Multipolar neurons: Search for multipolar neurons in glass slide 48 in your Histology slide box, cerebellar cortex of pig Golgi stain. Note: Three layers are recognized in the cerebellar cortex superficial gray matter of the cerebellum : 1 an outer molecular layer composed of few cells and many nonmyelinated fibers, 2 an intermediate layer comprised of flask-like cell bodies called Purkinje cells , which are multipolar neurons , and 3 an inner granular layer composed of tightly-packed cells and fibers.
Question: Why is the Purkinje cell considered a multipolar neuron? All multipolar neurons have two characteristics: -- more than two processes emanate from the cell body, and -- the cell body receives synaptic input just like the dendrites.
Neurons Three major categories of neurons are recognized: Bipolar neurons are relatively rare. The arrow points to an axon of a Purkinje neuron. At middle of the slide, cell bodies of three Purkinje cells neurons are visible as black, rounded, profiles. Cell processes, termed dendrites , extend superficially from the cell body into the molecular layer.
A small axon arrow emerges from each cell body and runs through the granue cell layer. Motor neurons of the spinal cord are part of the central nervous system CNS and connect to muscles, glands and organs throughout the body. These neurons transmit impulses from the spinal cord to skeletal and smooth muscles such as those in your stomach , and so directly control all of our muscle movements.
There are in fact two types of motor neurons: those that travel from spinal cord to muscle are called lower motor neurons, whereas those that travel between the brain and spinal cord are called upper motor neurons. As the name suggests, interneurons are the ones in between - they connect spinal motor and sensory neurons. As well as transferring signals between sensory and motor neurons, interneurons can also communicate with each other, forming circuits of various complexity.
They are multipolar, just like motor neurons. In the brain, the distinction between types of neurons is much more complex. Certainly, there are brain neurons involved in sensory processing — like those in visual or auditory cortex — and others involved in motor processing — like those in the cerebellum or motor cortex.
However, within any of these sensory or motor regions, there are tens or even hundreds of different types of neurons. In fact, researchers are still trying to devise a way to neatly classify the huge variety of neurons that exist in the brain. Looking at which neurotransmitter a neuron uses is one way that could be a useful for classifying neurons.
However, within categories we can find further distinctions. Some GABA neurons, for example, send their axon mostly to the cell bodies of other neurons; others prefer to target the dendrites. Furthermore, these different neurons have different electrical properties, different shapes, different genes expressed, different projection patterns and receive different inputs.
In other words, a particular combination of features is one way of defining a neuron type. 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. An early progenitor cell does not have the potential of a stem cell to make many different types of cells.
It can only make cells in its particular lineage. Early progenitor cells can self-renew or go in either of two ways. One type will give rise to astrocytes. The other type will ultimately produce neurons or oligodendrocytes.
Not all neurons are successful in their journey.
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