Download Biology 30 Unit 1: The Nervous System

Biology 30 Unit 1: The Nervous
System
The Nervous system has two main
divisions:
The Central Nervous System (CNS) and
The Peripheral Nervous System (PNS)
The CNS consists of the nerves of
the brain, and the spinal cord.
The CNS acts as a coordinating
center for incoming and outgoing
information.
The PNS consists of nerves that carry
information between the organs of the
body and the CNS.
The PNS can be further divided into
somatic and autonomic nerves.
The somatic nervous system controls
the skeletal muscle, bones, and skin.
The autonomic nervous system
controls the internal organs of the
body.
There are two main types of nerve
cells:
Glial cells (neuroglial cells)are nonconducting cells important for the
structural support and metabolism of
the nerve cells.
Neurons are the functional units of the
nervous system.
The anatomy of a neuron:
Dendrites receive information, either from the
environment or from other neurons.
Axons are extensions of the cytoplasm that
conduct nerve impulses away from the cell
body. The axon carries nerve impulses toward
other neurons or to effectors.
Most nerves are comprised of many axons held
together by connective tissue.
Many axons are covered with a white coat
of fatty protein called the myelin sheath,
which acts as insulation for the neurons.
Why do you think this is important?
The myelin sheath is formed by special
glial cells called Schwann cells.
The spaces between the Schwann cells
are called the nodes of Ranvier.
What is the purpose of these spaces?
All nerve fibres found within the
peripheral nervous system have a thin
outer membrane called the
neurilemma, which surrounds the
axon. The neurilemma is formed by
the Schwann cells and promotes the
regeneration of damaged axons.