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Flashcards in Peripheral sensory mechanisms Deck (41)
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What type of skin covers the palms of the hands and the soles of the feet?

Glabrous skin


What is glabrous skin specialised for?



How is glabrous skin specialised for somatosensation?

Skin ridges

Concentrated with receptors


Which broad class of receptors are found in glabrous skin?



Which four types of mechanoreceptors are found in glabrous skin?

Meissner corpuscles

Merkel complexes

Ruffini organs

Pacinian corpuscles


Describe the location of the mechanoreceptors in the skin?

Meissner corpuscles and Merkel complexes are located close to the surface

Ruffini organs and Pacinian corpuscles are deeper


Describe the axons that innervate the mechanoreceptors?

Large and myelinated


Where do the cell bodies of the axons that innervate mechanoreceptors lie?

In dorsal root ganglia


What are the endings of mechanorecepptors composed of?

Connective tissue


What are the connective tissue endings of each type of mechanoreceptor important for?

Determining the type of energy that the receptor will respond to


Which layers of the skin are the Ruffini and Pacinian corpuscles located in?

Ruffini corpuscles are located in the dermis

Pacinian corpuscles are located in the subcutaneous layer


What are the Ruffini and Pacinian corpuscles embedded in?

Connective tissue


Which receptors detect distortion of the skin?



What is the range of distortion detected by the mechanoreceptors?

10nm to sub-damaging distortion


What is the sensitivity and dynamic range of the mechanoreceptors to distortion of the skin?

0-1000 Hz


What is the receptove field of the mechanoreceptors that detect distortion of the skin?

10mm^2 to entire hand 


How do mechanoreceptors respond to mechanical distortion?

Mechanical distortion > Na channels opened by mechanical force > Na inflow > AP generated


Describe why radiating forces are important for mechanoreception?

Force applied to skin radiates > at some point, the mechanoreceptor will experience some of that force > generate AP if stimulus reaches threshold 


When will a mechanoreceptor generate an AP?

When the stimulus applied is strong enough to generate a large Na inflow that reaches threshold 


What happens if a stimulus does not cause Na to reach threshold?

No AP generated > we have no sensory experience of the event that is occurring 


Describe the difference between slowly adapting and rapidly adapting receptors?

SLOW: Show an initial bit of enthusiasm in response to a stimulus

Over time, encode the size of the stimulus

RAPID: Short initial excitement

After that, only respond when there is a change in stimulus 


Does the nervous system generally act like slowly adapting or rapidly adapting receptors?

Rapidly adapting


Which of the mechanoreceptors are slowly adapting? Which are rapidly adapting?

Slowly adapting: Merkel complexes and Ruffini organs 

Rapidly adapting: Meissner corpuscles and Pacinian corpuscles 


Where are Merkel complexes and Meissner corpuscles located?

Merkel complexes are located at the tips of epidermal ridges 

Meissner complexes are found near the skin surface


Which particular stimuli do each of the four mechanoreceptors respond to?

Merkel: indentation 

Meissner: transient response to skin movement

Ruffini: sustained response to skin movement

Pacinian: transient response to vibration


What types of connections do the axons of mechanoreceptors have in the spinal cord?

Local connections and ascending projections to the brain


Describe the difference in firing rate between tactile and nociceptive primary sensory afferents?

Tactile: don't change firing rate with increased force

Nociceptive: increased firing rate with increased stimulus, as well as increased firing once stimulus is removed 


Describe the receptive fields of each of the four types of mechanorecptor?

Merkel: small, high density

Meissner: small, high density

Ruffini: large, low density

Pacinian: large, low density


Why are all four mechanorecpetors required?

To build a profile of information and make judgements about what we are touching/feeling


When performing a simple manipulation task, what do each of the four mechanoreceptors encode?

Meissner: rate of force

Merkel: grip force

Pacinian: vibrations

Ruffini: hand posture