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Nervous tissue: Structure, Types and Function

In this article we will discuss about the Nervous tissue: – Definition, Structure, Types of Neuron, Classification of nervous tissue and Functions

Nervous tissue

Nervous tissue are highly specialised to transmitting the stimulus very rapidly from one place to another within the body
Nerve tissue is the main tissue of our nervous system

Structure of Nervous Tissue

Nervous tissue consists of two cells: nerve cells or neurons and Neuroglia (glial cell)

Neuron

They vary in shape and size, all neurons contains three parts- cell body, dendrites and axon
Cell body which contains the nucleus, cytoplasm and cell organelles
Dendrite is a highly branched cytoplasmic extension, responsible for receiving impulses
from outside & pass to the cyton
Axons are long stem-like projections emerging out of the cell, It conduct nerve impulse away from cell body

Neuroglia

Glial cells are non conducting cells that protect and nurture as well as support cells of nervous tissue.

Types of Neurons

Unipolar

Single process arises from cyton (1 Axon)
E.g. Nervous system of embryo

Bipolar

Two process arise from cyton (1 Axon and 1 dendron)
E.g. Retina (Rod and cones) olfactory epithelium

Multipolar

Neuron which one axon but many dendrons
E.g. Most of neurons of vertebrates

Nonpolar Neuron

No definite dendron/axon
Cell process are either absent or if present are not differentiated in axon and dendrons
Nerve impulse radiates in all directions
E.g. Hydra, Amacrine cell of Retina

Pseudounipolar

In this type, nerve cell has only axon but a small process develop from axon which act as dendron
E.g. Dorsal root ganglia of spinal cord

Classification of Nervous System

The nervous system is classified into the central, peripheral and autonomic nervous systems

Central Nervous System

Central Nervous System is often called the central processing unit of the body
It consists of the brain and the spinal cord

Brain

The brain is one of the important, largest and central organ of the human nervous system.
Brain control unit of the nervous system, which helps us in discovering new things, remembering and understanding, making decisions, and a lot more
It is enclosed within the skull
The human brain is composed of three major parts:
- Forebrain: The anterior part of the brain, consists of Cerebrum, Hypothalamus and Thalamus.
- Midbrain: The smaller and central part of the brainstem, consists of Tectum and Tegmentum.
- Hindbrain: The central region of the brain, composed of Cerebellum, Medulla and Pons.

Spinal Cord

The spinal cord is a cylindrical bundle of nerve fibers and associated tissues enclosed within the spine and connect all parts of the body to the brain
It begins in continuation with the medulla and extends downwards
It is enclosed in a bony cage called vertebral column and surrounded by membranes called meninges
The spinal cord is concerned with spinal reflex actions and the conduction of nerve impulses to and from the brain

Peripheral Nervous System

Peripheral Nervous System is the lateral part of the nervous system that develops from the central nervous system
PNS includes two types of nerve fibers
1. Afferent nerve fibers – These are responsible for transmitting messages from tissues and organs to the CNS.
2. Efferent nerve-fibers – These are responsible for conveying messages from CNS to the corresponding peripheral organ

Autonomic neural system

The autonomic neural system is involved in involuntary actions like regulation of physiological functions (digestion, respiration, salivation, etc.).
It is a self-regulating system which conveys the impulses from the CNS to the smooth muscles and involuntary organs (heart, bladder and pupil)
The autonomic neural system can be further divided into:
1. Sympathetic nervous system
2. Parasympathetic nervous system

Functions of the Nervous System

The master controlling and communicating system of the body
Sensory input: detects external and internal stimuli
Integration: processes and responds to sensory input
Control of Muscles and Glands
Homeostasis is maintained by regulating other systems
Center for Mental Activities

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