Page 80 - Understanding NCERT Science 09

then transmitting the stimulus very rapidly (processes) called dendrites. An individual
from one place to another within the body. The nerve cell may be up to a metre long. Many
brain, spinal cord and nerves are all composed nerve fibres bound together by connective
of the nervous tissue. The cells of this tissue tissue make up a nerve.
are called nerve cells or neurons. A neuron The signal that passes along the nerve fibre
consists of a cell body with a nucleus and is called a nerve impulse. Nerve impulses allow
cytoplasm, from which long thin hair-like us to move our muscles when we want to. The
parts arise (Fig. 6.12). Usually each neuron functional combination of nerve and muscle
has a single long part (process), called the tissue is fundamental to most animals. This
axon, and many short, branched parts combination enables animals to move rapidly
in response to stimuli.
Nucleus
Q movement in our body.
Dendrite uestions
1. Name the tissue responsible for

Axon 2. What does a neuron look like?
Nerve ending 3. Give three features of cardiac
muscles.
Cell body 4. What are the functions of
Fig. 6.12: Neuron-unit of nervous tissue areolar tissue?

What

you have

learnt

• Tissue is a group of cells similar in structure and function.
• Plant tissues are of two main types – meristematic and
permanent.

• Meristematic tissue is the dividing tissue present in the
growing regions of the plant.
• Permanent tissues are derived from meristematic tissue once
they lose the ability to divide. They are classified as simple
and complex tissues.
• Parenchyma, collenchyma and sclerenchyma are three types
of simple tissues. Xylem and phloem are types of complex
tissues.
• Animal tissues can be epithelial, connective, muscular and
nervous tissue.
• Depending on shape and function, epithelial tissue is
classified as squamous, cuboidal, columnar, ciliated and
glandular.

TISSUES 69

Rationalised 2023-24