The nervous system

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The nervous system
CNS and PNS:
The central nervous system is made up of the brain and the spinal cord, while the rest of
the nervous system is the peripheral nervous system.
1- The brain
2- A combination of the brain and the spinal cord (the
central nervous system)
3- The spinal chord
The spinal cord extends from the base of the brain, lying inside the
neural arches of the vertebrae. In the centre of the cord is a canal containing cerebro-spinal
fluid. Both the brain and the spinal cord are surrounded by three membranes called
meninges. The membranes help to secrete cerenro-spinal fluid, which fills in all the spaces in
the brain and spinal cord and also the space beneath the bones of the skull. The fluid helps to
absorb mechanical shocks to the brain (such as when you hit your head on something) and
also to provide nutrients and oxygen to the brain cells.
The peripheral nervous system is made up of sensory neurones that carry action
potentials from receptors towards the central nervous system, and motor neurons that
carry action potentials from the central nervous system to effectors.
It is made up of two systems with different functions. These are the somatic nervous
system and the autonomic nervous system. The somatic nervous system includes all the
sensory neurones and also the motor neurones that take information to the skeletal
muscles. So the neurones in a typical reflex arc are all part of the somatic nervous system.

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The autonomic nervous system includes all the motor neurones that supply to the internal
organs.
The Autonomic nervous system contains two more components to the nervous system.
These are the sympathetic nervous system and the parasympathetic nervous system.
The sympathetic nervous system is used to stimulate the body (E.G. make the heart rate
rise). It does this through releasing noradrenalin. Noradrenalin is very similar to the hormone
adrenaline and results are very similar effects on the body, for example pupil dilation and
bronchi dilation.…read more

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Noradrenalin is the transmitter substance that carries the impulses across most of
the synapses.
The parasympathetic nervous system has all its nerve pathways begin at the
brain, the top of the spinal cord or the very base of the spinal cord, unlike the
sympathetic nervous system.…read more

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The brain…read more

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Little is known about the brain, however over the years scientists have put a lot of effort
into investigating the anatomy and physiology of the brain as well as how it works. The brain
is a cream coloured organ surrounded
and protected by the bones of the
cranium and also by three membranes
called the meninges. These membranes
help to secrete serebro-spinal fluid,
which provides protection and
cushioning of the brain, as mentioned
previously.…read more

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Most types of
neurones contain an axon, which extends to distant parts of the body and connect with
thousands of synapses. They travel through the body in bundles called `nerves'. There are
hundreds of different types of neurons that exist in one single species such as a human,
with many different functions. These include sensory neurons, motor neurons and relay
neurons. In many species most neurons receive all their input from other neurons and send
their output to other neurons.…read more

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The Hierarchy sum up of the Nervous system…read more

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