Lab Frog Muscle (Guide Experiment)
Lab 6 Biomechanics of Frog Skeletal Muscle
I. Purpose
This exercise is designed to demonstrate some mechanical and physiological properties of skeletal muscle using the gastrocnemius muscle of a frog.
II. Performance Objectives
At the end of this exercise the student should be able to:
1. Define minimal (threshold), subminimal, maximal, and supramaximal stimulus. 2. Explain what is meant by a “graded” response. 3. Draw a diagram of the setup used in this lab exercise. 4. Calculate the work that is done in a given muscle. 5. Describe the function of a force displacement transducer. 6. Describe what happens to muscle contraction when the load is increased. 7. Define twitch, treppe, tetanus and incomplete tetanus. 8. Explain the difference between a single and double pith of the frog. 9. Post all data to Google Docs.
III. Introduction
The gastrocnemius muscle contains many muscle fibers. Each fiber has its own threshold and responds all-or-none when stimulated. It is known that all of the fibers in a muscle do not have the same threshold and that a stimulus applied to a muscle does not necessarily excite all the fiber in it. The threshold is that intensity (voltage) of stimulus which brings response. As the intensity (voltage) of the stimulus is increased above the threshold, more and more fibers are stimulated and the response becomes greater and greater. Eventually, however, a stimulus intensity (voltage) is reached beyond which the response is constant. This stimulus, called the maximal stimulus marks the point where all of the fibers in the muscle are stimulated and responding all-or-none. Stimuli above this maximal stimulus are called supramaximal stimuli. Stimuli below the threshold that do not initiate a mechanical response are called subthreshold stimuli.
The frog muscle is used in this laboratory exercise in place of mammalian muscle because of its tolerance to temperature change and handling. The results are similar to
I. Purpose
This exercise is designed to demonstrate some mechanical and physiological properties of skeletal muscle using the gastrocnemius muscle of a frog.
II. Performance Objectives
At the end of this exercise the student should be able to:
1. Define minimal (threshold), subminimal, maximal, and supramaximal stimulus. 2. Explain what is meant by a “graded” response. 3. Draw a diagram of the setup used in this lab exercise. 4. Calculate the work that is done in a given muscle. 5. Describe the function of a force displacement transducer. 6. Describe what happens to muscle contraction when the load is increased. 7. Define twitch, treppe, tetanus and incomplete tetanus. 8. Explain the difference between a single and double pith of the frog. 9. Post all data to Google Docs.
III. Introduction
The gastrocnemius muscle contains many muscle fibers. Each fiber has its own threshold and responds all-or-none when stimulated. It is known that all of the fibers in a muscle do not have the same threshold and that a stimulus applied to a muscle does not necessarily excite all the fiber in it. The threshold is that intensity (voltage) of stimulus which brings response. As the intensity (voltage) of the stimulus is increased above the threshold, more and more fibers are stimulated and the response becomes greater and greater. Eventually, however, a stimulus intensity (voltage) is reached beyond which the response is constant. This stimulus, called the maximal stimulus marks the point where all of the fibers in the muscle are stimulated and responding all-or-none. Stimuli above this maximal stimulus are called supramaximal stimuli. Stimuli below the threshold that do not initiate a mechanical response are called subthreshold stimuli.
The frog muscle is used in this laboratory exercise in place of mammalian muscle because of its tolerance to temperature change and handling. The results are similar to