpuscle? A. Discriminative touch, localization of touch, determining object characteristics B. Tapping, flutter, and movement detection in non-hairy skin C. Pressure and vibration sensations D. Movement sensation E. Skin stretch sensation

Answer 30

B

Question 31

What sensations are processed by the pacinian corpuscle? A. Discriminative touch, localization of touch, determining object characteristics B. Tapping, flutter, and movement detection in non-hairy skin C. Pressure and vibration sensations D. Movement sensation E. Skin stretch sensation

Answer 31

C

Question 32

What sensations are processed by the Ruffini corpuscle? A. Discriminative touch, localization of touch, determining object characteristics B. Tapping, flutter, and movement detection in non-hairy skin C. Pressure and vibration sensations D. Movement sensation E. Skin stretch sensation

Answer 32

E

Question 33

What sensations are processed by Merkel’s corpuscle? A. Discriminative touch, localization of touch, determining object characteristics B. Tapping, flutter, and movement detection in non-hairy skin C. Pressure and vibration sensations D. Movement sensation E. Skin stretch sensation

Answer 33

A

Question 34

What sensations are processed by hair follicles? A. Discriminative touch, localization of touch, determining object characteristics B. Tapping, flutter, and movement detection in non-hairy skin C. Pressure and vibration sensations D. Movement sensation E. Skin stretch sensation

Answer 34

D

Question 35

Muscle spindles are important for changes in muscle length. Which ending is important for limb dynamics and has **Ia fibers**? A. Primary endings B. Secondary endings C. Tertiary endings

Answer 35

A

Question 36

Muscle spindles are important for changes in muscle length. Which ending is important for static position of the limbs and has **II fibers**? A. Primary endings B. Secondary endings C. Tertiary endings

Answer 36

B

Question 37

What determines the size of a primary afferents receptive field?

Answer 37

Density of receptors

Question 38

What mechanoreceptors are rapidly adapting? * Meissner’s corpuscle * Merkel cell * Ruffini’s corpuscle * Pacinian’s corpuscle * Hair follicles

Answer 38

* Meissner’s corpuscle * Pacinian’s corpuscle * Hair follicles

Question 39

True or false: The somatotropic organization of primary somatosensory cortex is fixed and cannot be changed.

Answer 39

False

Question 40

True or false: In order to sense the spatial location of two separate stimuli on the surface of the digits, two separate populations of cortical neurons must be activated in primary somatosensory cortex.

Answer 40

True

Question 41

What is two-point discrimination?

Answer 41

Receptive fields of cortical neurons allow for precise localization of touch

Question 42

Can the somatosensory cortex reorganize?

Answer 42

**Yes!** It can reorganize in response to experience and injury.

Question 43

What is the name of the pathway that converts touch and proprioceptive information from the body and face to the cortex?

Answer 43

Posterior Column-Medial Lemniscal System (PCMLS)

Question 44

Touch, pressure, vibration, limb position, temperature and pain describe which type of sensations? A. Special sensations B. Visceral sensations C. Somatic sensations

Answer 44

C

Question 45

Vision, audition, vestibular, taste, and olfaction describe which sensations? A. Special sensations B. Visceral sensations C. Somatic sensations

Answer 45

A

Question 46

Noxious (pain), non-noxious (bladder/bowel distention or fullness) describe which type of sensations? A. Special sensations B. Visceral sensations C. Somatic sensations

Answer 46

B

Question 47

What is sensory transduction?

Answer 47

The process of receiving stimuli, converting it to neural signals, and conveying information about the stimuli to the spinal cord and brain.

Question 48

What does a proprioceptor detect?

Answer 48

Stimuli from muscles, joints, tendons

Question 49

How does the sensory system encode location and intensity of stimuli?

Answer 49

**Location**: Topographic arrangements in the CNS **Intensity**: frequency coding and population coding

Question 50

What is meant by top-down processing and sensory weighting and reweighting?

Answer 50

**Top-down processing**: The interpretation of the sensation is influenced by experience and knowledge. **Sensory weighting**: each sensory channel is multiplied by some weight and then the weighted variables are summed to produce a response modulated to the relevancy of the incoming afferents. **Sensory reweighting**: the *alteration of the weight assigned to a signal* in order to adapt to the environmental conditions and available sensory information.

Question 51

What sensations are processed by the three subsystems of the somatosensory system?

Answer 51

* *Exteroceptive (I)*: discriminative touch, pressure, vibration * *Exteroceptive (II)*: pain, temperature, crude touch * *Proprioceptive*: information from muscles tendons, joint capsules; signals awareness of body position and movement

Question 52

What is the difference between a group Ia fiber and a group II fiber?

Answer 52

**Group Ia**: Muscle spindles, golgi tendon organs; conduct at faster velocity; larger axon diameter **Group II**: *skin mechanoreceptors*, muscle spindles; *conduct as slightly slower velocity*; *slightly smaller axon diameter*

Question 53

Which mechanoreceptors contribute to our sense of limb position and movement?

Answer 53

Muscle spindles (primary endings)

Question 54

Which pathways convey touch and proprioceptive information from the body and face to the cortex, respectively?

Answer 54

**PCMLS**: conscious proprioception from body **Trigeminal system** proprioception from the face **Cerebellar tracts**: unconscious proprioception from the body

Question 55

A stroke of the ACA will result in what somatosensory deficits?

Answer 55

**Contralateral** loss of somatosensory sensation in the **lower limb** * *PCMLS*: discriminative touch, pressure, vibration, and proprioceptive sensation * *ALS*: crude touch, pain, temperature sensation

Question 56

A stroke of the MCA will result in what somatosensory deficits?

Answer 56

**Contralateral** loss of somatosensory sensation in the **face and upper limb** * *PCMLS*: discriminative touch, pressure, vibration, and proprioceptive sensation * *ALS*: crude touch, pain, temperature sensation

Question 57

A stroke of the PCA will result in what somatosensory deficits?

Answer 57

Visual field deficits, visual dysfunction, cognitive and behavioral dysfunction **Contralateral** hemiparesis, ocular motility disorder, and disturbances in consciousness, memory, and language; discriminative touch, pressure, vibration, and proprioceptive sensation (*PCMLS*); crude touch, pain, temperature sensation (*ALS*)

Question 58

True or false: Damage to the peripheral nerve in the PCMLS or ALS will result in contralateral somatosensory loss.

Answer 58

**False** Ipsilateral

Question 59

Which landmarks of the nervous system vary in response to nerve damage and subsequent deficits?

Answer 59

**Spinal cord** * PCMLS = ipsilateral loss below lesion * ALS = contralateral loss below lesions

Question 60

Neurons are arranged in functional units called ________.

Answer 60

cortical columns

Question 61

How do the afferents of somatosensory systems vary from that of the visual, auditory, and vestibular systems?

Answer 61

**Somatosensory**: pseudounipolar **Visual, auditory, vestibular**: bipolar