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SENSORY PHYSIOLOGY

SENSORY PHYSIOLOGY. BIOLOGY 305 LABORATORY. LAB PRACTICAL. Be Sure YOU Know: How to log on How to load software & settings (tutorial) How to set up hardware How to use the finger pulse transducer (w/o noise) How to define Aliasing and how to avoid it

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SENSORY PHYSIOLOGY

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  1. SENSORY PHYSIOLOGY BIOLOGY 305 LABORATORY

  2. LAB PRACTICAL • Be Sure YOU Know: • How to log on • How to load software & settings (tutorial) • How to set up hardware • How to use the finger pulse transducer (w/o noise) • How to define Aliasing and how to avoid it • How to define the Nyquest Frequency • How to determine a sufficient sampling rate • How to explain differences between analog & digital signals • How to change the display time/resolution (zoom) • How to place marks in the record • How to define & calculate: Period, Frequency, HR (+ units) • How to analyze a trace in the Analysis Window • How to print & use the Journal

  3. LAB PRACTICAL • How You Loose Points: • Forgetting to turn on iworx box • Noisy trace • Needing assistance from TA • Not completing exercise on time • Errors in calculations & equations • Omitting units

  4. THIS WEEK: REFLEX & REACTION TIMES Stimulus – Response Pathways: * Stimulus  * Receptor  * Afferent Path  * CNS  * Efferent Path  * Effector  * Response!

  5. THIS WEEK: REFLEX & REACTION TIMES • Investigation of Reaction Times: • Audio Stimuli • Prompted & Patterned Sounds • Visual Stimuli

  6. THIS WEEK: REFLEXES & REACTION TIMES Investigation of Reaction Times: • Possible Influences: • Number of neurons in afferent path • Number of synapses • Distance between stimulus and sensory part of brain • Presence of mylinated axons in pathway • Diameter of neurons in pathway • Amount of processing & integration in CNS • Efferent pathway NOT a likely influence

  7. THIS WEEK: REFLEX & REACTION TIMES • Reflex: • Stereotypical, rapid motor response • Does not require input from brain --HOWEVER-- • Brain can exert descending inhibition & dampen reflex

  8. NEXT WEEK: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

  9. 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

  10. 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

  11. 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

  12. THE CRAYFISH STRETCH RECEPTOR Superficial Extensor Muscle: • Two per abdominal segment • One on each side • Each contains 2 MROs, • One of each type

  13. THE CRAYFISH STRETCH RECEPTOR When Abdomen of Crayfish Bends: • S. extensor muscle is stretched • Sensory neuron receptors activated

  14. THE CRAYFISH STRETCH RECEPTOR Signaling: • Graded potentials (GP) generated by stretch sensitive dendrites • Ion channels • Action potentials (APs) produced at spike-initiating zone

  15. THE CRAYFISH STRETCH RECEPTOR For This Exercise: • We’ll record extracellularly from nerves that carry sensory info from MROs to CNS • Accomplished by curling crayfish tail to stimulate sensory receptors

  16. THE CRAYFISH STRETCH RECEPTOR Major Instruments: • Suction Electrode • Micromanipulator • Dissecting Scope

  17. THE CRAYFISH STRETCH RECEPTOR Major Instruments: • Amplifier • Digitizer (iWorx Unit) • Computer (LabScribe) • Audio Amplifier

  18. THE CRAYFISH STRETCH RECEPTOR Exercises: • Tapping Experiment • Elicit MRO1 & MRO2 • Increasing Stimulus Intensity • Observe MRO1 responses (freq) to sm, med, and large stimuli (stretch) • Adaptation Experiment • Observe responses to a stimuli of long duration and fixed intensity

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