South College AVL Clinical Anatomy 1: Neuro 3- Lecture 17

spinal cord

Bundle of nervous tissue that runs from the brain to the 1-3 lumbar vertebrae

Covering - meninges

Function: 2 way conduction pathway to and from brain

lumbar puncture

Spinal cord ends around L1 - L2

Dura and arachnoid Mater extend beyond spinal cord

Cauda equina - collection of nerve roots at the inferior end of vertebral canal

Ideal spot to remove CSF

Gray matter, white matter, spinal roots

What are the three components of the spinal cord?

gray matter

Horns

white matter

Contains tracts - fast signals

Dorsal roots (sensory branch - afferent) ventral roots (motor branch - efferent)

What are the two kinds of spinal roots?

Input (peripheral receptors to spinal cord) - Dorsal root (sensory) - dorsal horn (interneurons) - ventral horn (motor neurons) - venture root (motor) - output (spinal cord to effectors) OK

What is the order of input and output for gray matter and the spinal roots?

dorsal root ganglion

contains cell bodies of sensory neurons

ascending pathways

carry sensory information (input) to the brain

descending pathways

carry motor instructions to the effectors of the body

decussation, relay, somatotopy, symmetry

What are the four key points of the spinal cord "the highway"

Decussation

Crossover at medulla oblongata

relay

Chain of 2-3 neurons

somatotopy

Precise spatial relationship among the tract fibers that reflects the orderly mapping of the body (ex: sensory receptors in superior body regions lie medial roots to those from inferior body regions within same tract)

symmetry

Right and left sides

Stimulus - touch receptor activated (proprioceptor or temp receptors) - first order neuron (cell body of dorsal root ganglion) - second order neuron (cell body of dorsal horn)-

- Cerebellar cortex (proprioreceptors)

OR

- third order neuron (cell body thalamus) - primary somatosensory cortex

What are the general steps of the ascending pathway?

Dorsal column (medial lemniscal tract) - discriminative (fine) touch, vibration, proprioception - decussation (crossing over) - thalamus - primary somatosensory cortex

What is the dorsal white column ascending pathway?

Spinothalmic tract - non-discriminative (coarse) touch, pain, temp - decussation (cross over) - thalamus - primary somatosensory cortex

What is the spinothalmic tract ascending pathway?

Spinocerebellar tract - proprioception (muscle/tendon stretch) - no decussation - cerebellum

What is the spinocerebellar tract ascending pathway?

Gotta move - upper motor neuron (pyramidal cells - motor cortex, neurons - subcortical motor neuron) - lower motor neuron (spinal cord: ventral horn -somatic motor neurons, innervate skeletal muscles) - muscle moves

What is the general descending pathway?

Direct (pyramidal) and indirect pathways

What are the main descending pathways?

Direct (pyramidal) pathways - no synapsing occurs -

Lateral corticospial tract and ventral corticospinal tract - main pathway for muscles movement, fast/fine movements

What is the direct (pyramidal) pathway?

Indirect pathways (extrapyramidal)-

Tectospinal - mediate head movement response to stimuli (superior colliculi)

Vestibulospinal and reticulospinal - maintain balance (postural muscles)

Rubrospinal - control flexor muscles

What is involved in the indirect pathways?

Ventral horn of the spinal cord Dorsal

Upper motors neurons of the pyramidal tracts (corticospinal) synapse with lower motor neurons in the ________?

Ventral horn of spinal cord

Dorsal horn of spinal cord

Dorsal root ganglion

Thalamus

Primary motor cortex

Nerves

Bundles of axons in the PNS

Similar organization as muscles (box within a box)

Has coverings and vasculature

Nerves - fascicles - axons

What is the order of nerves (smallest to largest)?

olfactory, optic, oculomotor, trochlear, trigeminal, abducens, facial, vestibulocochlear, glossopharyngeal, vagus, accessory, hypoglossal

What are the 12 cranial nerves in order rostral to caudal?

Oh Oh Oh To Touch And Feel Very Good Vagina, Ah Heaven

What is the phrase to help us remember the cranial nerves?

Some say marry (for) money, but my brother says big brains matter most

(Sensory/motor/both)

What is the phrase to help us remember the function of the 12 cranial nerves?

CN 1: Olfactory Nerve

"Oh"

Tiny sensory nerves (filaments)

Synapse with the olfactory bulbs (brain structure)

The sense of smell (sensory)

What is the function of the olfactory nerve? "Some"

Present patient with faint, non-irritating odor and test both nostrils

How do we test for functioning of the olfactory nerve clinically?

CN 2: Optic Nerve

"Oh"

Retina - thalamus - visual cortex

Via: optic nerve, optic chiasma (partial crossover), optic tracts

Vision (visual acuity, visual fields, ophthalmoscope - optic disc and retinal vessels)

What is the function of the optic nerve? "Say"

CN 3: Oculomotor Nerve

"Oh"

Ventral midbrain - eye

"Eye mover"

Somatic motor fibers (supply 4/6 of extrinsic eye muscles) and parasympathetic motor fibers (constrict pupil, control lens shape for visual focusing)

Pupillary reflexes, extraocular eye movements, accommodation reflex

What is the function of the oculomotor nerves? "Marry"

CN IV: Trochlear Nerve

"To"

Mid brain - superior oblique muscle

Somatic motor fibers (1/6 extrinsic muscles), internal rotation of eye, depression of eye, assist with abduction of eye (EOM)

What is the function of the trochlear nerve? "Money"

Moves eye laterally, CN VI (abducens)

The lateral rectus muscle does what action? Controlled by what cranial nerve?

Depresses eye, and turns laterally, CN IV (trochlear)

The superior oblique does what action? Controlled by what cranial nerve?

III (oculomotor nerve)

Medial rectus, superior rectus, inferior rectus, inferior oblique are all controlled by what cranial nerve?

move eye medially

Functional medial rectus?

Elevate eye and turn medially

What is the function of the superior rectus?

Depress eye and turn medially

What is the function of the inferior rectus?

Elevates eye and turns laterally

What is the function of the inferior oblique?

CN V: Trigenminal Nerve

"Touch"

Pons

3 divisions: V1 -ophthalmic, V2 - maxillary, V3 - mandibular

Sensory and motor (both)

What is the function of the trigeminal nerve? "But"

CN V1: ophthalmic division

Superior orbital fissure

Supraorbital foramen

Sensation of anterior scalp, upper eyelid, upper nose, cornea, lacrimal glands (corneal reflex test, test skin sensation for pain, touch, temperature)

What is the function of CN V1 - ophthalmic division?

CN V2: maxillary division

Infraorbital foramen - infraorbital nerve

Sensation of nasal cavity mucosa, palate, upper teeth, skin of cheek, upper lip, lower eyelid (test, skin sensation for pain, touch, temperature)

What is the function of CN V2 - maxillary division?

Infraorbital nerve block

A local anesthetic block that blocks sensation by depositing anesthetic into the infraorbital foramen.

CN V3: mandibular division

Lingual nerve

Inferior alveolar nerve - mental foramen

Sensory and motor (anterior tongue, lower teeth, lower lip, skin of chin, temporal scalp -innervated by muscles of mastication)

(Test skin sensation for pain, touch, temperature, clenched teeth, open mouth against resistance, move jaw from side to side)

What is the function of CN V3 - mandibular division?

trigeminal neuralgia

Inflammation of trigeminal nerve (widely considered to produce most excruciating pain known)

Stabbing pain last for a few seconds to a minute

Can occur up to 100 times a day

Usually provoked by sensory stimulus (brushing teeth, wind hitting face)

CN VI: abducens nerves

"And"

Pons - lateral rectal muscle

Somatic motor fibers (supply 1/6 extrinsic eye mover muscles and eye abduction)

What is the function of the abducens nerve? "My"

CN VII: Facial Nerve

"Feel"

Pons - facial nerve - three functional branches

Sensory (afferent), parasympathetic (efferent), motor movement (efferent)

Sensory and motor

Somatic motor fibers (muscles of facial expression)

Parasympathetic motor fibers (lacrimal glands, nasal palliating glands, submandibular, and sublingual salivary glands)

Sensory (taste buds - anterior 2/3 of tongue)

(Test facial expressions, test taste of anterior tongue)

What is the function of the facial nerves? "brother"

(Pinky) temporal, (ring) zygomatic, (middle) buccal, (index) mandibular, (thumb) cervical

What are the motor branches of the facial nerves?(think of putting hand on your face)

Bell's Palsy

Inflammation of CN VII

Paralysis of facial muscles on one side

Rapid development - hours to days

Dry eye - can't close eye completely

Bell's palsy - peripheral nerve process

Stroke - central process

What is the difference between a stroke versus Bell's palsy?

lower face innervation

Facial muscles:

Innervated by contralateral cerebral hemisphere

Normal "crossover" pattern

upper face innervation

Facial muscles:

Innervated by both cerebral hemispheres

Frontalis muscle (frontal belly epicranius) - acute stroke usually spares the forehead because of bilateral cerebral hemisphere innervation (the other half of the brain not experiencing the stroke can compensate)

What is an example of bilateral cerebral innervation? Why is this clinically relevant?

Complete unilateral facial paralysis (effects CN VII)

Unlike stroke, Bell's palsy usually results in what?

CN VIII: Vestibulocochlear Nerve

" very"

Fibers arise from the hearing and equilibrium apparatus

Pons - CNVIII - inner ear

Sensory - hearing and balance

(Whisper, voice test, test hearing by air and bone conduction with tuning fork)

What is the function of the vestibulocochlear nerves? "says"

CN IX: Glossopharyngeal Nerve

"Good"

Pons - tongue and pharynx

Sensory and motor

Taste (posterior 1/3 of the tongue)

Touch, pressure, pain (tongue and pharynx)

Chemoreceptors - carotid body (monitor O2/CO2 - regulate RR)

Baroreceptors -carotid sinus (monitor BP)

(Check patient voice quality, say "ah" - soft palate rises, gag reflex, taste of the posterior tongue)

What is the function of the glossopharyngeal nerves? "Big"

Stylopharyngeus (elevate pharynx when swallowing)and ps motor fibers (parotid salivary glands)

What are two main muscles/components of the glossopharyngeal nerves?

CN X: Vagus Nerve

"vagina" and "wanderer/vagabond"

Medulla oblongata

Only CN to travel past head and neck

Sensory and motor

Transmit from thoracic and abdomina viscera

Aortic arch baroreceptors (BP)

Carotid/aortic body chemoreceptors (RR)

Taste buds (epiglottitis)

(Check patient's voice quality, say "ah" - soft palate rise, gag reflex)

What is the function of the vagus nerves? "Brains"

PNS - heart, lungs, abdominal viscera (regulate, HR, breathing, digestive activity)

Skeletal muscles of pharynx and larynx (swallowing)

What are the muscles/organs innervated by the vagus nerve?

CN XI: (Spinal) Accessory Nerve

"Ah"

Rootlet emerge from the spinal cord

Innervate trapezius and sternocleidomastoid

Head and neck movement (motor)

(Check: rotate head against resistance, shrug, shoulders against resistance)

What is the function of the (spinal) accessory nerves? " matter"

CN XII: Hypoglossal Nerve

"Heaven"

Mainly innervates the tongue

Motor

Movement of the tongue

Intrinsic and extrinsic muscles of the tongue

(Check: protrude and retract the tongue)

What is the function of hypoglossal nerve? "Most"

Optic nerve (CN II) - moving eye

(Optic nerve is for vision, not for moving the eye)

Which function is incorrectly matched with its associated cranial nerve?

Vagus nerve (CN X) - control, heart rate and digestive activity

Hypoglossal nerve (CN XII) - sticking tongue out

Optic nerve (CN II) - moving eye

Accessory nerve (CN XI) - shrugging shoulders

Each nerve emerges from the spinal cord - exiting through intervertebral Freeman of the vertebrae

Supply entire somatic region of the body (skeletal muscles and head) from the neck down (sensory and motor)

What is important to know about the spinal nerves?

C1-C8, T1-T12, L1-L5, S1-S5

Cervical nerves - ?

Thoracic nerves - ?

Lumbar nerves - ?

Sacral nerves - ?

C1 - C7 exit superiorly to the vertebrae

C8 exits inferiorly

(rest of the nerves run inferiorly)

What is important to note about the cervical nerves?

Spinal nerve (mixed: sensory and motor)

Dorsal root (sensory) and the ventral root (motor) come together to join what?

Dorsal ramus, sympathetic trunk (thoracic - ANS), ventral ramus, meningeal branch

What does the spinal nerve (mixed: sensory and motor) ran into?

terminal ganglia

located near organ innervated or embedded in wall of organ, part of parasympathetic nervous system

sympathetic trunk ganglia

lie in a vertical row on either side of the vertebral column - paired, sympathetic nervous system

Collateral ganglia (prevertebral ganglia)

Lie anterior to the vertebral column - unpaired, sympathetic nervous system

sympathetic division

Sympathetic trunk (thoracic spinal nerves only) and sympathetic trunk ganglion are part of what division?

just know: this division has its own ganglia and trunk

Sympathetic effect on visceral effector (increase heart rate, decrease G.I. motility)

What is the function of the sympathetic division?

parasympathetic division

Cranial nerves (oculomotor, facial, glossopharyngeal, vagus)

Sacral nerves (S2 - S4 controls genitalia, urinary bladder, ureters)

Parasympathetic effect on a visceral effectors (decrease heart rate, increase G.I. motility)

What is the function of the parasympathetic division?

Plexuses

complex interconnections/network of nerves

Voluntary (somatic) system

Formed by ventral rami

cervical, brachial, lumbar, sacral

What are the different plexuses?

C1-C5, cutaneous and motor branches

Which cervical nerves are involved in the cervical plexus? What are the branches of the cervical plexus that we care about?

Cutaneous branches of cervical plexus

Sensory - skin of neck, ear, posterior head, shoulder

phrenic nerve (C3-C5) - innervates diaphragm - keeps diaphragm alive

Damage to these nerve roots equals respiratory distress

“Hiccups” irritation of the phrenic nerve

What are the major nerves that innovate the motor branch of the cervical plexus?

C5-T1 (innervates the upper limb)

What are the nerves involved in the brachial plexus?

Roots - trunks - divisions - chords - *branches

What is the order that we need to remember for the brachial plexus? (Really tired? Drink coffee, bud)

Musculocutaneous, nerve, median nerve, ulnar nerve, radial nerve, axillary nerve

What are the major terminal branches that we care about?

musculocutaneous nerve

Courses inferior in anterior arm

Function:

Motor - flexor muscles in anterior arm (biceps brachii, brachialis, coracobrachialis)

Sensory - skin of lateral forearm