In mammals, there are three major components of the mind with two new structures, or subroutines. Neocerebellum, added to the cerebellum, looks like a growth at the base of the brain. The neocortex, therefore, is a product of the forebrain. Most mammals, though they have a neocortex, the additions are not large as relative to the brain stem. In the primate order, of which we are a part, they are larger; in humans, the neocortex is so large that the brain stem is hidden by a complicated mass of gray, neural matter. This remarkable increase of neocerebellar activity and neocortical tissue, gives humans the highest ratio of brain to body of all of nature’s children.
The mind, that noble faculty, that lavishes our exaltation is an organ made of different subset systems for differing mental processes. It contains millions of neurons and nerve cells, which transmit signals within the brain and to the body. Neurons connect through cellular junctions, the synapses, which allow neurons to transmit chemical signals across the active mind. When a cell receives a chemical signal, it changes. This leads to the bioelectrical signal through the cell. The mechanism of action relies on elemental activity sending bioelectric signals.
Sodium is a key element within a nerve cell. Dissolved sodium ions can be found in water and around nerve cells and pass in and out of the cell through proteins at the cell surface–the protein ion-channels. Before the initiation of action potential, the area surrounding the nerve cell contains a higher concentration of sodium than the cell itself. When chemical signals are interpreted by a nerve, sodium channels in the receiving nerve began to open as sodium enters the nerve cell. Sodium signals are the beginning of the active potential and starts with bioelectric signals within the cell. This mechanism is called depolarization.
The second part of the active / action potential is carried out by potassium. At the beginning of the action motive, potassium becomes high in concentration relative to the nerve cell and then allows it to return to its natural state. Depolarization and repolarization involves the occurrence of sodium and potassium at several times along the length of a receptive neuron, when the signal reaches the cell body and triggers a nerve response.
The third part of this abstract is the role of calcium in bioelectrical signals, signals which play a role in releasing chemicals into nerve synapses. This allows for chemical signals to be translated to the actuated potentiality. Calcium, like sodium, is another type of ion. It controls the release of chemical signals into the synapse; this activates the action potentiality; this allows calcium ions to enter the cell and, in doing so, causes chemicals, the neurotransmitters, to be released into a synapse wherein they behind to the receptive neuron and invoke bioelectric potentiality. Calcium is an ion, and controls the release of signals into the synapse to initiate active potentiality. Calcium ion channels transmit chemical signal on the surface of an open neuron. This allows calcium to enter the cell.
This addition of calcium causes neurotransmitters to be released into the synapse where they bind to the receptive neuron and initiate a bioelectric active potentiality. In addition, calcium plays a significant role in signaling long chains of nerve cells. When a cell begins as an active potential, the release of calcium produces chemical signals to neighboring cells. This leads transmission of bioelectric signals from one cell to another and, eventually, links to millions of cells to allow for the brain’s bioelectrical current.
In defining chemical elements of the mind, one would be remiss to dismiss dopamine, so I will describe the mechanism and its action among pathways. There are three primary corridors for transmission. The first is the mesolimbic pathway. This is how dopamine is translated from the ventral legmental area to the nucleus accumbens in the limbic system. This is, in essence, the reason for some, but not all, emotions, responses to joy, and fondness of pleasurable memories. It is this chemical Sigmund Freud referred to as the ‘Pleasure Principle.’ Therefore, through the passageway, it becomes more active in extroverts than introverts and cautious people. It is in the pathways of the limbic system where our memory takes shape; it achieves this by the integration of strong emotion (favorable) and memories of physical sensations, the mental simulation of a prior event. The simulation of coming events.
The mesocortical pathway transmits dopamine from the ventral legmental area to the frontal cortext. Dysfunctions of dopamine receptors in the prefrontal lobe can lead to schizophrenia. The third method, associated with the nigrostrital pathway, transmits dopamine from the substantia nigra to the stratum. This pathway is associated with motor control, right and left handedness, and builds the mind’s image of its carrier body. There are many people, since this is quite common, have, after losing a limb, the feeling of the limb still being there, the ‘phantom limb.’ It’s not that they imagine that it’s there and it’s not, it’s part of the architectural map the mind makes based on feedback from the nerve endings along the body that gives the ghostly feeling.
The final pathway is called the tuberoinfundibular pathway and it transmits dopamine from the hypothalamus to the pituitary gland and influences the secretion of certain hormones, hormones such as prolactin. The amount of this chemical directly influences mood, the growth of hair, and even weight. These four operating mechanisms of dopamine transmissions are closely intertwined with the subsystems of motivation and cognitive functions. The mesolimbic pathway is directly related to dopamine receptor transmission.
Body cells are different from neurons in the way that makes them suited for a specified role, the role of signal processing and communication. It is not too difficult to see how the mind could have evolved. There are a number of less specialized cells throughout the length of the body and in the nervous system, all specialized to carry out bioelectric function. All cells are surrounded by a membrane. This separates it from chemical composition of its interior and exterior. Chemical composition differentiation results in electrical potentiality and this causes depolarizations along the cell membrane. In most cells this depolarization doesn’t spread, but changes in the shape and arrangement of cells allows depolarization to propagate from one neuron to another, allowing quick and efficient electrochemical signals from one end of an animal to the other.
The nervous system in other animals, such as jellyfish, forms undifferentiated networks and coordinates the animals physical motion. The ‘skirt’ of a jellyfish opens and contracts in a coordinated manner. This allows the animal to move through the water. The nervous system in the Medusa jellyfish is relatively simple, a communication network which makes it possible for parts of the ‘skirt’ to open and contract.
The most simple organism with a specialized nervous system is the humble worm. It includes in its composition of distinction between the brain and the groups of nervous codons running along the length of the worm’s body. This kind of nervous system affords more complex behavior. Anterior brains connected to the nerve cord is the basic design for all organisms, from jellyfish to man, with central nervous systems. Although we can differentiate between a separate brain in these worms, it is not the case that its brain is the Operator–a concept we will come to in a later chapter. The Operator is not the Field Marshal presiding over actions of the central nervous system and body of the worm. With its brain removed, the worm is still capable of common biological functions; locomotion, burrowing, area mapping, burrowing, and mating. The same could be said of Creationists.
Ethologists, those who study animal behavior, have discovered an increased complexity in aspects of the brain and nervous system in respect to more ‘primitive’ assemblies. Giant fiber systems (found to some extent in the worms and jellyfish) allow conduction of nervous impulses which connect parts of the mind to specific appendages and muscles. These connections, or to be more precise, the genes, has influenced the evolution of the cockroaches and its understanding, by sensing movement in the air, are able to quickly escape the slowly hovering foot above them. To a roach, our movement is much slower than we perceive it. For example, if one were to look at the clouds, it seems they are barely moving. That’s based on a ‘relative’ perspective. The roach, in viewing us, sees us as barely moving–hence their ability to so ably escape our lumbering feet.
The insect mind is divided into specialized segments–again a topic we will come to later–three segments: the protocerebrum, the deutocerebrum, and the tritocerbrum. Among other organisms, insects display a wider variety of sensory receptors, more so than any other group of organisms, including vertebrates, which are sensitive to sound, odor, patterns, pressure, temperature, patterns of light, and the chemical composition of their surroundings.
These sensory organs allow for rapid communication within the tiny, capable brain located within.
Small by primate standards, abilities made possible by the insect brains are impressive. The insects are capable of a wide variety of complex behavior and movement. Locomotion, mating, aiding the survival of their progeny; they crawl, swim, fly, hop, burrow and even walk on water. Take for example the strategy of a female wasp when hunting for a host body. First it paralyzes the caterpillar with its venom and lays its eggs inside of the catatonic caterpillar. This is done so the offspring, ass thy grow, they will have plenty of food after hatching. The larvae eats all the muscles and fatty tissue, but saves the heart and lungs for last, when the wasp reaches maturity, it abandons the dead caterpillar. This relationship, in nature, is called symbiosis. It is another topic we will return to.
A species known as the Leafcutter ant harvest leaves. The leaves are brought into the nest and are used to cultivate gardens of fungus. The interesting thing about the Leafcutter ants is its metabolism; the food that it does it, is indigestible and the ants lack the enzyme in their stomach to process it. The way they get around this is by harvesting the mushrooms that grow on their dung. These ants aren’t the only species to have learned and exploited this trait.
Honeybees are social animals. There are different castes of society, workers, food gatherers, and soldier ants whose purpose is to protect the queen. When a spot of abundant food is found, the bees perform a kind of dance that signals to the other ants a location wherein there is a richness of food. This is the evolution of their brains, with complementary evolution of other body parts (phyla), and this has made insects the most numerous multicellular organism on planet Earth.
The brain is much larger and complex in vertebrates such as reptiles and amphibians. The spinal cord is protected within the vertebrae of the backbone. This has become a servant to the brain, a type of two-way highway of communication with different electrical connections separated in descending motor pathways and ascending sensory input differentiation. The brain, in vertebrates, is composed of a swelling of the anterior end of the spinal cord, the brain stem, the three major ones make up the three major parts of the vertebrae brain: the hindbrain, midbrain, and forebrain. The cerebellum is a distinct structure attached to the hindbrain.
Once a nerve cell has become differentiated it does not divide anymore. A single nucleus, with the same DNA, must serve an entire lifetime for the formation and maintenance of tens of thousands of synapses. It seems difficult to imagine a differential distribution of genetic material from a single nucleus to each of these tens of thousands of synapses unless we conjure up a mysterious “demon” who selectively channels this material to each synapse according to a pre-established code! The differential expression of genes cannot alone explain the extreme diversity and specificity of connections between neurons.
Additional understanding of the relation between the genome and the nervous system can be gained by considering Daphnia magna. Commonly referred to as the water flea or daphnid, this small fresh-water crustacean is familiar to many aquarium owners since it is relished by tropical fish. But what makes the daphnid interesting for our current purposes is that when the female is isolated from males, she can most conveniently reproduce by the asexual process of parthenogenesis, giving birth to genetically identical clones. In addition, the daphnid has a relatively simple nervous system that facilitates its study.
If its genome completely controlled the development of its nervous system, it should be the case that genetically identical daphnids should have structurally identical nervous systems. However, examination of daphnid eyes using the electron microscope reveals that although genetically identical clones all have the same number of neurons, considerable variation exists in the exact number of synapses and in the configurations of connections leading to and away from the cell body of each neuron, that is, the dendritic and axonal branches. As we move to more complex organisms, the variability of their nervous systems increases. This provides clear evidence that the structure and wiring of the nervous system are not the result of following a detailed construction program provided by the genes.
A particularly striking example of neuronal elimination in development involves the death of an entire group of brain cells: Most frequently, neuron death affects only some of the neurons in a given category. However, in one case a whole category of cells died. These particular neurons of layer I, the most superficial layer of the cerebral cortex, characteristically have axons and dendrites oriented parallel to the cortical surface rather than perpendicular to it, like the pyramidal cells. These cells were first observed in the human fetus but have since been found in other mammals. Purely and simply, they disappear in the adult.