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