SENSORY PHYSIOLOGY

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SENSORY PHYSIOLOGY

• BIOLOGY 305 LABORATORY

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THE CRAYFISH STRETCH RECEPTOR

• CRAYFISH
• Invertebrate in phylum Arthropoda
• subphylum Crustacea
• Also includes barnacle, crab, crayfish, lobster,
  shrimp
• Scientific name Procambarus clarkii
• Largely aquatic
• Characteristics include
• Hard exoskeleton
• Jointed, paired appendages
• Three body regions
• head
• thorax
• abdomen

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THE CRAYFISH STRETCH RECEPTOR

• Crayfish Nervous System
• Bilateral Symmetry
• Segmented Arrangement
• Each body segment contains a ganglion
• Axons carry info between ganglia
• Nerve roots branch off ganglia to periphery
• Contain sensory motor neurons

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THE CRAYFISH STRETCH RECEPTOR

• Purpose of Exercise
• Gain experience w/ classic neurophys. prep.
• Investigate stimulus-response properties of
  crayfish nervous system
• Observe characteristics of crayfish sensory
  system
• Encoding of stimuli
• Sensory adaptation
• Differentiate responses from two types of sensory
  organs

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THE CRAYFISH STRETCH RECEPTOR

• Muscle Receptor Organs (MROs)
• Located in abdomen
• Composed of a sensory neuron an associated
  muscle
• Superficial Extensor Muscle
• Sensory neuron has stretch-sensitive dendrites
  embedded in the muscle
• Two types MRO1 MRO2

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THE CRAYFISH STRETCH RECEPTOR

• Superficial Extensor
• Muscle
• Two per abdominal segment
• One on each side
• Each contains 2 MROs,
• One of each type

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THE CRAYFISH STRETCH RECEPTOR

• When Abdomen of Crayfish
• Bends
• S. extensor muscle is stretched
• Sensory neuron receptors activated

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THE CRAYFISH STRETCH RECEPTOR

• Signaling
• Graded potentials (GP) generated by stretch
  sensitive dendrites
• Ion channels
• Action potentials (APs) produced at
  spike-initiating zone

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THE CRAYFISH STRETCH RECEPTOR

• For This Exercise
• Well record extracellularly from nerves that
  carry sensory info from MROs to CNS
• Accomplished by curling crayfish tail to
  stimulate sensory receptors

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THE CRAYFISH STRETCH RECEPTOR

• Major Instruments
• Suction Electrode
• Micromanipulator
• Dissecting Scope

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THE CRAYFISH STRETCH RECEPTOR

• Major Instruments
• Pre amplifier/filter
• Digitizer (iWorx Unit)
• Computer
• Audio Amplifier

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THE CRAYFISH STRETCH RECEPTOR

• Exercises
• Tapping Experiment
• Elicit MRO1 MRO2
• Increasing Stimulus Intensity
• Observe responses (freq) to sm, med, and large
  stimuli (stretch)
• Adaptation Experiment
• Observe response to a stimulus of long duration
  and fixed intensity

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THE CRAYFISH STRETCH RECEPTOR

• Film Clip!