Muscle Physiology

MUSCLE PHYSIOLOGY Exercise 11
Acuesta, Patrisha Afalla, Antonette Hanns Beo, Jellie Ayz Bustamante, Jemimah Keziah Soriano, Jhon Cris

Introduction
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Muscle Contraction - the shortening of the muscle as a result of tension generated by muscle fibers; -Regulated by the production of calcium ions, stimulated via thermal, chemical, mechanical, and electrical stimuli

Objectives
BE ABLE TO:
1.

Make a muscle-femur preparation; Set up Kymograph; Demonstrate muscular contraction; Differentiate the types of muscle contraction.

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3.

4.

METHODOLOGY
1. Set up kymograph; smoke drum until the wax paper is covered in soot.

2. Prepare the frog’s muscle (gastrocnemius muscle); make sure the muscle doesn’t dry out by applying ringer’s solution . 3. Perform the ff. experiments: a. Simple twitch – single shock b. Summation – 2 quick shocks at maximum stimulation c. Treppe or Staircase effect – 5 shocks with increasing intensity and speed. d. Tetanus – repeated shocks with increasing intensity and speed until the muscle no longer responds.

Ringer’s sol’n Gastrocnemius electrode

Results
A.

Actual

B. Ideal

1 - Summation 2 - Treppe 3 - Tetanus 4 - Twitch

Discussion
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Single twitch – comprised of the latent period, wherein the muscle length is constant; contraction period, and the relaxation period The actual and ideal results were similar.

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Discussion
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Summation
An increase in the intensity of the shock causes a greater contraction. The waves overlap since the application of the stimuli was very rapid, the muscle wasn’t able to fully relax and the muscle fibers are re-stimulated. Calcium ions increase; stronger contraction.
Actual result was similar to the ideal.
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Discussion
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Treppe or Staircase effect
- contraction that occurs will develop a slightly higher maximum tension than the first stimulation. - The rise is a result of a gradual increase in the concentration of calcium ions.
There is deviation from the ideal result since the muscle wasn’t given enough time to relax ; The calcium ions weren’t completely removed so the contractions were stronger (mimicking summation)
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DISCUSSION
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Tetanus

- a result of sustained contraction wherein a muscle fiber is stimulated so rapidly that it does not relax at all between stimuli - Relaxation state is eliminated and the contraction state is prolonged.
Actual results show complete tetanus. Although it took a longer time to exhaust the muscle.

Q&A 1. What is the chemical composition of amphibian Ringer’s reagent?

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It is a salt solution containing Sodium chloride, Potassium chloride, Calcium chloride and Sodium bicarbonate in distilled water.

2. What purpose does amphibian Ringer’s reagent serve?
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It is used as a fluid and electrolyte replenisher and to prolong the survival time of excised tissues.

3. Identify the parts of a muscle twitch and duration of each The parts of a muscle twitch are: twitch.
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Latent period – the time between the application of the stimulus and the onset of contraction

- 2 millisecond delay between the onset of stimulus and twitch response
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Contraction phase – the time between the onset of contraction until the peak of tension - lasts between 10 to 100 milliseconds Relaxation phase – the time from the peak of tension until it returns to the base line

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4. In summation, why is the second contraction higher than the first? The second contraction is higher because
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there was a sudden change in the intensity of the stimulus (electric shock). The muscles are not yet relaxed from its previous contraction when the second twitch took place.

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5. What is the physiological basis of the “warming up” period The heating effect allows the muscles and required of athletes? tendons to become more extensible making stretching easier and more effective.

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Blood flow is increased therefore there is an increase in oxygen to muscle tissue. The increase in temperature causes a rise in enzyme and metabolic activity. This improves the efficiency of muscle

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6. Differentiate complete from incomplete tetanus?
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In incomplete tetanus, muscles contract but there is a period of relaxation between contractions. While complete tetanus has no relaxation between contractions.

7.What is fatigue? What causes fatigue?
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It is the decline in ability of a muscle to generate force. There are two main causes of muscle fatigue - limitations of nerve's ability to generate a sustained signal and the reduced ability of Calcium (Ca2+) to stimulate contraction