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Renin Angiotensin Mechanism.

Nervous Tissue.

 Tissue level of organization: Nervous Tissue.

Introduction:

  • Groups of cells having similar structure and performing similar functions are called “Tissue.”

  • Nervous tissue is a highly specialized tissue in the body and is present in the organs of Nervous system.

  • Nervous tissue is composed of two types of cells;

    • Neurons: they initiate, receive, conduct and transmit information.

    • Neuroglial Cells: They provide support to neurons and also perform some important functions.

Neuroglial Cells:

  • Neuroglia word is derived from: Nerve Glue.

  • Four types of neuroglial cells are found in the central nervous system;

  • Astrocytes: Forms connection between neurons and blood vessels, imp. Part of BBB (Blood Brain Barrier.)

  • Microglial Cells: Eat microbes and waste, Protection.

  • Oligodendrocytes: Insulation and synthesis of Myelin Sheath.

  • Ependymal cells: Helps in circulation of CSF (CerebroSpinal Fluid).

Neuron.

  • They are the main functional cells of the tissue where information is received, analyzed and stored.

  • Each nerve cell has following important parts;

    • Dendrites.

    • Cell Body.

    • Axon.

    • Axon terminal.

  • Dendrites are cell processes that carry impulses towards the cell, a neuron may have many dendrites.

  • Cell body is also called “Soma”, contains nucleus and regulates the functioning of neurons.

  • Axon is a long cell process that carries nerve impulses.

  • Axon terminals are endings of neurons where neurotransmitters are stored to be released in synapse.

  • Synapse is a minute space between two neurons, the impulse passes through synapse by means of chemicals called “Neurotransmitters”.

  • Some neurons containing a sheath of a fatty substance around the axon called ‘Myelin Sheath” are called as “Myelinated Neurons”.

  • The neurons which are not covered by Myelin sheath are called as ‘Non Myelinated Neurons”

  • Myelin sheath is covered by a type of glial cell called “Schwann Cell”.

  • The groove on the Myelinated neuron where myelin sheath is absent and axon is exposed is called the “Node of Ranvier”.

  • Transfer speed of nerve impulses is faster in myelinated neurons than in unmyelinated neurons.

Commonly Asked Questions

  1. Write a short note on,

    1. Nervous Tissue.

  2. Draw well labelled diagram of,

    1. Neuron.

  3. Why do nerve impulses travel faster through Myelinated neurons?
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