Neuroscience in the Classroom

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 21st Century Biology
(Est. 1991)
Allows students to work cooperatively
Students have completed and designed experiments
on projects such as
Brain Awareness Week
Weakly Electric fish
Zebrafish
Telemicroscopy
Thigmomorphogenesis
Tomography
3
Project BackgroundProject 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 BackgroundThe 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 BackgroundEvolution 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.
6
Electric Fish BackgroundEigenmannia 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 BackgroundOrganization 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 BackgroundA 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.
9
Electric Fish BackgroundPhysics 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 BackgroundPhysics 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 BackgroundThe 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 BackgroundThe 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 BackgroundThe Electric Organ and
the EOD
Below Weakly electric fish create a dipole
electric field to locate objects, communicate,
and navigate.
14
Electric Fish BackgroundThe 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 BackgroundHummers 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 BackgroundThe 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 others electrical
  signals, allowing the fish to operate in the same
  area.

17
Electric Fish BackgroundVestibular 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 BackgroundSources and Links

• http//www.life.edu/faculty/wilkinson/BSCI338/L11e
  lectrosense/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/electr
  ic_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/i
  mages/01.jpg
• http//www.psy.jhu.edu/fortune/data.html

19
Coming NextOutline of Workshop Activities

• Hummers and Clickers
• Circuit Board Activity
• Model presentation/anatomy
• Ice Cube/Vestibular System
• Neuron Activity

Contact Us! E-mail 21bio_at_sidwell.edu Website
http//www.21bio.org