Nervous SystemCali Hazel, Mary Kuttler.

Evolution of the Nervous System1) 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 SystemBrain• 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 SystemSomatic 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. Print.