Chapter 14:
Peripheral Nervous System
PowerPoint by John McGill
Supplemental Notes
by Beth Wyatt
Nervous System
Organization
I. SPINAL NERVES
• OVERVIEW
• DEFINITION
• Nerves That Extend Off the
Spinal Cord (Emerge From
the Spinal Cavity)
• NUMBER: 31 Pair
Spinal Nerves
I. SPINAL NERVES
• C1-C8
• CERVICAL NERVES
• T1-T12
• THORACIC NERVES
• L1-L5
• LUMBAR NERVES
• SACRAL NERVES
• S1-S5
• COCCYGEAL NERVES
• 1 PAIR
SPINAL NERVES are IDENTIFIED
BY LETTERS AND NUMBERS
• They are NOT “named.”
• LETTERS
• INDICATE REGIONS OF
VERTEBRAL COLUMN
• NUMBERS
• INDICATE HOW MANY OF
EACH TYPE (EACH PAIRED)
SPINAL NERVES are IDENTIFIED
BY LETTERS AND NUMBERS
• THE LETTERS AND NUMBERS
INDICATE WHERE THE NERVES
EXIT SPINAL CAVITY
• C1-C7 Exit Above C1-C7 Vertebrae
• C8 Exits Below C7 Vertebra
• Thoracics and Lumbars Exit Below
Their Respective Vertebrae
• Sacrals Exit Through Openings in
Sacrum
• Coccygeals Pass Over Coccyx
CAUDA EQUINA ( Horse’s Tail )
• Describes the
Appearance of the
Bottom of the Spinal Cord
• Reason: Spinal Cord
Ends at Bottom of the 1st
Lumbar Vertebra;
CAUDA EQUINA ( Horse’s Tail )
• Means That Lumbar,
Sacral, and Coccygeal
Nerves Hang in a
Bundle at the Bottom of
the SC Before Exiting at
Their Respective
Locations
• Causes the Bottom of
the Spinal Cord to
Resemble a Cauda
Equina
SPINAL NERVES ARE
MIXED NERVES
• The spinal nerves carry both
sensory and motor messages and
are called “mixed nerves.”
SPINAL NERVE STRUCTURE
• NERVE ROOTS: Join Spinal Nerves to Spinal Cord
• VENTRAL ROOTS
• NF OF EFFERENT NEURONS
• DORSAL ROOTS
• NF OF AFFERENT NEURONS
SPINAL NERVE ROOTS
RAMI (RAMUS)
• The Major Branches of a Spinal Nerve
• Each Spinal Nerve Has 2 Rami
RAMI (RAMUS) DESCRIPTION
• The spinal nerve trunk
emerges laterally from
the intervertebral foramen
• The trunk divides into two
major branches (The
anterior (ventral) and
posterior (dorsal) primary
rami (ramus, singular))
• The posterior primary
rami go to the back.
• The anterior primary rami
go to the sides and front
of the body, and to the
upper and lower
members.
DORSAL RAMUS
• AREAS SUPPLIED
• Provides Nerve Supply to Posterior
Head, Neck, and Trunk
• Contains Both Afferent and Efferent
(Somatic) Nerve Fibers
VENTRAL RAMUS (More Complex)
• AREAS SUPPLIED
• Lateral and Anterior Neck and
Trunk as well as Extremities
• Contains Both Afferent and
Efferent (Somatic & Autonomic)
Nerve Fibers
VENTRAL RAMUS (More Complex)
• NERVE PLEXUSES are
only found on ventral rami
• DEFINITION
• Complex Nerve Network
• The Ventral Rami of Most
Spinal Nerves Form
Plexuses (Not T2 - T12)
• Formed when the Ventral
Rami of Several Spinal
Nerves Exchange Fibers
• (Fibers Recombine) to
Form New Nerves that
Supply Specific Areas
VENTRAL RAMUS
(Comments from the text)
• Fibers of several rami join to form individual
•
•
•
•
•
nerves.
Each nerve emerging from a plexus contains
all the fibers that innervate a body region.
Destination is basis for nerve’s name.
The plexus reduces the number of nerves
needed to supply a body part.
Since plexi are composed of fibers from
different spinal nerves, damage to one spinal
nerve does not mean a complete loss of
function in a body region
But Instead, Partial Loss of Function in
Several Areas
MAJOR PLEXUSES (ALL ARE
PAIRED): CERVICAL PLEXUS
• CERVICAL PLEXUS
• Formed by the Ventral Rami of C1-C4
and a Branch of Ventral Ramus of C5
• Provides Nerve Supply to Neck and
Upper Shoulders and Part of Head
CERVICAL PLEXUS
MAJOR PLEXUSES (ALL ARE
PAIRED):BRACHIAL PLEXUS
• BRACHIAL PLEXUS
• Formed by the Ventral Rami of C5-T1
• Provides Nerve Supply to Lower
Shoulders and Arms
BRACHIAL PLEXUS
MAJOR PLEXUSES (ALL ARE
PAIRED): LUMBAR PLEXUS
• LUMBAR PLEXUS
• Formed by the Ventral Rami of L1-L4
• SACRAL PLEXUS
• Formed by the Ventral Rami of L4, L5,
& S1-S4
• *Note: Together the Lumbar and the
Sacral Plexuses (also the Coccygeal
Plexus) Are Known as the
Lumbosacral Plexus that Provides
Nerve Supply to the Lower Trunk
and the Legs
LUMBOSACRAL PLEXUS
Plexus Notes
• * Coccygeal Plexus: Formed by
S4, S5, and Coccygeal Nerves
GENERALIZATIONS
ABOUT SPINAL NERVES
• Spinal Nerves Are Not Named;
• However, the Nerves That Emerge
From Plexuses Often Are Named
• Examples: Phrenic Nerve, Sciatic
Nerve
• There is a Close Relationship
Between Where a Spinal Nerve
Exits the Spinal Cavity and the
Area the Nerve Supplies
CRANIAL NERVES
• DEFINITION
• Nerves That Attach
to the Undersurface
of the Brain (Mainly
the Brainstem)
• 12 Pair
CRANIAL NERVES
• IDENTIFICATION
• By Names and
Numbers
• NAMES
• MAY INDICATE
NERVE’S FUNCTION
• MAY INDICATE AREA
THE NERVE
SUPPLIES
• NUMBERS
• ROMAN NUMERALS
• ORDER IN WHICH
NERVE EMERGES
FROM ANTERIOR TO
POSTERIOR
NERVE TYPES
• Some Cranial Nerves Are Mixed, Some
•
•
•
•
Are Sensory, Some Are Motor
Saying to Remember Nerve Types:
Some Say Marry Money, But My
Brothers Say Bad Business Marry
Money
MIXED NERVES: V, VII, IX, X
SENSORY NERVES: I, II, VIII
MOTOR NERVES: III, IV, VI, XI, XII
NAMES, NUMBERS, FUNCTIONS
CRANIAL NERVE I
• OLFACTORY NERVE
• Sensory
• Function: Smell
CRANIAL NERVE II
• OPTIC NERVE
• Sensory
• Function: Vision
CRANIAL NERVE III
• OCULOMOTOR
NERVE
• Motor
• Functions:
• Eye Movements
• Regulation of
Pupil Size
• Accomodation
CRANIAL NERVE IV
• TROCHLEAR NERVE
• Motor
• Function: Eye Movements
CRANIAL NERVE V
• TRIGEMINAL NERVE
• Mixed
• Functions:
• Sensory: Sensations of Head and Face
• Motor: Chewing
CRANIAL NERVE V
CRANIAL NERVE VI
• ABDUCENS NERVE
• Motor
• Function: Lateral Eye Movements
CRANIAL NERVE VII
• FACIAL NERVE
• Mixed
• Functions:
• Sensory: Taste
• Motor:
– Facial
Expressions
– Secretion of
Saliva and Tears
CRANIAL NERVE VIII
• Vestibulocochlear
• Sensory Functions: Hearing and Equilibrium
CRANIAL NERVE IX
• GLOSSOPHARYNGEAL
NERVE
• Mixed
• Functions:
• Sensory: Taste (and
General Sensations
of Tongue)
• Motor: Swallowing,
Secretion of Saliva
• NOTE: This nerve is
also involved in the
reflexes of BP and
respiration.
CRANIAL NERVE X
• X VAGUS NERVE
• Mixed
• Functions:
• Sensory:
Sensations in
Organs Supplied
• Motor: Movements
of Organs
Supplied (i.e.,
Slows Heart,
Increases
Peristalsis)
CRANIAL NERVE XI
• ACCESSORY NERVE
Motor
• Functions:
• Turning Movements
of Head
• Shoulder Movements
• Movements of
Organs Supplied
• Voice Production
CRANIAL NERVE XII
• HYPOGLOSSAL NERVE
• Motor
• Function: Tongue Movements
Saying Used to Remember the
Names of the Cranial Nerves
•
•
•
•
•
•
On
On
Old
Old
Olympus‘
Olympus‘
Tiny
Tiny
Tops
Tops
A
A
•
•
•
•
•
•
Friendly
Friendly
Viking
Viking
Grew
Grew
Vines
Vines
And
And
Hops”
Hops”
•
•
•
•
•
•
•
Only
Old
Octopi
Trade
Tracks
At
Friendly
•
•
•
•
•
•
Vertebrate
Grasslands
In
Vagus
Ad
Hoc
III. FUNCTIONAL DIVISIONS OF THE
PERIPHERAL NERVOUS SYSTEM
• Based on Direction in Which
Neurons Conduct Nerve Impulses
• AFFERENT (SENSORY) DIVISION
• aa, like baa
• Af = toward
• Consists of all Afferent Neurons
• Includes all Spinal Nerves (Afferent
Fibers)as well as Cranial Nerves Which
are Sensory and Mixed (Afferent Fibers)
III. FUNCTIONAL DIVISIONS OF THE
PERIPHERAL NERVOUS SYSTEM
• EFFERENT (MOTOR) DIVISION
•
•
•
•
ee, like Lee or eff, like Jeff
Ef = away from
Consists of all Efferent Neurons
Includes all Spinal Nerves (Efferent
Fibers)as well as Cranial Nerves
Which are Motor and Mixed (Efferent
Fibers)
Two Efferent Subdivisions
OF THE PERIPHERAL NERVOUS SYSTEM
• Two Subdivisions (Based on Effectors)
– SOMATIC MOTOR NERVOUS SYSTEM
• Effectors are Voluntary: Skeletal Muscles
– THE AUTONOMIC NERVOUS SYSTEM
(Sympathetic & Parasympathetic
• Effectors are Involuntary: Cardiac Muscle,
Smooth Muscle, and Glands
ANS has 2 Divisions:
Sympathetic and Parasympathetic
• SYMPATHETIC DIVISION
• THORACOLUMBAR
• Nerves of the Sympathetic
Division Branch from
Thoracic Spinal Nerves
(T1-T12) and from some
Lumbar Spinal Nerves
(L1-L4)
• Explanation: Spinal Nerves
are Mixed, Their Efferent
Nerve Fibers are Somatic
and Autonomic; The
Autonomic Fibers are
Sympathetic Nerves
ANS has 2 Divisions:
Sympathetic and Parasympathetic
• PARASYMPATHETIC DIVISION
• CRANIOSACRAL
• Nerves of the Parasympathetic Division
Branch from some Cranial Nerves (III,
VII, IX, X, XI) and from some Sacral
Spinal Nerves (S2-S4)
• Explanation: Cranial Nerves III and XI are
Motor, the Remaining Cranial Nerves
Listed (VII, IX, X) are Mixed; Spinal
Nerves are Mixed; Efferent Fibers in All
These Nerves are Somatic and
Autonomic; The Autonomic Fibers are
Parasympathetic Nerves
b.
FUNCTIONS OF THE ANS
• OVERVIEW OF ANS FUNCTIONS
• ANS REGULATES AUTONOMIC
EFFECTORS IN WAYS THAT
MAINTAIN HOMEOSTASIS
• BOTH DIVISIONS:
• CONTINUALLY CONDUCT NI'S TO
AUTONOMIC EFFECTORS (TONICALLY
ACTIVE)
b.
FUNCTIONS OF THE ANS
• EXERT ANTAGONISTIC
INFLUENCES ON AUTONOMIC
EFFECTORS
– Ex: If Sympathetic Division Stimulates an
Autonomic Effector, then the
Parasympathetic Division will Inhibit the
Autonomic Effector
– *NOTE: ACTUAL EFFECT DEPENDS
ON WHICH DIVISION DOMINATES
(SITUATION)
• ANS INFLUENCED BY
CEREBRAL CORTEX AND
HYPOTHALAMUS
FUNCTIONS OF SYMPATHETIC DIVISION
• MAJOR FUNCTION
• DURING STRESS PRODUCES THE FIGHT OR
FLIGHT REACTION
• (SERVES AS THE BODY'S EMERGENCY
SYSTEM)
• Dominates during Stress (Physical or
Psychological)
• During Stress Produces "Fight or Flight“
Reaction
Fight or Flight" Reaction
• A Collection of Changes in Autonomic
Effectors which are Designed to
Prepare the Individual to Respond to
the Stress
• The Major Goal of all the Changes is
to Get Skeletal Muscles Prepared to
Expend Maximum Energy
SUMMARY OF MAJOR CHANGES THAT
OCCUR IN THE FIGHT OR FLIGHT REACTION:
• *CARDIAC MUSCLE:
• Rate/Strength of Heartbeat Increases
• *SMOOTH MUSCLE:
• Of Blood Vessels
• Coronary, Skeletal Muscle: Dilate
• Digestive Organ:
• Constrict
• Of Hollow Organs
• Respiratory Airways: Dilate
• Digestive Tract: Peristalsis Decreases
• *GLANDS
• Sweat Glands: Production of Sweat Increases
• Liver: Glycogen -----> Glucose
• Adrenal Medulla: Secretion of Epinephrine (Adrenalin)
Increases
SYMPATHETIC DURING
NONSTRESS
• DOMINATES SOME AUTONOMIC
EFFECTORS
• MAINTAINS THEIR NORMAL
FUNCTION
• Ex: Cardiac Muscle
FUNCTIONS OF
PARASYMPATHETIC DIVISION
• DOMINATES MOST
AUTONOMIC EFFECTORS
DURING NONSTRESS
• Rest and Repair Division
• Promotes Normal Digestive System
Activities
• (For Example: Peristalsis and
Elimination)
• http://www.octc.kctcs.edu/gcaplan/anat
/Notes/API%20Notes%20M%20%20P
eripheral%20Nerves.htm
• http://www.teachingbiomed.man.ac.uk/resources/wwwcal/c
ranial_nerves/page2.asp