Editor’s note: Physicians have a special place among the thinkers who have elaborated the argument for intelligent design. Perhaps that’s because, more than evolutionary biologists, they are familiar with the challenges of maintaining a functioning complex system, the human body. With that in mind, Evolution News is delighted to offer this series, “The Designed Body.” For the complete series, see here. Dr. Glicksman practices palliative medicine for a hospice organization.
Evolutionary biology is historical science. But that I mean it tries to explain the origin of life by looking only at what is needed to live and explaining it by guessing at historical circumstances. In contrast, physiology is operational science, in that, by looking at how what is needed to live functions within the physical and chemical laws of nature, it tries to explain how life actually works. But when it comes to question of the origin of life, non-operational science is important as well. In other words, it is important to consider what happens when what is needed to live is not functioning well enough to survive. Pathophysiology is “the physiology of disordered function,” or the science that explains how the body malfunctions and dies. It is representative of non-operational science.
Natural history museums often display human skeletons alongside those of other animals. Without any discussion of the physiology and pathophysiology of bone and calcium metabolism, these exhibits seek to convince the unwary that life must have come about by chance and the laws of nature alone. In contrast, museums of science and technology display the skeletal remains of different inventions with the intermediate models that led up to the modern versions. By discussing the science behind the technology and the problems and failures encountered along the way, they demonstrate the intelligence used to create them. When it comes to how bones fit into the origin of life, natural history museums only use historical science to show how life looks, whereas when it comes to human ingenuity, museums of science and technology add operational and non-operational science to show how inventions work and don’t work to prove their point.
My last article in this series showed that the molecular and cellular structure of bone is complex and that its relationship with the calcium metabolism makes it absolutely vital. The bone cells live within the bone they form. They include the osteoblasts, which take calcium from the tissue fluid surrounding the bone cells to form bone, and the osteoclasts, which break down and remove calcium from bone and deposit it into the bone tissue fluid. Ninety-nine percent of the body’s calcium is within its bones and ninety-nine percent of the calcium within the bones is in a crystalline form called calcium hydroxyapatite.
The remaining one percent of bone calcium is dissolved as calcium phosphate in the tissue fluid that surrounds the bone cells. Since this bone tissue fluid is in direct contact with the capillaries, it acts as a bridge by which calcium can move between the circulation and the bone. Through the bone tissue fluid, the body is able to not only supply the bone with its calcium needs, but also provide for its ongoing calcium needs. In other words, through tissue fluid and circulation, the bones act as a reservoir for the calcium metabolism of the body. Let’s look at the roles that non-bone calcium plays within the fluid inside and outside of the cells.
Just as sodium (Na+) and potassium (K+) become positively charged ions when dissolved in water, calcium becomes positively charged Ca++ ions in solution. The amount of Ca++ ions within a given amount of fluid is called the Ca++ ion concentration. Of the one percent of calcium outside the bones, only ten percent is present as Ca++ ions in solution outside the cells. This extracellular fluid includes the interstitial fluid, which surrounds the cells and the plasma in the blood. The remaining ninety percent of calcium outside the bones resides in the cells. However, most of this intracellular calcium is not dissolved in the cellular fluid (cytosol) but stored in many of its organelles. In fact, the concentration of Ca++ ions in the cytosol is about ten thousand times less than in the fluid surrounding the cells and in the blood. Since the kidneys constantly filter fluid, with its content of Ca++ ions, out of the circulation, if none of it could be brought back, the body would lose its total calcium content in about two months.
In addition to providing the calcium the bones need to protect the organs from injury and attachment for muscles so we can breathe, move around, and manipulate things, the Ca+ ions in the extracellular fluid are also vital for clotting. Without Ca++ ions in the blood, clotting would be impossible and every day injuries would be much more serious threats. However, there is another very important role the Ca++ ions outside the cells play, which affects all nerve and gland function, heart, and all other muscle function.
Nerve cells produce neurohormones and gland cells produce fluids, enzymes, and hormones. Under a controlled setting, these are released in response to an appropriate stimulus. For example, as noted previously, when the core temperature rises above normal, the sympathetic nerves release acetylcholine , telling the sweat glands to perspire. And when the blood glucose drops too low, the alpha cells in the pancreas release glucagon, telling the liver to release glucose from glycogen. Each of these actions takes place because of a specific signal. This signal is the sudden and massive movement of Ca++ ions into the nerve and gland cell through Ca++ ion channels caused by original stimulus (the rise in core temperature and the drop in blood glucose). This controlled, sudden, and massive influx of Ca++ ions into the cell is the universal signal telling the nerve cells to release their neurohormones and gland cells to release fluids, enzymes, and hormones.
Heart and other muscle cells work by contracting. This involves the contractile proteins within them interacting with each other in a specific way. When adequately stimulated, massive amounts of Ca++ ions enter the cytosol of the heart muscle cells from the surrounding fluid and are released from Ca ++ ion storage units (sarcoplasmic reticulum). This sudden rise of Ca++ ions allows the contractile proteins to interact and bring about contraction. The other muscle cells of the body work in a similar way. With adequate stimulation, they release massive amounts of Ca++ ions into the cytosol from the sarcoplasmic reticulum, making their contractile proteins interact to cause contraction. Just like for nerve and gland cells, it is this controlled, sudden, and massive influx of Ca++ ions into the cytosol that is the universal signal that brings about heart and other muscle cell function.
Controlled nerve, gland, heart and all other muscle function require that the ten thousand-fold difference between the Ca++ ion concentration outside and inside the cell be maintained. But, in trying to maintain this difference in Ca++ ion concentration, the laws of nature present the body with a dilemma. Diffusion is a law of nature that says chemicals in solution are always in motion and tend to move from an area of higher to lower concentration. Since Ca++ ions can diffuse across the plasma membrane, this means that diffusion tends to make Ca++ ions enter these cells. This movement into the cells would significantly increase the Ca++ ion concentration within them and if not opposed would make them non-functional.
If you read some of the earlier articles in this series you may have noticed that the dilemma that diffusion presents to the cell for Ca++ ions is similar to the one it faces for Na+ and K+ ions. The body solves that problem through millions of sodium-potassium pumps in the plasma membrane, which use energy to pump Na+ ions out of the cell while bringing K+ ions back in, against their natural tendency to go in the opposite directions. The innovation the cells use to overcome the natural force of diffusion so they can keep the Ca++ ion concentration in their cytosol ten thousand times less than what it is outside of them is the calcium pump.
There are calcium pumps within the plasma membrane of all of the cells of the body and within the sarcoplasmic reticulum of the heart and other muscle cells, which use energy to actively pump Ca++ ions out of the cytosol. In this way, the body maintains normal nerve, gland, heart, and all other muscle function.
Don’t you think it would be good for natural history museums to include in their displays on human skeletons information about the cellular and molecular make-up of bones, their relationship with the calcium metabolism, and the importance of Ca++ ions inside and outside the cell? Then, when they use the similarities between human skeletons and the ones of other animals to claim that life must have come about by chance and the laws of nature alone, the accompanying questions will be apparent. Where did the osteoblasts and osteoclasts come from and in which order? Where did the calcium pumps come from and how do they know how much calcium to send out of the cell to allow for nerve, gland, heart and all other muscle function? That would be educating the public about how life works instead of just how it looks.
Next time we’ll look at how the body acquires calcium. The process isn’t as easy as it is for water, glucose, and salt. In fact, the mechanism involved is just one more reason to wonder how evolutionary biologists can continue to claim that life has come about by chance and the laws of nature alone.
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