1. Neuroscience in the Classroom Hands-On Activities Using Weakly Electric Fish as a Model for the Study of Neurology November 8th, 2003

2. Project Background – 21 st Century Biology (Est. 1991) Students have completed and designed experiments on projects such as: Allows students to work cooperatively Weakly Electric fishZebrafish Thigmomorphogenesis Telemicroscopy Tomography Brain Awareness Week

3. Project Background Project Objective Introductory Neuroscience Muscle Physiology Anatomy Biochemistry Membrane Potential Sensory Physiology Behavior Evolution Electrical Physics Scientific Procedure Scientific Method Experimental Thought/Scientific Reasoning Protocol Writing Scientific Equipment and Techniques Data Analysis

4. Project Background The Electric Fish Model Historical Applications Electric Rays to cure health problems Studied as possible source of electricity Aided in studies of motor neuron transmissions and electric potential gradients Current and Possible Applications Military Biosensors Medical

5. Electric Fish Background Evolution and Habitat Above: Electroreceptor Evolution. Below: Habitat of Weakly Electric Fish. Both orders (mormyriforms and gymnotiforms) live in shallow, murky waters and hide in aquatic vegetation.

6. Electric Fish Background Eigenmannia virescens Habitat Member of the Gymnotiform class in South America Resides principally in the Magdalena and Amazon Rivers Nocturnal, generally timid Live in areas of low water flow Can grow in length to 45 cm Diet Generally, the diet for this species is the larvae of small insects Electric Organ Characteristics Myogenic electric organ Emits a wave-type frequency of 300 Hz (low frequency)

7. Electric Fish Background Organization of the Nervous System The nervous system is composed of two parts: Central Nervous System (CNS) Peripheral Nervous System (PNS) The nervous system has three functions: Sensory Input Integration Motor Output

8. Electric Fish Background A view of a Neuron Above: Neurons are made up of three parts: cell body, axons, and dendrites. Below: A computer representation of a neuron. The three types of neurons are sensory neurons, interneurons, and motor neurons.

9. Electric Fish Background Physics Review: Electricity and the Circuit Board Electrical Physics Circuit: path of an electric current Coulomb: unit of electrical charge Voltage: electrical difference, potential between two poles; volts (joule per coulomb) Current: flow of electrical charge; amperes (coulomb per second) Resistance: conductivity of a material; ohms (volt per amp) The Circuit Board Series: circuit where current through each resistor is the same and voltage is proportional to the resistance Parallel: circuit where voltage through each resistor is the same and current is proportional to the resistance.

10. Electric Fish Background Physics Review: Circuit Board Left: Capacitors and resistors are used to demonstrate key concepts of electrical physics. Right: Light bulbs are used to show electrical flow and intensity in a series or parallel circuit. They are also considered resistors.

11. Electric Fish Background The Electric Organ and the EOD Below: Anatomy of an electric organ. Left: Location of electric organ in the posterior of the fish. Usually has gelatinous texture with a large volume of cellular space. Composed of multinucleated cells myogenically or neurogenically derived.

12. Electric Fish Background The Electric Organ and the EOD Right : Electroreceptor located on fish body. Interprets information from the electric field. The two types of electroreceptors are ampullary and tuberous.

13. Electric Fish Background The Electric Organ and the EOD Below: Weakly electric fish create a dipole electric field to locate objects, communicate, and navigate.

14. Electric Fish Background The Electric Organ and the EOD Above: The electrical field generated by the fish is distorted by nearby objects. A good conductor (i.e. a living organism) is conducive to the electric force. A non-conductor (i.e. a rock) blocks it. The fish decides how to react to an object based on the distortion pattern it creates in the electric field.

15. Electric Fish Background Hummers vs. Clickers Above: All weakly electric fish emit either “hums” or “clicks” as a means of exploring their environment. Clickers emit a short, pulse-like EOD in bursts. Hummers emit a constant, wave-like EOD.

16. Electric Fish Background The Jamming Avoidance Response (JAR) When two fish with nearly the same frequency meet, one fish shifts its frequency slightly higher and the other fish shifts its frequency slightly lower. The shifts are simultaneous and reflexive. The process prevents the two frequencies from interfering and jamming each other’s electrical signals, allowing the fish to operate in the same area.

17. Electric Fish Background Vestibular and Acostico-Lateralis System Left: Section of nervous system in inner-ear that controls balance by maintaining the orientation of body. Processes orientation, acceleration, and movement information. The Acostico-lateralis system in fish is housed in the lateral line canal along the sides of the head and body. Electroreceptors are located there as well. Detects water movements.

18. Electric Fish Background Sources and Links http://www.life.edu/faculty/wilkinson/BSCI338/L11electrosense/ACL11-electro.ppt http://soma.npa.uiuc.edu/labs/nelson/electric_fish.html http://www.apta.org/Education/Continuing_Education/onLine_ceu_List/Vestib_Intro/ Page_2 http://www.sdsc.edu/~marty/cmda/jeol4000.jpg http://www.people.virginia.edu/~mk3u/mk_lab/electric_fish_E.htm “Echolocation in Fish: The Electric Organ Discharge.” Grass Instrument Company, 1993. www.enchantedlearning.com/.../ anatomy/brain/gifs/Neuron.GIF http://faculty.washington.edu/chudler/gif/spiback1.gif http://www.easi.org/nape/apslides/26_cns.gif www.monkeytime.com/sciencemaster/galleries/brain/images/01.jpg http://www.psy.jhu.edu/~fortune/data.html

19. Coming Next… Outline of Workshop Activities Hummers and Clickers Circuit Board Activity Model presentation/anatomy Ice Cube/Vestibular System Neuron Activity Contact Us! E-mail: 21bio@sidwell.edu Website: http://www.21bio.org