7.11.1 Muscle Disorders

There are many problems related to muscle which are generally called muscle disorder. Some common muscle disorders e.g., muscle fatigue, cramp and tetany are discussed here.

Muscle Fatigue

• When the muscles lose the ability to contract, the physiological state of muscles is called muscle fatigue.
• The other factors which contribute to muscle fatigue are accumulation of lactic acid and ionic imbalance.
• The cause of extreme fatigue is lactic acid which causes muscle pH to drop and the muscle to ache.

Cramp

• It is also known as tetanic contraction of entire muscle.
• It lasts for just few seconds to several hours, causing the muscle to become taut (tightly drawn) and painful.
• It is most common in thigh and hip muscles.
• It usually occurs at night or after exercise.
• It reflects low blood sugar level, electrolyte depletion, dehydration, irritability of spinal cord and neurons.

Tetany

• In tetany the body shakes from continuous muscle contraction and convulsion occur due to calcium imbalance.
• It results in the excitability of neurons and results in loss of sensation.
• If untreated the symptoms progress to spasm of larynx, paralysis and ultimately death occurs.

Table 7.3 Difference Between Tetany and Tetanus

Summary Table of Muscle Disorders

Science, Technology and Society Connections

Justify why do the muscles pull but do not push.

• Bones act as the levers, while joints perform as living fulcrums.
• Muscle, attached to bones by tendons and other connective tissue, exerts force by converting chemical energy into tension and contraction.
• When a muscle contracts, it shortens, in many cases pulling a bone like a lever across its hinge.
• Muscles move and by their motions we move.
• We are capable of performing a wide variety of actions, but despite this, muscle itself moves only by becoming shorter.
• They shorten and then they rest - in other words, a muscle can pull but it cannot push.

Reason out the rigor mortis.

• When death occurs, ATP is no longer made.
• It is a short-lived chemical and so it runs out fairly quickly.
• This causes the muscles to lock into position as cross-bridges that formed between actin and myosin filaments before death can no longer be broken.
• The skeletal muscles undergo a partial contraction that causes the joints to become fixed.
• This condition, rigor mortis (rigidity of death), happens in all body muscles.
• It appears about four hours after death and lasts about 34 hours.
• After this time, muscles proteins are destroyed by enzymes within the cells and so rigor mortis disappears.

Intermediate Level

Muscle Disorders

Difference Between Tetany and Tetanus

Science, Technology and Society Connections

Formula / Mathematical Form

Not applicable to this topic.

Solved Example

Not applicable to this topic (descriptive topic).

Important Points

• 1. Muscle disorders are problems related to muscle.
• 2. Common muscle disorders: muscle fatigue, cramp, tetany.
• 3. Muscle fatigue is loss of ability to contract.
• 4. Muscle fatigue is caused by lactic acid accumulation.
• 5. Lactic acid causes muscle pH to drop.
• 6. Muscle ache is a symptom of fatigue.
• 7. Cramp is tetanic contraction of entire muscle.
• 8. Cramp lasts from seconds to hours.
• 9. Cramp is common in thigh and hip muscles.
• 10. Cramp occurs at night or after exercise.
• 11. Cramp reflects low blood sugar, electrolyte depletion, dehydration.
• 12. Tetany is continuous muscle contraction and convulsion.
• 13. Tetany is caused by calcium imbalance.
• 14. Tetany causes excitability of neurons.
• 15. Tetany causes loss of sensation.
• 16. Tetany can progress to larynx spasms, paralysis, death.
• 17. Tetanus is a bacterial infection.
• 18. Tetanus is caused by Clostridium tetani.
• 19. Tetanus causes muscle stiffness and lockjaw.
• 20. Rigor mortis occurs after death due to ATP depletion.

Remember

• - Muscle fatigue = loss of ability to contract
• - Cramp = tetanic contraction of entire muscle
• - Tetany = continuous muscle contraction and convulsion due to calcium imbalance
• - Muscle fatigue causes = accumulation of lactic acid and ionic imbalance
• - Cramp causes = low blood sugar, electrolyte depletion, dehydration, irritability of spinal cord and neurons
• - Tetany causes = calcium imbalance
• - Tetany symptoms = muscle spasms, cramps, larynx spasms, paralysis, death if untreated
• - Tetanus = bacterial infection (Clostridium tetani)
• - Tetanus symptoms = muscle stiffness, spasms, lockjaw
• - Rigor mortis = muscles lock after death due to ATP depletion

Common Mistakes

• 1. Confusing tetany and tetanus — Tetany = calcium imbalance; tetanus = bacterial infection.
• 2. Mixing up the causes — Fatigue: lactic acid; cramp: dehydration; tetany: calcium.
• 3. Forgetting the role of lactic acid — Causes muscle fatigue.
• 4. Confusing cramp and tetany — Cramp = tetanic contraction of entire muscle; tetany = continuous contraction due to calcium imbalance.
• 5. Mixing up the symptoms — Tetany: convulsions; tetanus: lockjaw.
• 6. Forgetting the role of ATP in rigor mortis — ATP depletion causes muscles to lock.
• 7. Believing muscles can push — Muscles can only pull.
• 8. Mixing up the treatments — Tetany: address electrolyte imbalance; tetanus: immune globulin.
• 9. Forgetting the duration of rigor mortis — Appears about 4 hours after death; lasts about 34 hours.
• 10. Thinking muscle disorders are not serious — Some can be life-threatening.

Quick Revision

There are many problems related to muscle which are generally called muscle disorder. Some common muscle disorders e.g., muscle fatigue, cramp and tetany are discussed here. When the muscles lose the ability to contract, the physiological state of muscles is called muscle fatigue. The other factors which contribute to muscle fatigue are accumulation of lactic acid and ionic imbalance. The cause of extreme fatigue is lactic acid which causes muscle pH to drop and the muscle to ache. Cramp is also known as tetanic contraction of entire muscle. It lasts for just few seconds to several hours, causing the muscle to become taut (tightly drawn) and painful. It is most common in thigh and hip muscles. It usually occurs at night or after exercise. It reflects low blood sugar level, electrolyte depletion, dehydration, irritability of spinal cord and neurons. In tetany the body shakes from continuous muscle contraction and convulsion occur due to calcium imbalance. It results in the excitability of neurons and results in loss of sensation. If untreated the symptoms progress to spasm of larynx, paralysis and ultimately death occurs. The difference between tetany and tetanus is that tetany is caused by electrolyte imbalance while tetanus is caused by bacterial infection (Clostridium tetani).

60-Second Revision

• Muscle fatigue = loss of ability to contract
• Cramp = tetanic contraction of entire muscle
• Tetany = continuous muscle contraction and convulsion due to calcium imbalance
• Muscle fatigue causes = accumulation of lactic acid and ionic imbalance
• Cramp causes = low blood sugar, electrolyte depletion, dehydration, irritability of spinal cord and neurons
• Tetany causes = calcium imbalance
• Tetany symptoms = muscle spasms, cramps, larynx spasms, paralysis, death if untreated
• Tetanus = bacterial infection (Clostridium tetani)
• Tetanus symptoms = muscle stiffness, spasms, lockjaw
• Rigor mortis = muscles lock after death due to ATP depletion
• Warning: Tetany is caused by calcium imbalance; tetanus is caused by bacterial infection

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• 7. Support and Movement

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