Understanding Your Child’s Brain and Nervous System I What Science Tells Us

This foundational article is written as a guide for parents on how the brain and nervous system grow, connect, and shape behaviour.

Understanding your child’s brain and how it develops, is powerful and integral information for all parents and caregivers. Basics around brain development and how this impacts your child’s behaviour, emotional capacity and performance,  guides both how you understand your child, as well as assisting in how you best respond to your child and what will actually work.

The human brain is not fully developed until about 25 years old. We see progressive changes during childhood and adolescence and consider the brain ‘under construction’, with different periods of growth and development during different ages and stages.  

As our children grow up, we tend to think that they “should” be capable of a whole range of things – because all in all, a 10 year old for example, makes us feel like they are almost mini adults, able to do most of the duties of adulthood (ie. self care, socialising, reasoning, making some good choices at school etc). Because of this, when our 10+ little ones have a meltdown, or tantrum or some other emotional outburst, we often feel frustrated, and feel like they “should know better”. 

We need to understand that whilst children’s brains are developing rapidly and they do have a level of cognitive capacity, intelligence and verbal skills to do so many amazing things, even from todderhood – their ‘constructing’ brain, does still limit their capacity in so many ways. 

If we understand that the child and teen brain is still learning and growing, we tend to parent with insight, patience and awareness that allows us the calm to help and guide them in the right way. We, as adults in a young person’s life, can help mould their brains towards healthy growth and development by the way that we respond to them. 

For younger children, they often act on emotion and impulse - not defiance - because their higher-order brain systems are still very underdeveloped.

For older children, they are starting to integrate their brain to be able to access their thinking brain, but only when their lower brain states (brainstem and limbic system) are settled and calm. 

For teens, their brain is going through rapid growth, as well as having hormonal input, which impacts their ability to integrate their emotional brain with their thinking brain – hence, often we see a re-escalation period of emotionality and poor decision making. 

If we understand how the brain works, and accept the different milestones of development and how that impacts on a young persons ‘capacity’, then we are empowered to parent in a way that helps them be their best selves, rather than pushing/wanting or expecting them to be more ‘competent’ than they are neuropsychologically able to be. 

Importantly, this also allows us in therapy, to target tools and skills towards what their brain most needs help with, to bring about best outcomes for your family.

How The Brain Develops

Think of the brain as having two organising maps:

1. A vertical map: bottom to top - showing the evolution from primitive survival to complex thinking.

2. A horizontal map: left to right hemispheres - showing how we process information in complementary ways.

   
   

Both maps interact constantly and healthy child development is about integration across both directions.

Vertical Brain Map - Bottom to Top:

From birth through adolescence, the brain builds from basic survival functions to complex thinking and emotional control; much like constructing a house from the foundation up.

The Building Sequence

Brainstem (birth–1 year): The foundation. Controls breathing, heart rate, sleep, hunger — the body’s automatic systems that keep a baby alive and safe.

Midbrain & Limbic System (1–6 years): Adds emotional processing and social attachment. The amygdala detects threat or safety; the hippocampus starts forming memories; and the limbic system drives connection and feelings.

Prefrontal Cortex (7–25 years): The “thinking brain.” Responsible for reasoning, impulse control, planning, empathy, and self-regulation. It’s one of the last areas to fully mature, not reaching full development until the mid-20s.

Image courtesy of www.beaconhouse.org.uk

A child must have bottom layers regulated (body + emotions) before the top layer (thinking) can engage. That’s why we say, “Connection and regulation before reasoning or correction.”

If you are joining us in therapy, you will hear us talk about the “downstairs brain” and the “upstairs brain” to help children and parents develop skills to help settle the downstairs, and walk upstairs, for best coping and management. 

Horizontal Brain Map I Left and Right Hemispheres — Two Halves Working Together

At the same time the brain structures are developing in a bottom-top structure, there is another brain process occurring that is equally as important. 

The brain also has two hemispheres that process information differently but are designed to integrate over time.

Each hemisphere runs across all levels of the brain — brainstem, limbic, and cortex, but they specialize in different ways of processing.

Hemisphere	Main Functions	Developmental Notes
Right Brain	Emotion, sensory experience, facial recognition, intuition, creativity, attachment	Dominant in infancy and early childhood, helps babies read faces, tone, and body language.
Left Brain	Language, logic, sequencing, cause-and-effect thinking, problem-solving	Gradually strengthens through early school years, supporting literacy, reasoning, and self-talk for regulation.

Integration is when the two hemispheres communicate efficiently through a major fibre tract called the corpus callosum.

In young children, right-brain emotional floods can overwhelm them because the left brain (logic, words) is still learning to keep pace. As integration improves, kids can start to name feelings (“I’m frustrated”), which helps regulate them.

Adolescence brings another wave of brain re-wiring, refining integration between emotional and cognitive networks — explaining why teens can reason well sometimes but still get caught in emotional storms.

If you are joining us in therapy, we will help you and your child build skills to be able to access rooms ‘across the hallway’ of their brain – walk from the right to the left brain, so that they can manage their emotions and think clearly. 

Integration is Key

A regulated, integrated brain has both:

• Vertical integration - body ↔ emotion ↔ thinking (can walk from downstairs to upstairs)

• Horizontal integration - right ↔ left communication (can walk across the hallway from right to left).

Healthy regulation happens when information flows freely up, down, and across.

Children and teens need to build the skills to be able to freely walk around their ‘house’ feeling confident and in control. 

Example: A child feels angry (limbic, right side), notices the tight chest (brainstem–body), uses words to name it (left cortex), and then calms using reasoning (prefrontal).

If any connection is weak:

• Bottom-up integration gap = child becomes overwhelmed by emotions or sensory input (they “flip their lid”).

• Left-right gap = child can feel emotions but can’t name or make sense of them (“I don’t know what’s wrong”).

Understanding how the brain works, helps us understand and interpret challenges that a child might be having. If we understand where the construction gaps are – we can help children, parents and teens build skills, to close the gaps, improve brain growth and integration and subsequently have a calmer flow of behaviour and development. 

Timeline of Development

Age Range	Dominant Systems Developing	Observable Growth
0–2 yrs	Brainstem & right hemisphere	Sleep regulation, sensory comfort, attachment safety
2–6 yrs	Limbic & right–left integration begins	Emotional expression, language for feelings, early impulse control
7–12 yrs	Prefrontal cortex expansion, left hemisphere organisation	Planning, empathy, understanding rules, managing frustration
Adolescence–25	Integration between prefrontal and limbic	Balancing emotion, reasoning, identity, abstract thinking

The Brain and the Nervous System — The Body’s Command Center

The brain sits at the top of a vast nervous system network connecting every organ, muscle, and sensory receptor.

The central nervous system (CNS) refers to the brain and spinal cord and is the control center of our body.  

The automatic nervous system (ANS) is a part of the peripheral nervous system, which sends messages out from the brain and spinal cord and is largely responsible for human survival – hence operating automatically, controlling heartbeat, breathing, digestion, and the body’s stress response.

The ANS It’s made up of nerve pathways (anatomical structures) that connect the brain to organs, glands, and smooth muscles (ie. to our body and its functions). 

The ANS is deeply connected to the bottom layers of the brain — mainly the brainstem and limbic system:

• The brainstem monitors vital functions (heart rate, breathing, arousal).

• The limbic system triggers emotional states that activate the ANS (e.g., fear = sympathetic activation).

  
  

It has two main branches:

• Sympathetic Nervous System (the “Gas Pedal”)

Activates in response to stress or threat. Increases heart rate, breathing, and alertness, preparing the body to “fight, flee, or freeze.”

• Parasympathetic Nervous System (the “Brake”)

  
  

Calms the body down after stress. Slows heart rate, restores digestion, promotes rest and repair

Both are anatomical circuits: bundles of nerves that run from the brainstem and spinal cord to the body — via structures like the vagus nerve, thoracic ganglia, and adrenal medulla.

Healthy development means learning to switch smoothly between these systems. When the ANS is activated we need to learn how to cope when the “gas pedal” is on, and how to return to a calm state when safe.

Younger children depend on co-regulation with caring adults to learn this skill; repeated experiences of safety, soothing, and connection build strong neural pathways for self-regulation. Older children and teens who are experiencing emotional issues, may need to understand the difference between a real danger, that activates the ‘gas pedal’ and a perceived danger, and learn how to calm their ANS when it gets activated. 

The Brain and It’s Chemicals

The other aspect of our body that influences how we act, respond, feel and cope – is the chemical messages (neurotransmitters and hormones) that our body produces. 

Sympathetic system  (“gas”) uses:

• Norepinephrine (noradrenaline) as its main neurotransmitter

• Adrenaline (epinephrine) released into the bloodstream from the adrenal glands

These chemicals speed up heart rate, dilate pupils, increase blood sugar, and prepare the body for action.

Parasympathetic system (“breaks”) uses:

• Acetylcholine as its main neurotransmitter. This slows the heart, promotes digestion, and supports calm states.

So, the chemistry drives the effects, but the anatomy provides the wiring.

Puberty

During puberty, hormones surge and interact with the still-developing brain and nervous system.

Estrogen and testosterone amplify emotional sensitivity, reward seeking, and social motivation.

The amygdala becomes more reactive, while the prefrontal cortex (which manages reasoning and inhibition) is still maturing — explaining why teens can be emotionally intense or impulsive.

Sleep patterns shift (later melatonin release), and dopamine sensitivity peaks, driving exploration, peer connection, and risk-taking — all normal parts of brain-body development.

These hormonal-neural interactions don’t just cause chaos; they shape identity, motivation, and learning when guided within safe, supportive relationships.

In Summary

Parenting which fosters neuro‑growth depends on knowing how a child’s brain develops, so we can respond in developmentally appropriate ways. Experiences matter: repeated interactions (positive or adverse) shape neural pathways.

Early years build the foundations for safety and connection. Middle childhood strengthens thinking and emotional integration. Adolescence refines identity, regulation, and independence. Calm, consistent parenting supports the developing nervous system — helping children and teens learn to steer their own “gas and brake” effectively.

In short: connection, safety, and co-regulation grow the brain — and your relationship is the most powerful tool for your child’s healthy nervous-system development.

Read our other foundational articles to find out more about how we, at Manly Minds, use these neuro-psychological insights to support children and teens mental health and psychological therapy.