Introduction to the Nervous System

Gross Anatomy


Introduction to the Nervous System; Peripheral Nervous System



ASSIGNMENTS
Moore's Clinically Oriented Anatomy: 38-45
Grant's Dissector: none


WHEN YOU FINISH THIS SECTION, YOU SHOULD BE ABLE TO PERFORM THE FOLLOWING TASKS AND ANSWER THESE QUESTIONS
  1. Diagram and label a cross section of the spinal cord showing a typical spinal nerve.

  2. What is a dermatome? What is the clinical significance of a dermatome?

  3. What is the difference in function between a dorsal root and a dorsal ramus?

  4. What functional losses occur when a nerve or one of its major branches is injured?

  5. What is the prognosis (prognosis: the forecast for the outcome of a disease or injury) for recovery of function in a crushing nerve injury? In a cutting nerve injury?

  6. What is a rhizotomy?



GENERAL ORGANIZATION OF THE NERVOUS SYSTEM
NEURON
STRUCTURE OF A PERIPHERAL NERVE
Gross anatomically, you cannot dissect the connective tissues described above. However, it is these layers of connective tissue that give the peripheral nerve its strength and bulk. When you handle nerves in the gross lab, you are touching the epineurium of those nerves.

ANATOMY OF A TYPICAL SPINAL NERVE
DISTRIBUTION OF SPINAL NERVES
NERVE DAMAGE
Because nutrients travel away from the nerve cell body along its processes, injury results in the disconnection of the peripheral portion of the process from the cell and nerve function is lost distal to the site of injury. We will make use of this simple concept throughout the course when we discuss nerve injuries in clinical case settings.


ANATOMY TABLES FOR TODAY'S TOPIC

Anatomy of the Typical Spinal Nerve

NerveSourceBranchesMotorSensoryNotes
spinal n. formed at the point where the dorsal and ventral roots meet; it ends where the dorsal and ventral primary rami diverge dorsal primary ramus; ventral primary ramus to skeletal mm.; some levels carry preganglionic sympathetic axons (T1-L2) or preganglionic parasympathetic axons (S2-S4) general sense (touch, pressure, pain, heat, cold, etc.) from the entire surface of the neck, trunk and extremities; visceral pain (via the white ramus communicans and the sympathetic nervous system) there are 31 pairs of spinal nerves - 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal
dorsal primary ramus first branch off of the dorsal side of the spinal nerve numerous to the deep back mm.; sympathetic innervation to the skin general sense (touch, pressure, pain, heat, cold, etc.) to the skin of the back; proprioceptive sense from muscles, tendons and joints a mixed nerve containing both motor and sensory fibers
dorsal root from the dorsal surface of the spinal cord to the formation of the spinal nerve none none general sense (touch, pressure, pain, heat, cold, etc.); proprioceptive sense from muscles, tendons and joints dorsal root is entirely sensory in function; it is located dorsal to the denticulate ligament
dorsal root ganglion see notes see notes none a dermatome on one side of the body; it takes two dorsal root ganglia (right and left) at one segmental level to supply both sides of the body a sensory ganglion; located on the dorsal root - one per spinal nerve; location of the cell bodies of somatic afferent (sensory) neurons
ventral primary ramus first branch off of the ventral side of the spinal nerve numerous to skeletal mm. of the neck, trunk and extremities; sympathetic innervation to the skin general sense (touch, pressure, pain, heat, cold, etc.) to the skin of the trunk (except the back) and extremities; visceral pain via the white rami of the sympathetic nervous system; proprioceptive sense from muscles, tendons and joints (T1-L2) a mixed nerve containing both motor and sensory fibers
ventral root from the ventral horn of the spinal cord to the spinal nerve none to skeletal mm.; preganglionic sympathetic axons (T1-L2); preganglionic parasympathetic axons (S2-S4) none entirely motor in function; located ventral to the denticulate ligament; at all spinal core levels it contains GSE for skeletal mm.; at levels T1-L2 it contains GVE (preganglionic sympathetic) for blood vessels, sweat glands, thoracic viscera, abdominal viscera, pelvic viscera


Some of the material presented in these tables is contained in the book:
MedCharts Anatomy by Thomas R. Gest and Jaye Schlesinger
Published by ILOC, Inc., New York. Copyright 1995.

Content of tables edited for use in this course by Patrick W. Tank, Ph.D.
Copyright 2001, Department of Anatomy and Neurobiology, University of Arkansas for Medical Sciences.
Unauthorized use is prohibited.



COMPUTER ASSISTED INSTRUCTION
Sample Test Questions
Practice Practical Exam Questions
Crossword Puzzle
Links to Related World Wide Web Sites
Marvin Computer Lab Models
Anatomy Tables
Review Questions for Gross Anatomy & Embryology: 1. General Principles
The Anatomy Project: Neuroanatomy 3 (pertaining to the spinal cord)


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