when does brain activity start in a fetus

Prenatal Development ( Read ) | Biology | CK-12 Foundation

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First Chapter

By Michael S. Gazzaniga

Central to many bioethical problems of our time is the question, When should people negotiate the moral status of the embryo? When we had to call an embryo or a fetus from us? The fertilized egg is the starting point for the entity's soon-to-be to divide that will grow into a fetus and eventually become a baby. It is given that a fertilized egg is the beginning of life of an individual. It is well to remember that it is not the beginning of life, for both eggs and sperm, before uniting, representing life as every living plant or creature represents life. But is it right to attribute the same moral status to the human embryo that one attribute to newborns or, in this case, for every human being alive? Bioethics continues to grapple with the question. The implications of the initial determination of the moral status of far-reaching, affecting abortion, in vitro fertilization, biomedical cloning and stem cell research. Rational world waiting for the resolution of this debate.

This problem shows us how the field of neuroethics exceed that classical bioethics. When an ethical dilemma involving the nervous system, either directly or indirectly, those trained in the field of neuroscience have something to say. They can peek under the lid, therefore, and help us all to understand what the real situation and not biological. Is the brain reward? Does it work in a meaningful way?

Neuroscientists studying the organ that makes us uniquely human-brain, which allows for conscious life. They are constantly seeking knowledge on what areas of the brain maintain mental mind, part of the mental thoughts, or no thoughts. So at first glance, it might seem that neuroethicists can determine the moral status of the embryo or fetus is based on the presence of the type of biological material that can support the mental life and the kind that can not be-in other words, whether the embryo has a brain that functions at a level that supports mental activity. Modern brain science is ready to answer this question, but while neurobiology may be obvious, neuroethics running problems when trying to impose a rational, scientific facts about moral issues and ethics.

The Path to Conscious Living

Once the sperm meets the egg, the embryo begins its mission: to divide and differentiate, divide and differentiate, divide and differentiate. embryo starts out as a combination of two of these cells and ultimately should be about 50 trillion cells that make up the human organism. There is no time to lose-after only a few hours, three different regions of the embryo are obvious. These areas into endoderm, mesoderm, and ectoderm, the beginning of the three layers of cells will differentiate to become all the organs and parts of the human body. Ectoderm layers cause nervous system.

As the embryo continues to grow in the coming weeks, the basis of part of the embryo called the neural tube give rise to neurons and eventually other cells of the central nervous system, while the adjacent portion of the embryo called the neural crest finally be cell- cells of the peripheral nervous system (nerves outside the brain and spinal cord). Neural tube cavity causing brain ventricles and the central canal of the spinal cord, and in Week 4 of the neural tube develops three distinct bulge corresponding to the areas that will be the three main divisions of the brain: the forebrain, midbrain, and hindbrain. The initial signs of brain begins to form.

Although the fetus is now growing area that will become a specific part of the brain, not until the end of week 5 and week 6 (usually around 40-43 days) is not the first electrical brain activity began to occur. This activity, however, is not coherent activity of the type of underlying human consciousness, or even coherent visible activity on the nervous system of this shrimp. Just as the neural activity is present in a patient is clinically brain dead, early neural activity consists of firing neurons organized from primitive types. neuronal activity by itself does not represent an integrated behavior.

During the week of 8 to 10, brain development begins in earnest. Neuron breed and begin their migration throughout the brain. Anterior commissures,which is the first interhemispheric connection (small), is also growing. Reflex appeared for the first time during this period.

polar frontal and temporal brain clear during weeks 12 to 16, and the frontal pole (the neocortex) grew disproportionately faster when compared with the rest of the cortex. Cortical surface appear flat through the third month, but at the end of the fourth month grooves, or sulci, appear. (This evolved into the familiar folds of the cerebrum.) Of different brain lobes also become clear, and the neurons continue to proliferate and migrate across the cortex. At 13 weeks the fetus has begun to move. Around this time the corpus callosum, a large collection of fibers (axons of neurons) that allows for communication between the hemispheres, began to grow, forming a major part of the infrastructure for cross talk between the two sides of the brain. However, the fetus is not alive, self-aware organisms at this time; it was more like a sea snail, squirming a reflex-bound hunk of sensory-motor processes that do not respond to anything in a directed, purposeful way. Laying the infrastructure for brain mature and has a mature brain are two very different countries become.

Synapses-point where two neurons, the basic building blocks of the nervous system, come together to interact-shape in large numbers during the seventeenth and weeks that followed, allowing for communication between individual neurons. Synaptic activity underlie all brain function. Synaptic growth does not skyrocket to about postconception day 200 (week 28). However, at about week 23 the fetus can survive outside the womb, with medical support; Also around this time the fetus can respond to aversive stimuli. The main synaptic growth continued until the third or fourth month after birth. Continues to grow as the cortical sulci begin folding to create a larger surface area and to accommodate the growth of neurons and glial cells support them. During this period, neurons begin myelinate (isolation process that accelerates their electrical communication). In the thirty-second week, the fetal brain control breathing and body temperature.

By the time a child is born, the brain largely resemble adults, but are still far from finished with the construction. cortex will continue to increase in complexity over the years, and synapse formation will continue for a lifetime.

Argument

It is quick and easy neurobiology of fetal brain development. Embryonic stages revealed that fertilized eggs are clumps of cells without a brain; a process that starts generating the nervous system does not begin until after the fourteenth day. There are no ongoing or complex nervous system in place until about six months of pregnancy.

The fact that it is clear that the human brain is not feasible until week 23, and only then with the help of modern medical support, does not seem to have an impact on the debate. This is where the neuro "logic" to lose out. Moral arguments get mixed with biology, and the result is a stew of passion, conviction, and stubborn, illogical opinion. Based on the specific questions asked, I myself have different answers about when the moral status should be given to the fetus. For example, regarding the use of embryos for biomedical research, I found fourteen day cutoff used by the researchers into a perfectly acceptable practice. However, in assessing the fetus "one of us," and granting it the right to moral and human law, I put an age much later, at the age of twenty-three weeks, when life is sustained and the fetus that can, with a bit of a relief from the neonatal unit , survive and develop into a human being with normal brain thinking. It was the same age in which the Supreme Court has ruled that the fetus be protected from abortion.

As a father, I have a reaction to the perception of the Carnegie stage of fetal development: the image of Stage 23, when the fetus is about eight weeks old, show a little human. Until that stage, it is difficult to distinguish between swine embryos and human embryo. But then-bingo-up comes an early form of the human head, and apparently one more like one of us. Again, this is about eight weeks, more than two-thirds in the first trimester. I react to the sentiment that well in my perception of time that is striking, defining, and real. However, the level of knowledge of neuroscience, it could easily be said that my view is unreasonable. Brain at Carnegie stage 23, which has slowly been growing from roughly the fifteenth day, almost no brain that can sustain any serious mental life. If grown adults suffered major brain damage, reduces the brain's level of development, the patient would be considered brain death and organ donor candidate. Society has defined the point at which the brain does not quite function is no longer viable moral status. If we look at the requirements for brain death, and examine how they compare with developmental sequence, we see that the third trimester the baby's brain, or maybe even the second trimester baby, could be analyzed. So, why do I draw the line at Carnegie stage 23, when the knowledge of neuroscience to make it clear that the brain at this stage is not ready for prime-time live?

I'm trying to make the argument neuroethical here, and I could not avoid a "gut reaction." Of course, it is my gut reaction, and others may not have it at all. In recognizing that in me, however, I can appreciate how difficult this decision for many people. Although I can not imagine, and do not have, a gut reaction to seeing the blastocyst fourteen days-old, an entity the size of the dot on the i on this page, that dot can serve as a stimulus to the belief system of those who argue that all fertilized eggs are worthy of respect we have. However, I found assign moral status equivalent to a ball-fourteen days old and for premature babies cell conceptually forced. Hold them to be together is an act of sheer personal beliefs.

Continuity and the Potential Arguments

Obviously there is a point of view that life begins at conception. The continuity of the argument is that a fertilized egg will go on to become a person and therefore worthy of individual rights, because no doubt where a particular individual's life begins. If one is not willing to parse the scene after the development, it has become one of the arguments you can not argue with. Whether you believe it or not. While they were arguing this point to try to suggest that anyone who appreciates the sanctity of human life must see things like this, the fact is that this is simply not so. This view came, for the most part, from the Catholic Church, the religious rights of Americans, and even many atheists and agnostics. On the other hand, Jews, Muslims, Hindus, many Christians, atheists and agnostics and others do not believe. Certain Jews and Muslims believe that the embryo is feasible to set the moral status of "human" after forty days of development. Many Catholics believe the same, and many have written to me expressing their views based on their own reading of church history.

When we examine the issue of brain death, which is when life ends, it is also becoming clear that something else is at work here: the needs of our own brains to trust form. If we examine how a set of accepted rational, scientific facts can lead to moral judgments differ, we see the need to consider what affect the conclusions vary, and we can begin to let go of a problem neuroethical certain of the context of arbitrary where they may initially have considered.

Different cultures see different brain death. brain death is declared medically when a patient in a coma due to brain injury-stroke, for example-and do not have a response brainstem, leading to the EEG is flat (ie, no sign of brain activity recordings electroencephalography), or the ability to breathe independently. A survey published in the journal Neurology in 2000 compared to standards and regulations to declare brain death worldwide. The concept of brain death is accepted worldwide: even in the most religious society no one argues that human life continues to exist when the brain is irreversibly to function. What is different is the procedure for determining brain death. And social differences reveal how bioethics practices and laws can vary so wildly, for reasons that have nothing to do with science, but based on politics, religion, or, in many cases, personal beliefs that are different from the task force. For example, China does not have a standard, while Hong Kong has been well defined criteria-left, no doubt, of that which has beenunder British rule. Republic of Georgia requires doctors with five years of practice neuroscience determine brain death; This is not so in Russia. Iran requires the largest number of observations in twelve, twenty-four, and thirty-six hours with three doctors; and in the United States, several states have adopted the Uniform Definition of Death Act, including New York and New Jersey, both of whom have religious objections gap.

Examples of brain death illustrates how rules and regulations on issues of bioethics can be shaped and influenced by beliefs that have nothing to do with scientific facts accepted. No one debates that the line has been crossed when a loss of brain function such that life stops. What we differ on not even when the line should be drawn-most countries have the same definition of brain death. What differs most of which make calls and what tests used-difference, basically, how do you know when you get there, where "there" is.

So, too, we all seem to agree that there should be a point where the moral status should be given to the embryo or fetus. However, it seems that we have a hard time defining that point, regardless of the facts. , , ,

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