### Transcription of Image Text for Educational Website: 1. **A 19-year-old boy visited a dental surgeon for the removal of his left upper wisdom tooth.** He was fearful, as he knew that the procedure was painful. However, he was relieved to learn that he would not feel the pain as the doctor would numb his jaw using a local anesthetic injection. This drug blocks voltage-gated sodium channels. Explain what phase of an action potential will be affected and why. 2. **An autopsy report of a 52-year-old male showed that Mr. Charles was given an injection of intravenous potassium which led to his rapid death.** Define resting membrane potential (RMP), identify factors that contribute towards RMP, and why a high concentration of potassium in the ECF will impact the RMP and lead to rapid death. ### Explanation of Concepts: **1. Voltage-Gated Sodium Channels and Action Potential:** - **Phase Affected:** The action potential in neurons consists of several phases: depolarization, repolarization, and hyperpolarization. - **Impact of Anesthetics:** Local anesthetics that block voltage-gated sodium channels primarily affect the depolarization phase. This is because sodium ions (Na+) flow into the neuron to initiate depolarization, and blocking these channels prevents the action potential from occurring, thus inhibiting pain transmission. **2. Resting Membrane Potential (RMP) and Potassium:** - **Definition of RMP:** Resting membrane potential is the electrical potential difference across the membrane of a cell at rest, typically around -70 mV in neurons. - **Factors Contributing to RMP:** The RMP is maintained by the distribution of ions, such as sodium (Na+), potassium (K+), and chloride (Cl-), across the cell membrane, along with the selective permeability of the membrane to these ions and the activity of the sodium-potassium pump (Na+/K+ ATPase). - **Impact of Potassium:** High concentrations of potassium in the extracellular fluid (ECF) can lead to depolarization of the membrane, reducing the RMP. This depolarization can make neurons unable to repolarize, leading to a failure of the electrical activity necessary for life processes, potentially causing cardiac arrest and rapid death.