06: Overview Of The Sensory Systems; Somatosensory 1 Flashcards
True or false: Specific types of sensory information are carried along specific afferent pathways and processed by specific brain regions.
True
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
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.
True or false: The type of stimulus that a sensory receptor is adapted to respond to is considered the adequate stimulus for that receptor.
True
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.
False
This is known as the just noticeable difference.
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
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.
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.
False
Which of the following receptors detects stimuli from muscles, tendons, and joints?
A. Exteroceptors
B. Proprioceptors
C. Special sensory receptors
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
What does the sensory system do?
Transduces, encodes, and perceives information from in- or outside the body.
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
C
What is the difference between the absolute threshold and just noticeable threshold?
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.
A interoceptor detects…
A. Stimuli from the outside world
B. Stimuli from viscera
C. Stimuli from muscles, tendons, and joint capsules
B
A proprioceptor detects…
A. Stimuli from the outside world
B. Stimuli from viscera
C. Stimuli from muscles, tendons, and joint capsules
C
An exteroceptor detects…
A. Stimuli from the outside world
B. Stimuli from viscera
C. Stimuli from muscles, tendons, and joint capsules
A
How does the sensory system encode location of a stimuli?
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)
What is the difference between perception and sensation?
Sensation is the signal from the stimuli, whereas perception is the “response” to (integration of) the signal.
What is meant by bottom-up processing in perception?
Perceptions are built from sensory input
What is meant by top-down processing in perception?
Interpretation of sensations is influenced by thought about the sensation, knowledge, or previous experience.
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.
True
True or false: The primary afferents of the somatosensory system are pseudo-unipolar neurons.
True
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
A
True or false: The majority of the mechanoreceptors in the somatosensory system contain stress-gated ion channels selective for anions.
False
The majority of the mechanoreceptors contain stress-gated ion channels selective for CATIONS.
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.
C
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
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.
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
- Pacinian corpuscle
- Ruffini corpuscle
- Hair follicle
True or false: Merkel cells allow us to have discriminative touch.
True
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
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.
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
- Posterior Columns-Medial Lemniscal System
- Trigeminal system
True or false: The lower limb representation in primary somatosensory cortex is located in the posterior paracentral gyrus.
True
True or false: The primary proprioceptive afferents of the trigeminal system are located in the principal sensory nucleius.
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.
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
B
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
C
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
E
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
A
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
D
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
A
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
B
What determines the size of a primary afferents receptive field?
Density of receptors
What mechanoreceptors are rapidly adapting?
- Meissner’s corpuscle
- Merkel cell
- Ruffini’s corpuscle
- Pacinian’s corpuscle
- Hair follicles
- Meissner’s corpuscle
- Pacinian’s corpuscle
- Hair follicles
True or false: The somatotropic organization of primary somatosensory cortex is fixed and cannot be changed.
False
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.
True
What is two-point discrimination?
Receptive fields of cortical neurons allow for precise localization of touch
Can the somatosensory cortex reorganize?
Yes! It can reorganize in response to experience and injury.
What is the name of the pathway that converts touch and proprioceptive information from the body and face to the cortex?
Posterior Column-Medial Lemniscal System (PCMLS)
Touch, pressure, vibration, limb position, temperature and pain describe which type of sensations?
A. Special sensations
B. Visceral sensations
C. Somatic sensations
C
Vision, audition, vestibular, taste, and olfaction describe which sensations?
A. Special sensations
B. Visceral sensations
C. Somatic sensations
A
Noxious (pain), non-noxious (bladder/bowel distention or fullness) describe which type of sensations?
A. Special sensations
B. Visceral sensations
C. Somatic sensations
B
What is sensory transduction?
The process of receiving stimuli, converting it to neural signals, and conveying information about the stimuli to the spinal cord and brain.
What does a proprioceptor detect?
Stimuli from muscles, joints, tendons
How does the sensory system encode location and intensity of stimuli?
Location: Topographic arrangements in the CNS
Intensity: frequency coding and population coding
What is meant by top-down processing and sensory weighting and reweighting?
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.
What sensations are processed by the three subsystems of the somatosensory system?
- 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
What is the difference between a group Ia fiber and a group II fiber?
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
Which mechanoreceptors contribute to our sense of limb position and movement?
Muscle spindles (primary endings)
Which pathways convey touch and proprioceptive information from the body and face to the cortex, respectively?
PCMLS: conscious proprioception from body
Trigeminal system proprioception from the face
Cerebellar tracts: unconscious proprioception from the body
A stroke of the ACA will result in what somatosensory deficits?
Contralateral loss of somatosensory sensation in the lower limb
- PCMLS: discriminative touch, pressure, vibration, and proprioceptive sensation
- ALS: crude touch, pain, temperature sensation
A stroke of the MCA will result in what somatosensory deficits?
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
A stroke of the PCA will result in what somatosensory deficits?
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)
True or false: Damage to the peripheral nerve in the PCMLS or ALS will result in contralateral somatosensory loss.
False
Ipsilateral
Which landmarks of the nervous system vary in response to nerve damage and subsequent deficits?
Spinal cord
- PCMLS = ipsilateral loss below lesion
- ALS = contralateral loss below lesions
Neurons are arranged in functional units called ________.
cortical columns
How do the afferents of somatosensory systems vary from that of the visual, auditory, and vestibular systems?
Somatosensory: pseudounipolar
Visual, auditory, vestibular: bipolar
