Somatosensation Study Guide Flashcards
Lab (38 cards)
What is Nociception?
pain
What is somatosensation?
Tactile + Proprioception
the sense of touch
Occurs when there is a mechanical interaction between your body and another object
What is thermoreception?
temperature
What is proprioception?
sensory input from your internal body (e.g. stomach)
Hairy skin
skin with hair
ex: arms, back
What are the 3 types of cutaneous receptors?
-Mechanoreceptors
-Thermoreceptors
-Nociceptive receptors
What are mechanoreceptors?
= respond to mechanical stimulation or pressure
•Embedded in the epidermis and dermis
•Consists of a nerve fiber and an expanded ending
What are thermoreceptors?
a cutaneous receptor that codes absolute and relative changes in temperature
-reside in dermis and epidermal layers
-differently concentrated in different areas
What are nociceptive receptors?
a sensory receptor that responds to painful input, such as extreme heat or pressure
What are the different mechanoreceptors?
Meissner Corpuscle (FA I)
Merkel Complexes (SA I)
Pacinian Corpuscle (FAII)
Ruffini Endings (SAII)
Fast-adapting (FA)=
motion of objects against skin
responds with action potentials when the stimulus is applied and again when the stimulus is removed
Slow-adapting (SA)=
pressure and shape of objects
Remains active as long as the stimulus is applied
(continuous firing)
Total number of action potentials evoked per second is proportional to indention force applied
Type I mechanoreceptor=
small receptive field
Located at the dermal-epidermal boundary
Low threshold, small RFs
Meissner Corpuscle: FA type
Merkel Cell: SA type, steady downward pressure
Both respond best to low frequency vibrations
Type II mechanoreceptor=
large receptive field
Located deep in the dermis
Higher threshold, Large Res
Pacinian Corpuscle: FA type; fast & sudden pressure, high frequency vibrations
Ruffini Endings: SA type, sustained downward pressure & lateral skin stretch
What type of information does the Meissner Corpuscle (FA I) convey?
§ Specialized encapsulated nerve endings
§ Concentrated in thick hairless skin (particular finger pads)
§ Relay light touch and low frequency vibration sensations
§ Sensitive to “skin slip” like when you start to drop the item you are holding
Fast adapting
What type of information does Merkel cell neurite complexes (SA I) convey?
§ Oval-shaped mechanoreceptors
§ Abundant in highly sensitive areas like the fingertips
§ Essential for light touch
§ Sensitive to texture or form perception
§ Ex: reading braille
Slow adapting
What type of information does Pacinian corpuscles (FA II) convey?
§ Larger and fewer in number
§ Very responsive to vibration and pressure
§ Sensitive to fine texture perception and vibration
§ Ex: tell the difference between rough and smooth sandpaper, when an object you are holding and it hits something
Fast adapting
What type of information do Ruffini endings (SA II) convey?
§ Spindle shaped receptors
§ Found on hairless skin on the fingertips
§ Important for finger position when picking up objects
§ Ex: playing the piano
Slow adapting
What is two-point threshold?
=the minimum distance at which two stimuli (e.g., two simultaneous touches) are just perceptible as separate
=the smallest separation of two separate but adjacent points of stimulation on the skin that produces two distinct impressions of touch
Why do different areas of the body have different two-point thresholds?
The glabrous skin of the hand and forehead shows the greatest sensitivity (lowest threshold) for both: At this location, pain acuity is nearly at the level of tactile acuity.
On the hairy skin of the arm, however, pain and touch diverge. For example, the shoulder is more spatially sensitive than the forearm to pain, but the reverse is found for tactile stimulation.
Two-point threshold is low (that is, the ability to discern two very close points as separate is high) only when the density of receptors is relatively high, the receptive fields are small, and cortical convergence does not occur.
Tactile spatial acuity thresholds are mediated by the SA I (and possibly FA I) tactile receptors, which have relatively small receptive fields and high receptor densities
What is the relative distribution of cold and warm receptors?
The body has 30x more cold fibers than warm fibers
Most objects in our world are cooler than the normal skin temperature (30-36C or 86-97F)
What type of pain fibers do we have?
-myelinated A-delta fibers
-unmyelinated C fibers
Are our pain fibers myelinated or not?
Both
The myelinated A-delta fibers respond primarily to strong pressure or heat
The unmyelinated C fibers respond to intense stimulation of various sorts: pressure, heat or cold, or noxious chemicals.
What happens to the sensitivity of thermoreceptors when there is a prolonged increase or decrease in temperature?
When the body is exposed to a temperature for a long period of time, the skin becomes less sensitive and changes its perception
For particular locations of the skin, certain temperatures are perceived as neutral
Increasing the temperature is perceived as warm, but it eventually adapts and is perceived as “neutral”
If the temperature of this same location is dropped, even back to the previous “neutral” temperature, it will be perceived as cold
