Re: E = 1/2mv^2


tomgee wrote:
Randy Poe wrote:
yet everyone but you knows our retinas do not
respond to light,

No, nobody with a rudimentary knowledge of the retina
would say such a thing.

Patently false statement since I just said it.

Since you give me the obvious straight line, I am obligated
to use it: Patently demonstrating you have less than
rudimentary knowledge of the retina.

The retina consists of sensing
cells which absorb photons, and put out signals
in response to those photons.

I don't think so.

Hence, demonstrating your lack of knowledge. Read up
on "rods" and "cones" and what they do.

That means the retinas must have the means for
sensing and also for putting out signals. What are those means?

The sensing is done by means of visual pigments which
are sensitive to particular wavelengths. The rods and cones
are also known as "transducers". It is precisely their function
to convert energy received by the visual pigment into neural
signals. Look at any detailed description of the anatomy of
the retina, for instance here:

http://williamcalvin.com/Bk1/bk1ch11.htm

Notice the figure says "Transducer neuron (rod or cone) converts
light to voltage signal". Series of voltage spikes are how
nerves communicate. The spikes travel down the cell
wall to the "tree" of dendrites connecting to other
neurons, and are then picked up by those other
neurons.

Here's another link:
http://thalamus.wustl.edu/course/eyeret.html
"The outer segments of the rods and cones transduce
the light and send the signal through the cell bodies
of the ONL and out to their axons."

Neuron signals (action potentials) are initiated by opening
channels and pumping ions (Na+ I think) sufficiently
to create a critical voltage difference across the
membrane. What is missing from this picture on these
links is HOW exactly the transducer translates received
light into such a signal. That was a little harder to find,
but I did find at least one link that describes the clever
chemical engine the rod uses to do just that:
http://education.vetmed.vt.edu/Curriculum/VM8054/EYE/PHYSIO.HTM

- Randy

.

Relevant Pages

  • Re: Jeff Hawkins: Why Cant A Computer Be More Like A Brain?
    ... the retina is different from moment to moment. ... "sustained" responses in retinal bipolar and ganglion cells. ... signals, including proprioceptive signals, are not processed by the ... sensory cortices. ...
    (comp.ai.philosophy)
  • Re: Neural netss (was Re: death of the mind.)
    ... This means that any neuron can have more than one output. ... In actual biological NNs the signal eventually decays. ... Use inhibiting signals as well activating ones. ... neuron will have a single input and one or more outputs. ...
    (sci.cognitive)
  • Re: consciousness
    ... brain, but the thing we are sensing normally starts "out there". ... the signals is irrelevant to our conscious awareness. ... If you have two electrons in a wire, and one moves, it can cause the one ... But you haven't explained what happens if you take that neuron out of the ...
    (comp.ai.philosophy)
  • Re: Neural netss (was Re: death of the mind.)
    ... We can talk about motor program generators, ... > This means that any neuron can have more than one output. ... > Use inhibiting signals as well activating ones. ... > neuron will have a single input and one or more outputs. ...
    (sci.cognitive)
  • Re: Neural netss (was Re: death of the mind.)
    ... >> This means that any neuron can have more than one output. ... >> Use inhibiting signals as well activating ones. ... >> neuron will have a single input and one or more outputs. ... >> multiple outputs that enable the topology you're looking for. ...
    (sci.cognitive)