Touch receptors

r norman rsn_ at _comcast.net
Fri Feb 27 14:12:32 EST 2004


On 27 Feb 2004 01:43:15 -0800, tonyjeffs at aol.com (TonyJeffs) wrote:

>Hi
>I wonder if anyone could clarify the following...
>
>When Pacinian , Merkel, Ruffini, and Meissner  receptors send a signal
>along the associated axon, is it always an Action Potential? 
>Presumably a graded flow is not possible since it'd expire before it
>reached the sc?
>Is there usually/always a 1:1 relationship between receptor and neuron
>at the periphery, or can several receptors contribute to the
>initiation of an AP?
>
>Where the pacinian corpuscle wraps around a nerve ending, would it be
>right to call that a synapse - Is that what it is?
>
An action potential is the only way a signal can travel any
substantial distance (more than a millieter or two). There are some
animals so small that peripheral sense organs can signal the CNS
through graded potentials that spread passively with decay.  But all
vertebrates require action potentials to reach the CNS from the
periphery.

There are single axons with multiple receptor endings.

The pacinian corpuscle modifies the mechanical transmission of forces
and movements through the skin to the surface membrane of the sensory
axon.  There is no synapse there. However, at other sense organs where
the receptor is distinct from the sensory neuron (taste buds, hair
cells in the ear, etc) there is a definite synapse between the two
cells.





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