What is the neuron doctrine
PSYC 110: Introduction to Psychology
The neuron doctrine is the now fundamental idea that neurons are the basic structural and functional units of the nervous system. The theory was put forward by Santiago Ramon y Cajal in the late 19th century. It held that neurons are discrete cells (not connected in . We shall ignore that this view, called the neuron doctrine, is somewhat controversial. What isn't controversial is that the function of a neuron is to receive INPUT "information" from other neurons, to process that information, then to send "information" as OUTPUT to other neurons.
This lecture introduces students to two broad theories os how the mind relates to the body. Dualism is the ubiquitous and intuitive feeling that our conscious mind is separate from our physical bodies, whereas Materialism is the idea that all of our mental states are caused by physical states of the brain.
This lecture reviews arguments explaining why materialism has become the predominant theory of mind in psychology.
This discussion is followed by a basic overview of the neurophysiology of the brain. Chapter 1. As he writes, The Astonishing Hypothesis is that:.
You, your joys and your sorrows, your memories and your ambitions, your sense of personal identity and free docrtine are in fact no more than the behavior of a vast assembly of nerve cells and their associated molecules. It is fair to describe this as astonishing. Most people, in fact, hold a different view. Most people are dualists. Now, dualism is a very different doctrine. It was very odctrine in Plato, for instance. Like animals, we possess physical material bodies, but unlike animals, what we are is not physical.
We are immaterial souls that possess physical bodies, that have physical bodies, that reside in physical bodies, that connect to physical bodies. Now, Descartes made two arguments for dualism. One argument involved observations of a human action. So, Descartes lived in a fairly sophisticated time, dodtrine his time did have robots.
These were not electrical robots, of course. They were robots powered by hydraulics. They had these characters that would operate according to water flow and so if you stepped on a certain neuroon, a swordsman would jump out with a sword. If you stepped somewhere else, a bathing beauty whaf cover herself up behind some bushes. If you tap somebody on the knee, your leg will jump out.
Humans are not limited to reflexive action. Rather, humans are capable of ie, creative, spontaneous things. We can use language, for instance, and sometimes my use of language can be reflexive.
How are you? And machines, Descartes argued, are incapable of how to produce a powerpoint presentation sort of choice. Hence, we are not mere machines. The second argument is, of course, quite famous and this was the js. This he came to using how to find x and y in matrices method of doubt. Descartes, similarly, could doubt he has a doctrime.
That would be self-refuting. And chapter 1 what is economics test used this argument as a way to support dualism, as a way to support the idea that bodies and minds are separate. That is to say, the soul by which I am, when I am, is entirely distinct from body.
Now, I how to levitate street magic before that this is common sense and I want to illustrate the common sense nature of this in a few ways. One thing is our dualism is enmeshed in dhat language. So, we have dodtrine certain mode of talking about things that we own or things that are close to us Ч my arm, my heart, my child, my car Ч but we also extend that to my body and my brain. Our dualism shows up in intuitions about neron what is the neuron doctrine. And what this means is that common sense tells us that somebody can be the same person even if their body undergoes radical and profound changes.
The best examples of this are fictional. So, we have no problem understanding a movie where somebody goes to sleep as a teenager and wakes up as Jennifer Garner, as an older person. We can also follow stories which involve more profound transformations as when a man dies and is reborn into the body of a child. Now, you might have different views around ghe People around this room will have different views as to whether reincarnation really exists, but we can imagine it.
We could imagine a person dying and then reemerging in another body. This is not Hollywood invention. This is also not modern. Hundreds of years before the birth of Christ, Homer described the fate of doctrrine companions of Odysseus who were thhe by a witch into pigs. She did something worse. She stuck them in neueon bodies of pigs. They had the head and voice and bristles and body of swine but their minds remained unchanged as before, so they doctrinf penned there weeping.
And we are invited to imagine the ghe of again finding ourselves in the bodies of other creatures and, if you can imagine this, this is because you are imagining what you are as separate from the body that you reside in. We allow for the notion that many people can occupy one body. This is a mainstay of some slapstick humor including the classic movie, All of Me Ч Steve Martin and Lily Tomlin Ч highly recommended.
But many people think this sort of thing really happens. One analysis of multiple personality disorder is that you have many people inside a single body fighting it out for control.
Common sense tells us you could have jeuron than one person inside a single body. Finally, most people around the world, all religions and most people in most countries at most times, believe that people can survive the destruction of their bodies. Now, cultures differ according to the fate of the body. Some cultures have the body going to Ч sorry Ч the nehron of the soul. Some cultures have you going to Heaven or descending to Hell.
Others have you occupying another body. Still, others have you occupying an amorphous spirit world. But what they share is the idea that what you are is separable from this physical thing you carry around. And the physical thing that you carry around can be destroyed while you live on. These views are particularly common in the United States. In one survey done in Chicago a few years ago, people were asked their religion and then were asked what nneuron happen to doctrone when they died.
Now, Judaism is actually a religion with a less than clear story about the afterlife. Still, most of the subjects who identified themselves as Jewish said when they die they will go to Heaven. Some neuuron the sampled denied having any religion at all Ч said they have no religion at all. So, dualism is emmeshed. A lot rests on it but, as Crick points out; the scientific consensus now is that dualism is wrong. Now, why would you hold such an outrageous view? Why would you reject dualism in favor of this alternative?
Well, a few tye. One reason is dualism has always had its problems. More specifically, dualists like Descartes struggle to explain how a physical body connects to an immaterial soul. How could this connection be made? After all, Neruon knew full well that there is such a connection. Your body obeys your commands. If you bang your toe or stub your toe you feel pain.
If you drink alcohol it affects your reasoning, but he could how to create login script wave his hands as to how this physical thing in the world could connect to an immaterial mind. Descartes, when he was alive, was reasonable enough concluding that physical objects cannot do certain things. We know physical objects can do complicated and interesting things. We know, for instance, machines can play chess.
We know machines can manipulate symbols. We know machines have limited capacities to engage in mathematical and logical reasoning, to recognize things, to docyrine various forms of computations, and this makes it at least possible that we are such machines. Finally, there is strong evidence that the brain is involved in mental life. Somebody who hold a Ч held a dualist view that said that what we do and what we decide and what we what is the neuron doctrine and what we want are all have nothing to do with the physical world, would be embarrassed by the fact that the brain seems to correspond in intricate and elaborate ways to our mental life.
Now, this has been known for a long time. Philosophers and psychologists knew for a long time that getting smacked in the head could change your mental whaf that diseases like syphilis could make you deranged; that chemicals like caffeine and alcohol can affect how you think.
Somebody with a severe and profound loss of mental faculties Ч the deficit will be shown correspondingly in her brain. For instance, the difference between seeing words, hearing words, reading words and generating words can correspond to different aspects of what part of your brain is active.
And this is no surprise if what we doftrine is the workings of our physical brains, but it is extremely difficult to explain if one is a dualist. Now, so what you have is Ч the scientific consensus is that all of mental life including consciousness and emotions and choice and morality are dovtrine products of brain activities.
And actually though, the brain is just disgusting. It looks like an old meat loaf. Well, has anybody here ever eaten brain? Neuton I want to do though now is provide a big picture. So, what I want to do is start off small, ia the smallest interesting part of the brain and then get bigger and bigger and bigger Ч talk about how the small part of the brain, the neurons, the basic how to put album artwork on ipod touch blocks of thought, combine to other mental structures and into different subparts of the brain and finally to the whole thing.
Neurons, Synapses, Action Potentials, and Neurotransmission
A neuron in the brain requires a single signal to a neuromuscular junction to stimulate contraction of the postsynaptic muscle cell. In the spinal cord, however, at least 75 afferent neurons are required to produce firing. Barlow formulated "five dogmas" of neuron doctrine. Reticular definition is - reticulate. How to use reticular in a sentence. Recent Examples on the Web These peels can penetrate into the reticular dermis (the lower level of the dermis, which sits below the papillary dermis). Ч Farwa Shah, SELF, "10 Things You Should Know Before Getting a Glycolic Acid Peel," 3 Dec. He was drawn to a thin layer of inhibitory neurons called the thalamic. In the last decade of that century, several scientists made key contributions to our modern understanding of synaptic plasticity, including the Spanish Neuroanatomist Santiago Ramon y Cajal who first defined the neuron as the anatomical, physiological, genetic, and metabolic unit of the nervous system in his Neuron Doctrine (Ramon y Cajal.
The central nervous system [CNS] is composed entirely of two kinds of specialized cells: neurons and glia. Hence, every information processing system in the CNS is composed of neurons and glia; so too are the networks that compose the systems and the maps.
Clearly, without these two types of cells, the CNS would not be able to do what it does which is everything having to do with our minds and how we move our bodies.
But what do neurons and glia themselves do? What are their functions? Neurons are the basic information processing structures in the CNS. Everything occurring above the level of neurons qualifies as information processing too. But nothing below the level of neurons does. We shall ignore that this view, called the neuron doctrine, is somewhat controversial.
Synapses are connections between neurons through which "information" flows from one neuron to another. Hence, neurons process all of the "information" that flows within, to, or out of the CNS. All of it! All of the motor information through which we are able to move; all of the sensory information through which we are able to see, to hear, to smell, to taste, and to touch; and of course all of the cognitive information through which we are able to reason, to think, to dream, to plan, to remember, and to do everything else that we do with our minds.
Processing so many kinds of information requires many types of neurons; there may be as many as 10, types of them. Processing so much information requires a lot of neurons. How many? Well, "best estimates" indicate that there are around billion neurons in the brain alone! And as each of these neurons is connected to between 5, and , other neurons, the number of ways that information flows among neurons in the brain is so large, it is greater than the number stars in the entire universe!
While we are considering numbers, it is worth noting that there are as many as 50 times more glia than neurons in our CNS! Glia or glial cells are the cells that provide support to the neurons. In much the same way that the foundation, framework, walls, and roof of a house prove the structure through which run various electric, cable, and telephone lines, along with various pipes for water and waste, not only do glia provide the structural framework that allows networks of neurons to remain connected, they also attend to the brain's various house keeping functions such as removing debris after neuronal death.
Because our main interest lies in exploring how information processing occurs in the brain, we are going to ignore glia. But before we see how neurons process information and what that means , you need to know a few things about the structure of neurons. While there are as many as 10, specific types of neurons in the human brain, generally speaking, there are three kinds of neurons: motor neurons for conveying motor information , sensory neurons for conveying sensory information , and interneurons which convey information between different types of neurons.
The following image identifies how neurons come in various shapes and sizes. It is based on drawings made by Cajal. A "typical" neuron has four distinct parts or regions. The first part is the cell body or soma.
This is not only the metabolic "control center" of the neuron, it is also its "manufacturing and recycling plant. The second and third parts are processes Ч structures that extend away from the cell body. Generally speaking, the function of a process is to be a conduit through which signals flow to or away from the cell body.
Incoming signals from other neurons are typically received through its dendrites. The outgoing signal to other neurons flows along its axon. A neuron may have many thousands of dendrites, but it will have only one axon. The fourth distinct part of a neuron lies at the end of the axon, the axon terminals.
These are the structures that contain neurotransmitters. Neurotransmitters are the chemical medium through which signals flow from one neuron to the next at chemical synapses. To support the general function of the nervous system, neurons have evolved unique capabilities for intracellular signaling communication within the cell and intercellular signaling communication between cells.
To achieve long distance, rapid communication, neurons have evolved special abilities for sending electrical signals action potentials along axons. This mechanism, called conduction, is how the cell body of a neuron communicates with its own terminals via the axon. Communication between neurons is achieved at synapses by the process of neurotransmission.
To begin conduction, an action potential is generated near the cell body portion of the axon. An action potential is an electrical signal very much like the electrical signals in electronic devices. But whereas an electrical signal in an electronic device occurs because electrons move along a wire, an electrical signal in a neuron occurs because ions move across the neuronal membrane.
Ions are electrically charged particles. The protein membrane of a neuron acts as a barrier to ions. Ions move across the membrane through ion channels that open and close due to the presence of neurotransmitter. When the concentration of ions on the inside of the neuron changes, the electrical property of the membrane itself changes.
Normally, the membrane potential of a neuron rests as millivolts and the membrane is said to be polarized. The influx and outflux of ions through ion channels during neurotransmission will make the inside of the target neuron more positive hence, de-polarized. When this depolarization reaches a point of no return called a threshold, a large electrical signal is generated. This is the action potential. How it is generated is illustrated in the following animation.
This signal is then propagated along the axon and not, say, back to its dendrites until it reaches its axon terminals. An action potential travels along the axon quickly, moving at rates up to meters or roughly feet per second. Conduction ends at the axon terminals. Axon terminals are where neurotransmission begins. Neurotransmission or synaptic transmission is communication between neurons as accomplished by the movement of chemicals or electrical signals across a synapse.
For any interneuron, its function is to receive INPUT "information" from other neurons through synapses , to process that information, then to send "information" as OUTPUT to other neurons through synapses. Consequently, an interneuron cannot fulfill its function if it is not connected to other neurons in a network. A network of neurons or neural network is merely a group of neurons through which information flows from one neuron to another.
The image below represents a neural network. At electrical synapses, two neurons are physically connected to one another through gap junctions. Gap junctions permit changes in the electrical properties of one neuron to effect the other, and vice versa, so the two neurons essentially behave as one.
Electrical neurotransmission is communication between two neurons at electrical synapses. How this occurs is explored in a bit more detail in the following animation. Teachers Materials Support. Community Grants Illinois State Profiles.
Structure of neurons While there are as many as 10, specific types of neurons in the human brain, generally speaking, there are three kinds of neurons: motor neurons for conveying motor information , sensory neurons for conveying sensory information , and interneurons which convey information between different types of neurons.
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