The Underlying Complexities of Bipedal Locomotion

Many people fail to realize the complexity involved in such a simple act as getting up and walking down the street— something we do everyday, yet completely take for granted. Much progress has been made in understanding the basic processes that make up our everyday functioning, but we have far to go before a complete understanding is resolved.

A primary underlying difficulty in duplicating an action we perform every day- without even thinking about it- lies in the immense complexity of the human brain. It is made up a vastly complex system of interconnected neurons, each of which is working in parallel as a microscopic biomechanical computer. Hundreds of hormones and neurotransmitter molecules work in conjunction to influence the functioning of these networks of neurons, many of which are receiving input signals from outside sensory networks dispersed throughout the body.

Furthering the near unthinkable complexity of the human brain itself, one must take into account the number of peripheral systems influencing neural processing. Nerve impulses are continuously sent in from outside sensory systems, each of which is- in itself- an impressive system which has proven difficult for neuroscientists to understand.

An important part of walking and motion of the body lies in balance. Human athletes are capable of astounding feats of agility and grace. Balance is composed of at least three separate interactive components: sight, muscular input, and the vestibular system.

The visual system stands at the forefront of these sensory systems, as it relays an extraordinary amount of input to the brain that is necessary for survival. A sophisticated array of rods and cones detect light waves and translate these into electrical impulses that can be interpreted by the brain. The lens of the eye adjusts to keep objects in focus- more quickly and adeptly than the most advanced cameras we can engineer.

The second primary component of balance is input from nerve signals in muscles and joints, called proprioceptors. These nerves are extremely sensitive to changes in position and are found distributed throughout the limbs of the body. They input the positions of the body throughout its range of motions and allow the brain to construct a self-reference point for decision-making many hundreds of times per second.

The third major sensory system responsible for balance is the vestibular system. This consists of the inner ear and imbedded nerve cells which detect changes in fluid pressure within the ear. The signals from these nerve cells give the individual a sense of equilibrium in relation to the force of gravity, which contributes to a subjective model of motion and spatial orientation. In turn, this model influences the response of the muscular and visual systems.

Contributing stimuli from these complex interactive systems are what allow us to have our sense of balance: to stay upright, to move forward without falling, and to know the relation of our bodies to the environment.

After receiving the combined input from these separate sensory mechanisms, the brain processes the information and sends a response to correct the positioning of the body. It is this cooperative and highly parallel functioning of many interactive systems that both enables the gymnast to perform such magnificent feats and which enables us to perform the seemingly simple action of walking down the street.