Central Nervous System
Your brain and spinal chord together make up what’s known as the central nervous system. Nerves pass on sensory information to the brain via the spinal cord – for instance, whether something you’ve touched is hot – and the brain processes the information, then sends out instructions back through the spinal cord to the nerves about how to respond – for instance, take your hand away from the saucepan. The brain does the same thing with information passed on from the sensory organs involved in sight and smell.
The central nervous system also processes information from within the body, on how your internal organs are functioning – for instance, if your body is having difficulty digesting the food you’ve eaten, your brain might register this as a stomach ache. The central nervous system uses the spinal cord as the main route for all sensory information to and from the brain.
The brain and the spinal cord form one of the most complex biological structures we know, and scientists are still discovering new things about how they work. Your brain has three basic segments, the forebrain, midbrain and hindbrain. The thalamus is the part of the forebrain that processes sensory information from the nerves on its way to the core of the brain, the cerebral cortex. Only your sense of smell bypasses the thalamus and is controlled by a more primitive part of the brain – perhaps relating back to our earlier ancestry before homo sapiens developed, when we, like other animals, relied more heavily for survival on our sense of smell.