Procedure D Threshold Stimulation

1. To determine the threshold or minimal strength of electrical stimulation (voltage) needed to elicit a contraction in the frog muscle, follow these steps:

a. Set the stimulus duration to a minimum (about 0.1 milliseconds).

b. Set the voltage to a minimum (about 0.1 volts).

c. Set the stimulator so that it will administer single stimuli.

2. Administer a single stimulus to the muscle and watch to see if it responds. If no response is observed, increase the voltage to the next higher setting and repeat the procedure until the muscle responds by contracting.

Figure 19.4 Hold the frog's head between your thumb and index finger to pith (a) its brain and (b) its spinal cord.

Figure 19.4 Hold the frog's head between your thumb and index finger to pith (a) its brain and (b) its spinal cord.

Spinal Cord Attachment Head

Figure 19.5 (a) Separate the calcaneal (Achilles) tendon from the underlying tissue. (b) Tie a thread around the tendon, and cut its distal attachment.

Figure 19.5 (a) Separate the calcaneal (Achilles) tendon from the underlying tissue. (b) Tie a thread around the tendon, and cut its distal attachment.

Thread Veins Cirossis

3. After determining the threshold level of stimulation, continue to increase the voltage in increments of

1 or 2 volts until a maximal muscle contraction is obtained.

4. Complete Part B of the laboratory report.

Essentials of Human Physiology

Essentials of Human Physiology

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