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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. To epidermis/ocean water. Ampullary canal : filled with

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Shark Electric Sense

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  1. Shark Electric Sense Electrical Circuit Model and Active Membranes

  2. Shark goes coo-coo for E-fields! http://www.youtube.com/watch?v=Prq2HK8cT3A&feature=player_embedded

  3. Quick review: Ampullae of Lorenzini To epidermis/ocean water Ampullary canal: filled with Mucous-like, sugary gel Ampulla: Bulblike termination of canal Alveoli: individual “pouches” Receptor Cellsline bottom of ampulla. Electrical stimulus Neural signal Bv = blood vessel Mn = myelinated nerve From WaltmanActa Physiol. Scand. (1966) “The Fine Structure of Ampullary Canals of Lorenzini”

  4. Coding electricity in neural impulses/responses A cartoon model of the receptor cell making synapse onto nerve. • * Receptor cells are electrically active! • Exhibit all-or-nothing response • “Negative-going spikes” From Obara and Bennett: J Physiol (1972) “Mode of Operation of Ampullae of Lorenzini Skate, Raja

  5. Bioelectricity: Active Membranes and Action Potentials Action potential: fundamental unit of electrical communication

  6. Synaptic Transmission 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 neuronbrain And think of this as the nerve terminal that eventually reaches the brain For sharks, think of this as the receptor cell’s presynaptic ribbon

  7. Neural Signals: Spike Rates Receptor Cells Synapse Onto Sensory Neuron Sensory Neuron No stimulus: temporally uncorrelated spiking behavior

  8. Electrical Stimulus Causes Spike Rate to Increase in Frequency Spike Rate Coding: Linear Relationship between Ampullary Stimulus and Neuron Spike Rate Non-zero resting spike rate. But wait: Nerve is spontaneously active! HH Zakon, 1988; Obara 1976

  9. Neural Signals: No stimulus Receptor Cells Synapse Onto Sensory Neuron Sensory Neuron No stimulus: temporally uncorrelated spiking behavior

  10. Neural Signals: Stimulus Present Receptor Cells Synapse Onto Sensory Neuron Sensory Neuron With stimulus: Receptor cell activity synchronized.  Causes neuron to fire action potential

  11. 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. ActaPhysiol Scand Suppl 264:1

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