Скачать или смотреть Local Anesthetics | Sodium Channel and Action Potential

Welcome to our pharmacology video on local anesthetics! In this informative and engaging presentation, we will delve into the fascinating world of drugs that prevent pain by blocking nerve conduction.

Discover how these drugs work, their effects on nerve fibers, and the various factors that determine their potency and duration of action.

Join us as we explore the pharmacology behind local anesthetics and their impact on the human body.

Get ready to dive into a captivating journey of pharmaceutical knowledge and unravel the mysteries of these remarkable drugs.

▬ 📌 Local Anesthetics
Local anesthetics are drugs that block nerve conduction and prevent pain. They exist in different forms and block sodium channels in nerve fibers, stopping the generation of action potentials. While all nerve fibers are sensitive to local anesthetics, smaller fibers are more affected.

These drugs have varying potency, duration of action, and toxicity levels. They can also affect other tissues like the myocardium at high concentrations.

▬ 📌 Types of Local Anesthetics
Local anesthetics Amides
🔹Lidocaine - most widely used agent (90 minutes)
🔹Prilocaine
🔹Ropivacaine
🔹Levobupivacaine
🔹Bupivacaine - produces continuous epidural blockade during labor
🔹Esters
🔹Cocaine - Toxic agent; restricted use
🔹Benzocaine - surface anesthesia for non-inflamed tissue
🔹Tetracaine – used in ophthalmology to anesthetize the cornea (Toxic agent)
🔹Procaine

▬ 📌 Chemistry Of Local Anesthetics
Most local anesthetics are weak bases. Commonly used local anesthetics consist of a lipophilic end, which is often an aromatic ring, and a hydrophilic end, usually a secondary or tertiary amine. These are connected by an intermediate chain that incorporates an ester or amide linkage.

▬ 📌 Local Anesthetics Acting on Sodium Channels
Excitable tissues possess special voltage‐gated sodium channels that consist of:
🔸One large glycoprotein alpha-subunit (four identical domains, each containing, six membrane‐spanning alpha helices, from S1 to S6.)
🔸Sometimes two smaller beta-subunits.

Exactly how voltage‐gated channels work is not known, but their conductance is given by a formula discussed in the video.

At the resting potential, most H‐gates are open, and the M‐gates are closed. Let us see what happens in the depolarization through visual illustration in the video.

▬ 📌 What Is Action Potential?
Action potentials are electrical signals that occur in nerve cells, allowing them to transmit information. They are triggered by the opening of sodium channels, causing an influx of sodium ions into the cell. This depolarizes the membrane and leads to further activation of sodium channels, creating a chain reaction.

Eventually, the sodium channels close, and potassium channels open, causing repolarization. The sodium-potassium pump helps restore the cell's ion balance. Action potentials play a crucial role in signaling within the nervous system.

▬ 📌 Mechanism of Anesthetic Action
Local anesthetics enter nerve fibers and block sodium channels by binding to specific receptors. They can be either protonated or uncharged, but both types hinder the opening of the H-gate and enhance channel inactivation. With time, the number of functional channels reduces, preventing nerve impulses and resulting in nerve blockage. The effectiveness of local anesthetics is dependent on nerve stimulation rate, with more drug molecules accessing channels during openings. Thus, their blockage intensifies.

▬ 📌 Unwanted Effects of Anesthetics
✨Central nervous system (CNS) - sedation and light‐headedness, although anxiety and restlessness. twitching and visual disturbances.
✨Respiratory depression
✨Cardiovascular system- Cocaine causes vasoconstriction. All the other local anesthetics cause vasodilatation.

▬ 📌 Methods of Anesthesia Administration
There are multiple methods of anesthesia administration, depending upon the use.
🟠 Surface anesthesia
🟠 Infiltration anaesthesia
🟠 Nerve block - dental anesthesia, epidural, and spinal anesthesia
🟠 Intravenous regional anesthesia

With this, we have reached the end of this topic! We will be covering more Pharmacology topics, in the coming days. Stay tuned, only on sqadia.com!

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