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Nervous System
Cali Hazel, Mary Kuttler.
Evolution of the Nervous System
1) Protists do not have a nervous system due to the simplicity of
their structure. They are capable of response to their
environment but not in this way.
2) This is the start of cephalization (development of the brain).
Cnidarians have the simplest nervous system of the Animal
Kingdom, they have a network of nerves that conducts signals
from sensory cells to muscle cells. But their nervous system is
not centralized.
3) Many flatworms have a netlike nerve system like cnidarians
but some have a more organized and complex system with
a brain and spinal chord. The nervous system of Planarians is
in the form of a ladder.
4) The nervous systems of mollusks are very diverse. Some have
bivalves and no cephalization while others have slight
cephalization. The most advanced group of mollusks have
complex sense organs and are highly cephalized.
5) Annelids and Arthropods have repeating segments and an
anterior brain. Each individual segment has a ganglion, which is
a nerve chord.
6) Sea stars have a central nerve ring and a nerve that extends from
the ring into each arm. Each arm also contains a nerve net.
7) The nervous system of vetrebrates is the most cephalized and
contains complex sense organs to inhibit very complex activities.
Nervous Systems in Humans
• The human nervous system is broken into two main parts.
– The central nervous system
– The peripheral nervous system
• Both systems are broken into two parts
• In the central nervous system collections of neurons are
called nuclei and collections of axons are call tracts.
• In the peripheral nervous system collections of neurons are
called ganglia and collections of axons are called nerves.
Central Nervous System
Brain
• Weigh approximately 3 lbs.
• Contains 100 billion
nuerons (nerve cells).
• Contains trillions of glia
(support cells).
• The two hemispheres
communicate through a
bundle of nerve fibers
called the corpus callosum
Spinal Chord
• Is around 43cm long in
adult women.
• Is around 45 cm long in
adult men.
• Weighs around 35-40g.
• The vertebral column is the
back bone (collection of
bones) that houses the
spinal cord and is about 70
cm long.
The Brain
• Cerebral Cortex - Thought, Voluntary movement,
Language, Reasoning, Perception
• Cerebellum - Movement, Balance, Posture
• Brain stem - Breathing, Heart Rate, Blood Pressure
• Hypothalamus - Body Temperature, Emotions, Hunger,
thirst, Circadian Rhythms
• Thalamus - Sensory processing, Movement
• Limbic System - Emotions, Memory
• Hippocampus - Learning, Memory
• Basal Ganglia - Movement
• Midbrain - Vision, Audition, Eye Movement, Body
Movement
Periphial Nervous System
Somatic Nervous System
• Contains peripheral nerve
fibers.
• The fibers send sensory
information to the
central nervous system.
• Also they send sensory
information to motor
nerve fibers that project
to skeletal muscle.
Autonomic Nervous
System
• Three Parts, the
sympathetic nervous
system, the
parasympathetic nervous
system and the enteric
nervous system.
• Controls smooth muscle
of the internal organs
(viscera) and glands.
• The Sensory (afferent) neurons carry information into
the central nervous system from sense organs
• the motor (efferent) neurons carry information away
from the central nervous system (for muscle control).
• the Cranial neurons connect the brain with the
periphery
• the spinal neurons connect the spinal cord with the
periphery.
• Somatic neurons connect the skin or muscle with the
central nervous system
• the visceral neurons connect the internal organs with
the central nervous system.
Bibliography
• "Blindness Causes Structural Brain Changes, Implying
Brain Can Re-organize Itself to Adapt." Science Daily:
News & Articles in Science, Health, Environment &
Technology. 2010. Web. 05 Apr. 2011.
• Chudler, Erik H. "Neuroscience For Kids - Explore the
Nervous System." UW Faculty Web Server. 2010. Web. 05
Apr. 2011.
• Gregory PhD, Michael J. "The Nervous System
Organization." Clinton Community College. 2006. Web. 05
Apr. 2011.
• Evers, Christine A., Lisa Starr, Cecie Starr, and Ralph
Taggart. "34." Biology The Unity and Diversity of Life.
11th ed. Belmont, CA: Thomson Brooks/Cole, 2006. 574-95.
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