Lecture 4 Peripheral nervous System and Cranial Nerves

what is the neuron pathway for somatic nervous system?

one motor neuron to connect the central nervous system directly to skeletal muscles

what is the neuron pathway for autonomic nervous system?

One preganglionic neuron can synapse with multiple postganglionic neurons for a signal CNS to activate many target organs

which nervous system is the fight or flight

sympathetic

which nervous system is for housekeeping activities

parasympathetic

neurotransmitter of somatic nervous system

acetylcholine

neurotransmitter of autonomic nervous system

acetylcholine, epinephrine, or norepinephrine

effector organs of somatic nervous system

skeletal muscle

effector organs of autonomic nervous system

smooth muscle, cardiac muscle, glands

type of action in somatic nervous system

always excitatory

type of action in autonomic nervous system

can be excitatory or inhibitory

what is somatic nervous system controlled by

cerebrum

what is autonomic nervous system controlled by

homeostatic centers in the brain - pons, hypothalamus, medulla oblongata

where does sympathetic division originate from

T1 through L2

where does parasympathetic division originate from

from the brainstem and S1 through S4

where is the terminal ganglia for sympathetic division

at the sympathetic trunk (near the spinal cord)

where is the terminal ganglia for parasympathetic division

at the effector organs

what are the reference points for signal transmission for parasympathetic pathways

they are the nuclei where the pre-ganglionic cell bodies are located

what is the Eddinger-Westphal nucleus

a part of the oculomotor complex where and axons from those neurons travel with the fibers in the oculomotor nerve (cranial nerve III) that innervate the extraocular muscles

what are the reference points for signal transmission for sympathetic pathways

they are the ganglia where the post-ganglionic cell bodies are located

what is the superior cervical ganglion (SCG)

The main sympathetic ganglion associated with the eye

function of superior cervical ganglion (SCG)

Provides sympathetic innervation to the dilator pupillae muscle, aiding in pupil dilation (mydriasis). Also regulates vasoconstriction in the lacrimal gland to influence tear secretion indirectly

what structures does the superior cervical ganglion (SCG) influence?

blood vessels and sweat glands around the eye and forehead

what is the main sympathetic ganglion associated with the eye

Superior Cervical Ganglion (SCG)

which structure provides sympathetic innervation to the dilator pupillae muscle, aiding in pupil dilation (mydriasis)

Superior Cervical Ganglion (SCG)

what structure regulates vasoconstriction in the lacrimal gland, influencing tear secretion indirectly?

Superior Cervical Ganglion (SCG)

where does the axons of the olfactory nerve extend to

extend through the cribriform plate of the ethmoid bone into the olfactory bulb at the anterior end of the olfactory nerve

CN I dysfunction produce what

unilateral anosmia (loss of the sense of smell)

what is Esthesioneuroblastoma

rare cancer tumor arises from from olfactory epithelium in the nasal vault

what can cause anosmia (loss of smell)

head trauma

how does head trauma cause anosmia

cribriform plate fracture or anterior temporal lobe injury

the optic nerve is a white-matter tract surrounded by?

Schwann cells

four anatomic segments of the optic nerve

intraocular (1mm) intraorbital (30mm), intra canalicular (6-9 mm), intracranial/intracisternal (10mm)

what is the longest anatomic segment in the optic nerve

intraorbital, 30mm

what is the shortest anatomic segment in the optic nerve

intraocular, 1mm

key function of optic nerve

Transmits visual information from the retina to the brain, essential for vision

common disorders regarding the optic nerve

optic neuritis, glaucoma, ischemic optic neuropathy

define optic neuritis

Inflammation causing sudden, painful vision loss, linked to autoimmune diseases

define glaucoma

 Elevated intraocular pressure leads to gradual peripheral vision loss

define ischemic optic neuropathy

 Sudden, painless vision loss due to reduced blood flow, associated with vascular risk factors.

what are the clinical impacts of visual fields of the optic nerve

central scotoma, peripheral vision loss, altitudinal field defects

define central scotoma

Vision loss in the center (typical in optic neuritis)

peripheral vision loss is common in which condition

glaucoma and it results in tunnel vision (loss of nerve fibers)

define altitudinal field defects

Monocular/Binocular visual loss.

movement of medial rectus

move the eye inward (adduction)

movement of lateral rectus

move the eye outward (abduction)

movement of superior rectus

move the eye upward and slightly inward

movement of inferior rectus

move eye downwawrd and slightly inward

movement of superior oblique

Moves the eye downward and outward (intorsion and depression)

movement of inferior oblique

Moves the eye upward and outward (extorsion and elevation).

what are the superior branches that the oculomotor nerve innervates

superior rectus and levator palpebrae superioris

what are the inferior branches that the oculomotor nerve innervates

inferior rectus, medial rectus, inferior oblique

how does oculomotor nerve innervate the superior rectus

elevate the eyeball

how does oculomotor nerve innervate the levator palpebrae superioris

raise the upper eyelid

how does oculomotor nerve innervate the inferior rectus

depress the eyeball

how does oculomotor nerve innervate the medial rectus

adduct the eyeball

how does oculomotor nerve innervate the inferior oblique

elevate, abduct and laterally rotate the eyeball

which structures receive parasympathetic innervation from CN III:

sphincter pupillae and ciliary muscles

function of sphincter pupillae in parasympathetic innervation from CN III

constricts the pupil, reducing the amount of light entering the eye

function of ciliary muscles in parasympathetic innervation from CN III

contracts, causes the lens to become more spherical, and thus more adapted to short range vision

what is oculomotor ophthalmoplegia

restricted eye movement

what is ptosis

drooping of one eyelid

where does the trochlear nerve arise from

the trochlear nucleus of inferior colliculus in the midbrain

the trochlear nerve enters the orbit through the superior orbital fissure to innervate what

superior oblique muscle

the trochlear nerve enters the orbit through what to innervate the superior oblique muscle

superior orbital fissure

what is the smallest cranial nerve (length)

CN IV (trochlear)

which cranial nerve has the longest intracranial course and how long is it

CN IV, 7.5cm

consequences of paralysis of superior oblique muscle in CN IV

extorsion (outward rotation) of affected eye.

what do patient complains when CN IV is not working

Diplopia (double vision), weakness of downward gaze, neck pain from head tilting

what is the largest and thickest cranial nerve (width)

CN V (trigeminal)

what is CN V composed of

large sensory root that runs medial to a smaller motor root

where does the large sensory root of CN V emerge from and where does it travel to

lateral mid-pons and travel anteriorly through the pre-pontine cistern

function of CN V1 nerve (Ophthalmic Division)

Sensory to forehead, upper eyelids, and nose

what does CN V1 nerve (Ophthalmic Division) innervate

cornea, nasal cavity

function of CN V2 nerve (Maxillary Division)

Sensory to lower eyelids, cheeks, upper lip

what does CN V2 (maxillary division) innervate

upper teeth, maxillary sinuses

function of CN V3 nerve (Mandibular Division)

Sensory to lower lip, jaw, anterior tongue. Motor to muscles of mastication

what does CN V3 (mandibular division) innervate

lower teeth, some ear areas

in CN VI (abducens nerve), the nerve exits through the superior orbit and enter the orbit to innervate what muscle

lateral rectus muscle

function of CN VI (abducens)

control the lateral rectus muscle, which abducts the eye

motor supply of CN VII (facial)

Innervates the muscles of facial expression, the muscles of neck, and in the middle ear.

sensory supply of CN VII (facial)

Provides taste sensation to the anterior two-thirds of the tongue and supplies a small area of skin behind the ear.

parasympathetic supply of CN VII (facial)

Provides to the lacrimal glands (tear production), submandibular glands, and sublingual salivary glands, aiding in tear and saliva secretion.

function of CN VII (vestibulocochlear) in cochlear portion

has specialized cells within your ear detect vibrations from sound based on the sound’s loudness and pitch

function of CN VII (vestibulocochlear) in vestibular portion

has specialized cells can track both linear and rotational movements of your head —> information is transmitted to the vestibular nerve and used to adjust your balance and equilibrium

special sensory function of CN IX

taste sensation to the posterior 1/3 of the tongue

motor function of CN IX

the stylopharyngeus muscle acts to shorten and widen the pharynx, and elevate the larynx during swallowing

parasympathetic functions of CN IX

Send signal to the parotid gland

where does the two roots of CN X (vagus) emerge from

the lateral side of the medulla

sensory function of CN X (vagus)

The skin of the external acoustic meatus.

The internal surfaces of the laryngopharynx and larynx.

The heart and abdominal viscera (provides visceral sensation).

special sensory function of CN X (vagus)

Taste sensation to the epiglottis and root of the tongue

motor function of CN X (vagus)

Motor innervation to the majority of the muscles of the pharynx, and larynx.

parasympathetic function of CN X (vagus)

The smooth muscle of the trachea, bronchi and gastro-intestinal tract and regulates heart rhythm

what is CN XI (accessory) composed of

multiple cranial and spinal rootlets

where does the cranial rootlets emerge into in CN XI (accessory)

the lateral cerebellomedullary cistern below the vagus nerve

where does the spinal rootlets emerge from in CN XI (accessory)

upper cervical segments of the spinal cord

function of CN XII (hypoglossal)

It is the motor cranial nerve to intrinsic and extrinsic muscles of tongue

what is the longest cranial nerve (length)

CN X (vagus)