By Gregory Kellett, a cognitive neuroscience researcher at SFSU and UCSF, and science writer forLumos Labs.
Ever wonder about the workings of your nervous system? As mentioned in our previous post on cognition, the nervous system is responsible for integrating and processing information about your surroundings while directing action towards the achievement of goals; whether this be eating a tuna sandwich, serenading a lover or getting out of the way of a speeding bus. Physically, it is made up of your brain, spinal cord and peripheral nerves.
Let’s look at the structural components of this biological orchestra.
Neurons and Glia The basic functional units of the nervous system include neurons (cells who’s primary job is to communicate) and glia (cells which support neurons and their communication).
The average brain has about 100 billion neurons and about 9 times as many glia.
Neurons (with the help of glia) connect and coordinate senses such as sight, hearing, smell, touch and taste with the activity of your muscles and organs. They are either taking information in for integration, communicating with other neurons for information processing, or sending information out to generate action.
Glial cells (of which there are multiple types) do a variety of tasks to support the functioning of neurons, including removing waste, providing nutritional and structural suppor t and facilitating connections. Some glia have also been shown to communicate with neurons, as well as each other, in order to help coordinate neuronal activity.
Synapses and Neurotransmitters Synapses are the actual locations at which neurons communicate with each other, and a typical neuron has about 10,000 of them.
Neurons communicate at synapses through the use of neurotransmitters. Neurotransmitters are chemicals sent between neurons as well as the muscles and organs they work with. They attach to receptors on receiving cells, translating into one of three basic types of messages:
• Excitatory - Encouraging connected neurons and other related cells to “pass it on” or activate; perhaps prompting you to swat at that fly after being buzzed by the umpteenth time or dilate your pupils when the lights go out.
• Inhibitory - Suggesting that the receiving cell not continue passing on the signal or take action. This could be involved in the shutting down of appetite in response to the non-acquired taste of anchovies or the ability to ignore the radio in your car while figuring out how to get un-lost.
•Adaptive- Instructing a neuron to change something in its structure or the way it functions. This is the basis of plasticity where neurons may reduce or increase the number of connections, move them around and or adjust their sensitivity; all of which are part of the learning process.
Neurons which collaborate on a specific physiological function, such as hearing high pitches, moving your pinky or remembering to take the trash out, are considered to be part of a shared neural network. Typically these functionally related neurons will use only one or two of the over 100 different types of neurotransmitters available. Neurotransmitters, however, can and often are associated with several types of neural networks.
Serotonin is an example of a neurotransmitter involved with the regulation of multiple systems including mood, appetite, temperature, pain sensation and sleep.
Dopamine is the neurotransmitter of choice for neural networks dealing with reward, such as the feeling you get after winning an egg toss or eating a delicious meal. It is however also used by circuits involving memory and attention.
Complexity As much as we do know about how our nervous systems work, there is still much more to be discovered. One of the many areas where little is known involves how different neural networks, responsible for such diverse tasks as detecting movement, recognizing objects and generating action, can communicate between themselves. The mechanisms involved in coordinating the information from different specialized neural systems into a seamless experience of say, catching a ball, is still a mystery. This is referred to as the binding problem, and although there are plenty of theories, there are no clear answers as of yet.
As you can see, the interactions between our neurons, neurotransmitters and constantly shifting surroundings are complex…..especially when they are trying to grasp the complexity of interactions between neurons, neurotransmitters and constantly shifting surroundings;)