Which of the following is most susceptible to local anaesthetics? (OR) Sensitivity to hot in chronic pulpitis indicates stimulation of following fibers (OR) Radiating pain from pulp transmitted by (OR) Sensitivity to local anaesthetics is greater in:
**Question:** Which of the following is most susceptible to local anaesthetics?
**Core Concept:** Local anaesthetics are drugs that block the conduction of nerve impulses by reversibly inhibiting voltage-gated sodium channels in neurons, resulting in loss of sensation and motor function. Local anaesthetics are commonly used in clinical practice for pain relief during surgical procedures.
**Why the Correct Answer is Right:** The correct answer is C. Sensitivity to local anaesthetics is greater in unmyelinated C-fibers compared to A-delta and A-alpha fibers. Unmyelinated C-fibers are slower and less excitable, making them more susceptible to the local anaesthetic action.
**Why Each Wrong Option is Incorrect:**
A. Sensitivity to hot in chronic pulpitis indicates stimulation of A-delta fibers, which are less susceptible to local anaesthetics compared to C-fibers.
B. Radiating pain from pulp transmitted by C-fibers implies that C-fibers are involved, not sensitivity to local anaesthetics.
D. Sensitivity to local anaesthetics is less in A-alpha fibers because they are faster and more excitable compared to C-fibers.
**Why C is Right and the Others are Wrong:**
C. Sensitivity to local anaesthetics is greater in unmyelinated C-fibers. This is because C-fibers are less excitable and slower than A-delta and A-alpha fibers. As a result, local anaesthetics have a higher affinity for C-fibers, blocking their conduction and causing loss of sensation.
**Core Concept:** C fibers are unmyelinated and generally slower than A-delta and A-alpha fibers. They are involved in pain transmission and thermoception, particularly cold sensation.
**Why C is Right and the Others are Wrong:**
A-delta and A-alpha fibers are more excitable and faster than C-fibers. They are involved in transmitting information related to touch, pressure, and vibration, respectively. Therefore, they are less susceptible to the effects of local anaesthetics compared to C-fibers.
**Why C is Right and the Others are Wrong:**
B and D: Radiating pain from pulp indicates the involvement of C-fibers, not sensitivity to local anaesthetics. A-delta and A-alpha fibers are responsible for transmitting pain and temperature information, respectively, but they are not the focus of the question.
**Why C is Right and the Others are Wrong:**
C fibers are involved in the transmission of pain and cold sensation, making them more susceptible to the effects of local anaesthetics compared to A-delta and A-alpha fibers, which are involved in transmitting touch, pressure, and vibration, respectively.