Neuron /nerve cells is the basic fundamental unit of the nervous system. The brain contains many billions of Neuron that work together to produce sensation,thought, learning ,movement,emotion and many other processes.
Neuron comprise a cell body (soma), Dendrites, an axon that ends at a terminal.
Cell body (=Cyton or soma)
The cell body contains the nucleus, which contains the DNA, or genetic material of the cell surrounded by cytoplasm.The cytoplasm has mitochondria, Golgi apparatus, rough endoplasmic reticulum, ribosomes, lysosomes, fat globules, pigment granules, neurofibrils, neurotubules and Nissl’s granules.
The cell body is also the region of the Neuron in which an electrical impulse is generated .
Neurites:
The processes of neurons are called neurites. These are of two types: dendrites or dendrons and an axon or axis cylinder or neuraxon.
Dendrites (Dendrons):
These are usually shorter, tapering and much branched processes. They may be one to several. The dendrites contain neurofibrils, neurotubules and Nissl’s granules. They conduct nerve impulse towards the cell body and are called afferent processes (= receiving processes).This electrical impulse (action potential) propagates from the cell body, along the axon towards its terminal.
b) Axon:
Axon is a single, usually very long process of uniform thickness. The part of cyton from where the axon arises is called axon hillock. Most sensitive part of neuron is axon hillock.
It is an elongated fibre that transmits the impulse by altering the flow of sodium and potassium ions across the neuronal membrane. Many axons are surrounded by a myelin sheath,an insulating material that helps to prevent the signal from degrading.
The last step for the action potential is the axon terminals,also known as synaptic buttons. When the signal reaches the axon terminals it can cause the release of neurotransmitters.
When a neurotransmitter is released from axon terminal, it interacts with receptors on the Dendrites of the next Neuron and then the process repeats with the next Neuron.
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