Gross Anatomy: Neurology

Front 1

Basic Nervous System

Back 1

-composed of two types of cells: neurons and glia
-divided into the central nervous system (CNS) and the peripheral nervous system (PNS)
-The CNS contains the brain and spinal cord while the PNS contains the spinal and cranial nerves
-In the CNS a axon bundle is a tract, while in the PNS it is a nerve
-In the CNS a collection of somas is a nucleus, while in the PNS it is a ganglia

Front 2

Structure of a Nerve

Back 2

-A peripheral nerve is encased in the epineurium and contains lymphatics, fatty tissue, nerve fasicles, and blood vessels called vasa nervosum
-The nerve fascicles are encased in perineurium and contain several individual axons
-The individual axons are surrounded by a neurolemma (myelinated or unmyelinated) and a CT layer called the endoneurium
-There are 12 cranial and 31 spinal nerves

Front 3

Spinal Cord Segments

Back 3

-arising from each spinal cord "segment" are GSA and GSE fibers which innervate the dermatome and myotome
-At each segment is a dorsal and ventral horn which give rise to spinal nerve roots
-The ventral (anterior) root is comprised of efferent fibers carrying information from the CNS to the periphery while the dorsal (posterior) root is comprised of afferent fibers carrying information from the periphery to the CNS...At this point these branches are completely separate
-After the spinal nerve roots pass the intravertebral foramen they become mixed and then separate into a dorsal and ventral rami
-in other words the dorsal ramus IS NOT directly related to the dorsal root. It has a mixture of dorsal and ventral root
-The larger ventral ramus supplies the anterolateral body wall, hypaxial muscles, and the extremities
-The smaller dorsal ramus supplies the skin of the back, posterior scalp, facet joints, posterior ligaments of the spine and the epaxial (intrinsic back) muscles

Front 4

The PNS

Back 4

-divided into the somatic and visceral nervous systems
Somatic: Deals with body walls and extremities
1) Motor Component - Contains GSE somatomotor fibers that stimulate voluntary and reflex contraction of SKELETAL muscles
2) Sensory Component - Contains GSA somatosensory fibers that transmit information to the CNS concerning (each of these divisions run together)
a) Temperature, pain, heavy tough and heavy pressure from the body walls
b) Proprioception from muscles, tendons, and joints, and light touch/pressure and vibration from body walls

Front 5

Somatic Nervous System

Back 5

-There is only 1 neuron between the CNS and periphery
-The GSA fibers innervate the sensory receptors and have pseudounipolar somas in the dorsal root ganglion and then end in the dorsal horn
-The GSE fibers start right outside the spinal cord, travel through the ventral root and innervate skeletal muscle

Front 6

Dermatome

Back 6

-A specific area of skin supplied by the somatic afferents in a single spinal nerve is the dermatome - also involved in referred pain
-Nerves overlap (in the plexus) so that dermatomes overlap. Losing 1 spinal nerve or dorsal root will not produce complete anesthesia in an area
-The dermatomes contain cutaneous nerves (meissner or pacinian corpuscle, free nerve ending) which carry information from exteroceptors in the skin to the CNS. The cutaneous receptor is sensitive to a particular form of physical energy and tranduces it into a electrochemical signal. The receptors are also continuous with the pseudounipolar sensory neurons located in the dorsal root ganglia (NCC derived)
Ex:
1) Mechanoreceptors - respond to deformation or displacement. Include meissner (vibration and light touch) and pacinian (deeper deformation/pressure)
2) Thermoreceptors
3) Nociceptors - Free nerve endings that respond to damage tissue/pain

Front 7

Dermatome 2

Back 7

-the exteroceptive inputs as well as inputs from the proprioceptors enters the spinal cord via the central process of the neurons of the dorsal root ganglia
-The sensory fibers can either head to the brain or connect to efferent fibers via interneurons for reflex
-Nociceptors/Thermoceptors/some touch and pressure crossover immediately in the spinothalamic pathway
-Proprioception, touch, pressure, crossover in the medulla as part of the dorsal lambiscus (dorsal spinocerebellar) pathway

Front 8

Somatic Motor Control

Back 8

1) Stimulus is carried by a primary sensory neuron which travels all the way to the brainstem and crosses over
2) Connects to a secondary sensory neurons which goes to the thalamus to connect with a teriary sensory neuron
3) 3rd sensory neuron goes to the sensory cortex and via a interneuron it stimulates the upper motor neuron in the cerebral motor cortex
4)This travels down the spinal cord and stimulates a lower motor neuron, also known as a ventral or alpha-MN
5) The alpha-MN goes through the ventral horn and innervates a skeletal muscles for contraction

Front 9

Somatic Motor Control 2

Back 9

-The ventral roots convey axons of the lower motor neurons whose cell bodies are in the ventral horns of the spinal gray
-The cranial nerve motor control (9/12) are made by lower motor neurons from brain stem nuclei
-Each muscle fiber is innervated by a single alpha-MN, but each alpha-MN innervates many muscle fibers. What a alpha-MN innervates is the functional unit of a muscle
-Smaller, quicker muscles have less alpha-MN attached, while larger, slower muscles have more alpha-MN attached
-The basic structural unit of a muscle is the muscle fiber
-The terminal ends of alpha-MN branch repeatedly, lose their myelin sheaths, and terminate near the middle of muscle fibers at neuromuscular junctions

Front 10

Peripheral Nerve Injuries

Back 10

1) Irritative - Caused by acute or chronic mechanical trauma or inflammation
a) A sensory impulse can lead to pain or parasthesia (numb)
b) A motor impulse can lead to spasm
2) Destructive - May result from trauma or neuropathy (cutting a nerve, neurodegeneration)
a) If sensory cut then it can lead to anesthesia (no sensation) or hypersthesia (diminished sensation)
b) If motor cut then it can lead to paralysis or if cut incompletely then paresis (weakness)

Front 11

Visceral Nervous System Overview

Back 11

-deals with the internal organs and is divided into the motor (GVE) and sensory (GVA) components
1) Motor GVE - also known as the autonomic nervous system it controls smooth muscle, cardiac muscle, and glands
-Under the control of higher CNS centers (limbic system)
2) Sensory GVA -
a) Conveys visceral reflexes like baroreceptors and chemoreceptors
b) Visceral sensations like hunger, full, stress, anxious, nausea
c) Conveys vague and poorly localized organic pain like a stomach ache

Front 12

Autonomic Nervous System

Back 12

-divided into sympathetic and parasympathetic divisions - employ 2 neurons to target tissue
1) Sympathetic - arousal, fight/flight/freight, catabolic, and distributed to body of all vascular tissue
-Has a short preganglionic neuron that can control multiple long postganglionic neurons
-Preganglionic neurons transmits acetylcholine which binds nicotinic N on preganglionic receptor (on post-ganglionic neurons)
-Postganglionic neuron transmits dopamine, EPI, NOR to alpha/beta adrenergic on target organ. It is known as a adrenergic ending!

2) Parasympathetic - converse energy, restore body, anabolic, restricted to head, visceral of trunk, and erectile tissue
-Has a long preganglionic neuron that controls only 1 postganglionic neuron
-Preganglionic neuron transmits acetylcholine to nicotinic N receptor. Postganglionic neuron transmits acetylcholine to muscarinic receptor on target organ. It is known as a cholinergic ending!

Front 13

"Two-Neuron" Rule

Back 13

1) The first preganglionic (presynaptic) neuron is somewhere in the CNS
2) The preganglionic axon leaves the CNS and terminates by synapsing on the second neuron
3) The postganglionic (postsynaptic) neuron is located in a peripheral autonomic ganglion
4) The postganglionic axon leaves the ganglion and innervates smooth muscle, a gland, or the heart

-In the sympathetic NS the postganglionic neuron is a para or pre-vertebral ganglion near the CNS
-In the parasympathetic NS that postganglionic neuron is usually located in a ganglion on or in the walls of the target organ

Front 14

Innervation of PARA/SYM

Back 14

-organs which are dually innervated by the 2 divisions of the ANS typically produce opposing responses

Sympathetic - Eye dilation, decreased salivation, elevation in heart, bronchial dilation, decreased GI activity, ejaculation, vasoconstriction at skin BV and vasodilation at skeletal muscle BV, decreased secretion from pancreas endocrine

Parasympathetic: pupillary constriction, increased salivation, slow heart, bronchial constriction, increased GI activity, erection, increased pancreas secretion

Front 15

Parasympathetic Division

Back 15

-Known as craniosacral system because...
Preganglionic neuron cell bodies located in either the brain stem nuclei or ventral horns of S2-S4
-Preganglionic axons leave the brain stem nuclei for CN 3,7,9, and 10. The Vagus nerve provides parasympathetic innervation to the cervical, thoracic, and upper GI viscera
-Preganglionic axons leaving S2-S4 ventral roots (and rami) form the pelvic splanchnic nerves and innervate lower GI, pelvic, and perineatal organ (dick)

Front 16

Visceral Afferents

Back 16

-course along with parasympathetic nerves and convey visceral pain, sensation, and physiologic sensation from...
1) Mechanoreceptors - Respond to distention in the walls of the GI tract, respiratory structures, and the urinary bladder as well as baroreceptors in the arteries (have to piss)
3) Chemoreceptors - respond to change in partial pressure of gases, blood pH, and concentraton of H+ in stomach

Front 17

Parasympathetic Distribution

Back 17

1) Head - Structures receiving parasympathetic innervation supplied by CN 3, 7, and 1x
2) Neck, Thorax, Most of Abdomen - Innervated by Vagus
3) Rest of Abdomen and Pelvis - 1/3 transverse colon on including genitals receive PARA innervation from sacral nerves 2-3 via the hypogastric plexus

Front 18

Sympathetic Division

Back 18

-known as thoracolumbar system because...
-preganglionic neuron cell bodies are located in the intermediolateral horns of the T1-L2 segments
-Preganglionic axons leave the spinal cord in the ventral roots of the T1-L2 spinal nerves and then exit the vertebral canal on the T1-L2 spinal nerves
-The preganglionic axons leaving via T1-L2 spinal nerves go to bilateral chains of interconnected paravertebral ganglia called the sympathetic trunks
-The sympathetic trunks lie in paravertebral gutters along each side of the spine extending from base of skull to the coccyx

Front 19

Sympathetic Layout

Back 19

-After transversing the IV foramin, T1-L2 spinal nerves send preganglionic sympathetic fibers to the sympathetic trunk via the myelinated white rami. From here there are 4 options
1)Enter the chain and synapse at the nearest ganglia
2) Ascend the chain and synapse at a superior ganglion
3) Descend the chain and synapse at a inferior ganglion
4) Pass through the chain and synapse with prevertebral ganglia in the abdomen

Option 1: After synapsing at the trunk most postganglionic fibers rejoin the spinal nerves via unmyelinated gray rami for distribution to the body wall
-Jamie's summary - after the IV foramen the somatic fibers continue through the ventral rami. The autonomic fibers USUALLY go off the ventral rami to the sympathetic trunk via white rami, and then via gray rami they go back to the ventral rami because all body wall structures need autonomic innervation
-While the sympathetic nerves ONLY originate at T1-L2 via white rami, the sympathetic trunk extends the entire spinal column. Therefore, while white rami is only found at T1-L2, gray rami is found throughout the column so the sympathetic fibers can go back to the ventral rami

Front 20

Sympathetic Layout 2

Back 20

-body wall structures receiving sympathetic innervation...
1) sweat glands
2) arrector pilli - smooth muscle of hair follicles
3) vascular smooth muscle - vasocontriction of peripheral vessels except coronary arteries which dilate
...to turn off sympathetic stimulus you remove the stimulus

Front 21

Sympathetic Layout 3

Back 21

Option 2-3: Many postganglionic axons arising from cervical ganglia will leave the chain and form a periarterial plexus on the carotid artery and their branches to reach cranial and cervical viscera
Option 2-3: Some postganglionic fibers arising in cervical and upper thoracic ganglia will leave the chain as direct visceral branches to cervical and thoracic viscera like heart, lungs, and esophagus. At these organs postganglionic fibers from different parts of the trunk can communicate via a plexus to innervate the same organ (cardiac plexus innervates the heart)
-sympathetic and parasympathetic both innervate the same organ and also communicate via a plexus

Front 22

Sympathetic Layout 4

Back 22

-Just as GVE fibers leave via white rami and go out, GVA fibers from viscera come in through the white rami. The afferent and efferent travel together btw CNS and organ
-The visceral and somatic afferent fibers talk at the dorsal root ganglion and this is referred pain because the body doesn't know where the signal is coming from. GVA may stimulate GSA and produce referred pain. A heart attack will also produce pain in the arm known as referred cardiac pain (these fibers communicate at the same dorsal root ganglia

Front 23

Sympathetic Layout 5

Back 23

-for the preganglionic sympathetics that don't synapse in the sympathetic trunk, these are called splanchnic nerves
-These look for somewhere else to synapse so they do so anterior to the abdominal aorta at the prevertebral ganglia
-They have to pierce the diaphragm to reach this located and it is around the location of the common iliac arteries
-The prevertebral or preaortic ganglia travel along the anterior of the abdominal aorta
-Some of these pass through the prevertebral ganglia and synapse in the adrenal medulla
-Postsympathetic fibers that arise at the prevertebral ganglia reach their viscera by forming a periarterial plexus along arteries arising from the abdominal aorta

Front 24

Postganglionic Periarterial Plexus

Back 24

-The postganglionic fibers arising from the prevertebral ganglia can go to the GI tract and form the enteric nervous system going from the esophagus to the anal canal
-These are also known as auerbach's (myenteric) plexus between the two GI muscle layers
-These nerves facilitate contraction of smooth muscle sphincters and inhibit both peristalsis and glandular secretion

Front 25

Visceral Pain

Back 25

-visceral afferent (GVA) fibers in the abdomen and pelvis accompany sympathetic nerves (GVE) to transmit pain from
1) Nociceptors stimulated by distension of the GI tract (gas) and bladder (need to piss)
2) Strong contraction of smooth muscle in the wall of a visceral structure like the uterus

-Splanchnics (sympathetic fibers that don't synapse at trunk) take the GVA fibers from viscera to the dorsal root of spinal nerves T5-L2 via the white rami. The GVA may stimulate GSA fibers in the same spinal nerve dorsal roots and cause abdimopelvic referred pain
-Pain from abdominopelvic viscera is also consistently referred to specific regions of the body walls

Front 26

Additional Sympathetic

Back 26

-Larger division of the ANS and primarily in arteries, suprarenals, and skin
1) Cervical Sympathetic Chain -has 3 ganglia but NO white rami. Get sympathetic from white rami of thoracic white rami
a) superior cervical ganglia - largest sympathetic ganglia it lies opposite C2 and C3 and sends gray rami to C1-C4 and some cranial nerves
b) Middle cervical ganglion lies at C6 and sends gray rami to C5 and C6
c) Inferior Cervical Ganglion at C7 level often fuses with 1st thoracic ganglion to form the stellate ganglion and sends gray rami to C7 and C8

2) Thoracic Sympathetic Chain
-continuous with cervical chain and extends at neck of 1st rib to rib 10
-Passes the diaphragm and changes to the lumbar sympathetic chain
-Has a ganglion from each spinal nerve including white rami and sends a gray rami back to each spinal nerve

Front 27

Additional Sympathetic 2

Back 27

3) Splanchnic Nerves - Come from pre-ganglionic sympathetic fibers of T5-T12
a) Greater Splanchnic Nerve - Comprise T5-T10 fibers and 2nd cell bodies at celiac ganglion
b) Lesser Splanchnic Nerve - Comprise T10-T11 fibers and ganglia at superior mesenteric ganglion
c) Least Splanchnic Nerve - Comprise T12 fibers and synapse at renal ganglion

4) Lumbar Sympathetic Chain - begins after diapragm at medial arcuate ligament. Lies bilaterally against the bodies and intervertebral disc of the lumbar vertebral column. Has 4 ganglia
-upper 2 ganglia receive white rami communicans from spinal nerves
- all 4 send gray rami to the spinal nerves
-Passes inferiorly deep to the common iliac vessels to becme sacral trunk

5) Sacral Sympathetic Chain - Continues inferiorly until chains converge on the anterior aspect of the coccyx to form the

6) Ganglion Impar - small midline structure where the sympathetic chains come together and terminate

Front 28

Cranial Nerve Overview

Back 28

-Cranial nerves contain GVE/GVA/GSE/GSA
-Cranial nerves also have
1) Special Somatic Afferent (SSA) - Convey information that relate the body to the external environment.
a) Vision from retina
b) Sound from cochlea
c) Equilibrium from labyrinth (vestibular apparatus) of the inner ear

2. Special Visceral Afferent - Convey information associated with food ingestion like smell and taste

3. Special Visceral Efferent - Any fiber innervating skeletal muscles derived from the pharyngeal arches

Front 29

Cranial Nerve Locations

Back 29

1) Motor Group of Cranial Nerve Nuclei - Contain lower motor neurons giving rise to all the cranial nerve efferent fibers (GSE, SVE, GVE)

2. Primary Sensory Neurons - The neurons that give rise to cranial nerve afferent fibers are located in ganglia outside the CNS and project to secondary neurons in the dorsal gray of the brain stem

Front 30

Olfactory "Nerve"

Back 30

-not a true nerve
-receptors on the olfactory epithelium carry SVA fibers through the cribiform plate to the olfactory bulb and along the olfactory tract
-The cribiform plate of the ethmoid holds the olfactory bulbs and transmits rootlets of CN1 to the olfactory mucosa
-Olfactory mucosa very limited in humans to the upper nasal cavity
-pathology of the frontal lobes or floor of anterior cranial fossa can interfere with normal smell
-

Front 31

Olfactory Neurons

Back 31

-olfactory cells ("neurons") in the olfactory epithelium (mucosa) are primary sensory neurons that project their dendrites into the mucosa (cilia) and their axons to secondary olfactory neurons in the bulb and tract
-The olfactory epithelium is kept moist by the secretions of the olfactory glands, and it is in this moisture that inhaled scents are disolved

Front 32

Olfactory Neurons 2

Back 32

1) Unmyelinated central processes of the olfactory cells (olfactory axons) pierce the cribiform plate and enter the olfactory bulb
2. The "axons" synapse on secondary sensory neurons in the bulb whose central processes form the olfactory tract
3. The tract fibers project to all CNS structures concerned with olfaction collectively known as the rhinencephalon or nose brain
a) the piriform lobe is the site of primary olfactory cortex
b) Olfactory fibers also project to the hypothalamus
-Good smells leads to visceral responses like salvation and gastric secretion while bad smells lead to nausea

Front 33

Olfactory Lesions

Back 33

-Lesions of CN1 result in anosmia (loss of smell), hyposmia (decreased smell), and smell distortion
1) Olfactory axons vulnerable to lesions in acceleration/deceleration injuries of the head and neck causing them to shear
-if the nerve roots are sheared the injury can involve CSF leakage from the sub-arachnoid space next to the nasal cavity leading to a aluminum taste
2. You can also get tumors, abcesses, or meningiomas of the anterior cranial fossa
-caused by chronic smoking (toxic) and neurodegenerative diseases, and frontal lobe masses/abcesses
3. Sinonasal Inflammatory disease can block odorants from receptors compromising the sense of smell

Front 34

Olfactory Extra

Back 34

--olfactory epithelium has columnar cells, round cells, and bipolar neurons
-Bipolar neurons last for 30 days and are replenished by the round epitheliual cells
-The columnar epithelial cells maintain the structure
-Second order olfactory neurons (mitral cells) on the bulb synapse on tertiary neurons in olfactory cortex

Front 35

Optic Nerve Overview

Back 35

-SSA that mediates vision from rod and cone retina photoreceptors
-Rods and cones transduce light energy to electrical signal which triggers bipolar cells which are the primary sensory neurons of the visual pathway
-The bipolar cells synapse on ganglionic cells whose axons form the optic nerve
-after leaving the optic canal the nerve end at the middle cranial fossa optic chiasm where decussation occurs
-The optic fibers are vulnerable at this point to lesions of the pituitary gland and ventral diencephalon
-Optic nerve is more of a white matter tract because it is comprised of axons of secondary ganglionic nerves rather than primary bipolar nerves and it is covered with CNS myelin

Front 36

Optic Nerve Formation

Back 36

-The retina incompletely encircles the eye
-The ganglionic cell axons all converge to the optic disc, go posteriorly, pass through the sclera, and exit the eye
-Where they converge is the blind spot (no cones/rods)
In the retina...
1) Light passes through all the layers to stimulate the rods and cones (photoreceptor cells)
2) The signal is sent backwards first to the bipolar cells which are the primary sensory neurons fo the visual pathway
3) The bipolar cells and amacrine cells synapse with the ganglion cells
4) Ganglion axons at the surface of the retina create the optic nerve and lead to the chiasm

Front 37

Optic Nerve Formation 2

Back 37

1) Fovea Centralis - Most sensitive part of the retina that has a 1:1 ratio between cones and ganglion cells with no rods. Gives us maximal acuity and color vision
2) Lamina Cribrosa is the part of the sclera allowing ganglionic axons to leave the back of the eyeball and form the optic nerve. It is filled with small holes like the cribiform plate. Also passing through here is the central retinal artery
-Although the artery sends 4 branches through the optic disc it is a end artery who no collateral backup
-IMPORTANT to remember that the optic nerve looks more like a CNS tract. Why? Because a cross section shows that it is bathed in CSF and invested with all 3 meningeal layerss (pia, arachnoid, dura sheaths)

Front 38

Following the Optic Nerve

Back 38

-the eye is divided into a nasal visual field and a temporal visual field
-The retina is divided into a nasal retina and a temporal retina
-The nasal visual field projects onto the temporal retina and vice versa
-Axons from the nasal retina cross the midline at the optic chiasm while those on the temporal retina stay to their side
-Most axons in the optic tract terminal at the lateral geniculate nucleus of the thalamus
-Some axons project to the midbrain nuclei and provide visual imput for reflex maintaintence of balance, eye position, and control of the pupil size
-Visual inputs project to primary visual cortex surrounding the calcarine fissure in the occipital lobes of the brain

Front 39

Extraocular Eye Muscles Review

Back 39

1) Superior Rectus - Pulls the eye up and adduct (in)
2) Inferior Rectus - Pull the eye down and adduct (in)
3) Medial Rectus - Pull the eye adduct (in)
4) Lateral Rectus - Pull the eye abduct (out)
5) Superior Oblique - Back of eye to anterior trochlea pulley and posterior lateral across eye. Pull it DOWN and abduct (out)
6. Inferior Oblique - Across eye from lacrimal duct to sclera. Pull eye UP and ABDUCT (out)
7) Levator Palpebrae Superioris - opens the eye and runs from the orbit roof to the deep surface of the upper eye lid. Inn by CN III
8) The superior tarsal muscle (also known as Müller's muscle) is a smooth muscle adjoining the levator palpebrae superioris muscle that helps to raise the upper eyelid.

Front 40

CN II Lesions

Back 40

1) Prechiasmatic - To retina or optic nerve. Caused by...
a) Macular Degeneration
b) Glaucoma - Atrophy of optic disc due to fluid build up
c) Optic neuritis caused by MS, syphillis, or lyme disease
d) Facial Trauma
2. Chiasmatic Damage caused by..
a) Pituitary Adenomas
b) Interior Carotid Artery aneuryism
3) Postchiasmatic - Lesion to optic tract, LGN, or optic radiation
REMINDER: The nasal visual field projects to the temporal retina which does not cross over at the chiasm. The temporal visual field projects to the nasal retina which does cross over
...Therefore, information from the right half of each eye visual field (one nasal and one temporal) are carried by the left optic tract and vice versa

Front 41

CN II Lession 2

Back 41

1) Prechiasmatic Lesions - If a lesion occurs in the right optic nerve before the chiasm then you get monocular blindness
2) Chiasmatic Lesion - The optic tract cannot crossover successfully so only the tract from the temporal retina reaches the brain. Since the nasal visual field project to the temporal retina then you only have nasal visual, known as tunnel vission, or loss of peripheral (temporal) vision. This condition is known as bitemporal hemianopsia
3. Postchiasmatic Lesion - A lesion to the right optic tract after the chiasm cuts off the right eye temporal retina (right nasal vision) and left eye nasal retina (left temporal vision). You end up with loss of input from contralateral visual fields of both eyes. So you can see temporal in the right and nasal in the left. This is called right/left homonymous hemianopsia

Front 42

Optic Nerve Extra

Back 42

-Optic nerve thought as a CNS outgrowth called a nerve tract covered in glial cells
-each optic tract after the chiasm is carrying visual ifnormation from both eyes
-Other lesions include scotomas (blind spots) and papilledema (choked disc) due to increased intracrnail pressure near the optic foramen
-Increase pressure, like in the meninges subarachnoid space, can block venous return from the retina
-central processes of ganglionic cells travel via optic radiation to lateral geniculate body and occipital (visual) cortex

Front 43

Vestibulocochlear Nerve CN VIII Overview

Back 43

-Convey SSA input concerning sound from the cochlea and equilibrium from the semicircular canals of the vestibular system
-The nerve arises from the sulcus between the pons and medulla and travel laterally at the cerebello pontine angle
-CN VIII is transmitted through the internal acoustic meatus of the posterior cranial fossa

Front 44

CN VIII Lesions

Back 44

-Both CN7 and CN8 are vulnerable to the formation of benign acoustic neuromas (vestibular schwannoma) as they enter the meatus
-The benign neoplasm are encapsulated by the perineurium and compromise acoustic perception

Front 45

CN VIII Extra

Back 45

-CN VIII is 2 nerves
1) Vestibular Nerve (balance) arises from bipolar neurons in the vestibular ganglion and the distal fibers extend to hair cells in semicircular canals
2) Cochlear Apparatus (hearing) fibers arise from bipolar neurons in the spiral ganglion of the cochlea and distal fibers extend to hair cells in the cochlea
-Lesions to vestibular part of 8 cause dizziness, nausea and loss of balance
-Lesion to auditory part cause ipsilateral tinnitus (ear ringing) and deafness
-Because the two part travel together in the internal acoustic meatus with CN VII, pathology at this location like a acoustic neuroma will effect all 3

Front 46

Introduction to the Ear

Back 46

-3 main part
1) External Auditory Canal - Cartilagenous components laterall are continuous with the auricle and lead to the bony external acoustic meatus. The funnel shape tympanic membrane attaches to the malleus in the...
2) Middle Ear (Tympanic Cavity)
3) Inner Ear - Contains the semicircular canal and cochlea

Front 47

Introduction to the Membranous Labyrinth

Back 47

-In the otic capsule of the petrous temporal bone is the membranous labyrinth contained within a bony labyrinth
-Between the two labyrinth is a CSF like fluid called perilymph
-Within the membranous labyrinth is endolymph
-The membraneous labyrinth is divided into a cochlear duct (within the cochlea), a semicircular canal, and a utricle + saccule
-Within the otic capsule CN VIII divides into a vestibular and cochlear portion

Front 48

Cochlear Nerve

Back 48

-the cochlear nerve carries fibers for hearing and is composed of the central processes (axons) of neurons which have their cell bodies in the spiral ganglion
-Spiral ganglion are in the spiral canal (spiral organ) which is in the cochlea

Front 49

Processing Sound 1

Back 49

1) Sound waves induce vibration of the tympanic membrane and ossicles in the tympanic cavity
2) The stapes moves like a piston on the cochlea oval window generating pressure waves of perilymphatic fluid in the cochlea
-Cochlear made of 3 concentric coiled tubes. Tube in the middle is the cochlear duct with endolymph, the others have perilymph
3) Fluid wave moves around the scala vestibuli causing movement in the cochlear duct endolymph
4) As there is movement in the endolymph it forces movement in the basilar membrane of the organ of corti attached to the cochlear duct. This stimulate hair cells
5) The hair cells transmit action potential to bipolar neurons whose cell bodies are in the spiral ganglion also attached to the cochlea
-The fluid waves move across the cochlear duct at different locations corresponding to different frequencies
-The cochlear nerve runs through the cochlea modiolus and divides around the duct to form spiral ganglion and then hair cells which contact the basilar membrane of the organ of corti attached to the cochlear duct
6) The fluid wave of perilymph can move around the cochlear duct or through it to continue movement in the scala tympani which puts pressure on the round window causing it to move in and out of round window at opposite phase of the oval window
7) Action potential of spiral ganglion sends axon from the cochlear nerve to the cochlear nuclei located in the central pons

Front 50

Processing Sound 2

Back 50

-Processing of bilateral acoustic inputs begins in the brainstem but will project to acoustic inputs in temporal lobe cortex
-The time of arrival and intensity differences between ears allows for localization of sound
-Through brain stem pathways loud sounds can cause muscle contraction reflex by stimulating the CN VII and CN V. These will contract the stapedium ans tensor tympani (malleus) reflexively to decrease volume of sound or one's own speech

Front 51

Extra Cochlear Nerve

Back 51

-The hair cells ARE short cells that synapse on the bipolar spiral ganglion cells

Front 52

Vestibular Nerve

Back 52

-Responsible for helping to control posture, balance, and equilibrium
-vestibular nerve is made of central processes of bipolar neurons in the vestibular ganglion whose dendrites lead to the semicircular ducts
-Peripheral processes of vestibular ganglion convey inputs from...
1) Maculae of the utricle and saccule (otolithic organs), which detect linear acceleration and motion due to gravity and translational movement
2) From the ampullae of the semicircular canals which detect changes in angular motion and rotary accleration of the head in any direction relative to the vertical during quiet stance
-Vestibular nerve projections go to the medulla and vestibular nuclei

Front 53

Additional Balance Help

Back 53

-vestibular system primarily provides sensory inputs about the head so the CNS relies on other sensory inputs like...
1) Visual Inputs - convey info about movement with respect to the environment and direction of vertical
-Vestibulooculae reflex allow us to focus on a object even as our head moves
2) Proprioceptors - Convey input about joint position and muscle stretch, providing information concerning the relative alignment of body segments to each other
3) Postural Control - Done via innervation of the extensors of the posterior neck, back, and lower limb to support the body against the pull of gravity

Front 54

CN VIII Lesions

Back 54

Causes:
1) Viral labyrinthitis
2) Meniere's Disease (endolymph imbalance which confuse vestibular receptors)
3) Acoustic neuroma
4) Hypothalamus conflicting stimuli creat nausea

Symptoms
1) Deafness
2) Tinnitus
3) Dizziness
4) Vertigo
5) Nausea/Vomiting
6) Rhythmic oscillation of the eyes

Front 55

CN 3, 4, and 6 overview

Back 55

CN 3: Oculomotor nerve arises from the medial aspect of ther cerebral peduncles of the midbrain
1) GSE - innervate extraocular muscles. Each muscle innervation has its own nucleus
2) GVE - These are preganglionic parasympathetic that synapse in the ciliary ganglion. Ciliary innervates the pupillary constrictor and ciliary muscles.
-A parasympathetic postganglionic axon in the head like the ciliary ganglion usually piggy-back on branches of CN V

CN IV - Trochlear nerve exits the brain below the inferior colliculus on the dorsal aspect of the midbrain. Long intracranial course
1) GSE - Innervate superior oblique

CN VI - The abducent leaves the brain from the inferior pontine sulcus, pierces the dura mata and follows a long intradural course. Often involved in intracranial disease
1) GSE fibers innervate the lateral rectus

Front 56

CN 1 Opthalmic - Overview

Back 56

-Carries GSA fibers only which enter the superior orbital fissure
-3 divisions of CN V1 are known as NFL - nasociliary, frontal, and lacrimal
-These fibers innervate the cornea conjunctive and parts of sclera

Front 57

Testing the Extraocular Muscles

Back 57

-Challenge is that some muscles share a function so we need to test them separately. This is becuase we can produce the same movement from different nerves and different movements from the same nerve
-Testing these muscles can help us find legions in CN 3, CN 4, CN 6, the midbrain and pons

Front 58

Isolating the Elevators

Back 58

-doctor inscribes a H in space
1. Inferior Oblique - Both the inferior olbique and superior rectus look up so first you adduct the eye. This may seem counterintuitive since the superior rectus is used to adduct, but it actually moves it parallel to the transverse axis so it cannot generate torque and cannot mvoe the eye. Instead, the inferior olbique is put perpendicular to the TA so it makes maximal torque and is singled out. After this you elevate the eye

2. Superior Rectus - You do the opposite. First you abduct the eye so the IO is parallel to the TA and cannot generate torque. This makes the SR perpendicular to the TA and able to generate torque. Next you elevate the eye

Front 59

Isolating the Depressors

Back 59

1. Superior Oblique - Adduct the eye to eliminate the inferior rectus by making it parallel to the TA. Then depress the eye

2. Inferior Rectus - First abduct the eye to eliminate the SO by making it parallel to the TA. Then depress the eye

Front 60

Testing Muscles Innervated by CN III

Back 60

1) Superior Rectus - Look lateral and upward
2) Inferior Rectus - Look lateral and downward
3) Medial Rectus - Look medial
4) Inferior Oblique - Look medial and upward

-not common sense. If 2 muscles look up you move eye in opposite direction from one your interested in to place that one at a disadvantage. Then go in the common direction

Front 61

Lesions of CN 3,4,6

Back 61

-all pass through the cavernous sinus
-all are vulnerable to compression and lesions in the cavernous sinus due to
1) Septic Thrombosis
2) A internal carotid artery aneuryism in the cavernous sinus
3) Aneuryisms of components and branches of the cirlce of willis
4) Lateral expansion of the pituitary gland

Front 62

CN 3 Specific Lesions

Back 62

1) Ptosis (droopy) eyelid from paralyzed levator palpebre superiorsis
2) Muscle looks down and out cause no muscle to oppose lateral rectus (CN 6) and the superior oblique (CN 4)

Front 63

CN 6 Specific Lesions

Back 63

-without the lateral rectus the eyeball is adducted due to the unopposed pull of the medial rectus causing strabismus
-stabismus is the inability to direct both eyes towards the same object producing diplopia, or double vision

Front 64

CN IV Specific Lesion

Back 64

-with the loss of the superior oblique the eyeball is elevated and adducted
-the patient complains of a vertical diplopia when they try to depress their affected eye
-To reduce diplopia they will tilt their head

Front 65

Autonomic Innervation of the Eye

Back 65

-the shape of the lens is adjusted by the ciliary muscle contraction to keep a image in focus as it moves closer to the eye
-lens refracts light and makes it in focus
1) In normal vision the ciliary muscle is relaxed, the zonular fiber is tense, and the lens is flattened
2) For a object close to the eyes the ciliary muscle contraction allows for accomodation. The zonular fiber is lax and then lens is more rounded (more curved). Also, a contracted ciliary muscle allows for pupil constriction and convergence of the eyes

Front 66

The Pupil

Back 66

-the iris covers the lens and the central aperture of the iris is the pupil, the light part actually passes
-The pupil diameter is under active control of 2 antagonistic muscles
1) Pupil constrictor under control of the parasympathetic system
2) Pupil dilator under control of the sympathetic system
-light directed into the eye causes constriction
Pathosis
1) Maximum constriction of the eye is called miosis
2) Maximum dilation of the eye is called mydriasis

Front 67

The Pupil 2

Back 67

-CN 3 GVE fibers are parasympathetic fibers which synapse at the ciliary ganglion which innervates the pupillary constrictor and ciliary muscles (there are 4 parasympathetic ganglia on each side of the head)
1) The GVE fiber signal for CN III originates at the nucleus of edinger-westphal in the midbrain
2) The GVE preganglionic fibers are carried in the inferior division of the nerve
3) These fibers synapse on the ciliary ganglion inside the orbit
4) Postganglionic fibers are carried by a branch of the CN V(1) called the nasociliary nerve to the pupillary constrictor and ciliary muscles

Front 68

CN 3 GVE Lesions

Back 68

Lesion of...
1) Pupillary Constrictor - Pupil will be dilated and the pupillary light reflex will be lost (constriction of pupil in response to light)
2) Ciliary Muscle - Near vision is impaired and there is no accomodation of the lens
3 Dilation of the iris because dilator pupilliae is unopposed

Front 69

Sympathetics of the Head

Back 69

-most postganglionic sympathetic fibers supplying the head are distributed through the periarterial plexuses which surrounds the internal/external carotids

1) Superior Cervical Ganglion - Highest ganglion in sympathetic chain and innervates the head. The postganglionic fibers innervate the pupillary dilator and the superior tarsal muscle of the upper eyelid

1) Preganglionic sympathetic of the orbit starts at the T1-T2 cord segment
2) These fibers ascend through the cervical sympathetic chain and synapse in the superior cervical ganglion
3) The postganglionic fibers run in the internal carotid nerve and plexus and then enter the orbit
4) They run through the ciliary ganglion without synapsing and travel on ciliary nerves to reach their targets
a) Pupillary dilator - mydriasis
b) Superior Tarsal Portion of levator palpebrae superioris
c) Opthalmic artery and its branches. Branches of the opthalmic artery distribute to the forehead, and nose and include the supraorbital and supratrochlear artery

Front 70

Horner's Syndrome

Back 70

-interruption of the sympathetic pathway of the head leads to...
1) Fixed, constricted pupil (miosis)
2) Droopy eyelid (partial ptosis)
3) Loss of forehead sweating (anhydrosis) as the sympathetic innervation of the supraorbital and supratrochlear branches of the opthalmic artery are lost

Front 71

Extra Oculomotor

Back 71

-purely motor nerve
-GSE fibers supply striated muscle which are multipolar neurons with somas in the ocolomotor nucleus of the midbrain. Innervate all extraocular muscles except SO and LR
-GVE fibers run with GSE fibers until the ciliary ganglion
Superior Division: innervate levator palpebrae superioris and SR
INferior Division - Innervate MR, IR, IO, and root of the ciliary ganglion
-GSE fibers originate from ocoulomotor nucleus
-Check for lesions by looking for ptosis and having the patient look side to side

Front 72

Extra Trochlear

Back 72

-Composed of multipolar neurons that innervate ONLY the superior oblique
-Originates from the midbrain trochlear nucleus

Front 73

Extra Abducens

Back 73

-Composed of multipolar neurons that innervate ONLy the lateral rectus.
-GSE fibers originate in the pons, motor nucleus of VI (abducens nucleus)

Front 74

Autonomic Innervation of the Head

Back 74

Parasympathetic - major ganglia of head, the 4 are ciliary, otic, pterygopalatine (sphenopalatine), and submandibular
-Derived from CN III, CN VII, and CIX
-All of the cranial parasympathetic ganglia are located along or near a branch of CN V, and postganglionic fibers are often carried along branches of CN V ( funny cause the trigeminal itself contains NO autonomic fibers)

Front 75

Ciliary Ganglion Extra

Back 75

-Functionally related to the oculomotor N
Receives
1) Preganglionic parasympathetic fibers of CN III
2) Sympathetic root composed of postganglionic fibers arising in the superior cervical ganglion and reaching the ciliary ganglion via the internal carotid plexus. Do not synapse in the ganglion
3) Sensory root consisting of fibers of the nasociliary branch of V1
-it gives off both autonomic fibers as the short and long ciliary nerves
para - pupillary spinchter and ciliary muscle
sym - dilator pupillae and opthalmic artery

Front 76

CN V Overview

Back 76

-The nerve comes as a large sensory and small motor root from the lateral midpons within the posterior cranial fossa
-The afferent part (GSA) mediates sensation from
1) skin of face and anterior scalp
2) oral, nasal, and paranasal mucosa
3) dura
4) cornea and conjunctive (outer eye)
5) Teeth and gingiva
6) Nasopharynx
7) Proprioceptive input from 1st arch muscles and TMJ

Front 77

CN V SVE and GSA Overview

Back 77

SVE - brachial efferents innervate the first arch muscles and are limited to the mandibular division
-fibers arise from the motor or mastication nucleus of CN V in the tegmentum of the pons
-can get a monosynaptic jaw jerk reflex by tapping the mandible

GSA - project to the sensory nucleus (pons) of CN V which is divided into 3 parts
1) Mesencephalic nucleus - contains cell bodies of primary sensory neurons concerned with proprioception
2) Pontine Trigeminal Nucleus - facial touch sensation
3) Spinal trigeminal tract and nucleus - receives pain and temperature

Front 78

CN V Anatomical Locations

Back 78

-the trigeminal ganglion sits in the trigeminal impression on the middle cranial fossa in the dural meckel's cave
-The opthalmic division goes through the cavernous sinus to the superior orbital fissure to the orbit
-The maxillary division goes through cavernous sinus to the the foramen rotundum to the pterygopalatine fossa
-The mandibular division goes through the foramen ovale to the infratemporal fossa

-all 3 divisions have meningeal branches which innervate the dura of the anterior and middle cranial fossa
-includes falx cerebri in anteior CF and tentorium cerebelli in posterior CF
-the tentorial nerve is the meningeal branch of the opthalmic nerve

Front 79

Face and Scalp Dermatomes

Back 79

5 of them
1) Opthalmic Nerve branch of CN V
2) Maxillary nerve branch of CN V
3) Mandibular nerve branch of CN V (covers upper mandible)
4) Branches from cervical plexus (covers lower mandible)
5) dorsal rami of cervical spinal nerves (covers back of head and neck)

-to test the 3 CN V divisions you put light touch/pressure and pain on the skin of each area. Light touch/pressure can be traced to the pons while pain can be traced to the spinal trigeminal tract

***All 4 parasympathetic ganglia of the head are suspended from branches of CN V and send postganglionic fibers via terminal branches of CN V to reach their targets. Although they do not synapse in the ganglion and are NOT part of CN V they piggy-back on CN V

Front 80

CN V1 (opthalmic branch)

Back 80

-goes through the superior orbital fissure
-3 major NFL branches
1) Nasociliary
2) Frontal - passes through the orbit without branching
3) Lacrimal - goes to the lacrimal gland
...the ciliary ganglion piggybacks on the nasociliary nerve. Remember, ciliary ganglion receive both autonomic fibers, but only the para synapse here. The sympathetic sends long ciliary nerves to the cornea (corneal reflex)

Front 81

Divisions of CN Vi

Back 81

1) Lacrimal - innervate skin near lacrimal gland conjunctiva (clear mucous membrane that covers sclera and inner eyelid)
2) Frontal - broken into 2 parts
a) Supraorbital N - innervate forehead and scalp skin and part of frontal sinus
b) Supratrochlear - innervate conjunctive upper lid, forehead, and the lateral nose
3) Nasociliary - enters orbit through annular tendon and has 4 divisions
a) Infratrochlear - innervate lacrimal sac
b/c) Anterior and Posterior Ethmoidal Nerve - Branch off one after the other
d) Long ciliary nerve

Front 82

CN Vii - Maxillary Nerve

Back 82

-goes through the foramen rotundum and branches extensively in the pterygopalatine fossa
1) In Pterygopalatine Fossa
-zygomatic n
-pterygopalatine n (greater + lesser+' nasopalatine)
-Posterior Superior Alveolar N

2) Infraorbital Canal
-Middle Superior Alveolar
-Anterior Superior Alveolar
-Infraorbital

3) On Face
-inferior palpebral branches
-external nasal branches
-superior labial branches

Front 83

CN Vii - Closer Look 1

Back 83

1) Zygomatic - Runs to the orbit to give off the zygomatico - facial, orbital, temporal
2) Infraorbital - Goes through the infraorbital canal to give off the nasal, inferior palpebral (supply lower eyelid), and superior labial (supply upper lip)

Front 84

Superior Alveolar Nerves

Back 84

-these course along the maxillary sinus to form superior dental plexus which give rise to dental branches (tooth and gingivia)
1) Posterior Superior - In pterygopalatine fossa
2) Middle Superior
3) Anterior Superior -

Pathos
-infection of maxillary sinus can produce compression of the superior alveolar nerves leading to referred dental pain

Front 85

Pterygopalatine Ganglion

Back 85

Pterygopalatine Ganglion - Suspended from Vii within the fossa it receives preganglionic inputs from the greater petrosal nerve of CN VII. - The postganglionic parasympathetics are distributed by terminal branches of CN V. THe branches off of it are below
-anterior nose innervated by CN Vi while the posterior nose is
innervated by CN Vii
1) the nasopalatine nerve goes anteriorly through the septum and terminates by coursing through the incisive canal of the hard palate
2) Greater and Lesser Palatine Nerves

Front 86

Dental Blocks

Back 86

Block - Add anesthesia around a large nerve before it branches to the periphery
Infiltration - Let it seep through porous bone to nerve
1) PSA Injection - Needle pierces buccal part of the 2nd molar and is advanced above the roots of the third molar. M2, M3, and distal/palatal roots of M1 are numb
2) MSA - Anthesthetic is infiltrated above the root of the 1st maxillary premolar. The 2 premolars and mesial M1 are numb
3) ASA Injection - Needle infiltratyed in canine fossa above root of canine. The incisors, canine, lateral nose, and upper lip are numb. FIbers can cross midline so you must be careful
4) Nasopalatine Nerve (comes out incisal foramen) - anesthetic is injected into the incisive foramen on either side of the incisive papilla (primary hard palate)
5) Greater Palatine Nerve - Nerve may be blocked along a imaginery line halfway btw the midpalate raphe and the free gingival edge
6) Maxillary Nerve Block - Long needle is passed up through the greater palatine foramen and canal into the pterygopalatine fossa

Front 87

Mandibular Nerve CN Viii Overview

Back 87

-contains branchial motor fibers
-SVE fibers innervate the 4 muscles of mastication, the tensor tympani, the tensor veli palatini, the mylohyoid, and the anterior digastric
-divided into the main trunk, posterior, and anterior trunk

Front 88

Muscular Branches of CN Viii

Back 88

-after passing through the foramen ovale the nerve gives off
1) Deep Temporal Nerve (anterior)
2) Masseteric (Anterior)
3) Lateral Pterygoid (Anterior)
4) Mylohyoid (Posterior) - Innervate anterior digastric as well
5) Tensor Tympani (main) - attach to tendon which attach to malleus
6) Tensor Veli Palatini (main)
7) Medial Pterygoid Nerve (main)

Front 89

CN Viii SVE Lesions

Back 89

1) Paralysis of masticatory muscles
2) Atrophy of the muscles
3) Contralateral deviation of the soft palate and uvula
4) Ipsilateral deviation of jaw upon protrusion. With injury to the right mandibular division the unbalanced pull of the intact left lateral pterygoid causes chin to point to side of lesion

Front 90

CN Viii Sensory Introduction

Back 90

-4 main branches using the acroymn bail
B - Long buccal (anterior) - infratemporal fossa to cheek OVR the buccinator, does not innervate. Mediates sensation from both the skin superficial and mucosa deep to the biccinator muscle
A - auriculotemporal (posterior) - as 2 roots come off the posterior trunk they uncircle the middle meningeal artery and then connect to make the auriculotemporal N. It is vulnerable to fractures of the neck of the condyle
I - Inferior Alveolar (posterior)
L - Lingual

Front 91

Lingual Nerve

Back 91

-provides sensation to
1) Mucosa of the presulcal tongue/body/anterior 2/3
2) Floor of the mouth
3) Mandibular gingiva
-chorda tympani joins the lingual nerve in the infratemporal fossa
-it has SVA and GVE fibers. The GVE fibers synapse in the submandibular ganglion, and the postganglionic parasympathetics travel with terminal lingual branches to innervate the submandibular and sublingual salivary glands
-while the chorda tympani is responsible for taste sensation (special sense), the lingual nerve gives sensation due to touch, pain, and proprioception

Front 92

Dental Branches and Mandibular Block

Back 92

-the inferior alveolar nerve gives off the mental nerve and the dental branches (plexiform)
Mandibular Block - Gets entire side of the mouth. Able to get the inferior alveolar and lingual nerves with a single penetration. You deposit the anesthesia just above the mandibular foramen where the inferior alveolar enters and get the lingual as you retract the needle
-the inferior alveolar will numb the teeth with the lingual gets the lingual gingiva and anterior 2/3 of the tongue
Long Buccal Block - Complement the mandibular nerve because gewtting the gingival branches numb the buccal gingiva adjacent to the mandibular molars
Mental Nerve Block - This blocks a portion fo the inferior alveolar to get just the premolars and incisors. You direct the needle to the mucobuccal fold adjacent to the premolars and direct it towards the mental foramen

Front 93

CN Viii Lesions

Back 93

1) Trigeminal Neuralgia - brief lancinating burst of pain in one of more divisons of the 5th cranial nerve. Usually unilateral and limited to a division at a time. Usually adults, often seniors.
-may be caused by demyelination or compression of the sensory root endocranially (by the superior cerebellar artery), posthterpetic neuralgia, tongue piercing, ideopathic, but not dental origin
-Treatment include analgesics, anticonvulsants, surgical innervation, decompression, rhizotomy, gamma knife ablation
2) Herpes Zoster Infection
3) Gradenigo Syndrome
4) Dental or Facial trauma
5) Neoplasm - a benign trigeminal schwannoma or a cerebellopontine angle tumor
6) Hansen's Disease (Leprosy)

symptoms of a CN 5 lesion include
-loss of cutaneous sensation, distorted sensation, paralysis of mastication muscles,referred pain in ear, and loss of general sensation in the oral cavity

Front 94

Extra 1

Back 94

1) Cell body of CN V unipolar neurons is in the gasserian or trigeminal ganglion
-largest of the cranial nerves
D1 supplies - forehead, eyes, nose, temples, emninges, paranasal sinus, and part of nasal mucosa
D2 Supplies - maxillary dendition, lower eyelid, part of nose, upper lip, cheeks, hard palate, maxillary sinuses
D3 Supplies - mandibular dentition, lower lip, anterior 2/3 of tongue, portion of external ear, the external auditory meatus, the TMJ, and meninges
-all proprioceptive fibers in head arise from mesencephalic nucleus of V which arise in the brainstem and then jump to other cranial nerves to reach muscle and tendon

Front 95

CN V Reflexes

Back 95

1) Corneal (Blink) - When cornea of 1 eye is touched, both blink. CN Vi provides the afferent limb of the reflex and CN VII supply efferent limb through orbicularis oculi
2) Stretch Reflex of the Mandible - Protects mandible from displacement during vigorous head movement. The muscles of mastication prevent the mandible from swining downward during forceful exercise

Front 96

CN VII Overview

Back 96

Location: Emerges from the brainstem at the inferior pontine sulcus. Lies between the lateral pons and inferior cerebellum at the cerebellopontine angle. It's between the inferior/lateral pons, upper olive, and medial cerebellum

Parts:
1) Motor Root (larger)
2) Nervus intermedius (smaller but more used). Has the sensory and parasympathetic fibers

Movement:
1) Enter the temporal bone through the internal acoustic meatus and join at the geniculate ganglion
2) Courses through the facial canal with the petrous portion of the temporal bone

Front 97

Facial Canal Branches

Back 97

-afferent fibers in the nervus intermedius have their cell bodies in the geniculate ganglion

3 branches within the temporal bone facial canal
1) Greater Petrosal
2) Chorda Tympani
3) Nerve to Stapedius
-the rest of the nerve exits the stylomastoid foramen

Front 98

Greater Petrosal Nerve

Back 98

1) Exits the temporal bone at the hiatus of the facial nerve in the middle cranial fossa (MCF)
2) Exits the MCF through the foramen lacerum
3) Goes through the pterygoid canal with parasympathetic (GVE) and special visceral afferent (SVA) fibers to reach the pterygopalatine ganglion
4) Before reaching the pterygoid canal it is joined by the deep petrosal nerve to form the nerve of the pterygoid canal or vidian n.
-The deep petrosal has postganglionic sympathetic fibers from the superior cervical ganglion and travel via the internal carotid plexus

Front 99

Stapedius Nerve and the Rest

Back 99

-has special visceral efferent fibers and innervates the stapedius muscle (which is attached to the tendon and then the stapes)

Rest:
1) facial nerve trunk exits the cranial base through the stylomastoid foramen.
2) Before the parotid plexus it has 3 branches, posterior auricular nerve, digastric (posterior) nerve, stylohyoid nerve
3) The rest enters the parotid to divide into 2 major trunks, the temporofacial and cervicofacial.
4) The trunks divide into temporal, zygomatic, buccal, mandibular, and cervical nerves which innervate the muscles of facial expression
-Has branchiomotor (SVE) to innervate muscles of facial expression

Front 100

Chorda Tympani

Back 100

-Has parasympathetic and special visceral afferent fibers (taste)
1) Passes along the lateral wall of the tympanic cavity over tendon of tensor tympani
2) Exits the cranium through the iter chordae anterius at the medial end of the petrotympanic fissure to enter the infratemporal fossa
3) Joins the Lingual nerve of CN Viii and parasympathetic synapse in the submandibular ganglion and then it travels on terminal branches of CN V

Front 101

5 Segments of CN VII

Back 101

1) Labyrinthine - Passes the bony labyrinth housing the vestibular system
2) External Genu - include geniculate ganglion
3) Tympani - travels posteriorly and laterally along the medial wall of the middle ear cavity
4) Mastoid - Gives rise to the nerve of stapedius and chorda tympani in that order

Front 102

The Trunk

Back 102

-Use SVE fivers to innervate muscles of the 2nd arch - facial expression, stylohyoid, posterior digastric, stapedius
-Most ramify within the parotid plexus
-At parotid plexus the temporofacial and cervicofacial divisions split

Front 103

Painfully 2 Zebras Bit My Coccyx

Back 103

Mnemonic to remember the SVE fibers of CN VII
PA - Posterior Auricular Nerve
T - Temporal - Connect to frontalis, ask patient to raise eyebrows to check it out
Z - Zygomatic - Connect to obicularis oculi, ask patient to shut eye tight
B - Buccal. Connect to buccinator. Ask patient to pucker lips, bare upper teeth, and blow out/whistle
M - Marginal mandibular - Depress lower lip, show lower teeth
C - Cervical. Connect to platsyma. Ask patient to flare skin of the neck

Front 104

Chorda Tympani Expanded

Back 104

-conveys secretomotor fibers
-synapse in submandibular ganglion and innervate submandibular + sublingual salivary gland fibers
Parasympathetic Pathway:
1) Impulse originates from the Pons superior salivatory nucleus
2) Preganglionic fibers travel through the tympanic cavity and synapse in the submandibular ganglion
3) Postganglionic fibers piggyback on terminal branches of CN Viii (lingual nerve - they combine before the synapse) and innervate submandibular salivary gland (back of tongue) and sublingual salivary gland (above mylohyoid muscle)
-chorda tympani comes out of petrotympanic fissure and joins lingual nerve and postgang distribute w/branches of the lingual nerve
-unilateral cut of CT produce less saliva but not noticed cause patient still makes saliva on other side and a ton by the parotid

Front 105

Greater Petrosal Expanded

Back 105

-conveys secretomotor fibers, synapses in the pterygopalatine ganglion and innervates lacrimal gland, nasal, paranasal mucosa, and palatine gland
Parasympathetic Pathway
1) Signal starts in Pons superior salivatory nucleus
2) Preganglionic fiber travels through the facial canal and pterygoid canal to the pterygopalatine ganglion
3) Synapses in the ganglion and postganglionic branches piggyback on CN Vii

Front 106

CN VIII Lesions

Back 106

-tumors of parotid may compress/destroy facial nerve fibers
-for a parotid mass you should check back to the stylomastoid foramen and facial canal for the lesion

Front 107

Greater Petrosal More

Back 107

-during its course through the pterygoid canal the greater petrosal is joined by the postganglionic sympathetic fibers of the deep petrosal, which is coming off the internal carotid. Together they make vidian nerve.
1) Lacrimal Gland - The postganglionic autonomic fibers join the zygomatic branch of CN Vii, to a communicating nerve, to the lacrimal nerve of CN Vi to innervate this
2) Nasal Mucosa/Max Sinus - Innervated by postganglionic autonomic fibers which join posterior lateral nasal and nasopalatine branches of
CN Vii
3) Palatine Glands - These minor salivary glands are innervated by postganglionic autonomic fibers which join the greater/lesser palatine branches of CN Vii

Front 108

Taste Buds

Back 108

-these cells surround gustatory nerve endings of CN VII, IX and X
-detect water soluble tastants
-located at
1) Dorsum/Side tongue
2) Epiglottis
3) Lingual soft palate
4) Posterior oropharynx
-most are at troughs around the circumvallate papillae, anterior/parallel to the terminal sulcus. Some are on the fungiform and foliate papillae
-filiform are GSA fibers only

Front 109

Taste Buds CN VII

Back 109

-tongue is innervated by SVA (taste) fibers and GSA (general sensation/proprioception)
1) Anterior 2/3 Tongue Taste - chorda tympani innervate SVA taste fibers on the dorsal and lateral 2/3 margins of the tongue. Gustatory receptors go from the chorda tympani, to the geniculate ganglion, and then nucleus solitary of medulla
-nucleus solitarius of medulla gets taste input from CN VII, IX, and X
2) Anterior 2/3 Tongue Sensation - General sensory input from filiform papillae s conveyed via the lingual nerve (CN Viii)

Front 110

CN VII Taste Pathology

Back 110

-cutting chorda tympani produces gustatory dysfunction like ageusia (no taste), hypogeusia (diminished taste), or dysgeusia (perversion of taste)
-cutting chorda tympani removes a little taste cause you still have the other chorda tympani and the taste innervated by CN IX and X

Front 111

CN VII Ear Innervation

Back 111

-the posterior auricular nerve (after stylomastoid foramen) has both SVE and GSA fibers
1) SVE - innervate auriculares and occipitalis
2) GSA - Convey generation sensation from the following ear structures
1) skin of concha of external ear
2) Small patch of skin behind ear
3) Part of the superficial tympanic membrane (ear drum). However, due to so many things innervating the ear clinicians cannot distinuish GSA loss in ear with people who have facial lesion

Front 112

CN VII Bell's Palsy

Back 112

-caused by CN VII lesion at or distal to stylomastoid foramen
Symtoms
1) Loss of Facial Muscles - facial asymmetry with gravitational saggin of face/scalp
2) Paralysis of Frontalis - Inability to wrinkle forehead
3) Paralysis of Orbicularis oculi/oris - failure to retain tears and saliva
4) Paralysis of Buccinator - Cannot retain food in mouth

Front 113

CN VII Other Lesions

Back 113

-paralysis or paresis caused by inflammation or edema caused by..can be caused by viral infection
-effect of leson depends on the location - symptoms are dysgeusia, hyperacusia, and reduce lacrimation and salivation
1) Facial muscle can be affected whether motivated by voluntary, reflex, or emotional
2) Injury around Internal acoustic meatus - CN VII/VIII affected. Peripheral motor facial paralysis, hearing loss, vestibular dysfunction (dizziness)
3) To the Geniculate - Motor facial paralysis, taste disturbed (chorda), lacrimation and salivation
3) To the stapedius - motor paralysis, distubed taste and salivation
4) To the chorda - motor paralysis, disturb taste and salivation
5) To the foramen - motor paralysis

Front 114

CN XI Overview

Back 114

2 roots
1. Cranial root is from the nucleus ambiguous above the foramen magnum. They have SVE lower motor neurons that innervate the 3,4,6 pharyngeal arch muscles (laryngeal muscles except cricoarytenoid)
2. Spinal root from accessory nucleus within lateral ventral horn of upper 5 cervical cord segments. Has lower motor neurons GSE fibers innervating the SCM and trapezius
-after coming through the foramen magnum, the spinal root and cranial root will join and pass through the jugular foramen. After the foramen the cranial root will join the vagus

Front 115

CN XI Lesions

Back 115

-vulnerable as it crosses the posterior cervical triangle to innervate SCM first, then upper trapezius
1) Trapezius paresis - ipsilateral shoulder drop
2) SCM Paresis - weakness in contralateral rotation against resistance. Hard to move head to left against resistance with right lesion

Front 116

Cervical Plexus

Back 116

-The cervical plexus is a plexus of the ventral rami of the first four cervical spinal nerves which are located from C1 to C5 cervical segment in the neck
-There is anastomosis with accessory nerve, hypoglossal nerve and sympathetic trunk.
The branches of the cervical plexus emerge from the posterior triangle at the nerve point

Front 117

Cervical Plexus 2

Back 117

-innervate anterior and prevertebral cervical muscles and the diaphragm
1) Diaphragm is innervated by the phrenic nerve which arises from the ventral rami of C3, C4, C5
2) The ventral rami also form the ansa cervicalis which innervate 3/4 infrahyoid strap muscles
-the superior ansa comes from C1 (aka descendens hypoglossi) and the inferior root comes from C2 and C3. They unit and off it comes the ansa to innervate the muscles

Front 118

Cervical Plexus Cutaneous Innervation

Back 118

-4 main nerves
a) Lesser Occipital (C2)
b) Greater Auricular (C2/C3) - external ear + surroundings
c) Transverse cervical (C2/C3)
d) Suprascapular (C3/C4) - skin over the pectoral region. Diapraghm pain goes to C4 through GSA and can stimulate shoulder pain

-branches of the cervical plexus join with branches of CN V in the face to provide this cutaneous innervation
-these cutaneous nerves can be blocked by a injection at Erb's point. Excess infiltration can also affect trapezius, seen as a shoulder drop

Front 119

CN XII Overview

Back 119

-15-20 rootlets arise from the pre-olivary sulcus of the medulla and converge on the hypoglossal canal to make CN XII
-Has a single GSE fiber to innervate most intrinsic and all extrinsic tongue muscles
-Rootlets arise from the hypoglossal nucleus with lower motor neurons. Extends full length of the medulla

Front 120

CN XII Path

Back 120

1) after going across the foramen magnum they combine through the hypoglossal canal
2) It then courses inferiorly and laterally between the ICA and jugular vein with CN X, C1, and the superior cervical ganglion
3) Next it loops anteriorly above the hyoid to the tongue
4) Nerve goes lateral along the digastric/ECA/and hyoglossus within the digastric triangle and passes the mylohyoid
5) At this point to divides to supply hyoglossus, styloglossus, genioglossus, and all intrinsic tongue muscles

-CN XII at this point travels inferior to 2 sensory nerves of the tongue
1) Lingual Nerve (CN Viii)
2) CN IX - Which gives GSA and SSA of posterior 1/3 of tongue

Front 121

CN XII Lesions

Back 121

1) In a procedure called carotid endarterectomy where they enter the carotid bifurcation to remove plaque, the CN XII is vulnerable
2) CN XII Lesion around tongue - Test this put having the patient stick out their tongue. Under normal circumstances the tongue should protrude straight cause of bilateral genioglossus contraction. If there is a lesion to the right CN XII then ipsilateral contraction of the genioglossus will push the tongue towards the side with the lesion "lick the wounds"
-this ipsilateral lesion of CN XII can lead to
a) Ipsilateral atrophy of the genioglossus muscle (paralyzed)
b) fibrillation and fasciculation resulting in twitching and spasm of the tongue musculature
c) Mild dysarthria - difficulty in pronouncing D, T, and L sound

Front 122

CNXII and C1

Back 122

-CN XII is accompanied by fibers of the C1 ventral rami. After they join some C1 fibers will continue to ride with CN XII, and another will branch off the form the superior ansa or descendens hypoglossi
-The C1 fibers form
1) Superior Root of Ansa Cervicalis
and ride with CN XII to form
1) Innervate thyrohyoid
2) Innervate geniohyoid

Front 123

CN XII Extra

Back 123

-supplies multipolar motor neurons
-innervate all muscles of tongue EXCEPT palatoglossus
Extrinsic Tongue - Genioglossus, hyoglossus, styloglossus
Intrinsic Tongue - inferior/superior longitudinal fibers, vertical fibers, transverse fibers

Front 124

CN IX Extra

Back 124

Spinal Portion - Multipolar neurons
Clinical Test:
1) SCN - Look to opposite side
2) Trapezius - Elevate shoulders

Cranial Portion - Joins the vagus to make the vagoaccessory complex, giving rise to the laryngeal vagal branches. With Vagus it innervates muscles of 4-6 arches

Front 125

CN IX Glossopharyngeal Nerve Overview

Back 125

-rootlets of CN IX emerge from the medulla and exit the cranial cavity through the jugular foramen
5 functional components of CN IX
1) GSA - Derived from the spinal nucleus of CN V, it's responsible for afferent sensation from the tympanic cavity, auditory tube, posterior tongue, oropharynx, fauces, soft palate, and some auricle skin
2) SVA - Derived from the rostral end of the nucleus of the solitary tract it mediates taste from posterior 1/3 tongue
3) GVA - From the caudal end of the nucleus of the solitary tract it responds to the carotid body chemoreceptors and carotid sinus baroreceptors
4) GVE - Derived from the inferior salivatory nucleus it has preganglionic parasympathetic fibers to the otic ganglion
5) SVE - Derived from the nucleus ambiguus it has branchiomotor fibers that innervated the lone 3rd pharyngeal arch muscle, the stylopharyngeus

Front 126

CN IX Afferents - Closer Look

Back 126

-all afferent cell bodies GSA (sensation), GVA (carotid body/sinus), and SVA (taste) are localted in the superior and inferior ganglia around the jugular foramen
-the neurons are pseudounipolar sensory neurons

Front 127

CN IX Efferents - Closer Look

Back 127

-FYI: upper motor neurons carry the impulse in the CNS while lower motor neurons carry it from the CNS to the PNS effector muscle
1) SVE - LMN cell bodies are in the nucleus ambiguous of the medulla
2) GVE - Preganglionic parasympathetic neurons are in the inferior salivatory nucleus of the medulla

Front 128

The Tympanic Nerve

Back 128

-carries GSA and GVE fibers and branches at the inferior ganglion
1) Immediatley enters the tympanic bone through the tympanic canaliculus
2) In the tympanic cavity it ramifies to form the tympanic plexus and provides GSA sensation to the tympanic cavity, auditory tube, and mastoid air cells
-these mediate pain of otitis media (middle ear infection)
3) The GVE parasympathetic fibers of the plexus come together and form the lesser petrosal nerve which carries preganglionic fibers to the otic ganglion in the middle cranial fossa

Front 129

Lesser Petrosal Pathway and Lesion

Back 129

1) Preganglionic fibers arise from the medulla inferior salivatory nucleus
2) Runs with the tympanic nerve and then becomes to the lesser petrosal
3) Synapses at the otic ganglion which is suspended from CN Viii
4) Postganglionic fibers travel with CN Viii auricotemporal nerve to innervate the parotid gland

Frey's Syndrome - After surgery these GVE fibers can join a different pathway and innervate sweat glands in face instead of parotid. When given a meal, instead of inducing saliva, they induce facial sweating called gustatory sweating

Front 130

Carotid Sinus Nerve

Back 130

-comes off of CN IX after the inferior ganglion and has GVA fibers from
1) Baroreceptors in the carotid sinus (on internal carotid) to detect pressure changes
2) Chemoreceptors in the carotid body (between carotids) that detect pH changes
-lesion of the carotid sinus nerve can provoke fluctuations in the arterial pressure and HR

Front 131

Pharyngeal Branches

Back 131

-after the carotid sinus nerve comes off CN IX goes anterior towards the oropharynx area
-Off it come multiple pharyngeal branches that form a pharyngeal plexus near the middle constrictor muscle
-The pharyngeal plexus includes GSA fibers from CN IX, sympathetic fibers, and SVE (branchiomotor) fibers from CN X
-The GSA fibers supply sensation to the oropharyngeal mucosa and mediate the gag reflex which includes soft palate elevation and pharyngeal constriction - only way to test CN IX is my stimulating this reflex

Front 132

Muscular Branch (SVE)

Back 132

-the nerve gives off a muscular branch just superior to the pharyngeal which innervates the stylopharngeus, long muscle of the 3rd arch

Front 133

CN IX Further Movement

Back 133

-after giving off the above branches CN IX curves forward and enters the pharynx between the superior and middle constrictor muscles
-It heads towards the posterior 1/3 (root) of the tongue and divides into the tonsilar and lingual branches
-During tonsillectomy CN IX can be lesions which eliminates all sensation from the posterior 1/3 of the tongue

Front 134

Tonsilar and Lingual Branches of CN IX

Back 134

Tonsilar - supplies GSA sensation to the palatine tonsils, fauces, and soft palate (including oropharynx)

Lingual Branch - Supplies sensation (GSA) and taste (SVA) to the posterior tongue. Unique that the same fibers of CN IX convey taste and touch
-The posterior 1/3 tongue does not have small papillae, it has nodules of lymphoid tissue which are known as lingual tonsils
-posterior tongue = lingual tonsils

Front 135

CN IX Extra

Back 135

Lesion problems include
1) Loss gag reflex
2) No touch/taste in posterior tongue
3) No sensation in the oropharynx
4) Glossopharyngeal neuralgia with pain in the throat, auditory tube and behind the ear

-GSA have cell bodies in both ganglia, jugular and petrosal
-GVA has bodies in the inferior (petrosal) ganglia
-SVA has cell bodies in the inferior ganglion. Only lose a little taste of nixed
-SVE has cell bodies in the nucleus ambiguus
-GVE has cell bodies in the inferior salivatory nucleus AND otic ganglion. Injury leads to reduced salivation and dry mouth (partial if other intact)

Front 136

CN X Overview

Back 136

-has multiple rootlets that leave the medulla
-it is joined by fibers of CN XI cranial root (nucleus ambiguus) at the jugular foramen
-at jugular formane there is a superior (jugular) and inferior (nodose) ganglia. Both exclusively sensory
Jugular: somatic sensation - touch, pain, etc from the outside
Nodose: visceral sensation - chemoreceptors/pressure receptor, general gut feeling, taste

Front 137

CN X Functional Components

Back 137

1) SVE - LMN from nucleus ambiguus innervate 4th and 6th arch muscles of the larynx (intrinsic laryngeal muscle), pharynx (pharyngeal constrictors), palate (levator veli palatini, uvulae, palatoglossus, palatopharyngeus), and upper esophagus.
2) GVE - Preganglionic neurons from dorsal vagal nucleus innervate smooth muscle/glands from thoracic and abdominal viscera. Include heart, pulmonary system, upper GI muscles + glands
3) SVA -Superior solitary nucleus derived they have pseudounipolar cells in the nodose ganglion and transmit taste via the epiglottis and valleculae
4) GSA - Derived from the spinal nucleus of CN V, these pseudounipolar cells of the superior ganglion innervate the auricle, mastoid region, PCF meninges, larynx, pharynx, and external auditory canal
5) GVA - From the inferior solitary nucleus to the nodose ganglion they relay from visceroreceptors of larynx, pharynx, heart, esophagus, GI tract, trachea, bronchi, lungs, and also aorta receptors

Front 138

SVE Distribution (branchiomotor)

Back 138

1) Pharyngeal Branch - joins sympathetic trunk and CN IX to make pharyngeal plexus and innervate pharyngeal and palatal muscles

2) Superior Laryngeal Nerve - divides into 2 branches
a) External laryngeal nerve - parasympathetic innervation to the laryngeal muscle, the cricothyroid (lesion leads to low monotonous speech)
b) Internal Laryngeal - sensory fibers (discuss later)

3) Recurrent Laryngeal Nerve - innervate all laryngeal muscles EXCEPT cricothyroid (external laryngeal). Also laryngeal sensation, will discuss later
Right - travel to right subclavian
Left - travel to aorta.
-injury to EITHER one results in ipsilateral paresis or paralysis of the muscles leading to rough/raspy voice and fixed vocal cords. Due to its course, the left is very vulnerable to mediastinal/pulmonary pathology like lung tumor

Front 139

Vagus SVE Distrubtion Further

Back 139

-CN X SVE innervates more larynx/pharynx muscles except..
1) Stylopharyngeus in the pharynx - CN IX
2) Tensor Veli Palatini in the palate - CN Viii
3) All tongue muscles by CN XII except palatoglossus

Front 140

Unilateral Pharyngeal Plexus Vagal Lesion

Back 140

1) Vagus SVE in charge of efferent gag reflex by thrusting pharyngeal contrictor muscles forward in a symmetrical fashion. When on vagus is injured, the normal one pulls the constrictors asymmetrically in its direction. So normal left/lesion right leads to muscles being pulled to the left. This makes swallowing difficult
2) Unilateral lesion effects the levator veli palatini. This leads to asymmetry in palatal elevation observed in phonation or swallowing. Leads to nasal speech and nasal reflux of liquid

Front 141

Vagus Meningeal and Auricular Branch

Back 141

GSA fibers synapse in superior ganglion

Meningeal - Sends GSA fibers to the dura in the PCF

Auricular Branch - Goes from superior ganglion through the mastoid canaliculus to the temporal bone and exit through the tympanomastoid fissure to innervate external ear (auricle, external acoustic canal (part you stick finger into), part of lateral tympanic membrane
-ONLY cutaneous branch of vagus (skin)
-Mediates pain of otitis externa (swimmer ear) due to bacteria infection taking away cerumen (earwax)

Front 142

Internal Branch of Superior Laryngeal

Back 142

- innervates mucosa of the supraglottis larynx and mediates afferent limb of cough reflex
-innervates mucosa lining the valleculae and piriform recesses
-innervates the sensation of the laryngopharynx

Front 143

Vagus SVA Fibers

Back 143

-superior solitary nucleus through the inferior (nodose) ganglion
-travels on the internal laryngeal branch of the superior laryngeal nerve
-Mediates taste in epiglottis and valleculae

Front 144

Vagus GVA/GVE Fibers 1

Back 144

-travel together
GVE:
1) Pain or other sensation caused by distension of GI, respiratory structures, and the bladder
2) Baroreceptors
3) Chemoreceptors responing to changes in the oxygen/carbon dioxide partial pressure in the blood, the blood pH, and change in H+ ions in the stomach

GVA
1) Start in dorsal motor nucleus of the vagus in the medulla
2) Preganglionic fibers synapse in the terminal (enteric) ganglion around wall of viscera (many small)
3) Postganglionic go the heart/lungs, gut/pancreas/biliary tree, and the mucosa of the larynx and pharynx. Basically all smooth muscles and glands of thoracic and abdominal viscera

Front 145

GVA/GVE Vagus

Back 145

-GSA concern with touch/pressure/pain or outside structure, GVA concern internal pain and the chemo/baro receptors

-To reach the thorax and abdomen CNX travels through the deep neck within the carotid sheath (carotid/jugular/vagus)
-As it approaches the mediastinum to gives rise to the cardiac and pulmonary plexus

Front 146

Cardiac and Pulmonary Plexus

Back 146

Pulmonary Plexus: Parasympathetic vagal inputs facilitate contraction of smooth muscle which constricts the bronchial tubes

Cardiac Plexus: Superficial plexus under aorta arch and the deep plexus is on the tracheal bifurcation.
-the preganglionic fibers of the cardiac plexus synapse on small ganglia along the coronary arteries. Inputs lead to
1) Decelerated heart rate
2) Reduce strength of myocardial contraction
3) Vasoconstriction of coronary arteries

Front 147

Esophageal Plexus of the Vagus

Back 147

1) Inferior to the heart is the esophageal plexus made by vagal and sympathetic fibers
2) As the plexus approaches the diaphragm and abdomen they come together to make the anterior and posterior vagal trunks which pass through the esophageal hiatus
3) In the abdomen the vagus preganglionic fibers innervate abdominal viscera from the foregut and midgut
4) These fibers synapse in ganglia along the GI tract within the myenteric and submucosal plexuses of the gut
Their role in the abdominal viscera is...
1) inhibit contraction of sphincters
2) Stimulate glandular secretion
3) Stimulate contraction of smooth GI muscle promoting peristalsis

Front 148

Vagus Extra

Back 148

1) Motor fibers innervate pharyngeal and soft palate
2) Innervate intrinsic laryngeal muscles with CN XI
3) Visceral sensation to pharynx, larynx, trachea, eso, thorax, ab. Includes taste
4) General sensation to external ear, auricle, dura of PCF (confusing cause book says also oropharynx, but go with spears on this)
5) Parasympathetic innervation to the neck, thorax, ab. In ab it goes 2/3 across transverse colon

Branches:
Head - meningeal and auricular
Neck -
1) pharyngeal - to muscle/mucosa of pharynx and soft palate
2) Carotid Sinus
3) Superior Laryngeal
4) Superior Cardiac
5) Recurrent Laryngeal - has pharyngeal branches and also tracheal and esophageal
Thorax
-pulmonary and hepatic branches
Abdomen

Lesions lead to
dysphagia - difficult swallowing
dysphonia - impair speaking
aphonia - loss of voice
paresthesia of vagus innervation
gut motility/peristalsis problems

Front 149

Vagus Extra 2

Back 149

..to avoid confusion...
GSA - only go to external ear, tympanic membrane, and dura. Come from spinal nucleus
GVA - go to all sensation of larynx, pharynx, thorax and ab. GVA and SVA come from solitary nucleus

Superior Laryngeal - Receives GVA/SVA from the solitary nucleus and SVE from the nucleus ambiguus. The afferent go to the mucosa and taste buds above vocal fold through internal branch and the external branch has SVE with the critothyroid muscle (only intrinsic muscle, all other done by recurrent laryngeal)

Pharyngeal Branches - Has GVA from solitary nucleus and SVE from nucleus ambiguus. In charge of pharyngeal constrictor muscles, levator palati, palatoglossus, palatopharyngeus, salpinopharyngeus, and uvular muscles. Also sense from laryngopharynx and ?? epiglottis taste??...is it pharyngeal branch of internal branch of superior laryngeal??

Recurrent Laryngeal - Has SVE from nucleus ambiguus, GSA from the spinal nucleus, and GVA from solitary nucleus. Innervate mucosa below vocal folds using GSA and GVA and laryngeal intrinsic muscle with SVE (all except cricothyroid which external branch does)

Cardiac/Esophageal/Pulmonary - Has GVE from dorsal motor nucleus of X and GVA from solitary nucleus for smooth muscle and glands in this region

Front 150

Laryngeal Muscle Review

Back 150

* Intrinsic muscles of the larynx
o Posterior cricoarytenoid
o Lateral cricoarytenoid
o Interarytenoids
o Thyroarynteoids
o Cricothyroid
o Aryepiglottis
o Thyroepiglottis
* Extrinsic muscles of the larynx
o Laryngeal elevators
+ Digastric
+ Stylohyoid
+ Mylohyoid
+ Geniohyoid
+ Hyoglossus
+ Genioglossus
+ Thyropharyngeus
o Laryngeal depressors
+ Sternohyoid
+ Omohyoid
+ Sternothyroid
+ Thyrohyoid

Front 151

Otic Ganglion Extra

Back 151

-adheres to auricotemporal N of CN Viii in the infratemporal fossa.
-functional relation to CN IX
Receives/Sends
1) R: preganglionic fibers from inferior salivatory nucleus which travel with CN IX tympanic, then lesser petrosal, to the otic ganglion S: Postganglionic fibers that travel with auriculotemporal branch of CN Viii to the parotid

2. R: Sympathetic postganglionic fibers from superior cerivcal ganglion through the middle meningeal artery plexus, pass through and go to S: Parotid

3. Sensory root with fibers of CN Viii auriculotemporal branch

Front 152

Pterygopalatine Ganglion

Back 152

-in the pterygopalatine fossa below the maxillary nerve which it is attached to
-functional related to CN VII

1) R: Preganglionic fibers from lacrimatory nucleus of CN VII which travel with greater petrosal through pterygoid canal. S: Postganglionic fibers whcih piggyback on maxillary nerve to the orbit, nose, and soft palate. Provide innervation to lacrimal gland, and glands at nasal, palate, pharynx

2. R: Sympathetic fibers from sueprior cerivcal ganglion via the internal carotid to the deep petrosal S: Sympathetics through the same route as the parasympathetics

3. Sensory root of CN Vii

Front 153

Submandibular Ganglion

Back 153

-on the hyoglossus muscle near the submandibular gland. Attached to lingual branch of CN Viii
-Functionally related to CN VII

1) R: Preganglionic fibers from salivatory nucleus of CN VII. Go from chorda tympani through the petrotympanic fissure to the lingual branch of CN Viii and to the infratemporal fossa. They continue on the lingual branch to the ganglion S: Postganglionic fibers to the submandibular gland, sublingual salivary gland, and other minor glands

2) R: Sympathetic fibers from the superior cervical ganglion via the facial artery sympathetic plexus S: Same route as para

3) Sensory root with fibers on CN Viii lingual branch

Front 154

What is imprinting?

Back 154

At a single locus, only one allele is active; the other is inactive (methylation). Differneces in phenotype depend on whether the mutation is of maternal or paternal origin (e.g. Prader-Willi = paternal)