The Nervous System: A Basic Overview

The previous post established that psychological distress often reflects disruptions in a developing system: poor connectivity, distorted inputs, and misalignment across the domains of life. But what is the system itself? Understanding how the nervous system and brain actually function provides the biological foundation for everything discussed so far, and everything that follows. This post is intentionally more technical than the others. The diagrams and frameworks here are tools, reference points to return to as the series develops.

The Brain

The brain is the most complex organ in the entire world, remaining largely mysterious despite ongoing efforts to comprehend it. It controls every aspect of our body, with different regions specialising in distinct functions, yet transcends these individual areas, emerging as something far greater than the sum of its parts. The brain communicates through a vast network of 86 billion neurons via electrical and chemical signals, sending brain waves across multiple dimensions: top-down, anterior-posterior, and right-left.

Communication

Neurons communicate through electrical impulses, or action potentials, generated by the movement of ions (sodium, potassium, calcium) across their membranes. This electrical charge (action potential) travels down the axon toward the synapse. When it reaches the end of the neuron, it triggers the release of chemicals (neurotransmitters).

Neurotransmitters

There are hundreds of neurotransmitters (brain chemicals) but the most common ones are:

1. Acetylcholine: Learning, memory, attention, muscle contraction.

2. Dopamine: Reward, motivation, pleasure, motor control.

3. Serotonin: Mood, sleep, appetite, digestion, emotional regulation.

4. GABA: Relaxation, inhibitory control, prevents overstimulation.

5. Glutamate: Learning, memory, excitatory signaling.

6. Norepinephrine: Fight-or-flight response, arousal, attention, energy.

7. Epinephrine: Stress response, increases heart rate and energy.

8. Endorphins: Pain relief, euphoria.

   
   

With the most common neuropeptide that usually gets lumped with the transmitters:

• Oxytocin: Bonding, trust, social connection.

  
  

These chemicals jump across the synapse and bind to receptors on the dendrites of the next neuron, passing along the signal. When many neurons fire together in patterns, their electrical activity combines and creates brain waves, which can be measured as overall rhythms of brain activity.

Brain Waves

Gamma Waves (40 – 100 Hz): Gamma Brain Waves are the fastest brainwaves (high frequency) and the most recently discovered brain wave state, relating to simultaneous processing of information from different brain areas. These are involved in higher processing tasks as well as cognitive functioning. This is important for learning, memory and information processing.

Beta Waves (12 – 40 Hz): Beta Brain Waves are associated with normal waking consciousness — a heightened state of alertness, logic, and critical reasoning. The right amount of beta supports focused engagement across work, study, and performance. In excess, however, it sustains the stress response, driving prolonged cortisol elevation and the physiological wear that comes with it.

Alpha Waves (8 – 12 Hz): Alpha Brain Waves are dominant during quietly flowing thoughts, while you are in deep relaxation, or when you are slipping into a lovely daydream or during light meditation. Alpha is the frequency between our conscious thinking and subconscious mind. This is the Flow State Zone.

Theta Waves (4 – 8 Hz): Theta Brain Waves occur most often in sleep but are also dominant during deep meditation. In theta, the boundary between conscious and unconscious loosens, and vivid imagery, intuition, and information beyond ordinary awareness become accessible. This is also the Flow State Zone.

Delta Waves (0 – 4 Hz): Delta Brain Waves are the slowest but loudest brainwaves (low frequency). It is experienced in a deep, dreamless sleep and in very deep, transcendental meditation. These are also found most often in infants as well as young children. Deep sleep is important for the healing process, as it's linked with deep healing and regeneration.

Brain Dimensions and Areas

1.     Top-Down:

• Human/Cognitive Processes (Neocortex): Located in the outermost layer of the brain, responsible for higher-order cognitive functions such as reasoning, language, and conscious thought.

• Mammalian/Emotional Processes (Limbic System): Situated beneath the neocortex, involved in emotions, memory, and motivation.

• Reptilian/Survival Processes (Brainstem and Basal Ganglia): Located at the base of the brain, responsible for basic survival functions, including heartbeat, breathing, and reflexes.

2.   Anterior - Posterior

• Anterior (Front) - Cognitive Processes (Prefrontal Cortex): Involved in decision-making, planning, reasoning, and executive control.

• Middle - Motor Processes (Motor Cortex): Responsible for planning and executing voluntary movements.

• Posterior (Back) - Sensory Processes: Involved in processing and interpreting sensory information from the environment.

  
  

3.    Right-Left (Lateralisation):

• The brain is divided into two hemispheres, connected by the corpus callosum. Each hemisphere has specialised functions but works together to process cognitive, emotional, and motor information. The left hemisphere typically focuses on logic, language, and analytical tasks, while the right hemisphere is more involved with creativity, spatial awareness, and emotional processing.

The brain's neocortex contains four lobes (with two additional deeper lobes), each with distinct functions linked to a specific sense. It also houses motor and sensory processing areas, which include detailed representations of the body, often referred to as homunculi. These homunculi offer a fascinating map of how the brain organizes and prioritizes different body parts, placing special emphasis on regions that require fine motor skills and sensory precision.

Frontal Lobe

• Location: At the front of the brain, behind the forehead.

• Function: Involved in a range of complex cognitive functions:

  • Decision-making: Assessing options and making judgments.

  • Planning: Developing strategies and organizing actions.

  • Reasoning: Logical thinking and problem-solving.

  • Motor Control: Initiating and coordinating voluntary movements through the primary motor cortex.

  • Executive Functions: Managing attention, inhibiting inappropriate behaviors, and regulating emotions.

  • Social Behavior: Controlling social behaviors, understanding cues, and empathy.

  • Personality Expression: Shaping personality traits and individuality. 

Temporal Lobe (Hearing)

• Location: On the sides of the brain near the temples.

• Function: Responsible for auditory processing, memory, and language comprehension.

  
  

Occipital Lobe (Sight)

• Location: At the back of the brain.

• Function: Primarily responsible for visual processing and interpreting visual information.

  
  

Parietal Lobe (Touch)

• Location: Behind the frontal lobe, at the top of the brain.

• Function: Involved in sensory processing, spatial awareness, and integrating sensory information. 

Primary motor cortex (Precentral Gyrus):

• Location: In the frontal lobe, immediately anterior to the central sulcus.

• Represents different parts of the body in terms of motor control. The size of each area reflects the precision and complexity of movements (e.g., larger areas for hands and face).

  
  

Primary Somatosensory Cortex (Postcentral Gyrus):

• location: In the parietal lobe, immediately posterior to the central sulcus

• Represents the sensory input from the body. Similar to the motor homunculus, larger areas correspond to regions with greater sensory acuity (e.g., lips and fingertips).

Limbic System (Limbic Lobe) (Smell)

• Location: On both sides of the thalamus, including the hippocampus, amygdala, and cingulate gyrus.

• Function: Crucial for emotions, memory, and motivation.

Insular cortex (Insula lobe) (Taste)

• Location: Deep within the lateral sulcus, between the frontal and temporal lobes.

• Function: Involved in processing emotions, self-awareness, and interoception (sensing internal bodily states). Disgust sensitivity — both physical and social disgust.

Basal Ganglia

• Location: Deep within the cerebral hemispheres.

• Function: Involved in motor control, reward processing, and cognitive functions, specifically in initiating and modulating voluntary movements.

Corpus Callosum

• Location: A bundle of nerve fibers connecting the left and right hemispheres.

• Function: Facilitates communication between the hemispheres and helps coordinate their functions.

Diencephalon

• Location: Between the brainstem and cerebrum, consisting of the Thalamus, Hypothalamus, Epithalamus, and Subthalamus.

• Function: Relays sensory information, regulates homeostasis, controls hormone secretion, and coordinates physiological processes essential for health.

Cerebellum (Proprioception)

• Location: At the back of the brain, beneath the cerebrum.

• Function: Coordinates voluntary movements, maintains balance, and supports motor learning.

Brain Stem

• Location: At the base of the brain, connecting the cerebrum to the spinal cord (comprised of the Medulla, Pons, and Midbrain).

• Function: Controls vital functions for survival, such as heart rate, breathing, and blood pressure regulation.

I found it fascinating how areas like the insula not only focus on physical sensations but also on the social dimensions of the same feelings or responses. It highlights the interconnectedness of social relationships and the physical world for humans. I believe this also occurs with the cerebellum, which is crucial not just for physical balance but also for maintaining psychological equilibrium between the brain's hemispheres.

Brain Hemispheres

This is a table I have created to conceptualise the two hemispheres that I have found extremely useful.

Left Hemisphere / Yang / Masculine / Mind	Duality	Right Hemisphere / Yin / Feminine / Soul
Known / Order / Individual / External / IQ	General	Unknown / Chaos / Collective / Internal / EQ
Testosterone & Dopamine	Biochemical	Estrogen & Serotonin
Sympathetic State (Readiness)	Response	Parasympathetic state (Calm)
Conscious/Somatic Nervous System	Operation	Unconscious/Autonomic Nervous System
Prey/Aim (Positive emotion)	Awareness	Predator/Threat (Negative emotion)
Logical/Detailed “Parts”	Perception	Creative/Big Picture “Whole”
Objective/Material “Tool Based”	Attention	Transjective/Spiritual “Purpose Based”
Thinking/Intention “Decision Based”	Action	Feeling/Intuition “Pattern Based”
Verbal & Literal	Communication	Non-Verbal & Figurative
Western	Philosophy	Eastern
Right side body control (Fine motor skills)	Body control	Left side body control (Gross motor skills)

Duality

This row explores the fundamental duality in brain function, contrasting the left hemisphere (Yang/Masculine/Mind) and right hemisphere (Yin/Feminine/Soul) through general traits.

General

• Left Hemisphere:  Represents the world of order and the known, dealing with structured, predictable environments. It excels in organizing, categorizing, and imposing systems to manage complexity. It prioritizes the individual perspective, focusing on self-contained entities and external realities. Associated with IQ, it thrives in solving specific, measurable problems with clear solutions, like mathematical equations or logical puzzles.

  
  

• Right Hemisphere: Embodies the unknown and chaos, perceiving the world as a dynamic and interconnected whole. It is attuned to collective experiences, understanding the shared emotional and spiritual dimensions of human existence. With a focus on the internal, it processes intuition, feelings, and abstract concepts, which are hallmarks of emotional intelligence (EQ).

Biochemical

• Left Hemisphere: Influenced by testosterone, promoting competitiveness, assertiveness, and focus on achieving goals. It works with dopamine, the neurotransmitter of reward, which reinforces motivation and drives action toward desired outcomes. This combination fuels ambition, exploration, and external engagement.

  
  

• Right Hemisphere: Influenced by estrogen, fostering empathy, connection, and nurturing behaviors. Coupled with serotonin, which helps regulate mood and promote contentment, it creates a foundation for emotional well-being and internal harmony.

  
  

Response

• Left Hemisphere: Associated with the sympathetic state, the left hemisphere prepares the body for action, focusing on readiness and external challenges. It supports the body's fight-or-flight response.

  
  

• Right Hemisphere: Associated with the parasympathetic state, the right hemisphere supports relaxation and recovery. It facilitates the body's rest-and-digest function and fosters a state of calm.

  
  

Operation

• Left Hemisphere: Functions primarily through the conscious somatic nervous system, focusing on voluntary actions and movements.

  
  

• Right Hemisphere: Functions mainly through the unconscious autonomic nervous system, focusing on involuntary processes that maintain internal balance and bodily functions.

  
  

Awareness

• Left Hemisphere: Attuned to prey/aim awareness, promoting positive emotions like drive, ambition, and goal-setting, linked to testosterone. It helps maintain focus on external objectives and pushes toward accomplishments.

  
  

• Right Hemisphere: Aligned with predator/threat awareness, processing negative emotions such as fear, anxiety, and stress. The right hemisphere is sensitive to environmental cues and emotional resonance, ensuring awareness of potential threats or disruptions.

  
  

Perception

• Left Hemisphere: Focused on logical, detailed processing, breaking down complex information into smaller, more manageable parts. This hemisphere excels in analyzing facts and working through step-by-step tasks.

  
  

• Right Hemisphere: Processes information in a holistic, creative way, integrating various elements to perceive the bigger picture. It looks at the context rather than individual details, focusing on patterns and relationships.

  
  

Attention

• Left Hemisphere: Directed toward material, tool-based tasks that are outcome-driven. The left hemisphere thrives in situations that require precision, analytics, and focus on measurable goals.

  
  

• Right Hemisphere: Guided by Transjective and spiritual focus, it emphasizes a sense of purpose and connection. The right hemisphere directs attention to broader, intangible aspects of experience, considering meaning, intuition, and holistic principles.

  
  

Action

• Left Hemisphere: Driven by thinking and intention, it processes information logically and sequentially to make decision-based actions. This approach emphasizes planning, analysis, and calculated outcomes. It is quick to learn new systems and methods but slow to execute, ensuring precision and control.

  
  

• Right Hemisphere: Oriented toward feeling and intuition, the right hemisphere uses pattern recognition and contextual cues to guide action. It makes decisions based on emotional resonance or instinct, rather than structured logic. This hemisphere is slower to learn due to the need for more intricate connections, it is quicker to act, favoring spontaneity and adaptability.

  
  

Communication

• Left Hemisphere: Prefers verbal and literal communication, relying on explicit language and clear terms to convey ideas. This is essential for logical argumentation and factual discourse.

  
  

• Right Hemisphere: Relies on non-verbal and figurative communication, including tone, body language, metaphors, and symbols. This is crucial for expressing emotions, understanding implicit meanings, and connecting with others on a deeper level.

  
  

Philosophy

• Left Hemisphere: Resonates with Western philosophy, prioritizing logic, individualism, and the pursuit of knowledge and progress. It seeks to control and optimize the external world.

  
  

• Right Hemisphere: Aligns with Eastern philosophy, which emphasizes harmony, interconnectedness, and the balance of opposites. It seeks to adapt to and flow with the natural order.

  
  

Body Control

• Left Hemisphere: Controls the right side of the body, specializing in fine motor skills like writing, precise movements, and detailed tasks.

  
  

• Right Hemisphere: Controls the left side of the body, focusing on gross motor skills used in broader, fluid movements like dancing, sports, or spatial navigation.

  
  

THE NERVOUS SYSTEM

The key functions of the nervous system include:

1. Sensory Input: Gathering information from external stimuli (such as sight, sound, touch) and internal conditions (like temperature, stomach pain, and heart rate) and past interpretations.

2. Processing, Evaluation, and Decisions: Analysing the sensory information received in the present and past to interpret its meaning and significance to make a rational decision.

3. Motor Output: Initiating appropriate responses through voluntary or involuntary actions to maintain homeostasis, ensure safety, and enable interaction with the environment.

   
   

The different subsystems within the nervous system handle specific tasks: external and internal sensory information, voluntary and involuntary actions, and safety and survival responses that are decided by the CNS (central nervous system), the brain. This is displayed by the diagram below.

Central Nervous System (CNS): The Future

The CNS represents executive function and future-oriented thinking, primarily housed in the prefrontal cortex, which governs decision-making, problem-solving, and long-term planning. It acts as the top-tier controller, evaluating real-time sensory inputs from the limbic system (past) and brainstem (present) to make informed, strategic decisions. The CNS also sends motor outputs to execute those decisions, synthesizing inputs to facilitate adaptive responses.

Limbic System: The Past

The limbic system serves as the emotional and memory hub, processing past experiences to inform current decisions. Composed of structures like the amygdala, hippocampus, and cingulate gyrus, it relays emotional and introspective data to the CNS (prefrontal cortex) and brainstem. This emotional context influences the balance between sympathetic and parasympathetic activation and integrates past emotional states with present reactions, shaping the emotional responses that guide decision-making.

Peripheral Nervous System (PNS): The Present

The PNS includes all neural structures outside the CNS and limbic system, with the Thalamus as its central hub. It facilitates real-time interaction with the environment by processing and relaying sensory and motor information between the limbic system and CNS, operating both consciously and unconsciously. The PNS regulates goal-directed (aim) and protective (threat) responses through sympathetic and parasympathetic states, functioning along a dynamic spectrum. Additionally, it governs the somatic and autonomic nervous systems, ensuring seamless coordination between voluntary and involuntary actions.

• Sympathetic State - Activation (State of Readiness):

  • Engaged when the body perceives a challenge or stress.

  • Prepares the body for action: increased heart rate, heightened alertness, redirected blood flow.

• Parasympathetic State - Relaxation (State of Calm):

  • Engaged when the body perceives safety and calm.

  • Supports recovery: reduced heart rate, digestion, energy conservation, preparing the body for future action via CNS feedback.

    
    

Somatic Nervous System: Voluntary, Conscious, Exteroceptive

The somatic nervous system governs conscious motor control and the processing of external sensory information. It manages the voluntary movement of skeletal muscles and sensations from the skin, as well as regions involved in movement, such as the face and neck. Through communication with the brainstem via the spinal cord, sensory data is relayed to the thalamus for further processing and coordination. This system enables deliberate actions and a heightened perception of the external environment, making it essential for voluntary interaction with the world.

Autonomic Nervous System: Involuntary, Unconscious, Interoceptive

The autonomic nervous system regulates involuntary processes and the functions of internal organs. It oversees critical operations such as digestion, heart rate, respiratory rate, and hormonal balance, connecting with the brain's central hub (thalamus) via pathways like the Vagus nerve. This system plays a vital role in maintaining homeostasis by balancing internal bodily systems to respond effectively to both internal needs and external environmental changes.

Note

The diagrams and frameworks in this post are conceptual tools designed to make complex systems navigable. They simplify where necessary and prioritise practical understanding over exhaustive scientific precision. Where they diverge from established consensus, they do so in service of the broader framework, not to misrepresent the science.

CONCLUSION

The nervous system is not just the biological machinery of survival. It is the architecture through which we experience consciousness, form relationships, process the past, navigate the present, and plan for the future. Every domain of life explored in the domains post, every pattern of stress and misalignment, every disruption and disturbance discussed in the previous post: all of it runs through this system.

The hemisphere table in particular is worth returning to throughout the series. The left and right divide — masculine and feminine, conscious and unconscious, sympathetic and parasympathetic — is not just a neurological fact. It is a pattern that expresses itself across biology, behaviour, culture, and relationships in ways the next posts will explore in depth.

Understanding the architecture is one thing. Understanding how it shapes who we are — our individual character, our cognitive strengths, our patterns of thought and feeling — is the next step.