Lecture 10 & 11: PNS Flashcards
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
Cranial nerves
12 pairs
First 2 are extensions of cerebrum
CN III-XII have nuclei in brainstem; either sensory, motor, parasympathetic or a combination
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
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
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
Pituitary gland
Behind optic chiasm
Controls endocrine system
Early symptom of cancer/tumor: double vision
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
CNIV
Trochlear Nerve
Pure motor
Opening at superior orbital fissure
Extra ocular muscle - superior oblique muscle
CNV
Trigeminal Nerve
Sensory ganglion: semilunar ganglion
3 divisions: ophthalmic, maxillary, mandibular
Ophthalmic Branch (V1)
Pure sensory
Opening at superior orbital fissure
Supplies orbital cavity with sensory innervation
Some sensory fibers to sinus and forehead
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
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)
CNVI
Abducens Nerve
Pure motor
Opening at superior orbital fissure
Muscle that moves eye away from midline
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
CNVIII
Vestibocochlear Nerve Pure sensory Opening at internal acoustic meatus Vestibular: sense of balance/equilibrium Cochlear: sense of hearing
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
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)
CNXI
Accessory Nerve
Pure motor
Opening at jugular foramen
Supplies sternocleidomastoid and trapezius muscle
CNXII
Hypoglossal Nerve
Pure motor
Opening at hypoglossal canal
Muscles of the tongue
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
