Neuronal Communication

Ever wondered how you instantly pull your hand away from something hot? It all starts with sensory receptors - specialised nerve endings that act like biological sensors, detecting changes in your environment and converting them into electrical signals.

These receptors are incredibly specific. Your light-sensitive cells (rods and cones) in your retina only respond to light changes, whilst thermoreceptors in your skin and brain detect temperature shifts. Pacinian corpuscles sense pressure changes when something touches your skin. Think of them as biological transducers, changing one type of energy into electrical energy your brain can understand.

Neurones are the messenger cells that carry these electrical signals throughout your body. They've got a distinctive structure: dendrites receive signals, the cell body processes them, and the axon transmits them onwards. Many axons are wrapped in a fatty myelin sheath with gaps called nodes of Ranvier - this setup massively speeds up signal transmission.

Key Point: Each sensory receptor type is highly specific to one stimulus - you can't hear light or see sound because receptors only respond to their designated energy type.

The magic happens through nerve impulses - electrical signals that zip along neurones. At rest, the inside of a neurone sits at -60mV compared to the outside, maintained by the sodium-potassium pump constantly moving ions around. When stimulated enough to reach the threshold potential of -50mV, voltage-gated sodium channels burst open, causing depolarisation as the inside becomes positive $+40mV$. This triggers a cascade effect, with the signal racing along the axon as a wave of depolarisation.