Shark Electric Sense
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Transcript of Shark Electric Sense
SHARK ELECTRIC SENSE
Electrical Circuit Model and Active Membranes
Shark goes coo-coo for E-fields!
http://www.youtube.com/watch?v=Prq2HK8cT3A&feature=player_embedded
Quick review: Ampullae of Lorenzini
Ampulla:Bulblike termination of canal
Alveoli: individual “pouches”
Bv = blood vesselMn = myelinated nerve
From Waltman Acta Physiol. Scand. (1966) “The Fine Structure of Ampullary Canals of Lorenzini”
Ampullary canal: filled withMucous-like, sugary gel
Receptor Cells line bottom of ampulla.Electrical stimulus Neural signal
To epidermis/ocean water
Coding electricity in neural impulses/responses
From Obara and Bennett: J Physiol (1972) “Mode of Operation of Ampullae of Lorenzini Skate, Raja
A cartoon model of the receptor cell making synapse onto nerve. * Receptor cells are electrically active!
• Exhibit all-or-nothing response• “Negative-going spikes”
Bioelectricity: Active Membranes and Action Potentials
Action potential: fundamental unit of electrical communication
Synaptic Transmission
For sharks, think of this as the receptor cell’s presynaptic ribbon
And think of this as the nerve terminal that eventually reaches the brain
Step 1:Electrical Stimulus causes depolarization across membrane of receptor cells
Step 2:Voltage gated channels open, and Ca++ ions rush in.
Step 3:This triggers vesicle release. Electrochemical message sent to neuronbrain
Neural Signals: Spike Rates
Sensory Neuron
Receptor Cells SynapseOnto Sensory Neuron
No stimulus: temporally uncorrelated spiking behavior
Electrical Stimulus Causes Spike Rate to Increase in FrequencySpike Rate Coding: Linear Relationship between Ampullary Stimulus and Neuron Spike Rate
Non-zero resting spike rate.
HH Zakon, 1988; Obara 1976
But wait: Nerve is spontaneously active!
Neural Signals: No stimulus
Sensory Neuron
Receptor Cells SynapseOnto Sensory Neuron
No stimulus: temporally uncorrelated spiking behavior
Neural Signals: Stimulus Present
Sensory Neuron
Receptor Cells SynapseOnto Sensory Neuron
With stimulus: Receptor cell activity synchronized. Causes neuron to fire action potential
References HH Zakon, 1988. Sensory biology of aquatic animals: electroreceptrs
diversity in structure and function
Waltmann, 1966. Electrical Properties of the Ampullary Canals of Lorenzini, Acta. Physiol. Scand. 66: 1-60.
J Bastian, 1994. Electrosensory Organisms Physics Today, Feb 1994: 30-37
RW Murray, 1962. The Response of Ampullae of Lorenzini of Elasmobranchs to Electrical Stimulation. J. Exp Biol, 39: 119-128
S Obara and MVL Bennett, 1972. “Mode of Operation of Ampullae of Lorenzini of the Skate, Raja. J. Gen. Physiol., 60: 534-557.
B Waltman, 1966. Electircal properties and fine structure of the ampullary canals of Lorenzini. Acta Physiol Scand Suppl 264:1