The Initiation and Conduction of Action Potentials in the Optic Nerve of Tritonia

1974 ◽  
Vol 60 (3) ◽  
pp. 721-734
Author(s):  
RONALD CHASE
Keyword(s):  
Optic Nerve ◽  
Action Potentials ◽  
Sensory Cells ◽  
Refractory Periods ◽  
Graded Responses ◽  
Trigger Zone ◽  
A Site ◽  
Spike Waveforms ◽  
Cerebral Nerve ◽  
Primary Sensory Cells

1. The optic nerve of Tritonia contains axons of the five primary sensory cells. It joins a cerebral nerve about 2.0 mm from the eye and then travels another 2.5 mm to the central ganglia. 2. Large DC responses of positive polarity were recorded with suction electrodes in the presence of light. These graded responses are generator potentials passively conducted from a site of origin in or near the receptor somata. DC responses to light were not recorded at points central to the junction of the optic nerve with the cerebral nerve. 3. The shape of extracellular spike waveforms and the temporal relationship between soma and nerve spikes support the conclusion that action potentials are initiated in the optic nerve. In the,dark, spikes originate in portions of the nerve distant from the eye. When the eye is illuminated, the trigger zone shifts about 700 µm more proximal to the eye. 4. The shift in the spike trigger zone during illumination probably reflects an habitual accommodation of proximal portions of the nerve under the conditions of these experiments, and the prevalence of partially or completely silent optic nerves is probably due to more severe consequences of sustained depolarization. The sensitivity of the receptors, in combination with the passive properties of the nerve, makes the nerve susceptible to debilitating effects of maintained illumination. 5. The excitability of optic nerve fibres is extremely low. Absolute refractory periods are 25 msec, and relative refractory periods are as long as several hundred msec. When stimulated with just-suprathreshold voltages the nerve cannot support action potentials at frequencies greater than 1 Hz. 6. The Tritonia optic nerve appears to be transitional between transmission by graded responses and transmission by action potentials.

Classes of Light-Evoked Response in the Retina of Strombus

1979 ◽  
Vol 80 (1) ◽  
pp. 287-297
Author(s):  
FREDERICK N. QUANDT ◽  
HOWARD L. GILLARY
Keyword(s):  
Optic Nerve ◽  
Action Potentials ◽  
Input Resistance ◽  
Resting Potential ◽  
Recording Site ◽  
Charging Time ◽  
Rate Of Decay ◽  
Hyperpolarizing Response ◽  
Strombus Luhuanus ◽  
A Site

Two general classes of light-evoked responses were recorded intracellularly from the retina of Strombus luhuanus. In one class, retinal illumination caused depolarization, the amplitude of which was graded with light intensity. In the other, it produced hyperpolarization and concomitant inhibition of repetitive action potentials. There were two types of depolarizing waveform. Each was associated with a different type of intraccllular recording site, characterized on the basis of electrical properties in the dark. In general, the type of response with a more rapid rate of decay was recorded from a site which exhibited a lower resting potential, higher input resistance, and longer ‘membrane charging time.’ The two depolarizing responses and the hyperpolarizing response apparently each arose from a different type of neurone. The depolarizing types, at least one of which is a photoreceptor, apparently give rise to the cornea-negativity of the electroretinogram and ‘on’ activity in the optic nerve fibres. The hyperpolarizing type apparently mediates ‘off’ activity in the optic nerve.

scholarly journals Electrophysiological Organization of the Eye of Aplysia

1969 ◽  
Vol 53 (1) ◽  
pp. 21-42 ◽  
Author(s):  
Jon W. Jacklet
Keyword(s):  
Optic Nerve ◽  
Action Potentials ◽  
Secretory Granules ◽  
Cerebral Ganglion ◽  
Intracellular Recordings ◽  
Receptor Cells ◽  
Graded Responses ◽  
Graded Response ◽  
Inhibitory Interactions ◽  
Light Flashes

The eye of Aplysia californica was studied by electrophysiological and histological methods. It has a central spheroidal lens which is surrounded by a retina composed of several thousand receptor cells which are replete with clear vesicles, pigmented support cells, neurons which contain secretory granules, and glial cells. The thin optic nerve that connects the eye to the cerebral ganglion gives a simple "on" response of synchronized action potentials. Tonic activity occurs in the optic nerve in the dark and is dependent on previous dark adaptation. Micropipette recordings indicate that the ERG is positive (relative to a bathelectrode) on the outer surface of the eye and negative in the region of the distal segments of the receptors. Intracellular recordings show that receptor cells have resting potentials of 40–50 mv and respond to illumination with graded potentials of up to 55 mv. Dark-adapted receptors exhibit discrete bumps on the graded response to brief light flashes. Other elements in the retina that do not give large graded responses fall into two classes. One class responds to illumination with action potentials that are in synchrony with the extracellularly recorded compound optic nerve potentials. The other class is tonically active and is depolarized or hyperpolarized and inhibited upon illumination. It is apparent that complex excitatory and lateral inhibitory interactions occur among the elements of the retina.

Respiration-dependent Movements of the Column of Stylidium gvaminifolium

1981 ◽  
Vol 8 (1) ◽  
pp. 45 ◽  
Author(s):  
G.P Findlay ◽  
N Findlay
Keyword(s):  
Refractory Period ◽  
Angular Displacement ◽  
Metabolic Energy ◽  
Original Position ◽  
Firing Process ◽  
Mechanical Stimuli ◽  
Anaerobic Conditions ◽  
Absolute Refractory Period ◽  
Refractory Periods ◽  
Graded Responses

The column of the trigger plant, Stylidium graminifolium, when fully set responds to mechanical stimuli by flipping through an angle of about 4 radians in a fast firing movement lasting about 15-30 ms, and then slowly resetting to its original position in about 400 s. After resetting there is an absolute refractory period of about 500 s during which no further response to stimuli can be initiated, followed by a relative refractory period when graded responses increasing in rate and magnitude with time can be obtained. The resetting movement and the process, occurring during the refractory period, allowing subsequent firing to occur, are inhibited when the air surrounding the column is replaced by nitrogen. The firing movement, however, is not affected by these anaerobic conditions. Thus the firing movement is caused by passive physical forces, rapidly utilizing potential energy from a store built up during the previous resetting and refractory periods. Removal of the labellum, which the column touches when set, causes the column to oscillate with amplitude of about 3-3.5 radians and period of 1-2 ks. When the column is held at a constant angular displacement it develops an oscillatory torque with similar period. These oscillations are inhibited at all stages of the cycle by anaerobic conditions. It appears that the oscillatory behaviour is not a slowed-down firing process followed by normal resetting, but is linked throughout the cycle to the metabolic energy supply.

Fine Structure of the Eye of a Nudibranch Mollusc, Hermissenda Crassicornis

1967 ◽  
Vol 2 (3) ◽  
pp. 349-358
Author(s):  
R. M. EAKIN ◽  
JANE A. WESTFALL ◽  
M. J. DENNIS
Keyword(s):  
Electron Microscopy ◽  
Fine Structure ◽  
Optic Nerve ◽  
Light And Electron Microscopy ◽  
The Other ◽  
Sensory Cells ◽  
Nerve Fibres ◽  
Supporting Cells ◽  
Small Bodies ◽  
Receptor Cells

The eye of a nudibranch, Hermissenda crassicornis, was studied by light and electron microscopy. Three kinds of cells were observed: large sensory cells, each bearing at one end an array of microvilli (rhabdomere) and at the other end an axon which leaves the eye by the optic nerve; large pigmented supporting cells; and small epithelial cells, mostly corneal. There are five sensory cells, and the same number of nerve fibres in the optic nerve. The receptor cells contain an abundance of small vesicles, 600-800 Å in diameter. The lens is a spheroidal mass of osmiophilic, finely granular material. A basal lamina and a capsule of connective tissue enclose the eye. In some animals the eye is ‘infected’ with very small bodies, 4-5 µ in diameter, thought to be symbionts.

Excitability and electrical response of ischemic heart muscle

1960 ◽  
Vol 198 (6) ◽  
pp. 1143-1147 ◽  
Author(s):  
Chandler McC. Brooks ◽  
Jerome L. Gilbert ◽  
Martin E. Greenspan ◽  
Gertrude Lange ◽  
Hector M. Mazzella
Keyword(s):  
Action Potential ◽  
Blood Supply ◽  
Heart Muscle ◽  
Action Potentials ◽  
Electrical Response ◽  
Left Ventricular ◽  
Ischemic Heart ◽  
Monophasic Action Potential ◽  
Ventricular Muscle ◽  
Refractory Periods

Measurements were made of the changes in the monophasic action potential, excitability, durations of the refractory periods and conduction times in an area of left ventricular muscle during the development of ischemia subsequent to ligation of the ramus descendens anterior. The degree and duration of the ischemia produced varied greatly and effects were related thereto. It was found that action potentials shortened as did the refractory periods; thresholds fell momentarily and then rose progressively as tissue responsiveness failed due to continuing ischemia. Latency of responses increased, the action potentials decreased in amplitude and alternation occurred before the tissue became completely unresponsive. Early re-establishment of a blood supply caused a reversal of the abnormalities. The significance of these changes to the origin of arrhythmias is discussed.

Coupling of Calcium Homeostasis to Axonal Sodium in Axons of Mouse Optic Nerve

2002 ◽  
Vol 88 (2) ◽  
pp. 802-816 ◽  
Author(s):  
Yakov Verbny ◽  
Chuan-Li Zhang ◽  
Shing Yan Chiu
Keyword(s):  
Optic Nerve ◽  
Calcium Homeostasis ◽  
Action Potentials ◽  
Calcium Influx ◽  
Repetitive Nerve Stimulation ◽  
Strongly Coupled ◽  
Sodium Load ◽  
Calcium Clearance ◽  
Calcium Dyes ◽  
Ionophore Monensin

Axonal populations in neonatal and mature optic nerves were selectively stained with calcium dyes for analysis of calcium homeostasis and its possible coupling to axonal Na. Repetitive nerve stimulation causes a rise in axonal [Ca2+]i the posttetanus recovery of which is impeded by increasing the number of action potentials in the tetanus. This effect is augmented in 4-aminopyridine (4-AP; 1 mM), which dramatically increases the calcium and presumably sodium load during the tetanus. Increasing axonal [Na]i with the Na-ionophore monensin (4–50 μM) and ouabain (30 μM) retards posttetanus calcium decline, suggesting that efficient calcium clearance depends on a low level of axonal [Na]i. Posttetanus calcium clearance is not affected by K-mediated depolarization. To further examine coupling between axonal [Na]i and [Ca2+]i, the resting axonal [Ca2+]i was monitored as axonal [Na+]i was elevated with ouabain, veratridine, and monensin. In all cases, elevation of axonal [Na+]i evokes a calcium influx into axons. This influx is unrelated to activation of calcium channels but is consistent with calcium influx via reversal of the Na/Ca exchanger expected as a consequence of axonal [Na+]i elevation. In conclusion, this study demonstrates that calcium homeostasis in the axons of the optic nerve is strongly coupled to axonal [Na+]i in a manner consistent with the Na/Ca exchanger playing a major role in extruding calcium following nerve activity.

Intracellular characterization of identified sensory cells in a new spider mechanoreceptor preparation

1994 ◽  
Vol 71 (4) ◽  
pp. 1422-1427 ◽  
Author(s):  
E. A. Seyfarth ◽  
A. S. French
Keyword(s):  
Sensory Neurons ◽  
Action Potentials ◽  
Lucifer Yellow ◽  
Sense Organ ◽  
Sensory Cells ◽  
Cupiennius Salei ◽  
Bursting Neuron ◽  
Sensory Structures ◽  
Spider Cupiennius Salei

1. We have developed an isolated mechanoreceptor-organ preparation in which the intact sensory structures are available for mechanical stimulation and electrical recording. The anterior lyriform slit sense organ on the patella of the spider, Cupiennius salei Keys., consists of seven or eight cuticular slits, each innervated by a pair of large bipolar sensory neurons. The neurons are fusiform, and the largest somata are < or = 120 microns long. The innervation of the organ was characterized by light microscopy of neurons backfilled with neuronal tracers. Intracellular recording was used to measure the passive and active electrical properties of the neurons, in several cases followed by identification with Lucifer yellow injection. Both neurons of each pair from one slit responded with action potentials to depolarization by a step current injection. Approximately half of the sensory neurons adapted very rapidly and generated only one or two action potentials in response to a sustained depolarizing step, while a second group produced a burst of action potentials that adapted to silence in approximately 1 s or less. Recordings from identified neuron pairs indicated that each pair consists of one rapidly adapting and one bursting neuron. Measurements of cell membrane impedances and time constants produced estimates of neuronal size that agreed with the morphological measurements. This new preparation offers the possibility of characterizing the mechanisms underlying transduction and adaptation in primary mechanosensory neurons.

Emergence of Radial Nerve Dominance in Median Nerve Cortex After Median Nerve Transection in an Adult Squirrel Monkey

1997 ◽  
Vol 77 (1) ◽  
pp. 522-526 ◽  
Author(s):  
C. E. Schroeder ◽  
S. Seto ◽  
P. E. Garraghty
Keyword(s):  
Median Nerve ◽  
Squirrel Monkey ◽  
Ulnar Nerve ◽  
Action Potentials ◽  
Radial Nerve ◽  
Current Source ◽  
Short Latency ◽  
Nerve Transection ◽  
A Site ◽  
Stimulation Of

Schroeder, C. E., S. Seto, and P. E. Garraghty. Emergence of radial nerve dominance in median nerve cortex after median nerve transection in an adult squirrel monkey. J. Neurophysiol. 77: 522–526, 1997. Throughout the glabrous representation in Area 3b, electrical stimulation of the dominant (median or ulnar) input produces robust, short-latency excitation, evident as a net extracellular “sink” in the Lamina 4 current source density (CSD) accompanied by action potentials. Stimulation of the collocated nondominant (radial nerve) input produces a subtle short-latency response in the Lamina 4 CSD unaccompanied by action potentials and followed by a clear excitatory response 12–15 ms later. Laminar response profiles for both inputs have a “feedforward” pattern, with initial activation in Lamina 4, followed by extragranular laminae. Such corepresentation of nondominant radial nerve inputs with the dominant (median or ulnar nerve) inputs in the glabrous hand surface representation provides a likely mechanism for reorganization after median nerve section in adult primates. To investigate this, we conducted repeated recordings using an implanted linear multi-electrode array straddling the cortical laminae at a site in “median nerve cortex” (i.e., at a site with a cutaneous receptive field on the volar surface of D2 and thus with its dominant afferent input conveyed by the median nerve) in an adult squirrel monkey. We characterized the baseline responses to median, radial, and ulnar nerve stimulation. We then cut the median nerve and semi-chronically monitored radial nerve, ulnar nerve and median nerve (proximal stump) evoked responses. The radial nerve response in median nerve cortex changed progressively during the weeks after median nerve transection, ultimately assuming the characteristics of the dominant nerve profile. During this time, median, and ulnar nerve profiles displayed little or no change.

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