<p> Lab 1: Three Basic Excitatory Responses to Electrical Stimulation </p><p>Objectives for Lab 1: 1. Become familiar with a device that produces electrical current(s) suitable for transcutaneous electrical neural stimulation (TENS). 2. Learn to set a device to produce a continuous series of electrical pulses and to modulate (modify/change) the parameters of pulses, specifically amplitude, width, and rate. 3. Become familiar with sensory, motor and noxious responses produced when different current modulations are applied to the skin of a classmate at various amplitudes (intensities). </p><p>Begin today's exercise by selecting a TENS unit, attach a lead wire to channel one, and attach two small electrodes to the other end of the cable. Alcohol prep the skin over ONE of the following muscle belly areas: wrist flexors OR wrist extensors OR biceps OR triceps lateral head OR anterior deltoid Attach the electrodes. The less hair in the area, the better. Let your partner do the same to you.</p><p>Exercise 1 - Modulation of the Amplitude: Set the unit on Normal mode with a pulse rate of approximately 3 pps. Set width on 100 microsec.</p><p>A. Slowly turn up the Channel 1 amplitude (intensity) to a SENSORY RESPONSE level. Have your partner describe the sensation. </p><p>Questions:</p><p>Do you feel the sensory response at a rate of 3 pps? ie. is the device well calibrated?</p><p>Why, physiologically, do these sensations occur (what tissue, what is happening to it)?</p><p>B. Turn up the amplitude more until a MOTOR RESPONSE occurs. This is a level where one can first observe muscle contractions. Only a relatively small increase in intensity above the sensory level will produce this motor response. The muscle contractions are called muscle twitches. Note that only ONE muscle twitch occurs with EACH biphasic electrical pulse.</p><p>Questions:</p><p>Does the motor response occur at a rate of 3 twitches per second??</p><p>Why, physiologically do these contractions occur? What is a motor unit?</p><p>Is sensory response still present? Has it changed any?</p><p>C. Gradually turn up the amplitude until your partner experiences a NOXIOUS RESPONSE (discomfort). Do not stay at this level very long (duh). </p><p>Questions:</p><p>Why, physiologically does discomfort/pain occur?</p><p>Did the motor response change as you turned up the amplitude? EXERCISE 2 - Modulation of the Pulse Rate: Turn the amplitude to a mild motor response level, but still producing distinct ms twitches. LEAVE THE AMPLITUDE THERE!!! Then, SLOWLY increase the PULSE RATE until it at least 50 pps. (turn down the amplitude if necessary but DON’T LOSE THE MOTOR RESPONSE) </p><p>Question: How did the motor response change? </p><p>The quivering MOTOR RESPONSE, which is produced at pulse rates between about 6 and 25pps pps is called TREPPE*. As you continue to increase the pulse rate beyond 25 pps, the contractions become stronger and so rapid that the contraction begins to smooth out or fuse into one sustained, TETANIC CONTRACTION of the musculature. * Treppe can also be called “unfused or incomplete tetany”. </p><p>Note: The pulse rate at which treppe changes into a tetanic contraction varies among different persons & muscles!!! </p><p>This is what happened: As the pulse rate is increased, the individual muscle twitches begin to overlap and appear to fuse together or summate; the ms does not have time to relax completely between each contraction. </p><p>Questions: How does increasing the pulse rate only affect....</p><p>1) the sensory response? WHY?</p><p>2) the number of muscle contractions per second? WHY?</p><p>3) the force of the contractions? WHY?</p><p>4) list the pulse rate ranges used for producing the 3 motor responses: ms. twitch: ___ to ~___ pps treppe: ~___ to ~___ pps sustained titanic: ~___ to ___ pps</p><p>Exercise 3 – An Interesting Phenomenon: NEURAL ACCOMMODATION (ADAPTATION) Turn the amplitude back down to ZERO. Then set the pulse rate to ~50 pps; width still at 100 us. </p><p>A. Increase the AMPLITUDE to a sensory response level and LEAVE IT THERE FOR SEVERAL MINUTES. Keep the arm still during this time. In a few minutes, you will notice the sensory response will begin to lessen or decrease. </p><p>Q: Could this be some type of true physiological nerve fatigue or neurotransmitter depletion?</p><p>B. After an obvious reduction in the sensory response has occurred (neural accommodation), increase the amplitude a little bit. Did the sensory response return/increase? Why?</p>