A bipolar cell is a type of neuron which has two extensions. Bipolar cells are specialized sensory neurons for the transmission of special senses. As such, they are part of the sensory pathways for smell, sight, taste, hearing and vestibular functions They are found in the vestibulocochlear nerve, but reference to bipolar neurons is usually to cells in the retina.
A unipolar cell is a type of neuron in which only one protoplasmic process (neurite) extends from the cell body.Most neurons are multipolar, generating several dendrites and an axon: unipolar neurons are exceptions to this rule. These would be primary sensory neurons such as the ones found in the dorsal root ganglion. A multipolar neuron is a type of neuron that possesses a single (usually long) axon and many dendrites, allowing for the integration of a great deal of information from other neurons. These dendritic branches can also emerge from the nerve cell body. Multipolar neurons constitute the majority of neurons in the brain and include motor neurons and interneurons.
Dendrites are the branched projections of a neuron that act to conduct the electrochemical stimulation received from other neural cells to the cell body, or soma, of the neuron from which the dendrites project. Electrical stimulation is transmitted onto dendrites by upstream neurons (usually their axons) via synapses which are located at various points throughout the dendritic tree. Dendrites play a critical role in integrating these synaptic inputs and in determining the extent to which action potentials are produced by the neuron.Recent research has also found that dendrites can support action potentials and release neurotransmitters, a property that was originally believed to be specific to axons. The soma, or perikaryon or cyton, is the bulbous end of a neuron, containing the cell nucleus.
The word "soma" comes from the Greek ???? , meaning "body"; the soma of a neuron is often called the "cell body". There are many different specialized types of neurons, and their sizes vary from as small as about 5 micrometres to over 10 millimetre for some of the smallest and largest neurons of invertebrates, respectively.The soma contains many organelles, including granules called Nissl granules, which are composed largely of rough endoplasmic reticulum and free polyribosomes. The cell nucleus is a key feature of the soma. The nucleus is the source of most of the RNA that is produced in neurons.
In general, most proteins are produced from mRNAs that do not travel far from the cell nucleus. Nucleus - Derived from the Latin word for "nux", nut, the nucleus is the archivist and the architect of the cell.As archivist it contains the genes, consisting of DNA which contains the cell history, the basic information to manufacture all the proteins characteristic of that cell. As architect, it synthesizes RNA from DNA and ships it through its pores to the cytoplasm for use in protein synthesis.
An axon (from Greek, axis) also known as a nerve fibre; is a long, slender projection of a nerve cell, or neuron, that typically conducts electrical impulses away from the neuron's cell body. The function of the axon is to transmit information to different neurons, muscles and glands.In certain sensory neurons (pseudounipolar neurons), such as those for touch and warmth, the electrical impulse travels along an axon from the periphery to the cell body, and from the cell body to the spinal cord along another branch of the same axon. Axon dysfunction causes many inherited and acquired neurological disorders which can affect both the peripheral and central neurons. Myelin is a dielectric material that forms a layer, the myelin sheath, usually around only the axon of a neuron.
It is essential for the proper functioning of the nervous system.It is an outgrowth of a type of glial cell. The production of the myelin sheath is called myelination. In humans, the production of myelin begins in the 14th week of fetal development, although little myelin exists in the brain at the time of birth. During infancy, myelination occurs quickly and continues through the adolescent stages of life Schwann cells supply the myelin for peripheral neurons, whereas oligodendrocytes, specifically of the interfascicular type, myelinate the axons of the central nervous system.In the nervous system, a synapse is a structure in the neuron that permits a neuron to pass an electrical or chemical signal to another cell .
Santiago Ramon y Cajal proposed that neurons are not continuous throughout the body, yet still communicate with each other, an idea known as the neuron doctrine. The word "synapse" comes from "synaptein", which Sir Charles Scott Sherrington and colleagues coined from the Greek "syn-" . Synapses are essential to neuronal function: neurons are cells that are specialized to pass signals to individual target cells, and synapses are the means by which they do so.
