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Biology - Nervous System: Organisation

Nervous System: Organisation

The central and peripheral nervous systems

* many unicellular organisms can detect and respond to light, pH,
chemicals, contact, or by moving towards or away from the stimulus - even
though they do not have a nervous system

* some organisms, e.g. Hydra, have a simple network linking sensory cells
to muscle cells

View the video of Paramecium: a unicellular organism that has no nervous
system, but responds to stimuli such as touch and light.

* nerve cells are organised into functional units, including peripheral
pathways and a coordinating centre

* central nervous system (CNS): brain and spinal cord process and
coordinate information and redirect impulses appropriately; the brain is
also responsible for memory, intelligence and high order thinking such as
problem solving and reasoning

* peripheral nervous system (PNS): nerves transmit impulses to the CNS
from receptors; and motor nerves transmit impulses from the CNS to
effectors, which respond

* autonomic system: controls the body's involuntary responses, such as
the beating of the heart and the contraction of artery and gut walls - not
under conscious control

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