Question

While at the dermatologist’s office you notice a brochure for a product that promises to erase “crow’s feet” and “frown lines.” You are curious about what this product is and how it works. As you read the brochure you notice it is called Botox and is injected into the facial muscles. BOTOX® Cosmetic, or onabotulinumtoxin A, is only available by prescription. You know that this cosmetic is botulinum toxin, and you remember from your human anatomy & physiology course that it effects skeletal muscle contraction. You also remember hearing about fatal cases of botulism poisoning and wonder why it is being used for cosmetic purposes.

1. As previously mentioned, this toxin can cause a fatal disease known as botulism. If the toxin becomes systemic, it can block the release of ACh from nerves in other locations. Why do you think botulism can be fatal?

If it affected nerves to the brainstem, the brainstem would not be able to carry out its functions.

If it affected nerves to the lower extremity, the individual would be unable to walk.

If it affected cardiac nerves, the heart would stop beating.

If it affected the phrenic nerve, the diaphragm muscle would be paralyzed.

2. Some nerve agents have been used as bioweapons. Unfortunately, Sarin gas has been used as a bioweapon several times in other countries. Sarin is an acetylcholinesterase (AChE) inhibitor and even exposure to low levels can be fatal. Based on your knowledge of muscle physiology, why do you think Sarin has these effects?

The muscle will contract and relax normally, but inhibiting with acetylcholinesterase will decrease cardiac function.

Muscles will contract and be unable to relax, known as spastic paralysis. This can cause spasms of the diaphragm and bronchi, which lead to asphyxiation.

Muscles will be unable to contract, known as paralysis. If the diaphragm is paralyzed, breathing will not occur and death will occur by asphyxiation.

Muscles will contract but fatigue much faster. This will decrease skeletal muscle activity in the body.

3. Acetylcholinesterase inhibitors have therapeutic value in the treatment of some medical conditions and diseases. Which of the following do you think would be a clinical application of these drugs?

Muscular dystrophy, a genetic disease that results in abnormal muscle proteins and causes a loss of muscle mass.

Cosmetic treatment of wrinkles and frown lines.

Myasthenia gravis, a disease in which the ACh receptors are damaged and the muscle becomes progressively weaker.

Polio, a disease in which motor neurons are attacked and damaged.

Answer 1

1.

Answer: If it affected the Phrenic nerve, the diaphragm muscle would be paralyzed.

Rational: botulism is the fatal disease which makes the muscles weaker and leads to paralysis of muscles.

Because it stops the Ach. For example we can see when the phrenic nerve is affected, It will paralyse the muscles of the diaphragm. Because this nerve only supplies the muscles of diaphragm.

2.

Answer: Muscles will contract and unable to relax, known as spastic paralysis. This can cause spasm of diaphragm and bronchi, which leads to asphyxiation.

3.

Answer: Myasthenia gravis, a diseases in which the Ach receptors are damaged and the muscles becomes progressively weaker.

Rational: Because the myasthenia gravis is the medical condition which makes the muscles weaker, because of the dysfunction between the nerve and the muscles.