Physiograph Stimulator

Stimulator → electrodes → tissue (nerve or muscle) → contraction → recorded on physiograph Core components Electronic stimulator (pulse generator) Gives rectangular electrical pulses Controls: Voltage / current (strength) Pulse duration (width) Frequency (rate) Mode: single pulse / repetitive / tetanus trains Electrodes Nerve stimulation (preferred): bipolar platinum/stainless-steel electrodes on the sciatic nerve Direct muscle stimulation: electrodes placed on the muscle belly (used when nerve is cut/blocked) Preparation Common: frog gastrocnemius–sciatic nerve or sartorius muscle Mounted on a myograph/physiograph stand with: Fixed end Free end tied to lever/force transducer Physiograph (recording system) Mechanical lever + drum (kymograph-style) or electronic force transducer Often includes a time marker and event marker (stimulus marker) Standard connections (practical wiring logic) Stimulator output terminals → stimulating electrodes Tissue contraction → force transducer / lever Recording channel (physiograph) → displays twitch height, tetanus, fatigue curve Time-marker channel → gives time scale (e.g., 1 sec intervals) Key stimulator settings used in amphibian experiments Pulse type: square/rectangular Pulse duration: typically short (commonly around 0.1–1 ms for nerve; longer may be needed for direct muscle) Strength: start low and increase to find: Threshold stimulus Maximal stimulus Supramaximal stimulus (commonly used routinely to ensure every trial is comparable) Frequency (for tetanus): Low frequency → incomplete tetanus Higher frequency → fused tetanus Typical experiments that specifically