During the real MCAT, advanced-level topics - beyond the detailed list below - will certainly be explored, typically within a passage.
But it was not until after World War II that neuroscience began to emerge as a separate and increasingly vigorous scientific discipline that has as its ultimate objective providing a satisfactory account of animal including human behavior in biological terms.
This ambitious goal has as its basis the central realization that all behavior is, in the last analysis, a reflection of the function of the nervous system. It is the organized and coordinated activity of the nervous system that ultimately manifests itself in the behavior of the organism.
The challenge to neuroscience then, is to explain, in physical and chemical terms, how the nervous system marshalls its signaling units to direct behavior. The real magnitude of this challenge can perhaps be best judged by considering the structural and functional complexity of the human brain and the bewildering complexity of human behavior.
The human brain is thought to be composed of about a hundred billion nerve cells and about 10 to 50 times that number of supporting elements or glial cells. Some nerve cells have relatively few connections with other neurons or with such effector organs as muscles or glands, but the great majority receive connections from thousands of other cells and may themselves connect with several hundred other neurons.
This means that at a fairly conservative estimate the total number of functional connections known as synapses within the human brain is on the order of a hundred trillion But what is most important is that these connections are not random or indiscriminate: They constitute the essential "wiring" of the nervous system on which the extraordinarily precise functioning of the brain depends.
One major objective of modern neuroscience is therefore to unravel the patterns of connections within the nervous system—in a word, to map the brain. A second, related objective is to identify the differences that exist between nerve cells.
For although nerve cells have a number of properties in common—especially their abilities to respond to signals from other cells and to conduct signals along their processes—on morphological grounds alone, thousands of different classes of nerve cells are evident.
The morphological differences were the first to be recognized once techniques had been developed that reveal the form of individual neurons. Some cells were found to have only a single process, others just two processes, and still others—including the overwhelming majority of neurons in the brains of vertebrates—have several, often scores, of processes.
In most cases we can recognize a single process, the axon, that serves to conduct information—usually in the form of all-or-none signals known as action potentials or nerve impulses—to other cells. Variable numbers of receptor processes or dendrites receive information from other cells, integrate it, and relay it to the nerve cell body and beyond it to the axon.
But it is not only in the morphology of the processes that nerve cells differ. We now know that dozens of different classes of neurons can be recognized on the basis of the chemical messengers or neurotransmitters that they use to communicate with other cells.
The discovery in the early s that almost all nerve cells communicate with each other through the release of chemical neurotransmitters at specialized sites along the course and at the ends of their axons was one of the major events that marked the beginning of modern neuroscience.
Only in the past decade, however, have we come to realize that there may be not just a handful of chemical transmitters as was once thought, but perhaps a hundred or more, and that it is the subtle and distinctive actions of these transmitters that account for much of the functional complexity of the nervous system.
We have also come to realize that neurotransmitters can act upon other cells only if the cells have the necessary receptors to selectively bind the neurotransmitter. The interaction of the neurotransmitter with its appropriate receptor is what initiates the response of the target cell.
Again, it is only in the past few years that we have come to appreciate that the target cells can respond in several different ways depending on the nature of the transmitter, the types of receptors involved, and the mechanisms that the transmitter-receptor interaction activates.
In some cases the response of the target cells is rapid and transitory, with a time course of just a few thousandths of a second; in other cases the cell responds over a fairly long period—perhaps many seconds; and in certain situations the behavior of the target cell may be modified for many hours, or even days and weeks.
A third major task of neuroscience, therefore, is to understand how nerve cells generate signals, often over long distances, and how these signals change the various target cells with which the neurons are in functional contact.
The cellular and molecular mechanisms involved in nerve signaling and synaptic transmission are currently among the most intensively studied and best understood aspects of neuroscience.
Less well understood, but no less important, are the longer term changes in nerve cells that must underlie the acquisition and storage of information that we commonly refer to as learning and memory.
Although there is a vast body of literature on human learning and memory and on the effects of damage to various parts of the brain on its ability to acquire, store, and retrieve information, it is only relatively recently that the longer term effects of synaptic activity that must be involved in these processes have begun to be studied at the cellular and molecular levels.
The first insights that we have gained into these processes suggest that a wide variety of behavioral phenomena may well prove to be explicable on the basis of just a few general mechanisms such as the covalent modification of particular molecules involved in nerve signaling or the activation of specific genes and the synthesis of new proteins.
A fourth major objective of neuroscience is to account for the unusual cell biology of neurons. Although nerve cells share many properties with other cells, their special roles in the transduction of sensory information, in the transmission of signals over considerable distances, in being able to respond to signals from other cells, and, in turn, in being able to modify the activity of their target cells imposes on neurons a number of highly specialized functions.
These considerations raise a number of intriguing questions including 1 how the enormous phenotypic diversity seen among nerve cells is generated, 2 how different parts of each neuron become specialized to either receive or transmit signals, 3 how nerve cells are able to maintain such lengthy processes given that the genetic information is confined to the cell nucleus and most of the synthetic machinery is confined to the relatively small cell body, 4 how communication is maintained between the nerve cell body and its various processes, and 5 what changes occur in the cells in response to "experience" and aging.
The fact that most neurons have to survive and continue to function effectively throughout the life of the organism—for 70 or more years in the case of neurons in the human brain—is one of their most impressive characteristics. Recent developments in molecular and cell biology are beginning to influence the study of these phenomena, and there is every reason to be confident that they will soon be as well understood as the mechanisms involved in impulse conduction and synaptic transmission.
Undoubtedly the greatest challenge to contemporary and future neuroscience is to understand what might be referred to as the "information-processing" capacity of the brain—to determine how the various systems within the brain are organized and function to direct and mediate such behavioral phenomena as sensory perception, language function, motor actions, emotion, cognition, and thought.
Again, although we know from clinical neurology and pathology that the destruction of certain areas of the brain seriously impairs or effectively abolishes these capacities, how these higher functions are normally carried out remains largely unknown. That it has been possible to produce machines that can duplicate some aspects of these higher brain functions has suggested that developments in computer science and especially artificial intelligence may inform our understanding of how the brain functions in much the same way as molecular and cellular neuroscience have been informed by concurrent developments in molecular and cell biology.
But this remains to be seen, and for the present the single greatest challenge to neuroscience is to elucidate how the brain works.Sep 28, · The Nervous System and Human Behavior.
The human nervous system is can be viewed in two parts, which include the CNS (central nervous system) and the PNS (peripheral nervous system).
The brain and the spinal chord comprise the CNS, whereas the PNS connects the rest of the body, such as vital organs to the spinal chord and the ashio-midori.coms: 4. The nervous system has several parts, but the autonomic nervous system is what controls a number of our behaviors through the flight or fight branch or the slow down branch.
The fight or flight response, also called the sympathetic branch, is what causes someones heart to pound in fear or to sweat in a moment of stressful situation.
It is the organized and coordinated activity of the nervous system that ultimately manifests itself in the behavior of the organism. The challenge to neuroscience then, is to explain, in physical and chemical terms, how the nervous system marshalls its signaling units to direct behavior.
Pearson, as an active contributor to the biology learning community, is pleased to provide free access to the Classic edition of The Biology Place to all educators and their students.
Think Twice: How the Gut's "Second Brain" Influences Mood and Well-Being. The emerging and surprising view of how the enteric nervous system in our bellies goes far beyond just processing the food.
Human nervous system - Emotion and behaviour: In order to carry out correct behaviour—that is to say, correct in relation to the survival of the individual—humans have developed innate drives, desires, and emotions and the ability to remember and learn.