Peripheral nervous system Flashcards
The Peripheral Nervous System (PNS) consists
of _____
the parts of the nervous system outside of
the brain and spinal cord
The PNS includes
○ Cranial Nerves
○ Spinal Nerve Roots and branches
○ Peripheral Nerves
○ Neuromuscular Junction
CN I
- The Olfactory Nerve carries special viscerosensory information regarding the sense of
smell from the superior aspect of the lateral and septal walls of the nasal cavity. - Olfactory neurons pass through the cribiform plate and then synapse on secondary neurons within the Olfactory Bulb.
Where do olfactory bulb fibers go?
fibers project directly into the ventromedial aspect of the temporal lobe
CN II
The Optic Nerve extends from the retina of each globe and carries special somatosensory information regarding sight, entering through the optic canal.
What happens at the optic chiasm?
Information from both retinas mixes and breaks posteriorly as the Optic Tracts, which extend into the cerebral cortex.
○ Nerves from the medial half of each optic nerve
crosses to the opposite side
CN III
The Oculomotor Nerve originates from the medial midbrain and travels into the orbit through the superior orbital fissure where it performs several functions.
● It provides general somatic motor innervation to
four of the six extraocular muscles, as well as
the levator palpebrae superioris.
Which cranial nerve provides visceromotor parasympathetic innervation with preganglionic fibers that synapse in the Ciliary Ganglion, which project to the ciliary muscle and the pupillary sphincter?
CN III - oculomotor
Lateral retinal tracts recieve input from the _____ visual area
medial
CN IV
- The Trochlear Nerve originates from the lateral midbrain and travels into the orbit
through the superior orbital fissure and carries somatic motor fibers. - provides general somatic motor innervation to
the superior oblique muscle, which depresses
and medial rotates the globe.
____ is a very small nerve in cadaveric specimens and
travels within the anterior portion of the tentorial notch of the tentorium cerebelli before piercing the lateral cavernous sinus towards the eye.
Trochlear nerve
CN V
- The Trigeminal Nerve is the largest of the
cranial nerves and originates from the lateral
aspect of the Pons (mid pontine).
The largest of the cranial nerves
Trigeminal
Which nerve originates Within a dural space on the
petrous part of the temporal bone?
Trigeminal
Within a dural space on the petrous part of the temporal bone is the ______, which is a synapse location for incoming first-order sensory neurons.
Trigeminal Ganglion
Characteristics of Trigeminal - Opthalmic division (V1)
- contains only somatic sensory fibers, passes through cavernous sinus and the superior orbital fissure, and into the orbit.
- Provides sensory innervation to the orbit, the cornea, the nasal cavity, and the skin of
the forehead, parts of the scalp, and the nose (to the tip of the nose).
Characteristics of Trigeminal - Maxillary division (V2)
- passes through the cavernous sinus and foramen
rotundum, contains only somatic sensory fibers, and provides sensory innervation to some of the nasal cavity, the upper oral cavity, and maxillary region of the face through several branches in the mid-face.
Characteristics of Trigeminal - Mandibular division (V3)
- passes through foramen ovale and into the
infratemporal fossa, medial to the ramus of the mandible. - Contains special viscero- motor fibers that provide motor innervation to the muscles of mastication.
- Also contains somatic sensory fibers that provide sensory innervation to the lower oral cavity, ear, and lateral and mandibular part of the face
(“chin strap” distribution).
CN VI
- The Abducens Nerve originates in the Pons and extends from the medial inferior Pons,
basically at the pontine medullary junction (where pons and medulla meet). - It travels into the orbit through the superior
orbital fissure, and provides somatic motor
innervation to the lateral rectus muscle.
very small nerve in cadaveric specimens
and pierces the dura medial to the Trigeminal Nerve, traveling through the cavernous sinus on its way to the superior orbital fissure.
Abducens Nerve
CN VII
- The Facial Nerve originates in the Pons and extends from the mediolateral inferior Pons, basically at the pontine medullary junction, lateral to the Abducens Nerve.
- The Facial Nerve contains somatic
motor, somatosensory, and visceral
neuronal fibers.
Where does CN VII exit the skull?
The nerve leaves the cranium by entering the internal acoustic meatus and into the Facial Canal of
the temporal bone.
Three main branches of the facial nerve that arise within the facial canal
○ Greater Petrosal Nerve
○ Stapedial Nerve
○ Chorda Tympani
What does the greater petrosal nerve do?
Branch of facial nerve
Parasympathetic fibers - travels into the middle cranial fossa and joins with sympathetic fibers and
these then project into the face, innervating the glands of the nasal cavity, palate, and lacrimals.
What does the stapedial nerve do?
travels into the middle ear and provides motor innervation to the Stapedius muscle.
What does chorda tympani do?
travels into and through the middle ear, eventually joining with the lingual nerve branch of CN V3.
○ It provides parasympathetic visceral motor fibers to the submandibular ganglion, stimulating secretion from salivary glands.
○ It also provides special sensory fibers for taste from the anterior part of the tongue.
After giving off these three branches within the Facial Canal, the rest of the Facial Nerve exits the skull base through the _____ foramen and has many branches.
stylomastoid
CN VIII
● The Vestibulocochlear Nerve originates from the lateral Pontine-Medullary junction as
a dual root nerve that has the appearance of a double-barrel shotgun.
● It travels into the internal acoustic meatus alongside the Facial Nerve.
● It contains only special somato- sensory fibers for hearing and balance.
Which nerve travels into the internal acoustic meatus
alongside the Facial Nerve?
Vestibulocochlear nerve
Two roots of CN VIII
- The Vestibular Root, containing the
Vestibular Ganglion on the distal end, supplies
the utricle, saccule, and semicircular canals, the organ of balance.
● The Cochlear Root supplies the cochlea and its spiral organ, the organ of hearing.
CN IX
- The Glossopharyngeal Nerve
- It contains special sensory fibers (taste, posterior
tongue), visceral sensory, somatic motor, and visceral motor neuronal fibers. - These fibers provide innervation of the parotid
gland, the sensory function of the tympanic
membrane and auditory tube, the visceral
sensory function of the throat and tonsils, and
pressure information from the Carotid Sinus.
Origin of CN IX
The Glossopharyngeal Nerve originates from the superior lateral medulla and leaves the skull through the Jugular Foramen.
Origin of CN X
The Vagus Nerve originates from the superior
lateral medulla (just below CN IX) and also leaves
the skull through the Jugular Foramen.
CN X
Vagus nerve
- has visceromotor function in the throat and
neck, innervating muscles of the soft palate,
pharynx, and larynx alongside CN IX.
- It has extensive visceromotor and viscerosensory
function throughout the thoracic, abdominal, and
pelvic cavities.
- Major parasympathetic nerve
Origin of CN XI
Accessory Nerve
originates from the upper 5 or 6 cervical spinal nerves and ascends within the vertebral canal.
● It enters the skull as joined fibers through the Foramen Magnum and then exits the skull with the CNs IX and X through the Jugular Foramen.
CN XI
Accessory nerve
- It provides somatic motor innervation of the
Sternocleidomastoid muscle in the neck and then crosses laterally to innervate the Trapezius muscle.
Origin of CN XII
- originates from the inferior anterolateral
medulla as several tiny nerve roots that quickly join as one cranial nerve near the Vagus Nerve. - Exits the skull through the Hypoglossal Canal just superior to the Foramen Magnum
CN XII
Hypoglossal nerve
- It contains only general somatic motor fibers and innervates almost all the muscles of the ipsilateral tongue.
____ palsy causes ipsilateral tongue deviation.
CN XII
Origin of CN VIII
Originates from the lateral Pontine-Medullary junction as a dual root nerve that has the appearance of a double-barrel shotgun.
● It travels into the internal acoustic meatus alongside the Facial Nerve.
Origin of CN VII
- The nerve leaves the cranium by entering the internal acoustic meatus and into the Facial Canal of the temporal bone.
- After giving off these three branches within the Facial Canal, the rest of the Facial Nerve exits the skull base through the stylomastoid foramen
Where each branch of the Trigeminal nerve exits the skull
Opthalmic - superior orbital fissure
Maxillary - foramen rotundom
Mandibular - foramen ovale
Origin of CN IV
- Trochlear Nerve originates from the lateral midbrain and travels into the orbit through the superior orbital fissure
Origin of CN III
Oculomotor Nerve originates from the medial midbrain and travels into the orbit through the superior orbital fissure
Origin of CN II
- Optic Nerve extends from the retina of each globe and carries special somatosensory information regarding sight, entering through the optic canal.
There are ____ pairs of Spinal Nerves that arise bilaterally from each spinal cord segment
and pass through intervertebral foramina to the peripheral tissue.
31
From C1 through C7 the spinal nerves arise ____ the vertebrae
Above (C7 has a nerve going above and below it)
Everything below C7 has a nerve root coming out ____ the vertebrae
below
A central bulge disc at C4 will impact which nerve?
C5 (picture on slide 34)
T/F Posterior Rami are named for the nerve root
from which they originate
T - except C1-3
The Anterior/Ventral Rami are ____ than the posterior rami and form the peripheral nerves and plexuses that innervate the rest of the body.
larger
The Somatic Plexuses include:
○ Cervical plexus (C1-C4)
○ Brachial plexus (C5-T1)
○ Lumbar plexus (L1-L4)
○ Sacral plexus (L4-S3)
The Cervical Plexus innervates the ____
muscles of the neck and the skin over the neck and scalp.
The _____ innervates the pectoral girdle and upper extremity.
Brachial Plexus
The ____ innervates the lower anterior abdominal wall and the anterior thigh.
Lumbar Plexus
The Sacral Plexus innervates the _____
gluteal region, posterior thigh, and lower leg.
Sensory roots from each spinal cord segment correspond to the cutaneous sensory innervation of a particular area of the skin, which is known as a _____
Dermatome
____ are similar and represent the muscle mass that is innervated by a single spinal cord segment.
Myotomes
Monosegmentally innervated muscles are innervated by motor neurons from a single spinal cord segment and can be evaluated ______
by assessing tendon stretch reflexes.
_____ innervated muscles are innervated by neurons
whose anterior horn lower motor neuron nuclei extend over several spinal cord segments.
Polysegmentally
The ____ spinal nerves supply the region of the neck with innervation.
C1-C4
Nerves of the cervical plexus
■ Lesser Occipital Nerve (C2)
■ Great Auricular Nerve (C2-C3)
■ Transverse Cervical Nerve (C2-C3)
■ Supraclavicular Nerve (C3-C4)
The _____ is the motor part of the Cervical Plexus and arises from the anterior rami of C1-C3.
Ansa Cervicalis
The _____ originates from the C3-C5
anterior rami and innervates the diaphragm.
Phrenic Nerve
The Suboccipital, Greater Occipital, and 3rd Occipital nerves all emerge from the ____ of the posterior
head and neck.
deep occipital region
Roots of the Brachial Plexus emerge from the vertebral column between the anterior and middle scalene muscles, the _____, in the lateral neck.
Interscalene Groove
In the Brachial plexus, Anterior rami of spinal nerves ____ form the 5 Roots.
C5-T1
Which nerve roots form which trunks in the brachial plexus?
C5 and C6 come together to form the Upper Trunk; C7 forms the Middle Trunk; C8 and T1 come together to form the Lower Trunk.
Formation of the cords in the brachial plexus
○ Anterior divisions of C5-C7 form the Lateral Cord.
○ Anterior divisions of C8-T1 form the Medial Cord.
○ Posterior divisions of all trunks form the Posterior Cord.
The three cords divide into the five Terminal Nerves of the Brachial Plexus:
Medial and lateral cords: musculocutaneus, median and ulnar nerve
Posterior cord: axillary and radial nerve
The Lumbar Plexus arises from spinal nerves ____ and the Sacral Plexus arises from spinal nerves ____.
L1-L4 ; L4-S3/S4
Lumbar plexus is composed of:
○ The Iliohypogastric Nerve: L1 nerve root.
○ The Ilioinguinal Nerve: L1 nerve root.
○ The Genitofemoral Nerve: merging of fibers from L1 and L2.
○ The Lateral Cutaneous Nerve of the Thigh: merging fibers from L2 and L3.
○ The large Femoral Nerve: merging fibers from L2, L3, and L4 roots.
○ The Obturator Nerve: other fibers from the L2, L3, and L4 roots.
Sacral plexus is composed of:
○ The Superior Gluteal Nerve: L4 to S1 nerve roots.
○ The Inferior Gluteal Nerve: L5 to S2 nerve roots.
○ The Tibial Nerve: merging of fibers from L4 to S3.
○ The Common Fibular Nerve: merging fibers from L4 and S2.
○ The Sciatic Nerve: merging of the Tibial and Common Fibular Nerves.
○ The Posterior Cutaneous Nerve of the Thigh: fibers from the S1 to S3 roots.
○ The Pudendal Nerve: fibers from the S2 to S4 nerve roots.
