Answer: Bundles of axons in the central nervous system are called a "tract"
Explanation:
Axons(nerve fiber) consist of long slender projection of neurons or nerve cells that conduct and transmit impulses away from the neuron or nerve cell body. Axons are surrounded by endoneurium layer which contain protein fluid that surround each axon.
Bundles of axon in the CNS is known as tract. We have ascending tracts and descending tracts. The ascending tracts function are to conduct and carry impulses along the spinal cord to the brain while the descending tracts transmit and carry the impulses from the brain to lower regions (downward) of the body. Tracts are identified by their origin (where the bundle start) and also the end/termination of axon bundle.
The largest tracts are fasciculi gracilis and cuneatus which are known as ascending tracts.
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Answer: The diffusion of ions along the axoplasm is faster,in myelinated compare to unmyelinated,
Neurons are the structural and functioning units of nervous system.They are the vehicles for transmission of impulses as electrical signals from one part of the cells,and from one part of the body to another.
The basic structural components of a typical neuron are the cellbody, the axon, and the dendrites.
Based on structure neurons are classified as myelinated and unmyelinated.This is based on the the surrounding layer of myelin sheath around the axon. The myelin provides the insulating layer for the axon.And ensures fast movement of impluses.
In myelinated neurons the myelin sheath are interrupted at intervals by gaps along the length of the axon called Nodes of Ranvier. These gaps contains more Na-K channels for influx and out-flux of K and Na+ ions for transmission of impulses.
The cytoplasm of axon is called axoplasm,Since this is surrounded by myelin sheath which contains Na-K+ channels,The rate of diffusion of ions along these channels is faster for depolarization to take place than in unmyelinated neurons. Inaddtion as these ions diffusion increases,its jump faster at the nodes of Ranvier (saltatory conduction) to the next axoplasm which further speed up the rate of transmission.
Unmyeinated lacks myelin sheath,therefore the exchange and the rate of diffusion of ions along the axons is low.
Explnation:
Are you sure these are the only answer choices? I believe the answer would be Hippocampus, but it's not up there.
