In Depth: Organs and Circulatory
The human head is home to all the body’s major sensory organs, and the most important of these is the brain.
Although the nose, ears, tongue, nerves, and others parts are important, without a functioning brain, they’d all be useless.
Encased in the skull, the brain is the body’s centralized conveyor of all information. Much of its role involves receiving information from the rest of the body, interpreting that information, and then guiding the body's response to it.
Input that the brain interprets includes odor, light, sound, and pain, and these are gathered from organs located in the head. Major sensory organs located in the head include:
- Ears: The outer, middle, and inner ear are responsible for collecting auditory information. Sound waves travel through the ears and vibrate membranes and tiny bones. Those signals are sent to the brain via the vestibulocochlear nerve. Other than hearing, the inner ears also help with balance.
- Eyes: Light rays pass through the eye and refract through the vitreous humor, or liquid part of the eye. This stimulates the optic nerve, which then relays the information to the brain.
- Tongue: The taste buds collect tastes, and three nerves (facial, glossopharyngeal, and vagus) send the information to the brain where it is interpreted. The tongue also helps with speech; its movement inside the mouth helps form sounds that become words.
- Nose: Olfactory nerves in the upper nasal cavity send messages to the brain to help distinguish an infinite number of smells. The sense of smell also aids with taste.
- Nerves: Nerves all over the body help sense heat, cold, pain, pressure, and texture. The touch receptors, called tactile corpuscles, are mostly located in the dermis layer of the skin around hair follicles.
There is constant sensory information being sent to the brain, but it doesn’t always instruct the body to respond. For example, eyes always see the nose, but the brain blocks out the information for better vision, as the nose is stationary and unchanging. You can test this: close one eye and see how your nose magically appears.