The Nervous System
The nervous system is a highly complex system that coordinates its actions and sensory information by transmitting signals from one neuron to another across the body and brain receiving feedback. At an integrative level, the primary function of the nervous system is to control the body. It does this by extracting information from the environment using sensory receptors, sending signals that encode this information into the central nervous system, processing the information to determine an appropriate response, and sending output signals to activate a response. The evolution of a complex nervous system has made it possible for humans to have higher-level conceptual thinking, including abstract representation of concepts, complex social interactions and, mood disorders, such as depression and anxiety.
Neurocircuits and Systems
The nervous system detects sensory inputs, processes signals and responds, sometimes appropriately and sometimes not. The nervous system responds through messenger systems that impact the body, brain and behavior. The connections between neurons can form neural pathways, neural circuits, and larger networks that generate a person’s perception of the environment and influence mood and behavior.
Complex responses to stimuli rely on signal processing in the brain. Signals pass through stages of integration, involving different areas in the brain. At each stage, important information is taken from the signal, and unimportant information is discarded. The nervous system is able to detect relevant information from combinations of sensory signals; these sensory inputs are transmitted simultaneously and processed in different areas of the brain to assign meaning or importance and response in the form of action, reaction, or inaction.
One way to try to understand mood and pain disorders is to look at the behavioral and emotional response to nervous system input and analysis (meaning attached to input). In mood, behavioral and pain disorders, there is often a faulty, overly sensitive or insensitive, analysis of a sensory input to the brain. Often, an emotional processing center in the brain attaches a reaction that is out of proportion to the stimulus creating a higher level of pain and emotional distress, mood swings, depression and anxiety. Emotions are thought to be related to activity in brain areas that direct our attention, motivate our behavior, and determine the significance of what is going on around us. It’s easy to see how dysfunction in this system can have such a dramatic effect on our mood and behavior.
Our medications and therapies typically focus on making changes at the synaptic or cellular level. These changes to neurons then enable the neurons in a neurocircuit to function in a way that supports a healthy mood and perception of stimuli, including pain stimuli. To understand how medication and therapies work to repair the brain, understanding some basic principles related to nervous system function is necessary.
Cells in the nervous system are called neurons; they send signals to other cells through thin fibers called axons, which cause chemicals known as neurotransmitters to be released at junctions called synapses. Neurotransmitters are chemical messages sent from one nerve cell to another along a pathway. Groups of neurons organized to communicate with one another in distant parts of the brain are called neural circuits. Neural circuits have been found to be dysfunctional in psychiatric illnesses such as depression and anxiety, among others.
When neurons are damaged or malfunctioning, symptoms related to thought processes’, cognition, mood and behavior will arise. Sometimes the dysfunction is reversible through a process called synaptic plasticity, which allows a neuron to heal and begin to function properly. Many of the treatments we use enable neurons to recover and begin to function correctly by encouraging synaptic plasticity.