Nervous System
Parts of the Nervous System
• Brain
• Spinal Cord
• Nerves
Vocabulary to Know
• Homeostasis
– The regulation of steady, life-maintaining
conditions inside an organism, despite
changes in its environment
Nerve Cells
• Neurons
– Basic functioning units of the nervous
system
http://ilearn.senecac.on.ca/aahs/health/IHP/ottawa/anatomy/neuron/map/neuron.html
http://35.9.122.184/images/40-AnimalStructureAndFunction/
Neurons
• Made up of a cell body and branches
called dendrites and axons
– Dendrites receive messages from other
neurons and send them to the cell body
– Axons carry messages away from the
cell body
Any message carried by a neuron is called an impulse
Neurons
A message carried by a neuron is called
an impulse
Types of Neurons
• Sensory
• Motor
• Interneuron
Sensory Neurons
• Receive information
• Send impulses to the brain or spinal
cord
Interneurons
• Send impulses from sensory neurons
to motor neurons
Motor Neurons
• Conduct impulses from the brain or
spinal cord to muscles or glands
throughout your body
Synapse
• Small space across which an impulse
moves from an axon to the dendrites
or cell body of another neuron
Synapse
• An impulse reaches the end of an
axon
• Axon releases a chemical
• Flows across the synapse
• Stimulates the impulse in the dendrite
of the next neuron
• Impulse moves from neuron to neuron
http://www.med.harvard.edu/publications/On_The_Brain/Volume7/Number1/images/Neuron.jpg
An impulse moves in only one direction across a
synapse - from an axon to the dendrites or cell body of
http://mhln.com
another neuron.
Two Parts
• Central (CNS)
• Peripheral (PNS)
http://inside.salve.edu/walsh/cns_pns.jpg
Central Nervous System
• Brain
• Spinal cord
The Brain
• Coordinates body activities
• Made up of approximately 100 billion
neurons
• Divided into three major parts-
– the cerebrum
– the cerebellum
– the brain stem.
Cerebrum
• Largest part of the brain
• Thinking
• Memory is stored
• Movements are controlled
• Impulses from the senses are
interpreted.
Cerebellum
• Interprets stimuli from eyes, ears,
muscles
• Controls voluntary muscle movements
• Maintains muscle tone
• Helps maintain balance
Brain Stem
• Connects brain to spinal cord
• Made up of the midbrain, the pons,
– Act as pathways connecting various
parts of the brain with each other
• Medulla
– controls involuntary actions
http://www.cbituk.org/GRAPHICS/brain.gif
The Spinal Cord
• Extension of the brain stem
made up•ofBundles of neurons that carry from all parts of th
bundles of neurons that carry impulses
impulses from all parts of the body to
the brain and from the brain to all
parts of your body
The
Peripheral
Nervous
System
Your brain
Somatic
and spinal
cord are
and
Autonomic
connected
Systems
to the rest
The
of your
peripheral
body by
the
nervous
system has
peripheral
two major
nervous
divisions.
system.
The PNS
is made up
somatic
system
of 12 pairs
controls
of nerves
voluntary
from your
brain It
actions.
is made
called up
of the
cranial
cranial
nerves,and
spinal
and 31
pairs from
nerves that
go from the
your spinal
central
cord called
nervous
spinal
nerves. to
system
your
Spinal
skeletal
nerves are
muscles.
made up of
The
bundles of
sensory
autonomic
system
and motor
controls
neurons
involuntary
bound
together by
actions-
those not
connective
under
tissue. For
conscious
this
reason, a
Research
control-
Visit the
such as
single
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your heart
spinal
nerve can
Science
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breathing,
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digestion,
impulses
going to
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and
m for more
glandular
and from
information
functions.
the brain at
the same
about the
These two
nervous
divisions,
time. Some
system.
along with
nerves
contain
Make a
the central
brochure
nervous
only
outlining
system,
sensory
neurons,
recentup
make
medical
your
and some
advances.
body's
contain
only motor
nervous
system.
neurons,
but most
nerves
contain
both types
of neurons.
Peripheral Nervous System
• Connects body to brain & spinal cord
• 12 pairs of nerves from your brain
(cranial nerves)
• 31 pairs from your spinal cord (spinal
nerves)
– Bundles of sensory and motor neurons
held together by connective tissue
http://www.christopherreeve.org/Research/Research.cfm?ID=178&c=21
Peripheral Nervous System
• Two divisions
– Somatic
– Autonomic
http://abdellab.sunderland.ac.uk/lectures/Parmacology/Pics/anatomy/PNS.GIF
Somatic Nervous System
• Controls voluntary actions
• Made up of the cranial and spinal
nerves that go from the central
nervous system to your skeletal
muscles
Autonomic Nervous System
• Controls involuntary actions-those not
under conscious control-such as your
heart rate, breathing, digestion, and
glandular functions
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/autonomic.gif
Reflexes
• Involuntary, automatic response to a
stimulus
• Involves a simple nerve pathway
called a reflex arc