shark electric sense
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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. To epidermis/ocean water. Ampullary canal : filled with - PowerPoint PPT PresentationTRANSCRIPT
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SHARK ELECTRIC SENSE
Electrical Circuit Model and Active Membranes
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Shark goes coo-coo for E-fields!
http://www.youtube.com/watch?v=Prq2HK8cT3A&feature=player_embedded
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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
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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”
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Bioelectricity: Active Membranes and Action Potentials
Action potential: fundamental unit of electrical communication
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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
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Neural Signals: Spike Rates
Sensory Neuron
Receptor Cells SynapseOnto Sensory Neuron
No stimulus: temporally uncorrelated spiking behavior
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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!
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Neural Signals: No stimulus
Sensory Neuron
Receptor Cells SynapseOnto Sensory Neuron
No stimulus: temporally uncorrelated spiking behavior
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Neural Signals: Stimulus Present
Sensory Neuron
Receptor Cells SynapseOnto Sensory Neuron
With stimulus: Receptor cell activity synchronized. Causes neuron to fire action potential
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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