Nervous System Ch 25.1
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Transcript of Nervous System Ch 25.1
CHAPTER 25 SECTION 1
The Nervous System
Objectives:
Describe the relationship between the central nervous system and the peripheral nervous system
Compare the somatic nervous system with the autonomic system
List one function of each part of the brain
The Nervous System:
Controls almost everything you do…
The Nervous System:
The nervous system is the body’s central command post
2 basic functions: Gathers and interprets information
The NS responds to the information that is gathered
Two Systems Within a System:
Central Nervous System (CNS) Parts: Brain and spinal cord Function: processes and responds to all messages
coming from the peripheral nervous system
Peripheral Nervous System (PNS) Parts: all the parts of the nervous system except for the
brain and spinal cord; nerves Function: connects all parts of the body to the CNS;
uses specialized structures (nerves) to carry information
Central Nervous System:
http://static.howstuffworks.com/gif/adam/images/en/central-nervous-system-picture.jpg
Peripheral Nervous System:
http://faculty.etsu.edu/forsman/ftl_3_presentation/peripheral%20nerves.jpg
The Neuron
A nerve cell that is specialized to transfer messages in the form of fast-moving electrical energy
Electrical messages are called: impulses
Impulses may travel as fast as 150 m/s or as slow as 0.2 m/s
The Neuron
http://www.web-books.com/eLibrary/Medicine/Physiology/Nervous/neuron.jpg
The Main Parts of a Neuron:
Cell Body: the cell body of the neuron; it contains the nucleus (also called the soma)
Dendrites: the branching structure of a neuron that receives messages (attached to the cell body)
Axon: the long extension of a neuron that carries nerve impulses away from the body of the cell
Axon terminal: the hair-like ends of the axon
More Neuronal Parts…
myelin sheath - the fatty substance that surrounds and protects some nerve fibers
node of Ranvier - one of the many gaps in the myelin sheath - this is where the action potential occurs during saltatory conduction along the axon
nucleus - the organelle in the cell body of the neuron that contains the genetic material of the cell
Schwann's cells - cells that produce myelin - they are located within the myelin sheath
Information Collection:
Neurons are a type of nerve cell that carry impulses
Sensory neurons: gather information about what is happening in and around the body
Nerve endings are called receptors (detect changes)
Ex: receptors in your eyes detect light; sensory info is sent to the CNS for processing
Delivering Orders:
Motor neurons: neurons that send info from the brain & spinal cord to other systems
When muscles get impulses from motor neurons they respond by contracting
Ex: motor neurons cause muscles around your eyes to contract when you are in bright light; muscles make you squint
Nerves:
Nerve: a collection of axons bundled together with blood vessels & connective tissue
Most nerves have axons of both sensory & motor neurons
Axons are part of nerves but nerves are more than just axons
Somatic & Autonomic Nervous Systems:
The PNS has 2 main parts: The sensory part – Sensory Neurons The motor part – Motor Neurons
The motor part of the PNS has 2 kinds of nerves: Somatic Nerves Autonomic Nerves
Somatic & Autonomic Nervous Systems:
http://online.sfsu.edu/~psych200/unit5/u5m5.gif
Somatic Nervous System:
Most neurons are under our conscious control
These neurons stimulate skeletal muscles
Control voluntary movements: Writing, smiling, talking, jumping…
Autonomic Nervous System:
Do not require conscious control
Controls body functions that you don’t think about (digestion, heart rate)
Keeps body’s functions in balance (homeostasis)
2 divisions: Sympathetic Nervous System Parasympathetic Nervous System
Divisions of ANS & SNS:
Parasympathetic Nervous System: Nerves that control the involuntary movements
under normal conditions
Sympathetic Nervous System: Nerves that control involuntary movement under
STRESS conditions.
Divisions ANS & SNS:
http://www.becomehealthynow.com/images/organs/nervous/sympth_parasymth.gif
The Central Nervous System:
Receives info from the sensory neurons
Responds by sending messages to the body via motor neurons in the PNS
The control center: BRAIN Controls voluntary & involuntary actions
3 Main parts: Cerebrum, Cerebellum, Medulla
The Cerebrum:
The largest part
Where you think and store memories
Controls voluntary movements & experience senses
2 hemispheres (left & right) Left hemisphere directs the right side of the body Right hemisphere directs the left side of the body
The Cerebrum:
Left Hemisphere: Primarily controls activities like speaking, reading,
writing, and solving problems
Right Hemisphere: Primarily controls activities like spatial thinking,
processing music, and interpreting emotions
The Cerebrum:
http://library.thinkquest.org/4371/media/nervoussys2.jpg
The Cerebrum:
http://cwx.prenhall.com/bookbind/pubbooks/morris5/medialib/images/F02_11.jpg
The Cerebellum:
The 2nd largest part
Lies beneath the back of the cerebrum
Processes sensory information from your body (from skeletal muscles and joints)
Keeps track of the body’s position (keeps you from losing your balance)
The Cerebellum:
http://clarian.org/ADAM/doc/graphics/images/en/18008.jpg
The Medulla:
Part of the brain that attaches to the spinal cord
Approx. 3 cm long
Can’t live without it
Controls involuntary processes (blood pressure, body temp., heart rate, breathing)
The Medulla:
http://www.myschoolhouse.com/courses/c/3/Images/brain.gif
The Spinal Cord:
Part of the CNS
Made of neurons and bundles of axons that pass impulses to and from the brain
Protected by vertebrae
Communicate with PNS
Spinal Cord:
http://www.serious-injury-lawyers.org/images/spinal_big.jpg
Spinal Cord Injury:
Injury may block information to and from the brain
Some sensory and motor commands may not get through
Every year 1000’s of people are paralyzed by spinal cord injuries (car accidents, sports accidents)
Safety equipment is vital!!
Spinal Cord Injury:
http://www.nlm.nih.gov/medlineplus/ency/images/ency/fullsize/19619.jpg
Levels of Injury:
http://www.unistemcells.com/uploadfile/20081223174542617.jpg