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Axons often follow very precise paths in the nervous system, and how they manage to find their way so accurately is an area of ongoing research. Axon growth takes place from a region called the growth cone and reaching the axon target is accomplished with relatively few guidance molecules. Growth cone receptors respond to the guidance cues.
In neuroscience, the axolemma (from Greek lemma 'membrane, envelope', and 'axo-' from axon [1]) is the cell membrane of an axon, [1] the branch of a neuron through which signals (action potentials) are transmitted. The axolemma is a three-layered, bilipid membrane. Under standard electron microscope preparations, the structure is approximately ...
The Schaffer collateral is located between the CA3 region and CA1 region in the hippocampus. Schaffer collaterals are the axons of pyramidal cells that connect two neurons (CA3 and CA1) and transfer information from CA3 to CA1. [5] [6] The entorhinal cortex sends the main input to the dentate gyrus (perforant pathway).
Established collateral branches, like the main axon, exhibit a growth cone and develop independently of the main axon tip. Overall, axon elongation is the product of a process known as tip growth. In this process, new material is added at the growth cone while the remainder of the axonal cytoskeleton remains stationary.
Cross section of an axon: (1) Axon (2) Nucleus (3) Schwann cell (4) Myelin sheath (5) Neurilemma. In the nervous system, axons may be myelinated, or unmyelinated. This is the provision of an insulating layer, called a myelin sheath. The myelin membrane is unique in its relatively high lipid to protein ratio. [17]
[1] [2] [3] In the peripheral nervous system, this is known as a nerve fascicle, and has associated connective tissue. The main nerve tracts in the central nervous system are of three types: association fibers, commissural fibers, and projection fibers. A nerve tract may also be referred to as a commissure, decussation, or neural pathway. [4]
Such a pathway can trigger the assembly of new molecules, such as a fat or protein. Pathways can also turn genes on and off, or spur a cell to move. [1] Some of the most common biological pathways are involved in metabolism, the regulation of gene expression and the transmission of signals. Pathways play a key role in advanced studies of genomics.
A reconstruction of a pyramidal cell. Soma and dendrites are labeled in red, axon arbor in blue. (1) Soma, (2) Basal dendrite, (3) Apical dendrite, (4) Axon, (5) Collateral axon. One of the main structural features of the pyramidal neuron is the conic shaped soma, or cell body, after which the neuron is named.