The nervous system is the part of an animal's body that coordinates its behavior and transmits signals between different body areas.

1. NERVOUS SYSTEM
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2.  CELLS AND TISSUES
 Neurones
 Nerves
 Neuroglia
 CENTRAL NERVOUS SYSTEM
 Brain
 Spinal Cord
 PERIPHERAL NERVOUS SYSTEM
 Spinal nerves
 Thoracic nerves
 Carnial nerves
 Autonomic nervous system
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3. There are two types of nervous tissue
neurons and neuroglia .
Neurones working unit of the nervous
system.
Neurones are swupported by connective
tissue knoen as Neuroglia .
There are vast number of both cell type :1
trillion glial cells and 10 times fewer
neurones.
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4. Each neurone consists of a cell body and its
processes one axon and many dendrites.
Bundle of axons bound together are called
nerves .
Nerounes generate and tranasmit electrial
impules called action potentials.
The action potential travelling down the nerve
axon is an electric signal.
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5. Nerve cells vary considerably in size and shape
but they are all too small to be seen by naked
eye .
 Cell bodies form the grey of the nervous
system and are found at the periphery of the
brain and the centre of the spinal cord.
Groups of cell bodies are called nuclei in CNS
and ganglia in PNS.
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6. Axon, also called nerve fibre, portion of a nerve
cell (neuron) that carries nerve impulses away from
the cell body.
 A neuron typically has one axon that connects it with
other neurons or with muscle or gland cells. Some
axons may be quite long, reaching, for example, from
the spinal cord down to a toe.
 Most axons of vertebrates are enclosed in
a myelin sheath, which increases the speed of
impulse transmission; some large axons may transmit
impulses at speeds up to 90 metres (300 feet) per
second.
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7. Dendrites are projections of a neuron (nerve
cell) that receive signals (information) from
other neurons.
 The transfer of information from one neuron to
another is achieved through chemical signals
and electric impulses, that is, electrochemical
signals.
Dendrites also possess organelles that enable
them to alter protein density in response to
changes in frequency of neuronal inputs.
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8. In the central nervous system, a SYNAPSE is a
small gap at the end of a neuron that allows a
signal to pass from one neuron to the next.
Synapses are found where nerve cells connect
with other nerve cells.
. A single neuron may contain thousands of
synapses
. In fact, one type of neuron called the Purkinje
cell, found in the brain's cerebellum, may have
as many as one hundred thousand synapses.
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9.  Neurotransmitters are often referred to as the
body's chemical messengers.
 They are the molecules used by the nervous
system to transmit messages between
neurons, or from neurons to muscles.
Communication between two neurons happens
in the synaptic cleft (the small gap between the
synapses of neurons).
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10.  Sensory or afferent
nerves
 Afferent neurons
are sensory nerves
 These are sensory neurons
carrying nerve impulses
from sensory stimuli toward
the central nervous system
and brain.
 Afferent neurons carry
signals to the brain and
spinal cord as sensory data.
 Motor or efferent
nerves
 Cranial nerves and
spinal nerves extend from
the CNS to peripheral
organs such as muscles
and glands.
 The afferent or sensory
division transmits
impulses from peripheral
organs to the CNS.
 The efferent or motor divi
sion transmits impulses
from the CNS out to the
peripheral organs to
cause an effect or action.
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11. Neuroglia, also called glial cell or glia, any of
several types of cell that function primarily to
support neurons.
 It has since been shown that glucose, amino
acids, and ions—all of which influence neuronal
function—are exchanged between the
extracellular space and neuroglial cells.
Neuroglial cells provide homeostatic support,
protection, and defense to the nervous tissue.
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12. The brain and spinal cord are completely
surrounded by three layers of tissue .
 They are-
A. Dura mater
B. Arachnoid mater
C. Pia mater
SUBDURAL SPACE –between the dural and
arachnoid mater
SUBARACHNOID SPACE-between the
arachnoid and pia mater,contains CSF.
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