Table of contents Dedication. About the authors. Learn More. Book details. Product No. ISBN Release Date September Neurons have three basic parts: a cell body and two extensions called an axon 5 and a dendrite 3. The axon looks like a long tail and transmits messages from the cell.
Dendrites look like the branches of a tree and receive messages for the cell. Neurons communicate with each other by sending chemicals, called neurotransmitters, across a tiny space, called a synapse, between the axons and dendrites of adjacent neurons. Scientists think that neurons are the most diverse kind of cell in the body. Within these three classes of neurons are hundreds of different types, each with specific message-carrying abilities. How these neurons communicate with each other by making connections is what makes each of us unique in how we think, and feel, and act.
The extent to which new neurons are generated in the brain is a controversial subject among neuroscientists. Although the majority of neurons are already present in our brains by the time we are born, there is evidence to support that neurogenesis the scientific word for the birth of neurons is a lifelong process.
Neurons are born in areas of the brain that are rich in concentrations of neural precursor cells also called neural stem cells. These cells have the potential to generate most, if not all, of the different types of neurons and glia found in the brain.
Neuroscientists have observed how neural precursor cells behave in the laboratory. The science of stem cells is still very new, and could change with additional discoveries, but researchers have learned enough to be able to describe how neural stem cells generate the other cells of the brain. Neural stem cells increase by dividing in two and producing either two new stem cells, or two early progenitor cells, or one of each.
When a stem cell divides to produce another stem cell, it is said to self-renew. This new cell has the potential to make more stem cells. When a stem cell divides to produce an early progenitor cell, it is said to differentiate. Differentiation means that the new cell is more specialized in form and function.
Additional synapses are generated everywhere and begin operating. When the signal is reinstated, the previously coordinated information routes no longer exist and, as in the case of a child, the appropriate functions need to be learned from scratch. Since they are receiving no normal signals during the phase of brain malfunction, the nerve cells also become more sensitive in an attempt to find the missing input.
Once the signals return, this means they may overreact. Visualising the microscopically minute connections between the nerve cells is a major technical challenge.
The conventional microscopic techniques currently available, such as electron microscopy, always require preliminary treatment of the nerve cells that are to undergo examination. However, this causes the nerve cells to die, so that the alterations that occur in the cells cannot be observed.
To get round this problem, Wrosch and her team have developed a high-speed microscopy process along with special statistical computer software that make it possible to visualise the communication networks of living neurons. First, a video of the cells is made whereby an image is taken every 36 milliseconds.
A special dye is used to stain the cells to ensure that the individual cells flicker whenever they receive a signal. Stay on top of latest health news from Harvard Medical School. Recent Blog Articles. Health news headlines can be deceiving. Why is topical vitamin C important for skin health? Preventing preeclampsia may be as simple as taking an aspirin.
Caring for an aging parent? Tips for enjoying holiday meals. A conversation about reducing the harms of social media. Menopause and memory: Know the facts.
0コメント