Lecture 10 & 11: PNS Flashcards by megan lee

PNS

Collection of nerve fibers and ganglia (cluster of neuronal cell bodies)
12 cranial nerves
31 spinal nerves
Autonomic (visceral) nerve fibers
Associated sensory and anatomic ganglia

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Cranial nerves

12 pairs
First 2 are extensions of cerebrum
CN III-XII have nuclei in brainstem; either sensory, motor, parasympathetic or a combination

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Comparison of cranial nerves to spinal cord

Sensory nuclei = posterior horn
Motor nuclei = anterior horn
Parasympathetic nuclei = lateral horn in S2-S4
Sensory ganglia = dorsal root ganglia

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CNI

Olfactory Nerve
Pure sensory
Opening at cribriform plate of ethmoid bone
Sensory ganglia: olfactory bulb
Dendrites extend into nose to pick up smell, then form olfactory tract to convey smell to brain
Doesn’t pass through thalamus

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CNII

Optic Nerve
Pure sensory
Opening at optic canal
Some optic nerves cross midline at optic chiasm
After midline = optic tract to thalamus
At thalamus, it finds lateral geniculate nucleus and continues as optic radiation/optic projection fibers to visual cortex in occipital lobe

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Pituitary gland

Behind optic chiasm
Controls endocrine system
Early symptom of cancer/tumor: double vision

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CNIII

Oculomotor Nerve
Motor and parasympathetic
Opening at superior orbital fissure
Eye muscles (motor)
Iris muscles to change pupil (contract iris = decrease pupil size) (parasympathetic)
Parasympathetic ganglion: ciliary ganglion

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CNIV

Trochlear Nerve
Pure motor
Opening at superior orbital fissure
Extra ocular muscle - superior oblique muscle

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CNV

Trigeminal Nerve
Sensory ganglion: semilunar ganglion
3 divisions: ophthalmic, maxillary, mandibular

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Ophthalmic Branch (V1)

Pure sensory
Opening at superior orbital fissure
Supplies orbital cavity with sensory innervation
Some sensory fibers to sinus and forehead

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Maxillary Branch (V2)

Pure sensory
Opening at foramen rotundum
Sensory fibers to nasal cavity and upper half of oral cavity (teeth and palettes)
Projects to skin between lower eyelid and upper lip

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Mandibular Branch (V3)

Sensory and motor
Opening at foramen ovale
Lower half of oral cavity (teeth, pain temperature for anterior 2/3 of tongue), sensory fibers to skin covering mandible (sensory)
Muscles that move mandible for mastication (motor)

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CNVI

Abducens Nerve
Pure motor
Opening at superior orbital fissure
Muscle that moves eye away from midline

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CNVII

Facial Nerve
Motor, sensory, parasympathetic
Opening at internal acoustic meatus
Superficial muscles/muscles of expression (motor)
Taste on tongue on anterior 2/3 (sensory)
Sensory ganglion: geniculate ganglion
Sublingual and submandibular gland (both salivary) and lacrimal gland (tears) (parasympathetic)
Parasympathetic ganglion: Submandibular ganglion (salivary) and pterygopalatine (lacrimal) ganglion

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CNVIII

Vestibocochlear Nerve
Pure sensory
Opening at internal acoustic meatus
Vestibular: sense of balance/equilibrium
Cochlear: sense of hearing

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CNIX

Glossopharyngeal Nerve
Sensory, motor, parasympathetic
Opening at jugular foramen
Tiny muscles (motor)
Pain, temperature, taste in posterior 1/3 of tongue, and pharynx (sensory)
Sensory ganglion: superior and inferior ganglion
Parotid gland (largest salivary gland), carotid sinus and carotid body for blood pressure
Parasympathetic ganglion: otic ganglion

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CNX

Vagus Nerve
Sensory, motor, parasympathetic
Opening at jugular foramen
Larynx (sensory)
Sensory ganglion: superior and inferior ganglion
Muscles of pharynx and larynx (motor)
Parasympathetic innervation to thoracic viscera, and almost all abdominal viscera (stops at left 1/3 of transverse colon)

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CNXI

Accessory Nerve
Pure motor
Opening at jugular foramen
Supplies sternocleidomastoid and trapezius muscle

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CNXII

Hypoglossal Nerve
Pure motor
Opening at hypoglossal canal
Muscles of the tongue

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Spinal nerves

31 pairs
Connected to spinal cord by ventral (motor) and dorsal (sensory) root; therefore mixed nerves
Immediately splits into ventral (thicker) and dorsal ramus (mixed nerves)

Dorsal ramus

Do not communicate with each other

Supples deep muscles of the back and overlying skin

Ventral ramus

Communicates with each other forming a network/plexus to create more choices for different types of nerves

T1-T12 ventral ramus

Does not form plexus
T1-T11 form intercostal nerves
T12 forms subcostal nerve
Ribs prevent communication

Cauda eqina

Bundle of roots from lumbar, sacral, coccygeal spinal nerves that descend to respective foramina before emerging vertebral canal

Cervical spinal nerves

C1-C8 C1-C7 emerges above corresponding vertebrae C8 emerges between CVII and TI

Thoracic spinal nerves

T1-T12 Exit below the corresponding vertebrae Intercostal nerves travel in intercostal space to intercostal and abdominal muscles, and skin of ventral trunk

Dermatome

Area of skin innervated by single spinal nerve/spinal cord segment

Myotome

Skeletal muscle innervated by single spinal nerve/spinal cord segment

Nerve plexus

Intertwined network of nerve fibers

Somatic plexus

Ventral rami of spinal nerves (except T2-T11) Ventral rami communicate and redistribute their fibers Each branch of somatic plexus carries fibers from several spinal nerves Fibers from each ventral ramus go to several branches

Visceral plexus

Autonomic nerve fibers

Cervical plexus

Ventral rami of spinal nerves C1-C5 Cutaneous branches (lesser occipital nerve and greater auricular nerve) Ansa cervicalis Phrenic nerve

Cutaneous branch

Skin to entire neck and back of head (scalp)

Ansa cervicalis

Superficial muscles in front of neck

Phrenic Nerve

Diaphragm muscle

Brachial Plexus

``` C5-T1 form roots Roots form trunks (upper, middle lower) Each trunk divides to anterior and posterior division Divisions make 3 cords: lateral, medial and posterior Branches arise from the cords Musculo-cutaneous Radial Nerve Ulnar Nerve Median Nerve ```

Musculo-cutaneous

Mixed Muscles to anterior arm Skin on lateral forearm

Radial Nerve

Mixed Muscle to posterior arm and posterior forearm Skin to posterior arm, posterior forearm, back of hand

Ulnar Nerve

Mixed Muscle to anterior forearm, hand Skin to palmar of hand

Median Nerve

Mixed Muscle to anterior forearm, hand Skin to palmar of hand

Lumbar plexus

L1-L5 Lateral femoral cutaneous Obturator Femoral Nerve

Lateral femoral cutaneous

Skin to lateral thigh

Obturator

Mixed Muscle to medial thigh Skin to medial thigh, hip joint, knee joint

Femoral Nerve

Spinal segment of L2-L4 Muscle to anterior thigh Skin to anterior thigh, medial thigh and medial leg

Sacral plexus

``` L4-Co1 Superior gluteal Inferior gluteal Sciatic Nerve (common fibular/peroneal, tibial) Pudendal Nerve ```

Superior gluteal

Muscles to gluteal region

Inferior gluteal

Muscles to gluteal region

Sciatic Nerve

Spinal segment of L4-S3 Common fibular: mixed; muscles to anterior and lateral leg, skin to lateral leg and dorsum of foot Tibial: mixed; muscles to posterior leg and plantar of foot, skin to posterior leg and plantar of foot

Pudendal Nerve

Mixed Muscles to pelvic floor Skin to genitals