Somatosensory Processing Flashcards
Deformation of the DRG (free or encapsulated) by a mechanical stimulus _____ the threshold needed to evoke an action potential.
lowers
High-threshold channels characterize _____ (receptorss for pain).
nociceptors
Nociceptors are found predominantly in _____ _____.
smaller DRG
Nociceptors are activated by _____ pressures.
higher
Proprioceptors
Give information about the position of limbs and body in space.
Muscle spindles
Goldgi tendon organs
Stretching a mucle activates _____ on two types of afferent fibers:
mechanoreceptors
group 1a
group 2
Group 1a afferent fibers
large myelinated fibers
repidly adapting
Group 2 afferent fibers
myelinated fibers
slowly adapting
Tension of intrafusal fibers is also controlled by _____.
gamma motor neurons
from dorsal horn spinal cord
Large muscles for coarse movements have _____ spindles.
few
Extraocular muscles and uscles in the neck and hand have ____ spindles.
many
require precise control
Muscle spindles detect changes in _____.
muscle tension
Tactile afferents from body:
Dorsal column - medial lemniscal system
Afferents from face use the _____ (_____).
trigeminothalamic system
Trigeminal ganglion
Merkel receptors have _____ responses.
sustained
Meissner receptors are _____.
rapidly adapting
Pacinian receptors are _____.
rapidly adapting
Ruffini receptors have _____ responses.
sustained
Merkel receptors are responsible for _____ and _____ perception.
form
texture
Meissner receptors are responsible for _____ and _____.
motion detection
grip control
Pacinian receptors are responsible for _____ perception and _____.
vibration
tool use
Ruffini receptors are responsible for _____, _____, and _____.
tangential force
hand shape
motion direction
(stretch)
Slowly adapting afferents convey information about _____, such as size and shape.
spatial attributes
Rapidly adapting afferents convey information about ______: dynamic qualities of the stimulus.
changes in ongoing stimulation
Sensory axons are classified according to their _____, which governs their _____ and their _____.
diameter
myelination
conduction velocity
Dermatome
Cutaneous innervation related to a single spinal nerve
sensation
transduction
transmission
perception
inference
deduction
follow-up
5 primary tasks of sensory systems
transduction transmission inference deduction follow-up
5 qualities of information to encode
modality intensity duration location salience
5 factors that influence success or failure
fatigue adaption sensitization overlap/redundancy damage/overload
Dorsal root ganglia
contain the sensory neurons of the somatosensory system
Dorsal root is responsible for _____.
sense
Ventral root is responsible for _____.
motor
The _____ system is responsible for touch perception.
dorsal column-medial lemniscus system
The _____ is responsible for pain perception.
anterolateral system
The _____ projects to the cerebellum and controls timing of muscle contractions.
dorsal spinocerebellar tract
Proprioceptive afferents from the body lead to the _____ and _____.
cerebellum
dorsal column nuclei
The _____ somatosensory thalamus contains _____ afferents from the body.
central posterior lateral
medial lemniscus
The _____ somatosensory thalamus contains _____ afferents from the face.
ventral posterior medial
trigeminal lemniscus
the somatosensory cortex contains _____ __, __, _, and _.
Brodmann's areas 3a 3b 1 2
The _____ is a representation of the human body from the _____.
homunculus
somatotopic map
_____ serves as obligatory first step in cortical processing of somatosensory information.
Brodmann’s area 3b
_____ are functioal modules of the cortex.
Columns
Columns in the somatosensory cortex are _____.
functionally distinct
Reorganization of cortical maps in response to altered functional input is known as _____.
plasticity
Nociception
The neural encoding and processing of noxious stimuli
Noxious stimuli
stimuli that can elicit tissue damage and activate nociceptors
Nociceptors are sensory receptors that detect signals from _____ and respond to _____ released.
damaged tissue
chemicals
Nociceptors are _____ found in the skin, muscle, joints, bone, and viscera.
free (bare) nerve endings
Pain processing is _____ of normal cuteaneous processing.
independent
Peripheral axons responsible for normal stimulation _____ their frequency in response to painful stimuli.
do not increase
Nociceptive afferents only fire when _____.
stimuli reach high intensities
Direct stimulation of large fibers (1a, II, AB) _____.
does not produce pain
Peripheral nociceptive axons terminate in “_____.”
free endings
Nociceptors are found on _____ fibers (_, _)
small
Ad
C
C fibers are _____ and respond to _____, _____, and _____ stimuli.
polymodal
thermal
mechanical
chemical
_____ fibers lack myelination.
C
Type I Ad fibers respond to dangerous _____ and _____ stimulation.
mechanical
chemical
Type II Ad fibers respond to _____ stimulation.
thermal
_____ respond only to intense mechanical stimulation such as pinching, cutting, or stretching.
High threshold mechano-nociceptors
_____ respond to intense mechanical stimulation as well as to thermal stimulation.
Thermal nociceptors
_____ respond only to chemical substances.
Chemical nociceptors
_____ respond to all high intensity stimuli.
Polymodal nociceptors
_____ include high-threshold mechanoreceptors, polymodal nociceptors, and ‘‘silent’’ nociceptors.
Joint nociceptors
_____ include mechanoreceptors, thermal, silent and chemical nociceptors.
Visceral nociceptors
C and Ad fiber nerve endings contain _____ that respond to temp, pressure, and inflammatory agents.
transient receptor potential (TRP) channels
TRPV1 is activated by _____, _____, _____, and _____.
heat
anandemide
capsaicin
allyl isothiocyanate
TRPV1
Transient receptor potential vanilloid type-1
TRPV1 channels are also known as _____ and _____.
capsaicin receptors
vanilloid receptor 1
_____ are produced peripherally in response to injury.
Endovanilloids
ASIC
acid-sensing ion channel
Hyperalgesia
Increased sensitivity to painful stimuli
Hyperalgesia has a _____ effect at the level of the nociceptors.
peripheral
Tissue damage and inflammation release inflammatory mediators, such as _____, _____, and _____ which increase the sensitivity of nociceptors to _____.
prostaglandins
histamin
substance P
noxious stimuli
Most sensitizing pro-inflammatory agents activate the _____ pathway.
phospholipace C
Phospolipace C pathway phosphorylates TRPV1, leading to _____.
sensitization of TRPV1
Allodynia
Pain sensation in response to non-painful stimuli
Allodynia results from an increase in excitability of _____.
dorsal horn neurons
The _____ localizes painful or thermal stimuli and leads to the _____.
spinothalamic tract (lateral and anterior) thalamus (central lateral nucleus)
The _____ causes alertness and arousal in response to painful stimuli and leads to the _____.
spinoreticular tract reticular formation (through ret.form. of medulla and pons)
The _____ orients the eyes and head towards the stimuli and leads to the _____.
spinotectal tract
tectum (through periaqueductal gray matter)
The dorsal root ganglia pathway goes through _____.
Lissauer’s tract
Crossing of the anterolateral tract from left to right spinal cord occurs at the _____.
decussation
Visceral pain misperceived as somatic pain is called _____.
referred pain
Non-nociceptive fibers of the anterolateral tract terminate in _____.
layer 5
Unilateral spinal cord lesions lead to “dissociated sensory loss”:
contralateral: _____
ipsilateral: _____
reduction in pain/temp sensation
reduction in touch/pressure/vibration/proprioception
The anterolateral system from the body runs through the _____ and the _____.
spinothalamic tract
Ventral posterior lateral nucleos of the thalamus
The anterolateral system from the face runs through the _____ and the _____.
Trigeminothalamic tract
Ventral posterior medial nucleus of the thalamus
Sensory discriminative aspects of pain
location
intensity
quality
Affective motivation aspects
fear
anxiety
The anterolateral system is divided into _____ and _____.
sensory-discriminative
affective-motivational
The sensory-discriminative anterolateral system leads to the _____.
somatosensory cortex
Stimulation of the periaqueductal gray in the midbrain is _____.
analgesic
_____ in the spinal cord modulate pain perception.
Local interactions
Nociceptive information is modulated by simultaneous activity in _____.
touch fibers
Opiod
Peptide that binds to the same posynaptic receptors as opium
_____ is the active ingredient in the sap/seeds of opium poppies.
Morphine
Morphine, heroin, and synthetic opiates such as methadone and fentanyl are potent _____.
analgesics
3 groups of endogenous opioid receptor ligands:
endorphins
enkephalins
dynorphins
_____ modulate transmission of ascending pain signals.
Descending systems
_____ are released directly in the spinal cord to blunt the effects of nociceptor activation.
Enkephalins