Mr. Minderhoud is a teacher in Covenant Christian High School and a member of Hope Protestant Reformed Church, Walker, Michigan.
But now hath God set the members every one of them in the body, as it hath pleased him.
The human body is an unfathomable, marvelous work of God.
It is made up of a multitude of members—each of which has been created for a unique purpose that contributes to the complex, yet harmonious, workings of the body. These members can be categorized into ten major systems—the respiratory, circulatory, immune, muscular, skeletal, digestive, excretory, reproductive, endocrine, and nervous systems. Each system is governed by the ever-present hand of God to perform specific tasks for the well-being of the body. Each system demonstrates marvelous complexity, intricacy, and unity, both within itself and in its dependence on the other systems in accomplishing these tasks. When studying any particular system we are amazed at God’s work, especially when we consider that our bodies serve as a picture—a picture of the body of believers, united in Christ in the one goal of serving the Father and bringing Him all glory and honor. Hence, we see it can only be the work of an all-wise and omnipotent, sovereign Lord who created, governs, and sustains all things, uniting them for the specific purpose that His name be glorified in all its beauty and goodness. Let us keep that before us as we focus on a particular system within the body, the nervous system, and marvel at the handiwork of our God.
The nervous system consists of the brain, spinal cord, and nerve cells (neurons) that bring information to and from the brain. The basic function or role of the neuron as a whole is to transmit an electrical signal to the other cells in the body. These electrical signals are the means by which information is communicated throughout the body. For example, in order to move your arm, an electrical signal is sent to the bicep muscle with the command to contract. An electrical signal may be sent to the pancreas to stimulate it to secrete insulin, in order to decrease the sugar levels in your blood. Another electrical signal is sent to a particular group of cells in the brain, and the brain will interpret that signal as an image observed by the eye.
Regardless of where the electrical signal goes, the entire process of transmitting these signals to other places in the body is fascinating to God’s people, for it clearly demonstrates God’s sovereign hand that guides and directs all things. Furthermore, the transmission of electrical signals in the body demonstrates to us vividly how the human body functions in an orderly way with the goal of uniting individual parts of the body. Without this unity, particularly the unity brought about by the nervous system that communicates to all the cells, the body would be a collection of individual and disjointed parts that would accomplish nothing. To help us understand the transmitting of the electrical signals in the body and to see how they demonstrate God’s sovereign hand and unity within the body, let us consider a “building block” of the nervous system, the nerve cell or neuron, and three of its basic parts: dendrite (receiver of electrical messages), axon (conductor of electrical messages), and synaptic knobs (sender of electrical messages).
Neurons: The Dendrites
The first part of the neuron is composed of branched, tentacle-like extensions called dendrites. Picture an oak tree’s twisting and reaching mass of branches as a picture of the dendrites, for the word dendrite itself is derived from the Greek word for tree. The dendrites’ role is twofold. One role is to receive stimuli from within and without the body. Dendrites can recognize a variety of different external stimuli. These stimuli include the sensations of heat and pressure, as well as the complex sensations that produce vision, hearing, smelling, and taste. For example, when you place your hand on a hot element, it is the dendrites that are stimulated by the heat to send an electrical message to the brain. Dendrites can also recognize different internal conditions, including chemical imbalances within the body, changes in heartbeat and blood pressure, abnormal oxygen and carbon dioxide levels, and so on, triggering responses to these conditions. For example, when you work vigorously it is the dendrites of special neurons in the body that recognize that the oxygen levels in the blood stream are too low to provide the muscles with the oxygen they need in order to do the work, and these dendrites, therefore, send a message to the brain to rectify the problem. You either breathe more heavily or you quit the activity.
The second role of the dendrites is to receive electrical signals from neighboring nerve cells. When one nerve cell sends an electrical message to another nerve cell, it is the role of the dendrites to receive that electrical signal so that it may continue on to its proper destination.
Thus, we see the importance of dendrites in our body. Dendrites that do not work properly will disrupt our body’s ability to receive stimuli and hinder our ability to respond to them. One example is sufficient to demonstrate this. Leprosy is a disease that produces miserable skin lesions that often damage the dendrites in the nerve cells of the extremities. These neurons can be destroyed to such an extent that the leper cannot receive external stimuli in the affected areas. So, for example, a leprous hand cannot detect pain and will be easily damaged or misused to the point of deformity. The dendrites must do their work, and do so in cooperation with the other parts of the body, in order for things to work properly for the health of the body. May we learn to appreciate the unity that exists in our human bodies, and the contribution of each of its little members! May this also remind us of the value and importance of all the members in the Body of Christ! No one should be considered invaluable, for all of God’s people are members of Christ’s body and contribute to the whole and to the unity of that body.
Neurons: The Axon
The second part of the neuron is the axon. If the dendrites conjure in your mind a picture of the branches of a tree, then the axon would correspond to the tree trunk. The axon is like a long insulated wire that conducts the electrical impulse along the neuron. The transmission of the electrical impulse along this “wire” is very complex and demonstrates the handiwork of our God in its great intricacy, beauty, and unity.
Often people think that electrical impulses move through the nerve cells of the body like electricity runs through an electric wire. This, however, is not quite accurate. There is no mass of particles that bump into each other, like a long series of falling dominoes, and that transmit the message within the nerve cell. Rather the message is transmitted by a series of events that happen at one place in the neuron, and, in turn, trigger similar events elsewhere in the neuron. Think of the axon as a long corridor of classrooms. Each classroom has a door. Outside each classroom are eager students who crowd the door, trying to get into their respective classrooms. The teacher in the first classroom gets a phone call from the principal to begin class. This teacher opens his door, and into his classroom rush the eager students. The second teacher sees the students entering the first classroom and, recognizing this as the signal to begin her class, opens her door to her eager students. The message to start class is quickly passed down the corridor of classrooms in this way.
This analogy perhaps demonstrates the complex transmission of an electrical signal along the axon. Explained from a chemical standpoint, we need to recognize that each neuron is surrounded by a fluid containing sodium ions (ions are charged atoms—either positively charged or negatively charged). When no electrical impulse is being transmitted in the neuron, there are more sodium ions outside the neuron than inside it. God ordained this imbalance so that an electrical impulse could be transmitted. When a neuron is stimulated, it opens a gate in the walls of the axon and lets sodium ions rush inside. After a specific amount of sodium ions have rushed in, another gate farther down the axon opens and lets more sodium ions enter the neuron. This in turn stimulates the next gate to open, and so the process continues down the axon. This successive “opening of gates”—allowing sodium ions to rush into the neuron—constitutes the electrical impulse. Electricity is not literally moving “through” the neuron, but sodium ions simply move successively into the nerve cell. The electrical impulse has thus traveled from one end of the nerve cell to the other. From there the impulse is passed on to the synaptic knobs, which transmit the impulse to another cell. This too is an amazingly complex process, worthy of our attention in a future article.
Once transmission of the impulse has been completed within the nerve cell, the sodium ions within that cell must be pushed back out of the cell so that there are again more sodium ions outside the cell than within it. This imbalance is necessary in order for the neuron to be able to receive another stimulus that it may open its gates, let the sodium back in, and once more begin the entire electrical impulse process. This is accomplished by the use of a “pump,” which pushes sodium ions back out of the nerve cell, so that it is ready to conduct another impulse.
As a side note, one is amazed at the amount of energy used each day simply in pushing sodium ions out of the nerve cell. Remarkably, one third of all the calories one consumes in a day is used to pump sodium ions out of the nerve cells. This is amazing and makes us consider some of our lifestyles. How well will the nervous system function when there is not sufficient energy available to transmit the electrical signal? Is it any surprise that students do not do well academically when they arrive at school and have not had breakfast? Is a cup of coffee or a can of Mountain Dew sufficient in the morning? Can one work to his potential when he has not received proper nourishment for the past few hours? Do we send our children to school without breakfast, without the proper physical nourishment they need? Or, worse yet, do we send them off to school without family devotions, without the proper spiritual nourishment they need to battle sin and to live the life of covenant friendship with God? Without proper nourishment, systems within the body cannot function properly, and the body suffers. How necessary is the daily physical nourishment! The same is so true of spiritual nourishment. Without regular spiritual nourishment we slowly weaken and die. May God cause us to see the need for daily spiritual nourishment!
The Wondrous Works of God
“I meditate on all thy works; I muse on the work of thy hands” (Ps. 143:5).
We take up our daily routines oblivious to the fact that every moment of the day multitudes of tiny electrical signals are being issued and received by the brain and sent throughout the body in order for us to do the simplest of tasks. It is God who continues to maintain and guide every aspect of the workings of our body. God governs the very movement of the chemicals involved in the electrical signals that are issued and received by the cells of our bodies. No single cell, no single molecule, moves or has its being apart from the will and word of God. God is sovereign. He governs and directs these things, uniting them in a God-ordained purpose to contribute to the whole of the body. When we consider all the many parts working together and the intricate detail in which the body is woven together, we are awed by the clear evidence of our Creator and what a wondrous work He has fashioned. What a marvel our bodies are! May we be reminded of another Body, a multitude of members, sovereignly united in Christ its Head to give glory, honor, and adoration to the triune God. Our bodies are a true gift, both in their earthly intricacy and complexity, and for the spiritual picture they afford us! What wondrous things God has done. O Lord, our Lord, how excellent is thy name in all the earth!