Many chemicals can interfere with nervous transmission in a variety of different ways. We’ll be looking at the effects of nicotine found in tobacco, lidocaine used as an anaesthetic, and cobra venom transmitted via bites.
Nicotine is absorbed in the lungs and travels through blood to the brain, where it behaves as acetylcholine, resulting in binding to its respective receptors. This results in a stimulant effect which is the cause of its high addictive potential. Symptoms can be highly subjective, but usually fall under relaxation, sharpness and calmness.
Lidocaine can be applied topically to the skin via a patch or cream, as well as injected. It can numb specific areas and acts as a painkiller, hence is used as an anaesthetic in surgery, dental work, etc. It works by blocking voltage-gated Na+ ion channels, hence preventing the depolarisation of the post-synaptic neurone. No pain signals can be transmitted to the brain because no signals are created in the first place.
Cobra venom is a modified version of saliva which contains many different proteins which act to immobilise the snake’s prey, such as by stopping it breathing. It acts by blocking acetylcholine receptors on the diaphragm (found under the lungs and whose contraction enables breathing) and hence interrupting its activity.
The venom acts within half an hour, and if more than three quarters of receptors are blocked, breathing will stop and the victim will die unless antivenom or artificial ventilation is available.