Caution: Organs at Work - Part VII: Balance
Everybody knows that the gauges on the dashboard are put there to tell the driver about what is going on in his car. But how do they work? Each device is essentially a sensory transducer (L. transducere = to lead across) with a mechanism in place that allows it to detect a physical phenomenon and convert it into useful information which, depending on the situation, the driver ignores at his peril. One type of sensor, placed in the fuel tank, informs the fuel gauge on the dashboard about how much fuel is left, and on seeing it, the driver must decide how soon to fill up. Another type of sensor, placed within the engine block, informs the temperature gauge on the dashboard of how hot the engine is, and on seeing it, the driver must decide whether or not the car is safe to drive. To work properly, the car must have the right types of sensors, in the right places, providing the right gauges on the dashboard with the right information, otherwise the driver will not know the true situation and may end up running out of gas or permanently damaging his car.
This same principle (with the car) can be applied to the body and its ability to survive within the laws of nature. Previous articles in this series have shown that the body has a whole host of sensory transducers located in exactly the right places which provide the right information to the right organs to allow it to control its metabolism and internal environment. In general, these sensory transducers can be divided into three main types; chemoreceptors; which respond to chemicals, like the glucosensors in the alpha and beta cells of the pancreas that control the blood glucose, mechanoreceptors; which respond to motion and stretch, like the baroreceptors in the walls of the main arteries that supply blood to the brain for blood pressure control; and physical sensors; which respond to natural phenomena, like the thermoreceptors in the hypothalamus which controls the body's core temperature.
How all of this came about by just chance and laws of nature alone, as evolutionary biologists would have us believe, goes against all common sense, human invention and reverse engineering. After all, just like the sensors and the properly calibrated gauges on the dashboard, the systems needed to control things like blood glucose, blood pressure and core temperature are irreducibly complex in that each of them consists of different components each of which must be present and working properly to allow for life. Moreover, just as the driver has an inherent knowledge of what the gauges on the dashboard tell him about his car's function, since the blood glucose, blood pressure and core temperature must stay within a certain range for the body to survive, this means that these systems must also have an inherent knowledge of what these parameters must be for the body to survive, something I call natural survival capacity. Evolutionary biologists are great at imagining how all of these parts came together because they only deal with how they look but not how they must work within the laws of nature to allow for survival.
Like the rest of the body, the nervous system, which makes us aware of our surroundings, controls respiratory and cardiovascular function and lets us move about and manipulate things, needs different sensory receptors, located in the right places, to tell it what is going on inside and outside the body. After all, if the body could not feel the ground or balance itself because it didn't know where its arms and legs are in space or whether it was upside down or not, then how could our ancient ancestors have survived?
The nervous system has chemoreceptors that send information to the brain where it is interpreted as different tastes and smells. Physical sensors like the photoreceptors in the retina of the eye detect light and send information to the brain where it is interpreted as vision. Mechanoreceptors in the skin send information to the brain on things like touch, pressure and vibration while others in the muscles and joints send information to the brain on limb position and muscle movement. This article will look at the different ways the body uses to inform itself of where it sits in space with respect to gravity and how it goes about maintaining its balance.
What Gravity Does
Gravity is the force that makes things fall toward the earth. Experience shows that if you drop something and there is only air between your hand and the ground, the object will fall to the ground. An object’s center of gravity is a theoretical point about which its weight is evenly distributed. For an object that has a uniform density with a regular and symmetrical shape, such as a square piece of solid wood, the center of gravity is at its geometric center. Place a square solid wooden block on a table and push it more and more off the edge and it will fall to the ground when its center of gravity is no longer on the table.
The human body is made of muscles, organs, fat and bone, each with a different density. Although the physical outline of the body is symmetrical from side to side, its shape is very irregular. The center of gravity for most people, while standing or lying with their arms at their sides, is in the midline near their belly button (umbilicus). To be able to stay standing up the body’s center of gravity must remain between its two feet, both from side to side and back to front, otherwise it falls to the ground. Movement of the arms or legs away from the body or bending the spine in any direction changes the body’s center of gravity. Moreover, carrying an object, especially at a distance from the body, will also change its center of gravity. Finally, for our earliest ancestors to survive within the laws of nature they not only had to stay balanced while standing, but also walking, with only one foot, and running, with neither foot, in contact with the ground. In other words, the human body is an inherently unstable object which needs to take control to stay balanced.
How gravity affects the body must have been taken into account by human life as it evolved through intermediates to experience the sensation of balance and be able to maintain its equilibrium. Evolutionary biologists claim that our ability to stay balanced came about by chance and the laws of nature alone. I suspect that after you understand how the different sensory modes and the parts of the vestibular system work together in an irreducibly complex fashion, having the natural survival capacity through the brain to contend with the laws of nature so that our earliest ancestors could maintain their balance well enough to survive, you will come to see that when Darwinists teach their acolytes about the evolution of balance; it's the unbalanced trying to balance the unbalanced.
Organs for Balance
It is the job of the neuromuscular system to keep the body in position while balancing itself against gravity. Although the spinal cord provides reflexes that help it maintain its posture, it is largely the brain, particularly the brainstem and the cerebellum, that provides the coordinated motor patterns needed to maintain its balance. To be able to make ongoing adjustments the brain receives sensory data from mainly four different sources; the pressure receptors in the feet, the proprioceptors, particularly of the neck and the rest of the spinal column, the vestibular apparatus within the inner ear and the vision provided by the eyes.
The pressure sensors in the feet inform the brain of the body’s weight distribution relative to its center of gravity. Stand up and lean from side to side, and back and forth. Notice the difference in the pressure sensations felt from each foot with these movements, the feeling of imbalance and the immediate adjustments that must be made to stay standing.
The proprioceptors of the neck and the rest of the spinal column provide the brain with information about the relative position of the head and the rest of the body. Bend your neck forward and backward and then bend from your waist in any direction. Wherever your neck and spinal column go so goes your head and the rest of your body. Notice the feeling of imbalance as your center of gravity moves away from being between your feet and how you quickly have to adjust to prevent from falling to the ground.
The vestibular apparatus within the inner ear, consisting of the semicircular canals, the utricle and the saccule, contributes sensory information to the brain about the speed and direction of head and neck angular motion and linear and vertical body movement. In addition it helps to stabilize the retinal image.
See: Vestibular system
Like the three sides in each corner of a box, the three fluid-filled semicircular canals are oriented at right-angles to each other. The lateral canal is positioned like the bottom of the box, but is oriented about thirty degrees above the horizontal plane. The other two sides, the superior and posterior canals, are oriented vertically and at right-angles to each other like the front or back and either side of the box. In this way they are set up to provide the brain with three-dimensional information about the angular acceleration caused by head motion.
The lateral canal is most sensitive to spinning or rotating the head from right to left or left to right, whereas the vertically oriented canals are most sensitive to nodding the head up or down or flexing the head to the right or left shoulder and back again. Head motion in any direction naturally moves the fluid within the semicircular canals and stimulates hair cells which are sensory receptors. The nerve messages sent from the semicircular canals, (from each side of the head) are sent to each side of the brain through the vestibular branch of the same nerve that is involved for hearing (vestibulo-cochlear nerve) where they are processed and analyzed so the body can maintain its balance.
As noted above, the information provided by the semicircular canals on angular head motion helps to stabilize the retinal image. Think about it. When you are in motion, unless you focus on something, everything moves across your visual field at the same speed as you do. If you were unable to have controlled eye movements when your head moves in any direction, everything you look at would always be blurred. Imagine our earliest ancestors running up and down over hill and dale trying to find food or avoid becoming food, without being able to focus on anything? So how does the body do it?
It's called the vestibulo-ocular reflex. Look into a mirror and focus on your eyes as you rotate your head from side to side, up and down and then in any direction. Notice how your eyes automatically move in the opposite direction of your head so you can keep them in focus. This is also known as the doll's eye reflex and is often used by physicians (along with the corneal and pupillary light reflex) to assess brainstem function. It is the sensory information supplied by the semicircular canals on each side of the head about angular head motion that allows the brain to reflexively move the eyes in the opposite direction to maintain the retinal image so we can focus on things no matter how fast or in what direction we move.
The utricle and the saccule also contain fluid but in addition have tiny calcium crystals which overlie the hair cells within the sensory membrane. In response to linear motion the weight of the calcium crystals shear across the hair cells resulting in depolarization and excitation. The utricle and the saccule provide information on linear acceleration and gravity. The sensory neurons of the utricle are oriented in the horizontal plane and provide information on the body's back to front and side to side motion whereas the ones in the saccule are oriented in the vertical plane and give information on its up and down motion (like in an elevator) and the position of the head with respect to gravity.
Like for the semicircular canals, the sensory information from the utricles and saccules travels in the vestibular branch of the vestibulo-cochlear nerve to the brain. It is within the various parts of the brain where this information is processed and integrated with other sensory data and this allows the body to maintain its balance and along with it, its survival capacity within nature.
Vision from the eyes provides the brain with an image of the environment in which the body is located. Clinical experience teaches that with concentration, training and slow movement, vision, by itself, can often help maintain the body's equilibrium without information from the pressure sensors, the proprioceptors and the vestibular apparatus. Close your eyes and begin to walk, progressively increasing the speed as able. Notice how difficult it is to maintain your balance. This is because, closing your eyes makes you totally dependent on the pressure sensors in the feet, the proprioceptors of the spine and limbs and the vestibular apparatus. Now do this exercise again, but this time with your eyes open and you will verify that visual cues greatly contribute to being able to maintain your balance.
One of the first indications that a person may have a problem with their balance is when they inadvertently fall in the shower. While taking a shower most people close their eyes to shampoo their hair and then quickly turn their head and neck and often their whole body to rinse it off. In doing this maneuver (with their eyes closed) their brain can no longer use visual cues to maintain their balance. If a person has a condition like a sensory neuropathy (common in diabetics) which limits the reception of the sensory data from the feet, or Multiple Sclerosis, which slows the nerve impulse velocity in the brainstem, or degeneration of the cerebellum, which causes poor coordination, then they will come to realize how important their vision is for maintaining their balance when they take that first fall.
Real Numbers Have Real Consequences
Previous articles have shown that when it comes to the various parameters of life, like the blood glucose, blood pressure and core temperature (among dozens of others), real numbers have real consequences. Not just any blood glucose, blood pressure or core temperature will do. Each of them (along with dozens of others) must stay within a certain objective range that medical science can measure and express in a digital form. As one example; blood glucose below 60 units or above 400 units usually results in weakness and severe fatigue and as the blood glucose drops toward 20 units, or rises up toward 1,000 units, this results in worsening organ malfunction and usually death. When it comes to real numbers having real consequences, the same can be said for the nerves that serve the vestibular organs and the other sensory devices which allowed our earliest ancestors to stay balanced to survive.
When you stand up your buttocks is about one meter off the ground. If you lean too far over you could lose your balance and fall to the ground due to gravity. Since gravity makes all things accelerate to the ground at 10 m/sec2 it is possible to calculate how long it would take for you to hit it from one meter up (0.45 sec). This means that your nervous system has to react fast enough, in fact, in less than half a second, to prevent a fall.
The impulse velocity of a nerve is faster if it is larger in diameter and insulated with a fatty substance called myelin rather than being smaller and unmyelinated. The sensory and motor nerves involved in keeping your balance normally are large and myelinated and have an impulse velocity of about 100 m/sec (> 200 mph). Since it is at least three meters from most people's feet to their brain and back to their leg and lower spine, it only takes about 0.03 seconds for the nerve impulse to travel along the sensory nerve to the brain and back along the motor nerve (not counting the processing in the brain) to the leg and lower spinal muscles. This would give the neuromuscular system plenty of time to make changes to prevent a fall.
In contrast, the impulse velocity of the smaller and unmyelinated nerves that inform the body about pain is only about one meter/sec. This means that if the sensory and motor nerves involved in helping the body stay in balance, were like the pain nerve fibers it would take at least 3 seconds for the impulses to go from the feet to the brain and back to the legs and lower spine. Clearly, this would not be fast enough to prevent you from falling to the ground (0.45 sec). In fact, the sensory messages from your feet would have only traveled to just above your knee by the time you hit the ground. This also explains why when you are injured you can react very quickly to avoid further tissue damage but you don't experience the severe pain until a few seconds later.
The system the body uses to maintain its balance is irreducibly complex because of the different parts needed to make it work. But it also demonstrates natural survival capacity in that the impulse velocity of the sensory and motor nerves involved in these is sufficient to contend with the force of gravity. For, without this, no matter how sophisticated the sensors and muscles involved, it would have been impossible for our earliest ancestors to have been able to maintain their balance and live long enough to reproduce.
Remember, when it comes to life and the laws of nature, real numbers have real consequences. Without the right sensory devices informing the brain fast enough about the body's position in space and its relationship to gravity our earliest ancestors would have been as dizzy as coots. But of course, as most people who believe neo-Darwinism mistakenly teach, evolution would then have just made them develop some other innovation instead, because that would have been what they needed to survive.
Be sure to catch all of the articles in Dr. Glicksman's series, "Beyond Irreducible Complexity."
Howard Glicksman M. D. graduated from the University of Toronto in 1978. He practiced primary care medicine for almost 25 yrs in Oakville, Ontario and Spring Hill, Florida. He now practices palliative medicine for a Hospice organization in his community. He has a special interest in how the ethos of our culture has been influenced by modern science’s understanding and promotion of what it means to be a human being.
Comments and questions about this article or any of the previous ones are welcome.
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