Neurons – Class 11 | Chapter – 7 | Short Notes Series PDF

Neurons: Neurons are cells that can transmit signals called nerve impulses, or action potentials. An action potential is a quick rise and fall in the electrical membrane potential of the neuron, which transmits signals from one neuron to the next.

Parts of Neuron

Neurons vary in size, shape, and structure depending on their role and location. However, nearly all neurons have three essential parts: a cell body, an axon, and dendrites.

Cell body

Also known as a soma, the cell body is the core section of the neuron. The cell body contains genetic information, maintains the neuron’s structure, and provides energy to drive activities.

Like other cell bodies, a neuron’s soma contains a nucleus and specialized organelles. It’s enclosed by a membrane that both protects it and allows it to interact with its immediate surroundings.

Axon

An axon is a long, tail-like structure. It joins the cell body at a specialized junction called the axon hillock. Many axons are insulated with a fatty substance called myelin. Myelin helps axons to conduct an electrical signal.

Neurons usually have one main axon.

Dendrites

Dendrites are fibrous roots that branch out from the cell body. Like antennae, dendrites receive and process signals from the axons of other neurons. Neurons can have more than one set of dendrites, known as dendritic trees.

How many they have generally depends on their role. For instance, Purkinje cells are a special type of neuron found in a part of the brain called the cerebellum. These cells have highly developed dendritic trees which allow them to receive thousands of signals.

Types of Neuron

Neurons vary in structure, function, and genetic makeup. Given the sheer number of neurons, there are thousands of different types, much like there are thousands of species of living organisms on Earth.

However, there are five major neuron forms. Each combines several elements of the basic neuron shape.

  • Multipolar neuron: These neuron have a single axon and symmetrical dendrites that extend from it. This is the most common form of neuron in the central nervous system.
  • Unipolar neuron: Usually only found in invertebrate species, these neurons have a single axon.
  • Bipolar neuron: Bipolar neuron have two extensions extending from the cell body. At the end of one side is the axon, and the dendrites are on the other side. These types of neurons are mostly found in the retina of the eye. But they can also be found in parts of the nervous system that help the nose and ear function.
  • Pyramidal neuron: These neuron have one axon but several dendrites to form a pyramid type shape. These are the largest neuron cells and are mostly found in the cortex. The cortex is the part of the brain responsible for conscious thoughts.
  • Purkinje neuron: Purkinje neuron have multiple dendrites that fan out from the cell body. These neuron are inhibitory neuron, meaning they release neurotransmitters that keep other neurons from firing.

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By Team Learning Mantras