The Blueprint of the Nervous System
The nervous system is our body’s command centre, organised in a clear hierarchy. It processes information to coordinate all thoughts, feelings, and actions. This interactive diagram shows how it’s structured from major divisions to specialised subsystems. Click any component to learn about its role.
The Nervous System
Central Nervous System (CNS)
Brain
Spinal Cord
Peripheral Nervous System (PNS)
Somatic Nervous System
Autonomic Nervous System
Sympathetic
Parasympathetic
Select a component
Click on a part of the diagram to see its description here.
Conscious vs. Unconscious Responses
Our nervous system produces two main types of responses: conscious actions we control (Somatic NS), and unconscious reactions that happen automatically (Autonomic NS). This section compares these pathways and explores the ‘fight-or-flight’ response.
Mobilise or Conserve: The Autonomic Battle
The Sympathetic and Parasympathetic divisions work in opposition to manage our body’s energy and readiness. Use the buttons to see how each system affects key bodily functions to either prepare the body for action or calm it down.
Sympathetic: Fight or Flight
Increases arousal for vigorous activity. It speeds up heart rate and breathing, diverts blood to muscles, and slows non-essential functions like digestion.
The Spinal Reflex Arc: A Survival Shortcut
The spinal reflex is an unconscious, protective action initiated by the spinal cord, bypassing the brain for an immediate response to danger. Click ‘Next Step’ to walk through the reflex arc and see how sensory information travels to trigger a motor response before the brain even registers pain.
Stimulus
Spinal Cord
Effector
Step 0: Ready
Click the button to begin the reflex arc simulation.
The Language of Neurons
All psychological functioning is enabled by neural transmission—the way specialized cells called neurons communicate. Information travels as an electrical signal down a neuron and is transmitted chemically to the next. This section explores the neuron’s anatomy and the transmission process.
Anatomy of a Neuron
Dendrites
Receive signals
Soma
Integrates signals
Axon
Transmits signal
Myelin Sheath
Speeds up signal
Axon Terminal
Releases chemicals
Chemical Messengers: The Lock & Key
Communication between neurons happens at the synapse via chemical messengers called neurotransmitters. The process is precise: a specific neurotransmitter (the ‘key’) must fit a specific receptor (the ‘lock’) to pass on its message, which can be excitatory (‘go’) or inhibitory (‘stop’).
The Synapse: A Chemical Handshake
Ready
Click ‘Transmit’ to visualize the lock-and-key process of neurotransmission.
‘Go’ vs ‘Stop’: Excitatory & Inhibitory
Glutamate (Glu): Excitatory
The brain’s primary ‘go’ signal. Glutamate makes the postsynaptic neuron more likely to fire. It is vital for learning and memory by helping to strengthen synaptic connections.
GABA: Inhibitory
The brain’s primary ‘stop’ signal. GABA makes the postsynaptic neuron less likely to fire, calming nervous activity and preventing over-stimulation. It is crucial for managing anxiety.
The Malleable Brain: Synaptic Plasticity
The brain isn’t static; it’s physically reshaped by experience. This is synaptic plasticity—the strengthening or weakening of connections between neurons based on their activity. This process is the biological basis of all learning and memory.
LTP vs. LTD: Strengthening and Weakening Connections
Interact with the models below. Repeated stimulation leads to Long-Term Potentiation (LTP), where connections grow stronger (‘sprouting’). A lack of stimulation results in Long-Term Depression (LTD), where unused connections are trimmed away (‘pruning’).
Long-Term Potentiation (LTP)
“Neurons that fire together, wire together.”
Long-Term Depression (LTD)
“Use it or lose it.”
