grade 10 topic

2. •The basic unit of the
nervous system is the
nerve cell. Nerve cells are
called neurons. There are
billions of neurons in the
body.

3. There are twelve to fourteen billions of
neurons in one part of the brain alone. A
neuron has a cell body containing the
nucleus. Projecting out from the cell body
are root-like structures. These are the
dendrites and axons. Dendrites carry
impulses towards the cell body. A cell may
have as many as 200 dendrites carrying
impulses toward the cell body. A single
dendrite can be over one meter long.

4. Axons carry impulses away from
the cell body. Axons pass
impulses to the dendrites of
other neurons or cell body of
muscle cells. Axons can be
grouped together into cable-like
bundles called nerves.

7. The Nerve Impulse
Neurons are cells with the special
ability to carry signals or impulses.
Thoughts, emotions, learning, and
many body functions are carried
by nerve impulses in the neurons.

8. A nerve impulse cannot jump from one
neuron to another. When a nerve
impulse comes to the end of an axon, it
produces the chemical, called
neurotransmitter, to be released. The
chemical crosses the space between
neurons called synapse and stimulates
the nerve impulse to start in the next
dendrite.

10. The nervous system is assisted by
five sense organs - the eyes, ears,
nose, tongue, and skin. These sense
organs are constantly receiving
information from the environment
and sending messages to the brain.
These senses aid in the survival of
human beings.