Our Intelligent Bodies

Gary F. Merrill

• Publisher: Rutgers University Press Medicine
• Year: 2021
• Print ISBN: 9780813598529, 9780813598512
• eBook ISBN: 9780813598536
• Topic: Biological Sciences
• Subtopic: Physiology
• Index: Biological Sciences

Human intelligence isn't just located in the brain. Our bodies are marvelously sophisticated and complex, with a variety of autonomic systems that help maintain our health without us ever having to think about them. But how exactly do all these physiological structures actually work?In Our Intelligent Bodies, physiology professor Gary F. Merrill takes you on a guided tour through the human body. You'll learn how our eyes are designed to detect unimaginably small bursts of light and how our ears contain bundles of tiny hairs, each one attuned to different sound frequencies. You'll also discover how our hearts are smart enough to compensate for skipped beats and irregular rhythms and how our pulmonary system adjusts for low oxygen levels. You'll even find out why the gut is sometimes called the "second brain," its reflexes controlled by millions of neurons.Written in a fun, easy-to-comprehend style and filled with illuminating analogies, Our Intelligent Bodies also brings readers up to date on cutting-edge research into the wonders of human physiology. It will give you a new appreciation for the smart decisions our bodies are making when our brains aren't paying attention.

1

Intelligence

INTELLIGENCE DEFINED

Intelligence has been defined as one’s capacity for logic, abstract thought, understanding, self-awareness, communication, learning, emotional knowledge, memory, planning, creativity, and problem-solving. It is also the ability to perceive and/or to retain knowledge or information and to apply it. Intelligence is most widely studied in humans but has also been observed in nonhuman animals. Artificial intelligence is intelligence in machines and computer software (https://en.wikipedia.org/wiki/Intelligence, August 15, 2019).

The word intelligence derives from the Latin verb intelligere, “to comprehend” or “to perceive.” A form of this verb, intellectus, became the medieval technical term for understanding and a translation for the Greek philosophical term nous. This term, however, was strongly linked to teleology and to the concepts of the active intellect (also known as the active intelligence) and the immortality of the soul. Such an approach to the study of nature was rejected by early modern philosophers including Francis Bacon, Thomas Hobbes, John Locke, and David Hume, all of whom preferred the word understanding in their English philosophical works. Hobbes, for example, in his Latin De Corpore, used intellectus intelligit (translated in the English version as “the understanding understandeth”; Goldstein, S., et al., eds., Handbook of Intelligence: Evolutionary Theory, Historical Perspectives, and Current Concepts [New York: Springer Science + Business Media, 2015]) as a typical example of a logical absurdity. The term intelligence has therefore become less common in English-language philosophy but was taken up later with the scholastic theories it now implies.

To some, the definition of intelligence is controversial. Indeed, when two dozen prominent experts were asked to define intelligence, they gave two dozen different definitions. Some psychologists have suggested the following definition: a general mental capability that among other things involves the ability to reason, plan, solve problems, think abstractly, comprehend complex ideas, learn quickly, and learn from experience. Intelligence is not merely book learning or test-taking smarts. Rather, intelligence reflects a broader and deeper capability to comprehend our surroundings—to “catch on,” “make sense” of things, or “figure out” what to do.

Individuals differ from one another in their abilities to understand complex ideas, adapt effectively to the environment, learn from experience, engage in various forms of reasoning, and overcome obstacles by “taking thought.” We have different intelligence quotients (IQs). One’s IQ is computed based on the norm for his or her age group and circumstances. That norm is assigned a value of 100. Therefore, one’s IQ can be either above or below 100. Although differences between individuals can be substantial, IQ is never entirely consistent among humans. One’s intellectual performance will vary on different occasions, in different domains, and as judged by different criteria (http://www.unn.edu.ng/publications/files/ABULOKWE%20AMAECHI%20CLEMENT.pdf).

The widely varying human capacity to learn, store, and recall information can be illustrated by game shows such as Jeopardy!. Most contestants who qualify to be on the show are eliminated from the competition after a single round. Ken Jennings, however, holds the record for the longest winning streak on the show. He is also the second-highest-earning contestant in American game show history. In 2004, Jennings won 74 consecutive matches of Jeopardy! (nearly four months of appearances) before being defeated on his 75th appearance by challenger Nancy Zerg. Jenning’s total earnings on Jeopardy! were $3,196,300, consisting of $2,520,700 over his 74 wins; a $2,000 second-place prize in his 75th appearance; a $500,000 second-place prize in Jeopardy! Ultimate Tournament of Champions; a $100,000 second-place prize in Jeopardy! Battle of the Decades; as well as half of a $300,000 prize in the IBM challenge, when he competed against Watson, the computer designed by IBM engineers.

The Oxford English Dictionary and Intelligence

According to the Oxford English Dictionary (www.oxforddictionaries.com), intelligence is the ability to acquire and apply knowledge and skills. Intelligence is also a person or being with the ability to acquire and apply knowledge and skills, according to Oxford. Further, intelligence is the collection of information of military or political value, and it is also the people employed in the collection of military or political information (The Oxford American Dictionary and Language Guide, New York: Oxford University Press, 1999). From the Oxford English Dictionary Online comes the following discussion of the U.S. Central Intelligence Agency and the gathering of covert intelligence: “the launching of the Central Intelligence Agency (CIA) on 18 September 1947 signaled an American addition to the customary use of the word intelligence.” Referring to mental capacity, the word had carried one of two principal meanings. The first, archaic by 1947, simply indicated news. The second meaning covered information, at least partly clandestine and sometimes processed and analyzed, that might be of strategic importance (oed.com, August 15, 2019).

The advent of the CIA encouraged an additional meaning that had already been gathering pace and would solidify in the near future. The expanded definition came to embrace not just the gathering and cognitive processes but action as well. First in CIA parlance and then in general American usage, intelligence came to include covert operations, or the effort to influence politics in foreign countries by undercover means.

Deployment of the word intelligence was a way of making covert action more respectable. The battle was already half-won, as covert operations had come to be accepted and even admired in the Second World War, and the anxieties generated by the Cold War were predisposing people to accept peacetime practices that they might previously have questioned. But intelligence still had a better reputation than covert operations. It had come to be seen as a magic wand. There was a widespread belief that had U.S. intelligence not been in disarray, it could have prevented the Japanese attack on Pearl Harbor. Equally popular was the belief that improved intelligence had helped achieve victory in the naval battle of Midway and in the wider war. The word intelligence came to confer a respectability behind which the dirtiest of “dirty tricks” could hide (The Oxford American Dictionary and Language Guide, New York: Oxford University Press, 1999; accessed August 15, 2019).

Merriam-Webster’s Learners Dictionary and Intelligence

According to Merriam-Webster (learnersdictionary.com), intelligence is “the ability to learn or to understand or to deal with new or trying situations; reason; also the skilled use of reason; the ability to apply knowledge to manipulate one’s environment or to think abstractly as measured by objective criteria” (as tests; Merriam-Webster’s Collegiate Dictionary, deluxe edition, 1998). The innate ability to “solve problems,” “overcome obstacles,” and “deal with trying situations” is among the definitions I will use to describe our intelligent bodies at the organ systems, organ, tissue, cell, subcellular, and even molecular levels. In arguing this way, I hope to persuade the reader that signs of intelligence as defined here and above are found ubiquitously throughout the human body. As a disclaimer, however, I do not think that each cell or subcellular organelle has its own little brain.

Physical and Physiological Concepts That Imply Intelligence

Homeostasis—Walter B. Cannon (October 19, 1871–October 1, 1945) was an American physiologist who chaired the department of physiology at Harvard University circa 1906 to 1942. He was president of the American Physiological Society from 1914 to 1916. Cannon wrote the book The Wisdom of the Body that was first published in 1932. In his book and elsewhere, Cannon championed and popularized the idea of “physiological homeostasis” (extended from Claude Bernard’s ideas of the constancy of the body’s internal environment, i.e., the milieu interieur).

In 1915, Cannon coined the phrase “fight or flight” to describe an animal’s response to threats. He outlined four tentative propositions to describe the general features of homeostasis:

1. 1. Constancy in an open system, such as our bodies, requires mechanisms that act to maintain this constancy. Cannon based this proposition on insights into the ways by which steady states—such as glucose concentrations (blood sugar), body temperature, and acid-base balance—are regulated.
2. 2. Steady-state conditions require that any tendency toward change automatically meets with factors that resist change. An increase in blood sugar (a potential problem) results in thirst as the body attempts to dilute the concentration of sugar in the extracellular fluid. It also results in the release of insulin as the body helps the cells acquire access to elevated glucose.
3. 3. The regulating system that determines homeostasis consists of a number of cooperating mechanisms acting simultaneously or successively. Blood sugar is regulated by insulin, glucagon, and other hormones that control its circulating concentrations in the plasma, its release from the liver, and its uptake by the tissues (the solution to the problem of excess or insufficient circulating concentrations of blood sugar).
4. 4. Homeostasis occurs not by chance but by the result of organized self-government and physiological intelligence.

Cannon’s proposition number four above sounds like an application of intelligence as defined earlier. So the processes of elevations in blood sugar (following ingestion of a meal), stimulation of thirst, balanced and coordinated release of insulin from the pancreas, and later release of glucagon from the liver are all part of an organized, self-governing, intelligent system functioning at the molecular, subcellular, cellular, tissue, and organ-systems levels. The physiological end results of such coordination are homeostasis of circulating concentrations of blood sugar, energy balance, and sustained health and well-being of the body. Homeostatic regulation of blood sugar is only one part of an endless list of physiological functions that intelligently sustain our physical bodies. Here is a short list of others I will describe in later chapters: body water and its distribution, blood flow and its regulation, body salt and electrolyte balance, and control of blood pressure.

According to Cannon, steady-state conditions require that any tendency toward change automatically meets with factors that resist change. A physiological process that is in the steady state is one that is not changing with time. Consider your own blood pressure. When you go for your annual medical examinations, you might be more or less excited. Perhaps you are anxious about being on time, being delayed in traffic, or missing work. You might park the car then walk briskly to the doctor’s office. By the time the nurse escorts you into the examination room, wraps a pressure cuff around your upper arm, and listens for sounds as she deflates the cuff, your blood pressure is probably elevated. It would not be unusual for the nurse to call out numbers such as 135 over 85 or 140 over 90, especially in patients other than young adults, teens, and children. These numbers for systolic and diastolic pressures are on the modestly high side of normal. Even though elevated blood pressure is common with aging in older people, the above numbers can be nerve-racking during a hurried doctor’s visit.

On occasions when I have been lying quietly for 15–20 minutes on an examination bed in my own laboratory, a research assistant (or other student being trained how to monitor blood pressure) can measure my blood pressure, and the numbers are about 120 over 80. These are noticeably lower than those mentioned above, and they fall within the physiological range for a healthy adult. The two sets of data were obtained under widely differing conditions. In the doctor’s examination room, we are usually seated and often nervous about what lies ahead. Under such conditions, neither we nor our cardiovascular systems are in Cannon’s “steady state.”

Conversely, when lying quietly on my own examination bed, none of the above disturbances apply. If my research assistant measures my blood pressure immediately after instrumenting me, then again at 5-minute intervals during a 15–20 minute period, he will most likely find my pressures elevated on the first trial, a bit lower on the next, and not changing in the third and fourth measurements. In other words, after 15–20 minutes of resting quietly in the supine position, the physiological factors that regulate my blood pressure have reached Cannon’s “steady-state” conditions, and my cardiovascular system is in a state of homeostasis.

Alternatively, if I have a 1-gallon container filled with water then punch a hole in the bottom of the container, the water will flow out at a rate determined by gravity and the size of the hole. The larger the hole, the greater the rate of flow, and the less time it will take for the water to escape. If I have a stopwatch and a graduated cylinder, I can collect some of the escaping water and calculate its rate of flow from the container. Imagine the hole is a small one and the rate of outflow is 100 milliliters per minute. After about 20 minutes at this rate, the container will have only about half its original volume (1 gallon is about equal to 4 liters or 4,000 milliliters). In 20 minutes more, the container will be empty. However, if I begin pouring water into the container when it is half empty, and if the rate of inflow (pouring) is 100 milliliters per minute, then the rates of inflow and outflow will be equal, and the container will remain half full for as long as the exercise is sustained. At such a point in time, the volume of water in the container is said to be “in equilibrium” because the two rates of flow are equal.

Now imagine that we substitute the 1-gallon container with a 1.25-gallon human circulatory system and the blood in it (about 5 liters). Imagine also that one’s heart pumps those 1.25 gallons of blood around the entire system each minute. This rate of circulation, called the cardiac output, supplies the needs of all organs and tissues of the body with nutrients and oxygen each minute. The same circulating volume also removes waste products from the respiring cells and delivers them to excretory organs (e.g., carbon dioxide is exhausted by the lungs, and excess water and electrolytes are excreted by the kidneys). Under steady-state, homeostatic conditions, the rates of supply and demand for oxygen, as one example, are equal, and the body is in physiological harmony for oxygen. But what happens if we “punch a hole” in this circulatory container?

When blood is lost from the circulatory system faster than it can be replaced, the person is hemorrhaging. Hemorrhage leads to a reduced volume of circulating blood and to a state of hypovolemia (low blood volume). Hypovolemia causes a fall in blood pressure and a reduced supply of oxygen and nutrients to the tissues. Without the homeostatic mechanisms described by Cannon and others, this person could bleed to death. With homeostasis, the proper physiological adjustments will be made, and the person will survive.

Beyond Humans: Animal Intelligence

Solomon said about ants, “Go to the ant, thou sluggard; consider her ways and be wise” (Proverbs 6:6), and “The ants are a people not strong, yet they prepare their meat in the summer” (Proverbs 30:25). While thinking about animal intelligence, one biologist wrote that ants are so much like humans that they are an embarrassment to us. They farm fungi, raise aphids as livestock, launch armies to war, use chemical warfare (sprays) to alarm and confuse enemies, capture slaves, engage in child labor, and endlessly exchange information. The world of the ant has been intensely scrutinized in recent decades. And the notion that ants demonstrate signs of cognition has not been lost on these investigations. It is increasingly clear that some scientists have taken King Solomon’s advice to heart.

Among ants, chemical communication can be compared to the human use of auditory, tactile, and visual communication. We shake hands to greet one another, and we give directions using fingers, arms, head nods, and other gestures. With ants, however, there is no cultural transmission of communication. For them, everything must be encoded in their genes. In humans, only basic instincts are carried in the genes of a newborn. Additional skills must be learned from other members of the community as the child grows and develops. It might seem that this cultural continuity gives us a great advantage over ants. However, ants’ fungus-farming and aphid-herding crafts are sophisticated when compared to the agricultural skills of humans millennia or even centuries ago. The farming methods of ants have at least been sustainable since Solomon’s time.

Intelligently, ants do not litter the environment with plastic bags, sandwich wrappers, plastic bottles, and cigarette butts. Moreover, recent evidence suggests that the crop...

Table of contents

• Cover
• Title Page
• Copyright Page
• Contents
• Preface
• Chapter 1. Intelligence
• Chapter 2. Physiology of Light and Vision
• Chapter 3. Hearing and Sound
• Chapter 4. Proprioception and Balance
• Chapter 5. Acid, Base, and pH Regulation
• Chapter 6. Cardiovascular Hemodynamics
• Chapter 7. Respiration and Its Control
• Chapter 8. Kidneys and Body Water
• Chapter 9. Gut and Nutrient Flow
• About the Author