The cellular communication language

You are standing in the kitchen, cooking a delicious Thai curry for dinner. While reaching behind the pan for the onions and chili peppers you accidently touch the edge of the boiling hot pan! Before actually consciously realizing it your hand automatically shoots away from the object that hurt your hand so much. When you finally get what happened you put your hand under cold water. But how is it possible for your body to react so fast and how does the information that you touched a boiling hot pan sent from the sensory cells in your fingers to your brain cells and back to muscle cells in your hand to tell to retract your hand?

First of all, there are different manners of communication between cells in your body. Some cells are neighbors while others are so far away it is like they live at the other side of the country, however even these signals that have to travel large distances through the body reach their final destination. Signaling to cells that are neighbors or live in the same neighborhood is called paracrine signaling (figure 1) and signaling to cells far away from each other is called endocrine. A cell can also sent information to itself, this is autocrine signaling. In the communication between cells, there are a couple of different stages. Taking the example of burning yourself, the first thing that happens is the stage called reception. A sensory cell is triggered to send a signal to your brain because it receives a pain signal. This signal is sent, because transduction has taken place, this means that different proteins in the cell have activated each other and made the cell send a signal directly to the nervous system or first other cells, however eventually the signal is sent through the nervous system to the brain. In the brain this signal of pain is processed, and you feel the pain when this signal has reached the brain, not before that moment. But all these signals your body is constantly receiving and sending that you don’t notice the minute delay. In your brain a signal is sent from the signal receiving area to the part of the brain which takes care of muscle reflexes when you experience extreme pain suddenly. From here a signal is sent via the nervous system to the muscle cells in your arm, this makes your body retract your hand from the painful and, in this case also, hot object.

Figure 1: Autocrine, paracrine and endocrine
signaling. www.muirspathology.com

 Now it is more clear how signals are sent within the body, but what are these signals exactly? There are different types of molecules which are sent by cells to be received by other cells within your body. One type of very well-known signal molecules are hormones, examples of these can be the sex hormones, testosterone and estrogen. The actual structure of these hormones is not very different, but different enough for the human body to be able to read the difference. When you go into puberty hormones are sent all over your body to influence different processes, hormones are able to travel large distances in the body. Not all cells however are sensitive or influenced by a specific hormone, estrogen will not be recognized by a cell in the tissue of your toe, but breast cells have estrogen receptors to which estrogen can bind and change the cells behavior. Another example of a signaling molecule is a neurotransmitter, these are the signaling molecules of the nervous system and travel through the nerves in your body to pass on signals from one part of the body to the other. Dopamine is a neurotransmitter which makes you feel 

good, there are different drug which have the same kind of structure as dopamine and can bind to the same receptor to create the same response of feeling really good, making these kind of drugs very addictive.

Just try to imagine the amount of information sent through your body by communicating cells, the amount you are imagining probably doesn’t come close to the actual amount. Also how fast all these processes go is incredible and extra reason to be happy with your fast responding body the next time you accidently touch a boiling hot pan while cooking.

By Laurine van Gijn, 8/10/2015