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Many bipolar cells are specialized sensory neurons (afferent neurons) for the transmission of sense. As such, they are part of the sensory pathways for smell, sight, taste, hearing, touch, balance and proprioception. The other shape classifications of neurons include unipolar, pseudounipolar and multipolar. During embryonic development ...
Humans have between 10 and 20 million olfactory receptor neurons (ORNs). [3] In vertebrates, ORNs are bipolar neurons with dendrites facing the external surface of the cribriform plate with axons that pass through the cribriform foramina with terminal end at olfactory bulbs.
Bipolar neurons have two main dendrites at opposing ends of the cell body. Many inhibitory neurons have this morphology. Unipolar neurons, typical for insects, have a stalk that extends from the cell body that separates into two branches with one containing the dendrites and the other with the terminal buttons.
The newly generated neurons migrate to different parts of the developing brain to self-organize into different brain structures. Once the neurons have reached their regional positions, they extend axons and dendrites, which allow them to communicate with other neurons via synapses.
Neurons may lack dendrites or have no axons. The term neurite is used to describe either a dendrite or an axon, particularly when the cell is undifferentiated. Most neurons receive signals via the dendrites and soma and send out signals down the axon. At the majority of synapses, signals cross from the axon of one neuron to the dendrite of another.
The development of the nervous system in humans, or neural development, or neurodevelopment involves the studies of embryology, developmental biology, and neuroscience.These describe the cellular and molecular mechanisms by which the complex nervous system forms in humans, develops during prenatal development, and continues to develop postnatally.
Neuroimaging and postmortem studies have found abnormalities in a variety of brain regions, and most commonly implicated regions include the ventral prefrontal cortex and amygdala. Dysfunction in emotional circuits located in these regions have been hypothesized as a mechanism for bipolar disorder. [1]
Neurons are necessary for all connections made in the brain, and thus can be thought of as the "wires" of the brain. As in computing, an entity is most efficient when its wires are optimized; therefore, a brain which has undergone millions of years of natural selection would be expected to have optimized neural circuitry.