Reference no: EM132787314

Scenario: On vacation in Hawaii, Jill and John decide to try some exotic food offerings. At the sushi bar, they notice that "fugu" is offered but is quite expensive. Since higher price usually means higher quality, they decide to go for it (even though they don't know what it is). Jill, being the more adventurous one, tries it first, likes it, and finishes it off. Within 20 minutes, however, she started to feel strange - her lips and tongue felt numb, like when the dentist gives you a shot of local anesthetic to numb you up before he drills on your tooth. But then her face and arms felt weird - like she couldn't feel them or move them. John, being a paramedic, realized that she needed medical attention right away, suspecting it was a severe allergic reaction.

At the hospital, however, the doctors were more concerned and questioned them carefully on what was ingested. When John mentioned "fugu", their treatment became much more aggressive as they intubated her, put her on a ventilator and attempted nasogastric suctioning to empty the stomach contents.

Meanwhile, John got on his smart phone and looked up "fugu". He found out it was also known as the Pufferfish and contained a toxin called Tetrodotoxin. Tetrodotoxin is a neurotoxin that blocks voltage gated sodium channels.
Prognosis: The doctor told John that she must be watched carefully over the next few hours, as she could develop more severe paralysis, involving respiratory muscles and even the heart. Thankfully, she made it through the night and was expected to make a complete recovery, with no residual effects, as the toxin is eliminated from her system.

Questions:

1. What is the action potential?

2. Explain what happens in the depolarization phase of the action potential.

3. Tetrodotoxin blocks voltage gated sodium channels. As a result, will action potentials occur when tetrodotoxin is present?

4. If the tetrodotoxin remains in Jill's system, the doctors are concerned about her paralysis spreading to the respiratory muscles and the heart, causing respiratory and cardiac arrest. Why would this be so?

5. The local anesthetic used by dentists (Lidocaine®) is also a voltage gated sodium channel blocker. It is also used when suturing a wound, to cause local anesthesia. Explain why you do not feel the pain and also feel numb when injected with lidocaine.

* Often, when lidocaine is for minor surgeries, epinephrine is added to it. Epinephrine causes vasoconstriction, which means that it closes down the blood vessels to that area. This allows the lidocaine to remain in that local area for a longer period of time (it is not removed by the blood since there is less blood coming to the area) and also helps to diminish bleeding.