1. Chapter 13
Nerves of Steel

2. 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.

3. The Structures of the Nervous System
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.

4. 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)

5. Parts of the Neuron The neuron consists of the following:
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. 5

6. Supporting Role
Neuroglia, or glial cells, are the supportive cells of the nervous system.
Hold together nerve cells
The combining form gli/o means glue.

7. Supporting Role Neuroglial (glial) cells consist of the following:
Astrocytes
Cover surfaces of capillaries
Blood Brain Barrier
Astrocytes and capillary walls
Regulates passage of nutrition and chemicals to brain
Microglia
Phagocytic cells for fighting infection and for healing

8. Oligodendrocytes Schwann cells Hold nerve fibers together
Form myelin sheath in CNS
Schwann cells
Found outside CNS
Form the neurilemma and a thin layer of myelin around nerve fibers

9. 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. 9

10. The Gap
The space between two neurons or between a neuron and a receptor is the synapse.
The combining forms for synapse are synaps/o and synapt/o.
Chemical substances called neurotransmitters are released into the space to allow information to be relayed. 10

11. 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.

12. 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.) 12

13. 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, the arachnoid membrane, and the pia mater.

14. 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.

15. 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.

16. 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.

17. 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 the lower part of the body and is the pathway for impulses going to and from the brain. 17

18. 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.

19. 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….31 pairs

20. Cranial Nerves Facial (expression, saliva, taste) Olfactory
Acoustic (hearing, balance, equilibrium)
Glossopharyngeal (swallowing)
Vagus
Slows heart
Increases peristalsis
Accessory
shoulder movements,
turning head,
Hypoglossal (tongue movements)
Olfactory
Optic
Oculomoter
Trochlear (eye movement, proprioception)
Trigeminal (head/face, chewing movements)
Abducens abduction of eye)

21. Spinal Nerves Named after corresponding vertebrae
Supply sensory and motor fibers to the
region of the body in the area where
they emerge from spinal cord

22. 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
“rest and restore”

23. Sympathetic Parasymapthetic
Dilate pupils
Accomadates eyes to distance
Dilates bronchial tubes
Heart rate increases
Blood vessels constrict
(skin and viscera)
Blood to muscles
GI and bladder relax
Sphincter muscles contract
(prevent leakage)
Constricts pupils
Near objects vision
Constricts bronchial tubes
Slower heart rate
Dilates blood vessels
GI contractions increase
Relaxation of sphincter muscles

26. Diagnostic Procedures
Myelography
Diagnostic study of the spinal cord
Injection of contrast dye
Myelogram is produced-record of the spinal cord
after dye is injected

28. Pupillary Light Reflex
Response of pupil to a bright light source
PLR
Light shone in one eye causes both eyes to constrict (normal)
Used to assess neurological damage

30. Cerebrospinal Fluid Tap
Insert needle/ catheter
Obtain fluid from cisterna magnum
(subarachnoid space between cerebellum and medulla)
Or Lumbosacral area

32. Medical Terms for the Nervous System
Additional terms for nervous system tests, pathology, and procedures can be found in the text.
Review StudyWARE to make sure you understand these terms.