Copyright © 2006 Thomson Delmar Learning Chapter 13 Nerves of Steel The Nervous System

Copyright © 2006 Thomson Delmar Learning

Chapter 13

Nerves of Steel

The Nervous System


The Functions of the Nervous System

• The nervous system coordinates and controls body activity

• The nervous system detects and processes internal and external information and formulates appropriate responses


The Structures of the Nervous System

• There are two major divisions of the nervous system:– The central nervous system (CNS)

consists of the brain and spinal cord– The peripheral nervous system (PNS)

consists of the cranial and spinal nerves, autonomic nervous system, and ganglia


The Structures of the Nervous System

• The basic unit of the nervous system is the neuron

• There are three types of neurons:– sensory (also called afferent)– associative– motor (also called efferent)


Parts of the Neuron

• The neuron consists of– a cell body (soma)– dendrites

• Carry impulses toward the cell body

• Combining form is dendr/o

– an axon• Carries impulses

away from the cell body

• Combining form is ax/o


The Gap

• The space between two neurons or between a neuron and receptor is the synapse– The combining forms

for synapse are synaps/o and synapt/o

– Chemical substances called neuro-transmitters are released into the space to allow information to be relayed


Supporting Role

• Neuroglia or glial cells are the supportive cells of the nervous system– The combining

form gli/o means glue.

• Glial cells consist of – astrocytes– microglia – ependymal cells– oligodendrocytes– Schwann cells


Surrounding Structures

• Myelin is a protective covering over some nerve cells including parts of the spinal cord

• Myelin serves as an electrical insulator

• Myelin is interrupted at regular intervals along the length of a fiber by gaps called nodes of Ranvier


Nerves

• A nerve is one or more bundles of impulse-carrying fibers that connect the CNS to other parts of the body

• Combining forms for nerve or nerve tissue are neur/i and neur/o


The CNS

• The central nervous system is made up of the brain and spinal cord

• The combining form for the brain is encephal/o

• The combining form for the spinal cord is myel/o (remember myel/o also means bone marrow)


The Meninges

• The meninges are a three-layered membrane that surrounds the CNS– The combining forms

for the meninges are mening/o and meningi/o

– The three layers of the meninges are the dura mater, arachnoid membrane, and the pia mater


The CSF

• Cerebrospinal fluid (CSF) is the clear, colorless ultrafiltrate that nourishes, cools, and cushions the CNS

• CSF is made by the choroid plexus that lines the ventricles of the brain


The Brain• The brain is the

enlarged and highly developed portion of the CNS that lies in the skull and is the main site of nervous control– The cranium is

the portion of the skull that encases the brain

• crani/o is the combining form for skull

• encephal/o is the combining form for brain


The Brain Divisions• The brain is divided

into three main parts:– Cerebrum is the

largest part and is responsible for receiving and processing information

• cerebr/o– Cerebellum is the

second largest part that coordinates muscle activity

• cerebell/o– Brainstem connects

the cerebral hemispheres with the spinal cord and supports basic life functions


The Spinal Cord• The spinal cord is the

continuation of the medulla oblongata of the brainstem

– The combining form for spinal cord is myel/o

• The spinal cord passes through an opening in the occipital bone called the foramen magnum

• The spinal cord carries the tracts that influence the innervation of the limbs and lower part of the body and is the pathway for impulses going to and from the brain


The Discs

• The spinal cord is housed within vertebrae to protect it from injury

• The vertebrae are protected from each other by intervertebral discs located between the vertebrae

• Intervertebral discs are layers of fibrocartilage that form pads separating and cushioning the vertebrae from each other


The PNS• The peripheral nervous system consists of cranial and spinal

nerves, the autonomic nervous system, and the ganglia– The cranial nerves are 12 pairs of nerves that originate from the

undersurface of the brain– The spinal nerves arise from the spinal cord and supply sensory and

motor fibers to the body region associated with their emergence from the spinal cord


The ANS

• The autonomic nervous system is that part of the peripheral nervous system that innervates smooth muscle, cardiac muscle, and glands

• There are two divisions of the ANS:– sympathetic: fight or flight– parasympathetic: maintains normal

body function


Medical Terms for the Nervous System

• Additional terms for nervous system tests, pathology, and procedures can be found in the text

• Review the Flash! CD program to make sure you understand these terms

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Copyright © 2006 Thomson Delmar Learning Chapter 13 Nerves of Steel The Nervous System