Effect of Fatigue on Simple Muscle Curve

Summary

This experiment demonstrates the effect of fatigue on the simple muscle curve. The procedure involves isolating the sciatic nerve and gastronomic muscle, stimulating the muscle with sub-maximal electrical shocks, and recording the muscle's contractions. As fatigue sets in, the amplitude of the contractions decreases, and the muscle fails to relax fully, leading to a state called contracture remainder. Recovery is achieved by stimulating the muscle directly after washing away metabolites. The experiment highlights the causes of fatigue, such as neurotransmitter depletion, ATP loss, and metabolic waste buildup, and explores methods to delay fatigue.

Takeaways

• 😀 The experiment aims to demonstrate the effect of fatigue on a simple muscle curve by isolating the sciatic nerve and gastronomous muscle.
• 😀 The procedure involves recording three consecutive contractions followed by additional contractions at different time intervals (10th, 20th, 40th, etc.).
• 😀 As muscle fatigue sets in, the amplitude of contraction decreases, and the muscle fails to relax completely, resulting in a shifted baseline.
• 😀 Contracture remainder occurs when the muscle remains contracted without returning to the baseline after stimulation.
• 😀 After reaching a point of feeble contraction, direct stimulation of the muscle generates a small direct muscle curve known as the 'direct curve'.
• 😀 Recovery from fatigue is observed after washing away metabolites and re-stimulating the sciatic nerve, resulting in a 'recovery curve'.
• 😀 Fatigue leads to a reduction in contraction height, with a shift in baseline, and failure of the muscle to fully relax, indicating contracture.
• 😀 The causes of muscle fatigue in isolated nerve-muscle preparations include neurotransmitter exhaustion, ATP depletion, accumulation of waste products, hypoxia, and decreased sensitivity at the neuromuscular junction.
• 😀 The site of fatigue in nerve-muscle preparations is the neuromuscular junction, where the neurotransmitter acetylcholine gets exhausted and waste products accumulate.
• 😀 Muscle fatigue causes physical changes such as muscle rigidity, swelling, decreased excitability, and reduced contractility.
• 😀 To speed up recovery, fresh neurotransmitters (acetylcholine) must be released, and waste metabolites should be removed, either through washing or blood circulation in live muscle tissue.

Q & A

What is the aim of the experiment described in the script?

The aim of the experiment is to demonstrate the effect of fatigue on the simple muscle curve.

What apparatus is used in the experiment to record the simple muscle curve?

The apparatus used includes a myograph drum, with the drum set to the fastest speed, and a single induction shock for electrical stimulation.

How is the muscle preparation done before starting the experiment?

The muscle preparation involves dissecting a frog to isolate the sciatic nerve and the gastrocnemius muscle.

What is the procedure followed to record the muscle contractions?

The procedure involves applying submaximal electrical shocks to the muscle, setting the drum to its fastest speed, and recording three consecutive contractions in quick succession. Afterward, additional contractions are recorded at intervals, such as 10th, 20th, 40th, etc.

What changes are observed in the muscle contractions as fatigue sets in?

As fatigue sets in, the amplitude of the muscle contractions decreases, and the muscle fails to relax completely, leading to a shift in the baseline and incomplete relaxation (contracture remainder).

What is the direct muscle curve, and how is it recorded?

The direct muscle curve is recorded by stimulating the muscle directly after the sciatic nerve is fatigued. This curve shows a small amplitude but indicates the muscle's response to direct stimulation.

What is the recovery curve, and how is it obtained?

The recovery curve is obtained after washing the nerve-muscle preparation to remove metabolites and stimulating the sciatic nerve again. This curve shows the muscle's recovery after fatigue.

What causes the observed fatigue in the muscle?

Fatigue is caused by the exhaustion of neurotransmitters (acetylcholine), depletion of ATP, accumulation of waste products like lactic and pyruvic acids, and decreased oxygen levels at the tissue level.

Where does fatigue primarily occur in the nerve-muscle preparation?

Fatigue primarily occurs at the neuromuscular junction, as the synapse is vulnerable to factors like hypoxia and acidic conditions.

How can the recovery from fatigue be hastened in a nerve-muscle preparation?

Recovery can be hastened by washing the nerve-muscle preparation with Ringer solution to remove metabolites and provide fresh nutrients, or in the body, by ensuring blood circulation to clear waste products and supply ATP.