Neuron Logo

THE STANDARDIZED NEURON
from
PROCESSES IN BIOLOGICAL VISION


Last Update 05 July 09             Rhodonine™ and Activa™: See Citation Page

***CURRENTLY HAS NO CACHE IN HEADER ***

This page is reproduced from a Table in the Appendix of the text, PROCESSES IN ANIMAL VISION, entitled The Standard Neuron.

The following tables are developmental tools of the author. They will be continually updated and expanded. An analyst must await parameter values from the experimentalists in most cases. Any suggested values for the tables are greatfully accepted. The utility of these tables is directly proportional to their completeness.


INTRODUCTION

Sources of information

The following table relies heavily on Afifi & Bergman1 as a source of recent information consolidated by one author or group. It is also draws upon the comprehensive tabulation of the (non-electrical) parameters of the node and paranode region of a large cat a axon by Berthold & Rydmark2 in Waxman et. al. (Their Table 2-3) Where a parameter is not available in these sources, other sources have been used as appropriate (giving extra weighting to the more recent literature). These include Barret & Barret3 in 1982 for a myelinated neuron and XXX in 19XXX for the large feline alpha-axon. However, this author has taken the liberty to modify names and features to conform to this work. This is particularly true with regard to electrical parameters defined as relating to resistors. Any errors or inconsistencies are strictly the responsibility of this author. For a consistent set of values for a myelinated frog neuron, see Stampfli4 (1981).

Clarification before proceeding

Numerically, the dominant class of neurons in an animal do not generate action potentials. It is only neurons involved in the projection function, defined as stage 3 in this work, that generate action potentials. All other neurons operate in an analog signal environment.

When speaking of analog circuits, inhibition is a foreign concept compared to negation. Similarly, excitation is a poor choice of words compared to addition or summation.

The electrical mechanisms employed in the neural system are much more complicated than usually taught in an introductory physics course. The simple relationship known as Ohm's Law does not apply to many aspects of vision [Section 11.1.1.4]. Even the concept of a simple resistor is not adequate. There are real resistors, and equivalent resistors and even effective resistances. Each of these increasingly complex concepts has a place in vision.

The introduction of equivalent resistors and effective resistances in place of real resistors plays a crucial role in understanding the thermodynamics of both the visual and neural systems. It is the absence of real resistors that accounts for the remarkable thermal efficiency of the neural system. Much of the waste byproducts of the neural system are removed as chemical substances instead of as heat. This method of operation effectively bypasses some cherished thoughts concerning the Second Law of Thermodynamics. These considerations are treated in depth in Chapter 11.

The main text has shown that the series resistances and the shunt resistances related to the electrolytic conduits of neurons are of such value as to be inconsequential in the neural system. There are no real resistors of significance in the neural system of animals. This is not to say that there are not resistive impedances within the visual system. However, these resistive impedances are not due to physical resistors. They are due to a unique characteristic of the neural system. A majority of the membranes forming the lemma of the neural system are very high quality insulators. This is due to their symmetrical molecular structure. However, in certain areas, these membranes exhibit asymmetric molecular structures. In those cases, they are representative of very high quality electrical diodes.

The asymmetrical membranes of a cell wall may be represented electrically as a simple diode or, as is frequently the case, a diode in parallel with a current source. The resulting circuit is highly asymmetrical electrically and its equivalent resistance is frequently a function of the test set used to measure it. This is because the test set frequently introduces additional voltages and currents into the circuit. As a result, many of the "resistances" recorded in the neural literature are suspect. In general, the instantaneous equivalent resistance of a diode must be accompanied by a description of the voltage across it at the time of the measurement.

The above diode in parallel with a current source is the electrical equivalent of the actual biological situation where an asymmetrical membrane is involved in an electrostenolytic process providing electrical power to the neural system. In this case, the measured resistive impedances are unique in that they do not dissipate power. They are part of a reverseable electrolytic process.

The presence of resistive impedances in the absence of resistors highlights a problem in the literature of the neural system of animals. The biological community has used what is known in their literature as a "Herman Cable" since about 1905. It has been described as a leaky cable made up of resistors and capacitors only. The Herman Cable does not do justice to the exquisitly designed neural system of animals. It is mandatory that the typical conduit be considered for what it is, a high quality coaxial transmission line. Such a structure is found to exhibit real capacitance and real inductance but virtually no real resistance. However, the transmission characteristic of the cable does have an effective resistive component. This resistive component is related to a dispersion of energy rather than a dissipation of energy over the length of the coaxial line.

External negative feedback has not been found at the circuit level in the neural system. It probably does not occur. It does occur in the overall performance of several servomechansims systems. The most common form of feedback in the neural system is internal negative feedback.

ORGANIZATION OF THE MATERIAL

The following material begins with a table of data applicable to virtually all neurons and applies specifically to an idealized nominal or FUNDAMENTAL NEURON.

Following this initial section, sections are provided that apply to specific morphologically identified types of neurons. These include:

I PROPERTIES OF THE FUNDAMENTAL NEURON

II PROPERTIES OF THE PHOTORECEPTOR CELLS(reserved)

III PROPERTIES OF THE SIGNAL MANIPULATION NEURONS (reserved)

IV CHARACTERISTICS of the PROJECTION NEURONS

I PROPERTIES OF THE FUNDAMENTAL NEURON

The FUNDAMENTAL NEURON has been described on a separate page of this site. The morphology of the prototypical FUNDAMENTAL NEURON is that of a pyramid cell. It exhibits three distinct signal terminals and its hillock provides a suggestion as to where the Activa is located. Frequently, the surface texture of the different lemmas of the neuron suggest where the electrostenolytic processes are found. This is frequently detailed in the area of the hillock.

TABLE 1

THE PROPERTIES OF THE (NOMINAL) FUNDAMENTAL NEURON


Gross Physical Properties (based on the common bipolar neuron of retinal morphology)

1. DETAILED PHYSICAL PROPERTIES
 Property Nominal valueComment or range
DENDRITES
    Projection cellPhotoreceptor cell
Diameter
 main stem
 propagules   600Å O.D.
 arborization
 microtubules 240Å240Å240Å O.D.
 neurofilaments 100Å100Å100Å O.D.
Length
 main stem
 propagules   
Content of dendroplasm
Thickness of dendrolemma
Diameter of reticulum
Location of electrostenolytics
avg. rest. potential of dendroplasm
intrinsic potential of the dendrolemma
Signal current transport vel. in plasma
Content of dendroplasm
PODITESGenerally same as dendrites
AXONS
Diameter
 main elem. (unmyelinated)2 microns
 pedicel~2.5 microns
Length
 main elem. (unmyelinated) <2 micronsto avoid oscillation
 internodes (myelinated) 2 mm. max. 200-2000 microns
Content of axoplasm
Thickness of axolemma8 nm.
Diameter of reticulum
Content of the axoplasmNo protein synthesis apparatus
fluid
vesicles (generally spherical)
     in bulk of      axoplasm40-160 micron D. 40-160, Dispersed in axoplasm
     Synaptic      space300-600 nm. D. Ordered between arcXXX and lemma. Coincident with imps.
tubules (microtubules)25 nm. Indef. length (within reticulum)
neurofilaments 7-10 nm. D.
microfilaments Paired chains of protein molecules
mitachondria Concentrated near microtubules but not restricted to axoplasm
Transport within axoplasmNo protein synthesis apparatus
fast particle transport*100-400 mm/day Toward axon
     Retrograde      component of anterograde component
slow particle transport*0.25-3 mm/day
Charge transport2 meters/sec.
JUNCTIONS
Diameter
Thickness 100 Å (10 nm.)
Composition Hydronium In liquid crystalline form
* Fast and slow particle transport are probably a part of a continuum based on individual particle cross-section and density in the solvent.



2. STATIC ELECTRICAL CHARACTERISTICS
 Property  Nominal value Comment or range
Location of the electrostenolytic process
At synapse (pedicel) within cavity of pedicel
At Node of Ranvier At sides of paranode
Within Hillock On Hillock surface
Location of the Junction (Activa)
At synapse (pedicel) on walls of cavity
At Node of Ranvier in center of perinode
Within Hillock between dendrite and axon
Diameter of the Junction
At synapse (pedicel) frequently multi-elem, array
At Node of Ranvier frequently multi-elem. array
Within Hillock characteristics undocumented
Nominal impedance of axoplasm110-114 ohm-cm From Stampfli*
Under current cutoff conditions
Intrinsic potential of the axolemma*-150 mV. Under current cutoff conditions
Average resting potential of the axolemma*-70 mV. The reticulum (conduit) is resistive
Maximum capacitive overshoot*+40 mV. Of "action potential"
* Stampfli (1981) provides a good table of electrical parameters for a myelinated frog neuron
** All values at 300 K.



3. DYNAMIC ELECTRICAL CHARACTERISTICS
    Property              Nominal value Comment or range
Signal current transport velocity in the plasma
Intraplasma, phase velocity >4,400 m/sec.For eight micron myelinated
Fundamental unit, group velocity >[get value from text XXX] For eight micron myelinated
Regenerator circuit parameters
The Action Potential @ ~20 Celsius Fitting in-vitro data of Bowe, et. al. for Wistar rat tissue in modified Krebs solution of unspecified temp. and containing no bioenergetics
     Quiescent to Intrinsic volt. diff. 65 mV.
     Quiescent to Switching volt. diff. 63 mV.
     Rising waveform time constant 0.18 msec.
     Switching time after initiation 0.6 msec.
     Falling waveform time constant 1.8 msec.
     Rate of rise of waveform 1,400-1,600V/s.at 18Celsius
The Action Potential @ 37 Celsius Typical for mammals
     Quiescent to Intrinsic volt. diff. ?? mV.
     Quiescent to Switching volt. diff. ?? mV.
     Rising waveform time constant ?? msec.
     Switching time after initiation ?? msec.
     Falling waveform time constant ?? msec.
Transmission line parameters (8 m axon, 15 m O. D.)
     Characteristic impedance 8,500 Ohmseight micron myelinated (15 m OD
     Shunt capacitance 4.4 x 10-10 F/m
     Series inductance 3.22 x 10-2 H/m
     Series resistance negligible
     Shunt conductance negligible
     Attenuation constant 0.12 per 100 m.
     Dispersion coefficient negligiblepossible pulse sharpening
Node to Node, group velocity44 m/sec. Eight micron myelinated
     Regenerator delay 0.19 msec.


4. SIGNALING CHARACTERISTICS
 Property  Nominal value Comment or range
Pulse to pulse interval
     Luminance channel3 msec to inf. No pulses in darkness
     Chrominance channel
Nominal33 msec. Nominal 30 Hz in darkness
Minimum3 msec. ~ 300 Hz.
Maximum200 msec. ~ 5 Hz.
. Review chapter 2 through 4 of Kandel before writing up this Standardized neuron

II PROPERTIES OF THE PHOTORECEPTOR CELLS

(reserved)

III PROPERTIES OF THE SIGNAL MANIPULATION NEURONS

(reserved)

IV PROJECTION NEURON CHARACTERISTICS

A. SUBJECTIVE/ARCHITECTURAL CHARACTERISTICS

GANGLION CELLS LEADING TO THE MAGNO, PARVO CELLULAR BODIES & THE PRETECTUM

(Caution: M & P are used interchangeably in the literature of the ganglion cells)

Kandell et. al.5 have provided a list of subjective properties of the ganglion cells leading into the LGN. Their nomenclature is contrary to that of the cytologist looking at the retina who use M to denote a midget and P to denote a parasol ganglion cell. The following table follows their format but modifies their nomenclature and adds data related to the signaling channel between the foveola* (the central part of the fovea) and the Pretectum. See text.

AttributeCell terminal location
Lateral Geniculate Body of ThalmusMid-brain
Magnocellular bodyParvocellular body Pretectum
(Cytologists cell type)Parasol ganglion cell Midget ganglion cellParasol ganglion cells
Percentage of all ganglion cells~10 ~80<1%
Distribution on retina*Densest in fovea? Densest in fovea?Limited to foveola
Conduction Velocity~15 meters/sec~6 meters/sec ~15 m/s. (est.)
Central projection
Ganglion cells:LGN, magnocellularLGN, parvocellular Pretectum
LGN cells to:V1, layer 4CaV1, layer 4Cb
Pretectum cells:V5
Chromatic contentNo Opponent data,Raw spectral data,
P & Q channelsS, M & L channels
Luminance informationYes, R channelNoCan be used to compute
R channel
Contrast sensitivityHigh, typically >60:1 Low, typically <20:1High
Spatial resolutionvariablevariableHighest,
0.089 millirad pixel
Temporal resolutionHigh, typically >60 Hz Low, typically <30 HzHighest, ~60-90 Hz

* Kandel, et. al. do not distinguish between the fovea and the foveola within it.

References

1) Afifi, A. & Bergman, R. (1998) Functional neuroanatomy: text and atlas. NY: McGraw-Hill

2) Berthold, C. & Rydmark, M. (1983) anatomy of the paranode-node-paranode region in the cat, Experientia, vol. 39, pp. 964-975

3) Barret & Barret in 1982

4) Stampfli, R. (1981) Overview of studies on the physiology of conduction in myelinated nerve fibers. In Demyelinating disease: basic and clinical electrophysiology, waxman, S. & Ritchie, J. ed. NY: Raven Press pp. 11-23

Kandell, E. Schwartz, J. Jessell, T. (2000) Principles of Neural Science. McGraw-Hill page 581,