The Somatosensory System Flashcards
The somatosensory system reports the body’s interactions with its immediate surroundings via “touch and feel” sensing of ______ against the skin, and via _____ sensations
contact pressure; thermal
Its peripheral receptors are “tuned” to _____ among different qualities of the various stimuli to which they are responsive, e.g. texture and shape, hot vs. cold, innocuous vs. noxious
discriminate
the structural organization that gives rise to “somatotopic mapping” ensures
that _____ of the stimulus as applied to the body can be accurately identified
location
somatosensory reporting relies upon two “design characteristics”: _____ and _____.
Discrimination and location of the stimulus
somatotopic mapping → gives rise to _____, but note that location of individual receptive
fields within each dermatome is also mapped
dermatomes
peripheral somatosensory neurons are located in the ______, and is classified as?
dorsal root ganglia; pseudo-unipolar
the ______fiber travels as part of a peripheral nerve to enter the spinal cord via a dorsal root
afferent sensory
whereas somatosensory signals from the skin project into the brain via _____, allowing precise perception of location on the body surface
labeled lines
What does not use the labeled line concept to provide sensory inputs to the brain?
Visceral receptors
_____ receptors are broadly distributed, but they give rise to relatively few centrally projecting fibers
visceral
non-nociceptive and nociceptive fibers arising from the viscera therefore have a relatively large receptive field, which means _____ discrimination of the precise location
poor
in addition, _____ afferent fibers tend to synapse on spinal relay neurons that also convey somatic (body surface) sensory input
visceral
visceral stimuli may therefore be perceived as originating from a _____ site → our brain may refer neural signaling arising from visceral receptors to a _____ location
somatic
This is why people who is having heart problems will show signs of shoulder and neck pain
Even for heart attack, the brain perceives the signal as signal from the _____ of the body, where as it’s from the heart. “Shoulder and neck pain”
surface
peripheral fibers conveying _____ somatosensory afferent
signals are classified alphabetically (“A” and “C”)
non-proprioceptive
What fiber type?
-large diameter, heavy myelin sheath (fastest conducting)
− these may also be referenced as _____.
A-alpha; “Type 1”
What fiber type?
-medium diameter, myelinated
− these may also be referenced as _____.
A-beta; “Type 2”
What fiber type?
-small diameter, myelinated
A-delta
What fiber type?
-unmyelinated (slowest conducting)
C fibers
fibers conveying PROPRIOCEPTIVE afferent signals from muscle are classified numerically [from type I (_____) to type IV (_____)]
largest; smallest
Large Aα and Aβ (or Type 1 and 2) somatosensory fibers convey _____ information from the skin
Mechanical
smaller Aδ and unmyelinated C somatosensory fibers convey _____ information and _____.
thermal; pain
Mechanoreceptors in the skin provide our sensation of _____ and _____.
touch; feel
glabrous skin of the hands and feet contain four types of mechanoreceptors:
Superficial? (2)
Deep? (2)
Superficial: Merkel’s disk and Meissner’s corpuscle
Deep: Ruffini corpuscle and Pacinian corpuscle
Superficial receptors (Merkel's disk and Meissner's corpuscle): Give rise to \_\_\_\_\_afferent fibers. -Have no end organ
Aα (Type1)
Deep receptors (Ruffini corpuscle and Pacinian corpuscle) •give rise to \_\_\_\_\_afferent fibers. • are embedded within an end organ structure (sensory nerve ending).
Aβ (Type2)
the receptive field is the _____ to which an applied stimulus will
trigger signaling along a particular afferent sensory fiber
spatial domain
The size (surface area) of the Type 1 (Aa) fibers of the receptive field is determined by the distribution of the multiple receptors that collectively feed into one particular fiber, which are _____ exposed to the stimulus energy (force of applied pressure).
DIRECTLY
The size (surface area) of the Type 2 (Aβ) fibers of the receptive field is determined by the _____ within which the sensory nerve ending is embedded, through which the stimulus energy (applied pressure) is transmitted to the sensory nerve ending.
end-organ structure
The cutaneous mechanoreceptors are also classified as either _____ or _____ adapting to “report” different characteristics of the applied stimulus
slowly; rapidly
slowly adapting:
• _____ signaling (at a relatively steady frequency) throughout the duration that the stimulus is applied
• continued reporting → the stimulus is _____
maintains; sustained
rapidly adapting:
• maintains signaling just while the
stimulus intensity is _____
• reports “_____” and “_____”, and more generally, variations in the stimulus intensity
changing; “stimulus on” and “stimulus off”
Merkel’s disk and Meisner’s corpuscle are _____ mechanoreceptors.
superficial
Which type of mechanoreceptors consist of a individual mechanosensitive nerve terminals associated with a small
flattened non-neural epithelial cell (the “end organ”)?
Superficial mechanoreceptors: Merkel’s disk and Meisner’s corpuscle
