Q: Local anesthetics block the:
(A). Sodium channel
(B). Potassium channel
(C). Both sodium and potassium channel
Have you ever wondered how local anesthesia “magically” numbs the patient? In brief, local anesthetic molecules work by blocking the sodium channel and interfering with depolarization. As a result, the nerve is NOT “fired” (triggered), and therefore, the patient does NOT feel the pain.
To fully understand, we have to see how a nerve works. (This is directly from StudentRDH Local Anesthesia review for the WREB and CSCE that you can purchase here)
- When a stimulus reaches a neuron, depolarization
- During the depolarization phase, the gated sodium ion channels on the neuron’s membrane suddenly open and allow sodium ions (Na+) present outside the membrane to rush into the cell.
- As the sodium ions quickly enter the cell, the internal charge of the nerve changes from -70 mV to -55 mV.
- When this firing threshold of -55 mV is reached, membrane permeability to sodium increases dramatically and sodium ions enter the axoplasm (the inner portion of the nerve cell) even more rapidly.
- As a result, the inner portion of the nerve cell reaches +40 mV.
- With repolarization, the potassium channels open to allow the potassium ions (K+) to move out of the membrane (efflux). As this happens, the electrical potential gradually becomes more negative inside the nerve cell until the original resting potential of -70 mV is attained again.
To summarize, sodium ions (Na+) enter the nerve membrane during depolarization, and potassium ions (K+) leave the nerve membrane during repolarization.
Answer: (A). Sodium channel
Now our constant struggle, how to memorize this information. Can you create a story on your own?
Wake Up Memory Technique (WMT) for the dental hygiene boards
What if NA was an acronym for “Nerve” “Access”? If you block this Na+ (by the way, Na+ is the equivalent of sodium, called natrium), you DON’t get “Nerve Access.” By the way, nerve access is a word that I created for the sake of the WMT. That is what local anesthesia does. In normal conditions, the NA channels open to create senses. If the NA (nerve access) channels close, you get numb!
If you have any questions regarding local anesthesia, just let me know! Do you want to see the sub chapters we have under the course of Local anesthesia? StudentRDH has a fantastic course that provides everything you need without requiring you to read the entire textbook. The quizzes also provide immediate feedback so you can learn faster. Taking the WREB or CDCA boards? No problem! We offer a mock exam that simulates that particular format for the local anesthesia boards. You know where to find me! (At clairej@StudentRDH.com.)
Related information: FAQ for the WREB local anesthesia exam or FAQ for the CDCA local anesthesia exam77