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STRUCTURAL COMPONENTS OF PNS 12 CRANIAL NERVES 31 SPINAL NERVES
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THE PERIPHERAL NERVOUS SYSTEM
FUNCTION OF PNS
• CARRIES MESSAGES AWAY FROM CNS
• CARRIES MESSAGES TOWARD CNS
STRUCTURAL COMPONENTS OF PNS
• 12 CRANIAL NERVES• 31 SPINAL NERVES
FUNCTIONAL COMPONENTS OF PNS
• AFFERENT/SENSORY DIVISION• EFFERENT/MOTOR DIVISION
– SOMATIC NERVOUS SYSTEM– AUTONOMIC NERVOUS SYSTEM
CRANIAL NERVES
• ORIGINATE FROM FOREBRAIN AND BRAIN STEM
• MOST ARE MIXED NERVES• A FEW ARE SENSORY ONLY
CRANIAL NERVE GANGLIA
• SENSORY CELL BODIES OUTSIDE CNS
• CELL BODIES OF MOTOR NEURONS ARE LOCATED IN NUCLEI IN CNS
CRANIAL NERVE NUCLEI
• NUCLEI IN CNS– SOMATIC MOTOR NEURONS– VOLUNTARY CONTROL
• VISCERAL MOTOR NEURONS– PART OF PARASYMPATHETIC DIVISION OF
AUTONOMIC NERVOUS SYSTEM– ALL BUT VAGUS SERVE ONLY STRUCTURES IN
NECK AND HEAD• NUMBERED I – XII
CRANIAL NERVE I• OLFACTORY NERVES• ARISE FROM RECEPTOR CELLS IN EPITHELIA OF NASAL
MUCOSA• PASS THROUGH CRIBIFORM PLATE• ENTER OLFACTORY BULBS• PASS BACK THROUGH OLFACTORY TRACT• TERMINATE IN RHINENCEPHALON • MEDIAL SIDES OF TEMPORAL LOBE• ENTIRELY SENSORY• SENSE OF SMELL
CRANIAL NERVE II
• OPTIC NERVE• ACTUALLY BRAIN TRACTS
– OUTGROWTHS OF EMBRYONIC DIENCEPHALON• ORIGINATE IN RETINA OF EYES• ENTERS BRAIN THROUGH OPTIC FORAMEN OF
SPHENOID• TWO NERVES MEET IN OPTIC CHIASMA• SENSORY ONLY• VISION
DECUSSATION AT OPTIC CHIASMA
• TWO OPTIC NERVES MEET AT CHIASMA• NERVE FIBERS FROM MEDIAL HALF OF
EACH RETINA CROSS OVER TO OTHER SIDE• NERVE FIBERS FROM LATERAL HALF OF
EACH RETINA REMAIN ON SAME SIDE• OPTIC TRACT CONTINUES ON FROM OPTIC
CHIASMA• EACH OPTIC TRACT CONSISTS OF FIBERS
FROM RETINA OF BOTH EYES
OPTIC TRACTS• SOME OPTIC TRACT FIBERS TERMINATE IN SUPERIOR
COLLICULI – SUBCONSCIOUS VISUAL REFLEXES
• MOST OF FIBERS TRAVEL TO LATERAL GENICULATE BODIES OF THALAMUS– SYNAPSE WITH NEURONS THAT FORM OPTIC RADIATIONS
• OPTIC RADIATIONS ARE THIRD ORDER NEURONS– PASS THROUGH INTERNAL CAPSULE
• TERMINATES IN VISUAL CORTEX OF THE OCCIPITAL LOBE
CRANIAL NERVE III
• OCULOMOTOR NERVE• EMERGE FROM THE MIDBRAIN• JUST SUPERIOR TO PONS• ENTER ORBITS THROUGH SUPERIOR
ORBITAL FISSURES• SOMATIC MOTOR NEURONS• PROPRIOCEPTIVE SENORY NEURONS• FOUR OF SIX EXTRINSIC MUSLCE HTAT
MOVE EYEBALL
EYE MUSCLES INNERVATED BY CRANIAL NERVE III
• SUPERIOR RECTUS• MEDIAL RECTUS• INFERIOR RECTUS• INFERIOR OBLIQUE MUSCLE• LEVATOR PALPEBRAE• INTINSIC MUSCLE OF EYE
– SHAPE OF LENS– SIZE OF PUPIL
PARASYMPATHETIC COMPONENTS
• PREGANGLIONIC (PRESYNAPTIC) NEURON
• POST GANGLIONIC (POSTSYNAPTIC) NEURON
• CILIARY GANGLIA
CRANIAL NERVE IV
• TROCHLEAR NERVE• ARISE BELOW INFERIOR COLLICULI• DORSAL SURFACE OF MIDBRAIN• ONLY CRANIAL NERVES TO EXIT FORM
DORSAL SURFACE• ENTER ORBITS THROUGH SUPERIOR
ORBITAL FISSURES• SOMATIC MOTOR NEURONS• PROPRIOCEPTIVE SENSORY NEURONS
EYE MUSCLES INNERVATED BY CRANIAL NERVE IV
• SUPERIOR OBLIQUE MUSCLES
CRANIAL NERVE V• TRIGEMINAL NERVES• EMERGE FROM LATERAL SIDES OF PONS• THREE DIVISIONS• OPTHALMIC
– SUPERIOR ORBITAL FISSURE• MAXILLARY
– FORAMEN ROTUNDUM• MANDIBULAR
– FORAMEN OVALE• MAJOR SENSORY NERVES OF FACE
GANGLIA OF CRANIAL NERVE V
• TRIGEMINAL/SEMILUNAR GANGLIA– LOCATED AT THE POINTS WHERE DIVISIONS
JOIN BEFORE ENTERING BRAIN
SOMATIC MOTOR NEURONS
• IN MANDIBULAR NERVE• INNERVATES MUSCLE OF
MSTIDCATION– MEDIAL AND LATERAL PTERYGOID– MASSETER– TEMPORALIS– ANTERIOR BELLY OF DIGASTRIC
CRANIAL NERVE VI
• ABDUCENS• ARISES IN METENCEPHALON• EXIT BELOW BRAIN STEM• ENTER ORBITS THROUGH SUPERIOR
ORBITAL FISSURES• SOMATIC MOTOR NEURONS• PROPRIOCEPTIVE SENSORY
NEURONS
EYE MUSCLES INNERVATED BY CRANIAL NERVE VI
• LATERAL RECTUS MUSCLES
COORDINATION OF EYE MOVEMENTS
• REQUIRES COORDINATION OF CRANIAL NERVES III, IV AND VI.
CRANIAL NERVE VII
• FACIAL NERVE• ARISE AT LOWER BORDER OF PONS• LATERAL TO ABDUCENS• LEAVE THROUGH THE INTERNAL
AUDITORY MEATUS TO THE STYLOMASTOID FORAMINA.
• PASS FORWARD ACROSS CHEEK• PIERCES PAROTID SALIVARY GLAND
DIVISIONS OF FACIAL NERVES
• MOTOR• SENSORY• PARASYMPATHETIC
MOTOR
• MUSCLES OF FACIAL EXPRESSION
SENSORY
• PROPRIOCEPTION• TASTE BUDS ON NATERIOR TWO
THIRDS OF TONGUE• CELL BODEIS ARE GOUND IN
GENICULATE GANGLIA IN PETROUS PORTION OF TEMPORAL BONE
PARASYMPATHETIC
• LACRIMAL GLAND• MUCOUS GLANDS OF NASAL CAVITY• SUBLINGUAL AND SUBMANDIBULAR
SALIVAR GLANDS• PTERYGOPLATINE GANGLIA• SUBMANDIBULAR GANGLIA
CRANIAL NERVE VIII
• VESTIBULOCOCHLEAR NERVE– VESTIBULAR– COCHLEAR
• ARISE FROM INNER EAR RECPTORS• PERTROUS PORTIONS OF TEMPORAL BONE• EXITS THROUGH INTERAL AUDITORY
MEATUS• ENTERS BRAIN STEM JUST BELOW PONS
COCHLEAR DIVISION
• ORIGINATES IN SPIRAL ORGAN– COCHLEA OF EAR
• SPIRAL GANGLIA• HEARING
VESTIBULAR DIVISION
• ORIGINATES IN AMPULLAE OF SEMICIRCULAR DUCTS, SACCULE AND UTRICLE
• VESTIBULAR GANGLIA• EQUILIBRIUM
CRANIAL NERVE IX
• GLOSSOPHARYNGEAL NERVE• MIXED NERVE• EMERGES FROM MEDULLA • EXITS THROUGH JUGULAR
FORAMEN
SENSORY COMPONENTS
• FROM TASTE BUDS OF POSTERIOR THIRD OF TONGUE
• FROM MUCOUS MEMBRANES OF PHARYNX, TONISL AND MIDDLE EAR CAVITIES
• FROM RECEPTORS THAT MONITOR BLOOD LEVELS OF OXYGEN AND CARBON DIOXIDE– CAROTID BODIES
• BLOOD PRESSURE– CAROTID SINUS
• SUPERIOR AND INFERIOR GANGLIA
SOMATIC MOTOR COMPONENTS
• STYLOPHARYNGEUS MUSCLES• JOIN WITH CRANIAL NERVES X AND
XI TO INNERVATE OTHER PHARYNGEAL STRUCTURES
PARASYMPATHETIC COMPONENTS
• SYNAPSE IN OTIC GANGLIA• INNERVATES PAROTID SALIVARY
GLANDS
CRANIAL NERVE X
• VAGUS NERVE• ONLY CRANIAL NERVE NOT
RESTRICTED TO HEAD AND NECK• ARISE FROM SIDES OF MEDULLA• EXITS THROUGH JUGULAR
FORAMEN• ENTERS THORAX AND ABDOMEN
SOMATIC MOTOR COMPONENT
• VOLUNTARY MUSCLE OF PHARYNX, AND LARYNX
SENSORY
• FROM TASTE RECEPTORS IN BASE OF TONGUE
• SENSORY INPUT FROM VISERA– PROVIDE INPUT FOR REGULATION OF
HEART RATE, RESPIRATION, BLOOD PRESSURE, DIGESTION, ETC.
– NAUSEA AND DISTENSION
CRANIAL NERVE XI• ACCESSORY NERVE• TWO NERVES
– ONE RISES FROM MEDULLA– ONE RISES FROJM CERVICAL REGION
• SPINAL COMPONENT ENTERS THROUGH FORAMEN MAGNUM
• JOINS CRANIAL COMPONENT AND LEAVES THROUGH JUGULAR FORAMEN
• SUPPLIES MUSCLE SOF LARYNX AND PHARYNX• TRAPEZIUS AND STERNOCLEIDOMASTOID
CRANIAL NERVE XII
• HYPOGLOSSAL NERVES• ARISE FROM ANTERIOR MEDULLA• EXIT THROUGH HYPOGLASSAL CANALS• LOCATED BELOW TONGUE• CLOSE RELATIONSHIP TO FIRST CERVICAL
SPINAL NERVE• SOMATIC MOTOR NEURONS• PROPRIOCEPTIVE SENSORY NEURONS
ANSA CERVICALIS
• FIRST THREE CERVICAL NERVES• SO CLOSELY ASSOCIATED WITH
HYPOGLOSSAL THAT THEY APPEAR TO ARISE FROM THE CRANIAL NERVE
SPINAL NERVES• 31 PAIRS• LEAVE VETERBRAL
CANAL BY APSSING THOUGH INTERVERTEBRAL FORAMINA
• FIRST PAIR EXIT BETWEEN OCCIPTIAL BONE AND ATLAS
• SECOND –SEVENTH CERVICAL EMERGE ABOVE VERTEBRAE
• REST PASS BELOW VERTEBRAE
FORMATION OF SPINAL NERVES
• UNION OF VENTRAL AND DORSAL ROOTS
• VENTRAL ROOTS CONTAIN MOTOR NEURONS
• DORSAL ROOTS CONTAIN SENSORY NEURONS
• ALL SPINAL NERVES ARE MIXED NERVES
BRANCHES OF SPINAL NERVES• DORSAL RAMUS
– INNERVATES SKIN AND MUSCLES OF BACK• VENTRAL RAMUS
– VARIES ACCORDING TO BODY REGION– T2 – T 12 PASS THOUGH INTERCOSTAL SPACES TO
SUPPLY SKIN AND MUSCLES OF LATERAL AND ANTERIOR BODY WALLS
– CERVICAL, LUMBAR AND SACRAL REGIONS FORM PLEXUSES TO INNERVATE SKIN, MUSCLES AND JOINTS OF UPPER AND LOWER LIMBS
DERMATOMES
• SYSTEMATIC DISTRIBUTION OF SPINAL NERVE RAMI
• AREA OF SKIN SUPPLIED BY A SINGLE SPINAL NERVE
• ESPECIALLY REGULAR IN BACK REGION
• VARIES SOMEWHAT IN OTHERS
PLEXUSES
• INTERMINGLING OF VENTRAL RAMI• CERVICAL• BRACHIAL• LUMBOSACRAL
– LUMBAR– SACRAL
• DO NOT DUPLICATE CUTANEOUS DISTRIBUTION
CERVICAL PLEXUS
• VENTRAL RAMI OF FIRST FOUR CERVICAL NERVES
• INNERVATES MUSCLES AND SKIN OF NECK, SHOULDER AND CHEST
• CONNECT WITH CRANIAL NERVES X, XI AND XII
• PHRENIC NERVE
BRACHIAL PLEXUS• VENTRAL RAMI OF LAST FOUR CERVICAL
NERVES • FIRST THORACIC NERVE• IINERVATES BACK AND UPPER LIMBS• MAJOR NERVES
– AXILLARY – RADIAL– MUSCULOCUTANEOUS– ULNAR– MEDIAN
LUMBOSACRAL PLEXUS
• INNERVATE SKIN AND MUSCLES OF BUTTOCKS, PELVIS, LOWER ABDOMEN, LOWER LIMBS
• LUMBAR PLEXUS• SACRAL PLEXUS
LUMBAR PLEXUS
• VENTRAL RAMI OF TWELTH THORACIC – SOME FIBERS
• VENTRAL RAMI OF FIRST FOUR LUMBAR
SACRAL PLEXUS
• VENTRAL RAMI OF LAST TWO LUMBAR
• VENTRAL RAMI OF FIRST FOUR SACRAL
• LUMBAR NEURONS REACH PLEXUS BY WAY OF LUMBOSACRAL PLEXUS
• SUPPLY LOWER BACK, PELVIS, LATERAL SURFACE OF THIGH AND LEG, AND DORSAL AND VENTRAL SURFACE OF FOOT
REPAIR OF DAMAGED NEURONS
CLINICAL CONDITIONS
NEURITIS
• INFLAMMATION OF NERVE • OFTEN TIMES MORE DEGENERATIVE THAN
INFLAMMATORY• CHARACTERIZED BY
– SHARP, STABBING PAINS• CAUSES
– MECHANICAL DAMAGE– PROLONGED PRESSURE– VASCULAR DISORDERS– PATHOGENIC ORGANISMS
BELL’S PALSY
• PERIPHERAL INFLAMMATION OF CRANIAL NERVE VII
• MUSCLES OF FACIAL EXPRESSION• CAUSES DIFFICULTY IN SPEAKING
AND EATING• FACE SAGS ON AFFECTED SIDE
SHINGLES
• INFECTION OF DORSAL ROOT GANGLION
• HERPES ZOESTER• CAUSES PAIN AND FLUID FILLED
VESCILES • ALONG PATH OF PERIPHERAL
SENSORY NERVES