Question

Activity 4: • What was the peak voltage at R1 and R2 when you first stimulated the neuron using 30mV? • What does TTX do to voltage-gated Na+ channels? • What does lidocaine do to voltage-gated Na+ channels? How does the effect of lidocaine differ from the effect of TTX? • Can someone affected by TTX be treated? • Pain-sensitive neurons (called nociceptors) conduct action potentials from the skin or teeth to sites in the brain involved in pain perception. Where should a dentist inject the lidocaine to block pain perception?

Answer 1

1. Wires R1 and R2 are recording electrodes utilized in recording the change in voltage in the axon. R1 is located 2 cm apart stimulation wires and R2 is 2 cm away from R1. They record the extracellular voltage. The voltage at action potential is observed is the threshold voltage. Thus, the peak voltage was 30 Mv.

2. TTX caused a reversible blockade of voltage-gated sodium channels in axonal membranes. Thus, there was no action potential generated due to TTX.

3. Lidocaine resulted in the blockade of voltage-gated sodium channels, and prevented sodium ions from entering towards the channel. The effect produced by lidocaine is reversible where the effect due to TTX is non-reversible.

4. There is no known antidote for TTX. The respiratory support and hemodynamic control can be made until TTX is completely excreted by the body.

5. The dentist must inject lidocaine nea rto the sensory receptors located near the teeth, thus lidocaine must be injected in the gums to block the perception of the pain.