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1. CLASS – 9TH - ‘A’
CLASS TEACHER – SUDHA MAM
TISSUE:

2. It is hard to imagine a moment during our waking hours when our senses are not
in use. We are constantly bombarded with sensory input, from a delicious aroma
wafting our way to a painful stubbed toe. All of this information is processed by our
brain every millisecond. Some sensory experiences are positive, and some we'd
rather forget. But none of our senses would even function without the existence of
our nervous system.
There are several main components of our nervous system, and they are composed
of nervous tissue. The word tissue tends to elicit the thought of wiping runny
noses. But in terms of our body, tissue is defined as a group of cells with the same
general functions forming organs and other body parts. Of the five main types of
body tissue, nervous tissue is responsible for receiving, sending, and processing
sensory input. In this lesson, learn about the components of nervous tissue and
gain a better understanding of how it works for our body.
What Is Nervous Tissue?

3. Nervous tissue makes up three major parts of our nervous system: nerves,
the spinal cord and the brain. Our nervous system consists of two main parts:
the peripheral and central nervous systems. The peripheral nervous
system consists of the nerves that extend to all reaches of the body- the periphery.
The central nervous system is made up of the spinal cord and brain and is the
central processing center for all stimuli.
Peripheral nervous tissue consists of nerves made up of nerve cells called neurons.
Nerves extend all over the body, from the tips of the fingers to internal organs. They
form a long line of connectivity, like a chain of paper clips linked together. Nerves
connect to the spinal cord, which in turn, connects to the brain. So when you feel a
stimulus in your toe, for example, the sensory impulse must travel from the nerves,
all the way to the brain and back in order for you to process that feeling.

4. Our nervous tissue allows us to experience stimuli and then make a
response. For example, imagine a scenario in which you are attempting to hammer
a nail into the wall. After two tries, you accidentally hammer your finger. Now let's
freeze that moment. At the actual split-second that contact is made, there is no
pain. At least not yet. But wait a millisecond, and the throbbing begins. Why did it
take time before you felt the pain?
Let's zoom in on the nerve cells themselves to better understand the entire process.
Neurons are an extremely unique type of cell specialized just for work within the
nervous system. They consist of a cell body and then appendages that reach out
from that central body. If you took a spoonful of paint and threw it on the floor,
you might end up with a shape similar to a neuron.
The extensions, or appendages coming from the receiving end of the cell body are
called dendrites. Dendrites have many different branches, like dozens of little
fingers grasping for the incoming information. These can be very long, up to a
meter in humans. On the transmitting side of the cell body, we find a long
extension called the axon. Like the barrel of a gun, the axon fires the impulse to
the next neuron.
Functionof NervousTissue:

5. Nervous tissue is one of four major classes of tissues. It is specialized tissue
found in the central nervous system and the peripheral nervous system. It consists
of neurons and supporting cells called neuralgia.
The nervous system is responsible for the control of the body and the
communication among its parts. Nervous tissue contains two categories of cells—
neurons and neuralgia.
Definition of Nervous Tissue:

6. STRUCTURES OF NEURON:

8. About Dendrites:
Dendrites are responsible for responding to stimuli; they receive
incoming signals towards the cell body. The axons are responsible for
transmitting impulses over long distances from cell body. The cell body
is like a factory for the neuron. It produces all the proteins and contains
specialized organelles such as nucleus, granules and Nissl bodies.
Schwann Cells:
In the peripheral nervous system, Schwann cells are neuroglia cells that support
neuronal function by increasing the speed of impulse propagation. The
Schwann cells are underlain by the medullary sheath. The medullary sheath is
interrupted at intervals by the nodes of Ranvier.
SOME IMPORTANT TERMS:

9. About Axon:
An axon is a long, slender projection of a nerve cell, or neuron, that
typically conducts electrical impulses away from the neuron's cell body. Axons are
also known as nerve fibers. The function of the axon is to transmit information to
different neurons, muscles and glands. In certain sensory neurons (pseudounipolar
neurons), such as those for touch and warmth, the electrical impulse travels along
an axon from the periphery to the cell body, and from the cell body to the spinal
cord along another branch of the same axon.

10. The insulating envelope of myelin that surrounds the core of a nerve fiber
or axon and that facilitates the transmission of nerve impulses, formed
from the cell membrane of the Schwann cell in the peripheral nervous
system and from oligodendroglia cells. Also called medullary sheath .
Nodes of Ranvier, also known as myelin-sheath gaps, occur along a
myelinated axon where the axolemma is exposed to the extracellular space.
Nodes of Ranvier are uninsulated and highly enriched in ion channels,
allowing them to participate in the exchange of ions required to regenerate
the action potential.
Myelin Sheath
Nodes Of Ranvier:

11. Definition: the somewhat enlarged, often club-shaped endings by
which axons make synaptic contacts with other nerve cells or with effecter
cells (muscle or gland cells). Axon terminals contain neurotransmitters of
various kinds, sometimes more than one.
Neuron A is transmitting a signal at the axon
terminal to neuron B (receiving).
Features: 1. Mitochondrion. 2. Synaptic vesicle
with neurotransmitters. 3.Autoreceptor. 4. Synapse
with neurotransmitter released
(serotonin).5.Postsynaptic receptors activated by
neurotransmitter (induction of a postsynaptic
potential). 6. Calcium channel. 7. Exocytose of a
vesicle. 8.Recaptured neurotransmitter.
Axon Terminals:

12. Help Of Reference Books:

14. VIDEOS FOR NERVOUS TISSUE
FUNCTIONS