How It Works: Electrical Impulses Through the Nervous System

⚙️ How It Works: Electrical Impulses Through the Nervous System

The nervous system transmits information as electrical impulses along neurones. The pathway for a conscious response follows this sequence: a stimulus is detected by sensory receptors (for example, light hitting the retina), sensory neurones carry the electrical impulse toward the CNS, relay neurones within the CNS process the information, and motor neurones carry the impulse away from the CNS to effectors such as muscles or glands.

At every junction between two neurones there is a synapse — a tiny gap of approximately 20 nanometres. Electrical impulses cannot cross this gap directly. Instead, when the impulse reaches the end of a neurone, it triggers the release of neurotransmitters into the synaptic cleft. These chemical messengers diffuse across the gap and bind to receptor proteins on the next neurone, triggering a new electrical impulse. This chemical step introduces a slight delay but also allows for signal amplification, inhibition, and integration of information from multiple sources.

The nervous system enables rapid, short-lived, and very precise responses. Unlike hormones, which travel in the blood to all parts of the body, nerve impulses travel along specific neurone pathways to target exactly one effector. This precision is why you can move a single finger without moving the whole hand.