How do nerves work?


How do we feel the different types of sensation? How do the nerves receive them differently?

In: Biology

There are basically different types of nerves which respond to different types of stimuli so one will respond to pressure and another to pain.

So, I’ll try my best here. There are two pathways, nerves that sense things (stimuli) and nerves that trigger things to happen.

Nerves that sense external things like hot/cold, pressure generally through the skin or other bodily changes internally can transmit an electrical signal from one to the next leading back to the brain or spinal cord (these are called sensory neurons and form the afferent pathway if you’re interested).

The brain is made up of slightly different nerve cells called interneurons and processes the electrical ‘message’, basically working out what’s happening, then can trigger a response.

The response travels in the same manner but in the opposite direction, from the brain back down to whatever needs to respond. Let’s say if it’s a response to touching something hot with your hand, the signal will travel to muscles in your arm triggering them to contract and therefore move your arm away. (These are motor neurons and form the efferent pathway).

The strength of the signal the brain receives affects the response so if you touch a really hot surface, the receptors at the end of those sensory nerves in your fingers for example will be overloaded with stimulation and keep firing electrical ‘messages’ which essentially helps your brain figure out that it’s a priority to do something. Whereas if it’s something more benign, like someone you like holding your hand, a signal will still send a ‘message’ to your brain so it can figure out what you are sensing but it doesn’t need to tell your hand to pull away and might instead trigger a release of hormones that make you feel good. If a sensation is incredibly tiny, it might not even trigger the sending of the ‘message’ through the nerve cell – like how you might not even notice if a tiny fly lands on your arm until you see it. The stimulation has to pass a threshold so that your brain is able to prioritise and respond properly rather than being distracted by absolutely everything.

How the nerves actually send the signal is a bit more complicated and it’s to do with different ions (chemical elements that carry either a positive electrical charge or a negative electrical charge) moving in or out of the nerve cell in sequence along the the long thin part of the nerve called the axon, when that movement of electrical charge reaches the end of the individual nerve cell it triggers movement of some chemicals between that nerve cell and the next one (called neurotransmitters, and the gap between is called a synapse). And the process begins again in the next cell all along the pathway to the brain or from the brain. Of course this all happens incredibly quickly.

I hope that answered your question and wasn’t too simple or complicated