Download Neuroscience in the Classroom

Neuroscience in the
Classroom
Hands-On Activities Using Weakly
Electric Fish as a Model for the Study
of Neurology
November 8th, 2003
Project Background – 21st Century Biology
Allows students to
work cooperatively
(Est. 1991)
Students have completed and
designed experiments on
projects such as:
Zebrafish
Brain Awareness Week
Weakly Electric fish
Telemicroscopy
Thigmomorphogenesis
Tomography
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
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
Electric Fish Background
Evolution and Habitat
Below: Habitat of Weakly
Electric Fish. Both orders
(mormyriforms and
gymnotiforms) live in shallow,
murky waters and hide in
aquatic vegetation.
Above: Electroreceptor Evolution.
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)
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
Electric Fish Background
A view of a Neuron
Below: A computer
representation of a
neuron. The three
types of neurons are
sensory neurons,
interneurons, and
motor neurons.
Above: Neurons are made up of three
parts: cell body, axons, and dendrites.
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.
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.
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.
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.
Electric Fish Background
The Electric Organ and the EOD
Below: Weakly electric fish create a dipole electric field
to locate objects, communicate, and navigate.
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.
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.
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.
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.
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
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: [email protected]
Website: http://www.21bio.org