DEAR DOCTOR K: What are the body parts, or systems, that help us balance?
DEAR READER: Our daily balancing acts require intricate coordination between body systems. These include the central nervous system (brain and spinal cord), the vestibular system (brain and inner ear), the visual system (brain and eye), and a vast web of position-sensing nerves called proprioceptors.
• A part of the brain called the cerebellum oversees balance and movement. It receives sensory information, such as sight, sound and touch, from our nerves. Another part oversees other aspects of balance, such as attention, planning and movement. It also supplies memories important to balance. For example, when you face a balance challenge like a slippery sidewalk or rocky path, you have a memory of how you moved your body in the past to deal with such situations.
• The spinal cord serves as a bridge between brain and body. Nerves along its length receive feedback from the peripheral nervous system, a lacework of nerve fibers that branch out from the central nervous system. The spinal cord also initiates reflexes, such as the quick-stepping response to an unexpected push. It delivers commands to the muscles too, telling them to make voluntary movements.
• The body’s balance mechanism, called the vestibular system, is housed in the inner ear and is made up of three semicircular tubes that consist of bone-encased membranes filled with fluid and lined with hair cells. As you move, fluid in the canals shifts and bends the hair cells, which send messages to the brain telling it how much you moved and in which direction.
• In the visual system, the eyes send visual information to the brain, continually logging where you are in relation to surrounding objects.
• The position-sensing nerves called proprioceptors are responsible for proprioception – the ability to perceive where your body is in space. Found primarily in muscles, tendons and joints, proprioceptors stream information to the brain, which instructs muscles to contract as conditions change (when you’re on uneven ground, for example).
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