Beneath a thin covering of material, there lies a mainstay of power. As fuel is injected into the chamber, it is burned to create raw power. The pistons rapidly begin to slide, creating a force strong enough to drive the machine that it has been destined to serve. Are we referring to a high performance sports car? No. Within our bodies, fuel is being burned, and the “pistons”—our muscles—are moving constantly, so that we can pick up a cup of coffee on a dark, dreary morning. The body can accomplish amazing things—from feats of brute strength, to the fine-tuned practice of painting. It is because of the decisive design of muscles—the engines of the body—that we can function with near perfection.
The human body contains nearly 700 individual muscles anchored to the skeleton, which provide pulling power to allow for mobility. These muscles constitute about 40 percent of the body’s weight (Gillen, 2001, p. 46). They can be categorized into three different groups: skeletal muscle (voluntary), visceral muscle (involuntary), and cardiac muscle (in the heart). Each of these three types of muscles performs functions that work to keep the body in constant motion. First, let us focus on the muscles that we consciously use each and every day—skeletal muscles.
SKELETAL MUSCLES (VOLUNTARY MUSCLES)
When one thinks of muscles, the skeletal muscles usually are the most common types that come to mind. They allow for the most amazing physical achievements, from sports to sculpting. How do they work, though? Are they just a simple system of pulleys? In reality, the skeletal muscles are far more complex than one could ever imagine possible in nature.
Skeletal muscles are almost always dependent on each other in order to perform everyday tasks. For example, imagine a person who has biceps, but does not have any opposing muscles (triceps) to counteract the bending motion of his bicep. Once the bicep flexes, the arm cannot re-extend itself, because there is no opposing muscle to contract and pull the arm back to its original position. This form of cooperative counteraction is found in numerous places, such as the legs, feet, mouth, and eyes.
Many of the muscles of the body, such as those connected to the skeleton, can be compared to a modern steel cable. Just like a cable—which is made up of smaller units of wire—muscles are made up of a collection of muscle fibers, and are encased in a thin, transparent covering called the sarcolemma. These smaller fibers then consist of bundles of miniscule structures, myofibrils. Finally, myofibrils are formed by bundles of the smallest unit of the muscle—myofilaments. When we see a steel cable, we know that it has been created by someone. When we look at the complexity of muscles, it is logical to say that they were created as well.
Myofilaments, though they are small, play a very important role in the contraction of the muscles. Myofilaments come in two groups: myosin and actin. When fuel (glucose) is used in the body, much of it is stored within the muscles. When the time comes for the muscles to contract, the actin filaments will combine with handle-like projections on the myosin strands. These projections will grip the actin and pull it inwards. This interaction is occurring in thousands of places at once, producing the visible pull of a muscle. It is because of this work that muscles consume 90% of the energy created by the body (Sharma, 1996).
Although the skeletal muscles are very powerful and complex, they would be only a lump of useless matter if not for their interactions with the nervous system. Before you can raise your hand to your mouth to drink a hot cup of coffee, your brain must be able to tell your arm to bend; it must tell the muscles that work your fingers to wrap themselves around your mug. It must then direct your mouth to open, and tell your tongue to help you swallow the liquid. The communiqués that flow from the brain to the muscles are extraordinary, to say the least. In order to transmit signals, nerves extend from the brain and spinal cord, and are intertwined within the muscles. The interaction of the nerves and muscles works like this:
Voluntary movement of head, limbs, and body is caused by nerve impulses arising in the motor area of the cortex of the brain and carried by cranial nerves or by nerves that emerge from the spinal cord to connect with skeletal muscles. The reaction involves both excitation of nerve cells stimulating the muscles involved and inhibition of the cells that stimulate opposing muscles (“Nervous System,” 2003).
In other words, in order to move the arm, there must be one set of nerves to stimulate the bicep to contract. Another set is used to inhibit the muscle that is on the opposing side—in this case, the tricep. If these two systems did not work in perfect synchronization, then movement would be nearly impossible.
The skeletal muscles are so exceedingly complex that they are not even completely understood by scientists. Patrick R. Hunziker and his colleagues mentioned this in regard to the complexity of muscles:
Motion generated by muscle contraction does well illustrate this fact: Physics (cf. electric potentials within a cell), physical chemistry (cf. free intracellular calcium), biochemistry (cf. myosin phosphorylation), mechanics (cf. bending of the myosin heads during the crossbridge cycle) are by far insufficient to explain motion (2002, p. 521).
Our highest-level sciences, such as physics and chemistry, are insufficient to explain the means by which voluntary movement of muscles is carried out. What does this tell us about the complexity of muscles?
Once the complexity of just one muscle has been identified, imagine the complexity of a group of these muscles working together! Geoffrey Simmons, in his book, What Darwin Didn’t Know, pointed out:
More than 50 muscles about our face and scalp help us express our feelings, protect our eyes, chew our food, swallow the food, whistle, and say whatever. It takes 12 of the 32 muscles in the face to create a smile—that’s two to furrow the brow, two to raise the eyebrows, two to pull one corner of the mouth up and out, two to pull the other corner of the mouth, two to raise the upper lip and flare the nose, and two to pull the lower lip down. Twelve muscles move our eyes (2004, pp. 223-224).
When these muscles are all in perfect working order, they can perform any variety of facial expressions. The slightest problems with any stimulation from nerves can cause permanent facial distortions. Medical problems such as strokes, Bell’s palsy, and brain tumors will cause face droop, because a nerve is not properly stimulating those muscles. It is only because of the impressive design of muscles that we can perform simple tasks like walking or smiling.
(INVOLUNTARY OR SMOOTH MUSCLES)
Visceral muscles, unlike skeletal muscles, are not attached to the bones in the body. Rather, they are found in many of the systems of the body, such as the digestive and circulatory systems. These muscles are much slower moving than skeletal muscles, which must be able to perform larger, more specialized tasks (Gillen, p. 50). On the other hand, these muscles are in constant motion, and they are untiring in their work. Even when all voluntary muscles are at rest, the visceral muscles are hard at work. The digestive system is moving food; the urinary tract is moving urine; vessels in the circulatory system are expanding and contracting to maintain homeostasis; the eye is adjusting to incoming light; the diaphragm is causing the lungs to expand and contract. And this is only a small list of the numerous roles that visceral muscles play in the body.
Say, for example, that a piece of food has just been swallowed, and it is pushed into the esophagus by the tongue. How does the food reach its destination? A combination of gravity, and what is known as peristalsis, moves the food along its path in the digestive system. Peristalsis is essentially a series of consecutive contractions of the involuntary muscles lining the esophagus, stomach, intestine, etc. These contractions cause a wave-like motion of the digestive tissue, slowly moving the food along the tract. In the midst of this process, the average person will not be aware that any of this is occurring.
Smooth muscle can perform many other unconscious movements, all controlled by the autonomic nervous system (ANS). Bakewell commented:
The ANS is predominantly an efferent system transmitting impulses from the Central Nervous System (CNS) to peripheral organ systems. Its effects include control of heart rate and force of contraction, constriction and dilatation of blood vessels, contraction and relaxation of smooth muscle in various organs, visual accommodation… (1995, p. 1).
Each of these muscular functions can occur simultaneously, accomplishing life-sustaining feats in utter silence. If the muscles were not in perfect working order, or if the nerves did not stimulate them properly, the body would not be able to survive.
CARDIAC MUSCLES (HEART MUSCLES)
The cardiac muscles are possibly the most interesting of the three groups of muscles. They work in the same fashion as skeletal muscles when it comes to contraction. Then what makes cardiac muscle so unique? There has never been a case where someone had to think to contract their heart muscle. Cardiac muscle allows the heart to pump 1½ gallons of blood per minute through the body, for a total of 56 million gallons in an average life span (Stein, 1992, p. 73). That much blood could fill 69 Olympic swimming pools! To pump this much blood, these cells continue to contract throughout life, not bowing under their endless labor. The cardiac muscles may contract at least 2 billion times in one lifetime!
Within the heart, there lies a network of nerves and muscles that are nearly self-sufficient when it comes to contracting and pumping blood. Unlike other organs in the body, the heart has little interaction with the body’s nervous system. The heart’s neuromuscular system works independently from the rest of the body by using its own miniature version of a nervous system. This is done with a series of nodes in the heart that act as stations for sending and receiving electrical impulses, which stimulate the heart muscle. The reaction for pumping blood begins with the sinotarial (SA) node, the pacemaker for the cardiac muscle cells. When this node fires, it creates an electrical stimulus that causes the heart cells to contract at the top of the heart (the atria). As a result of this contraction, the blood contained in the top portion of the heart is pushed to the bottom chambers, called the ventricles. The electrical stimulus will travel from the SA node to the atrioventricular (AV) node, and eventually to the purkinje fibers, causing a string of contracting muscle. This coordination cannot have any flaws whatsoever. Each portion of the heart must contract at the correct time, and with the proper force. A flaw will result in medical problems such as atrial fibrillation (heart flutter), and can eventually lead to poor blood flow in the body, as well as countless other complications.
Muscles, even though they are not visible, exhibit their design every time they are utilized. Many scientists may want to refer to muscles as products of genes and evolution, but logic and common sense point to a “First Cause,” as Darwin himself would put it (as quoted in Francis Darwin, 1898, 1:282). Can such complexity be accounted for, even by billions of years? Can random mutations and natural selection “choose” to design such wonderful masterpieces? Hardly.
Bakewell, S. (1995), “The Autonomic Nervous System,” Update in Anesthesia, [On-line], URL: http://www.nda.ox.ac.uk/wfsa/html/u05/u05_010.htm.
Darwin, Francis (1898), Life and Letters of Charles Darwin (New York: D. Appleton).
Gillen, Alan L. (2001), Body by Design (Green Forest, AR: Master).
Hunzikera, Patrick R., Martin Stolzb, and Ueli Aebib (2002), “Nanotechnology in Medicine: moving from the Beach to the Bedside,” Chimia, 56:520-526.
“Nervous System” (2003), Microsoft Encarta Encyclopedia [On-line], URL: http://www.bioproject.info/Subclass_Placental_mammals/Order_primates/
Sharma, Vijai P. (1995), “Breathing, Muscles and the Mind—The Tools of Fitness, Pt. 1,” Mind Publications, [On-line], URL: http://www.mindpub.com/art197.htm.
Simmons, Geoffrey (2004), What Darwin Didn’t Know (Eugene, OR: Harvest House).
Stein, Sara (1992), The Body Book (New York: Workman).
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