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I. INTRODUCTION TO NEUROSCIENCE

THE NERVOUS SYSTEM (NS) CONSISTS OF

Peripheral Nervous System (PNS)

o Divided into Autonomic and Somatic Nervous System.o Autonomic subdivided into Sympathetic (SNS) and Parasympathetic Nervous System (PSNS).o Somatic contains Cranial Nerves (except the Optic Nerve - CN II, which is a continuation of the

Brain), and all 31 pairs of Spinal Nerves.

Central Nervous System (CNS)

o Contains Brain and Spinal Cord.

PERIPHERAL NERVOUS SYSTEM (PNS)

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AUTONOMIC -VS- SOMATIC NERVOUS SYSTEMS

The autonomic system generally acts slower. The last inter-neuronal synapse of a somatic nerve is in the CNS (in the spinal column), while the last

inter-neuronal synapse of an autonomic nerve is in a peripheral ganglion.

THE AUTONOMIC NERVOUS SYSTEM

Consists of Sensory and Motor Neurons and their Axons that communicate the CNS with internal organs,muscles and glands.

Autonomic Reflex: Autonomic efferent fibers can be initiated in response to different types of afferentsignals:

Visceral Afferent Fibers: Transmission of visceral pressure, stretch, and noxious-stimuli.o Cell bodies of these sensory neurons are located in the sensory ganglia of CN VII, IX, and X.o Enteroreceptors are specialized fibers to transmit these visceral signals.

Somatic Afferent Fibers: Transmition of Temperature, pain, and light. Cognitive Input from higher learning centers: Perceived threats, anxiety, excitement, and sexual arousal

can all influence autonomic motor responses.

Property PARASYMPATHETIC SYMPATHETIC

Anatomical Origin CRANIO-SACRAL: CN III, VII,IX, X, and the Pelvic SplanchnicNerves

THORACO-LUMBAR

Preganglion Axon:Postganglionic Axon

Long Preganglion Axon and shortpostganglionic Axon; Ratio isnearly 1:1, yielding discrete effects

Short Preganglionic Axon andlong postganglionic axon; ratio is1:many, yielding diffuse effects.

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Location of Upper Cell Bodies Brainstem nuclei and sacralsegments

Intermediolateral segments ofthe thoracolumbar spinal cord

Location of InterneuronalGanglia

In or very near the target organ Paravertebral and PrevertebralGanglia, far away from targetorgans

Principle Neurotransmitter Acetylcholine Norepinephrine

Other Neurotransmitters found Vasoactive Intestinal Peptide(VIP), which results in synthesis ofNO ------> vasodilation

Neuropeptide Y

Somatostatin

Enkephalins

Principle NeurotransmitterReceptors at target organs:

Muscarinic acetylcholinereceptors, at the end organs.

Also Muscarinic Autoreceptorson the postganglionic terminal,providing feedback inhibition forrelease of Ach.

β-Adrenergic Receptors (cAMPsecondary pathway)

α-Adrenergic Receptors(IP3/DAG secondary pathway)

Neurotransmitter Inactivation Acetylcholinesterase is theprimary way

Reuptake is the primary methodof getting rid of NorE.

Ocular Reflex Miosis: constriction of pupil is areflex to light

Accommodation: Initiated byafferent signals from optic nerve ------> Contract ciliary muscle ------>increase natural curvature of lens ------> focus for near vision

Lacrimation via Facial VII.

Pupillary Dilation: Radialsmooth muscle of pupil contracts

Ciliary Muscle Relaxation

These neurons for these reflexescome from Superior CervicalGanglion ------> Carotid Plexus

Digestive Reflex Salivation via ChordaTympani (VII) andLingual (IX)

General increase in GI smoothmuscle tone

Liver promotion of glycogenesis

Salivation via sympathetics fromexternal carotid plexus

General Relaxation of GI smoothmuscle tone

Liver induction of glycogenolysisand gluconeogenesis

Anal Sphincter contraction

Respiratory Reflex Bronchoconstriction

Vagal innervation of smoothmuscle in trachea and bronchi.

Bronchodilation

Cardiac Reflex Decrease heart rate by vagalinnervation SA node

Increase heart rate by innervationof SA Node

Increase heart contractility

Sexual Reflex Penile Erection—vasodilationinvolved NO and possible VIP

Ejaculation

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SYMPATHETIC NERVOUS SYSTEM

Pathway of sympathetic spinal nerves out of the spinal cord:o From spinal cord, the dorsal root and ventral root of each sympathetic nerve join to form the White

Communicating Ramus.o The White Communicating Ramus goes to the Paravertebral Ganglia, on either side of the spinal

cord.o PREGANGLIONIC NERVE: Once in the Paravertebral Chain, it can do one of four things:

It

Prevertebral Ganglia: The prevertebral ganglia receive preganglionics from the ThoracicSplanchnic Nerves.

There are four major prevertebral ganglia: Celiac Ganglion Superior Mesenteric Ganglion Inferior Mesenteric Ganglion Aorticorenal Ganglion There are four major thoracic splanchnic nerves, which go straight through the paravertebral chain

to synapse in the prevertebral ganglia. Greater Thoracic Splanchnic (T10) Lesser Thoracic Splanchnic (T11) Least Thoracic Splanchnic (T12)

o POSTGANGLIONIC NERVE: For those nerves that synapse in the paravertebral chain, they can doone of two things afterwards:

ADRENAL MEDULLA: Releases 80% Epi and 20% NorEpi into bloodstream.o It is innervated by sympathetic preganglionics, which have come by way of the celiac ganglion, but

they didn’t synapse there.o It is sympathetic cholinergic, with nicotinic ganglionic acetylcholine receptors.

ADRENERGIC RECEPTORS:o Beta Receptors: Activated by Isoproterenolo Alpha Receptors: Activated by Phenylephrine

GANGLIONIC NICOTINIC CHOLINERGIC RECEPTORS: Both sympathetic and parasympatheticneurons use acetylcholine. Their receptors are of the nicotinic type, but they are different structurally in thatthey respond differently to drugs.

GROUND PLEXUS: Autonomic postganglionics are unmyelinated. Near the target organ they divide toform a meshwork-like web called a ground-plexus.

Axonal Varicosity: The autonomic axon becomes wider near the target.

NEUROEFFECTOR JUNCTION: The name of an autonomic synapse. It is not proper to call it asynapse.

It is not called a synapse because there are no ultrastructural membrane specializations between theneuron and the target cell. Thus it not a synapse.

Prejunctional Element: Autonomic name for the presynapse. Postjunctional Element: Autonomic name for the postsynapse.

Autonomic Tone: The continual visceral innervation of target organs. It is the job of autonomic nerves tomodulate, either up or down, the tone of the target organ, rather than to discretely stimulate it.

Denervation Supersensitivity: As a compensatory mechanism, a target loses autonomic innervation; itbecomes hypersensitive to said neurotransmitter.

Hypersensitivity due to increased synthesis of neuroreceptors. SYMPATHETIC LESIONS:o Preganglionic Lesion: Not so much hypersensitivity at target.o Postganglion Lesion: Pronounced Hypersensitivity because there is no longer a way for

neurotransmitter reuptake to occur!!

FIVE WAYS TO AUTONOMICALLY REGULATE END-ORGAN ACTIVITY

Antagonistic Effects on the same organ: Sympathetic and Parasympathetic have same effect.o Heart, Respiratory Passageso Urinary Bladdero Gut

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Antagonistic Effects through opposing organs: Sympathetic and Parasympathetic innervate differenttargets to achieve antagonistic effects.o Pupil (Pupil dilator and pupil constrictor)o Anal Sphincter

Agonistic Effects on complementary organs: Salivary glands Agonistic Effects on the same target organ: Innervation by only one component: Lots of end organso PARASYMPATHETIC ONLY: Lacrimal glands (CN VII), Nasopharyngeal Glands (CN VII),

Tracheal / Bronchial Glandso SYMPATHETIC ONLY: Tarsal Muscles of eyelid. Loss of this function (drooping eyelids) is called

Ptosis, a component of lost sympathetic innervation, or Horner’s Syndrome. Ecocrine Sweat Glands are cholinergic sympathetic. They are present all over and are responsible

for thermoregulation. Apocrine Glands = Sebaceous Sweat Glands. Mainly in axilla. They receive adrenergic innervation.

PENILE ERECTION:

Parasympathetic vasodilation of penile arteries to yield erection. Sympathetic constriction of vas deferens and seminal vesicles for ejaculation.

SYMPATHETIC CIRCULATORY REFLEXES: Conform to the needs of fight or flight.

Vasodilation of pathways leading to the heart and lungs. Vasoconstriction of pathways in the portal / GI system.

CENTRAL NERVOUS SYSTEM (CNS)

FIVE MAIN DIVISIONS OF THE CNS

Cerebral Hemispheres (Telencephalon): Higher perceptual, cognitive, and motor functionso White Matter—myelinated, in the centero Grey Matter: Cell bodies composing the cerebral cortex.o Lateral Ventricles: Filled with cerebrospinal fluid.o Basal Ganglia: Important role in modulating motor activity and emotional tone.

Diencephalon: Integrates and routes sensory and motor informationo Dorsal Thalamuso Subthalamuso Epithalamuso Hypothalamus

Brainstem—divided into three divisionso Medulla Oblongata (Myelencephalon): Associated with part of CN XIII, and CN IX, X, XI, and XII.o Pons (Metencephalon): Associated with CN V, VI, VII, and part of CN VIII.o Midbrain (Mesencephalon): Associated with CN III and IV

Cerebellum: Coordination of skeletal muscle activity Spinal Cord -- 31 pairs of spinal nerves give SEGMENTATION to the bodyo Dorsal Root -------> Dermatomeso Ventral Root ------> Myotomeso Developmentally, they originate from formation of the somites.

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FUNCTIONAL DIVISIONS OF THE BRAIN

PRE-CENTRAL GYRUS - Cerebral Cortex in front of the Central Sulcus:

FRONTAL LOBES - Responsible for effecting voluntary motor activities, and foresight and judgment.

POST-CENTRAL GYRUS - The other cerebrocortical lobes (SENSORY LOBES) are responsible for oneor another sensory

PARIETAL LOBES - Primary Somatosensory Cortex (Touch). TEMPORAL LOBES - Primary Auditory Cortex (Hearing)o Dominant Temporal Lobe is responsible for Language (Broca's and Wernicke's areas).

OCCIPITAL LOBES - Primary Visual Cortex (Sight).

CROSSING OF FUNCTION: The left side of the brain controls the right half of the body.

Stimulation of the PRE-CENTRAL GYRUS will cause motor stimulation on the opposite side of thebody.

Stimulation of the POST-CENTRAL GYRUS will cause sensation to occur on the opposite side of thebody.

SENSORY TRACTS: Sensory highways go up the spinal cord, converge on the Thalamus, and are thendistributed to the proper location in the Post-Central Gyri of the opposite side of the body.

There are considered to be two different sensory systems:o Primary Sensory Tracts - Somatic sensationo Discriminative Touch and Proprioception information.

MOTOR TRACTS: There are two different motor tracts that convey information from the Pre-CentralGyri to the destination motor units.

Corticospinal Fiber System: Travels down spinal cord to influence motor units on the opposite side ofthe body.

Corticobulbar Fiber System: Influences the head and neck via the four cranial nerves that provideparasympathetic motor innervation to the head and beck region.

CRANIAL NERVES

Nerve CN Source Branches Motor Sensory Notes

Olfactory I

Filaments ofthe bipolarolfactoryepithelial cellsconstitute theOlfactory n.

Second orderOlfactorynerve cellbodies locatedin the olfactorybulb

None Smell (SVA)

Multipleolfactoryfilaments passthrough thecribriformplate to exit the

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anterior cranialfossa andsynapse in theolfactory bulb;the olfactorytract carries thesignal from thebulb toolfactorycortex of theforebrain

Optic IIGanglion layerof the retina tothe forebrain.

None None Vision(SSA)

The course ofthe optic nerveis: through theoptic canal tothe opticchiasma, thenthe optic tractto the lateralgeniculatebody and opticradiation

Oculomotor III

Oculomotornuclei of themidbrain(extraocularmuscles);accessoryoculomotornucleus(nucleus ofEdinger-Westphal -preganglionicpara-sympathetic)

Superior br.,Inferior br.

GSE:* Superiorbr.: levatorpalpebrae,superioris m.& superiorrectus m.* Inferior br:medial rectusm., inferiorrectus m.,inferioroblique m.;GVE:Ciliary m. &sphincterpupillae m.(preganglionicpara-sympatheticaxons go tothe ciliaryganglion viathe para-sympatheticroot, post-ganglionicpara-sympatheticgo from theciliaryganglion tothe eyeballvia shortciliary nn.)

None

Passes throughthe superiororbital fissureto exit themiddle cranialfossa

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Trochlear IVTrochlearnucleus of themidbrain

None

Superioroblique m. ofthe eye(GSE)

None

Passes throughthe superiororbital fissureto exit themiddle cranialfossa; it is thesmallestcranial nerveand the onlycranial nerve toarise fromdorsum ofbrainstem

Trigeminal V

Motor rootarises from thetrigeminalmotor nucleusin the pons(SVE). Sensorypart arises fromthe trigeminalganglion(GSA) andprojects intothe pons to theprimarysensorynucleus of V ormore inferiorlyto the nucleusof the spinalroot of V(medulla andupper spinalcord)

Ophthalmic,Maxillary &Mandibulardivisions

SVE:anterior bellyof thedigastric m.,mylohyoidm., tensorveli palatinim., tensortympani m.;muscles ofmastication:temporalism., masseterm., lateralpterygoid m.,medialpterygoid m.

Skin of theface; mucousmembranesof the nasaland oralcavities;generalsensation(GSA) to theanterior 2/3of the tongue

Some brs.carry pre- orpostganglionicpara-sympatheticfibers; thetrigeminal n.divides intothree divisionsat thetrigeminalganglion; SVEsuppliesmuscles of 1stpharyngealarch origin

Ophthalmicdivisionof thetrigeminal n.

V1 Trigeminalganglion

Meningeal br.,lacrimal n.,frontal n.,nasociliary n.

None

(GSA) skinof theforehead,upper eyelidand nose;mucousmembrane ofthe uppernasal cavity,frontal sinus,ethmoid aircells andsphenoidsinuses

Passes throughthe superiororbital fissureto exit themiddle cranialfossa;The lacrimal n.receivespostganglionicpara-sympatheticaxons to thelacrimal glandfrom thezygomatico-temporal br. ofzygomatic n.

Maxillarydivisionof thetrigeminal n.

V2 Trigeminalganglion

Meningeal br.,posteriorsuperioralveolar n.,pharyngeal,

None

GSA: skin ofthe upper lip,cheek, lowereyelid;mucous

Passes throughthe foramenrotundum toenter thepterygopalatine

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posteriorsuperior medialand lateralnasal brs,nasopalatine n,greaterand lesserpalatine nn,zygomatic n.,infra-orbital n.

membrane ofthe palate;teeth andgingiva ofthe maxillaryalveolararch; themucousmembranelining mostof the nasalcavity; themucousmembranelining themaxillarysinus

fossa; thepterygopalatineganglion isassociated withit in thepterygopalatinefossa;postganglionicpara-sympatheticfibersdistribute withbranches of themaxillarydivision tomucous glandsof the nasalcavity andpalate; thezygomatic n. &its brs. carrypostganglionicparasympa-thetic axons tothe orbit toreach thelacrimal n. andlacrimal gland

Mandibulardivisionof thetrigeminal n.

V3

Trigeminalganglion;motor rootarises from thepons

Meningeal br.,medialpterygoid andlateralpterygoid nn.,masseteric n.,anterior andposterior deeptemporal nn.,buccal n.,auriculotemporal n., lingual n.,inferioralveolar n.

SVE:mylohyoidm., anteriorbelly of thedigastric m.;tensortympani m.,tensor velipalatini m.;muscles ofmastication(temporalis,masseter,medialpterygoidand lateralpterygoid)

GSA: skin ofthe lower lipand jawextendingsuperiorlyabove levelof the ear;mucousmembrane ofthe tongueand floor ofthe mouth;lower teethand gingivaof themandibularalveolar arch

Passes throughthe foramenovale to exitthe middlecranial fossa.The oticganglion isassociated withthe medial sideof V3 belowthe foramenovale; theauriculo-temporal n.carriespostganglionicpara-sympatheticaxons to theparotid gland.The sub-mandibularganglion isassociated withthe lingual n.near thesubmandibulargland.

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Postganglionicpara-sympatheticsfrom thesubmandibularganglionsupply thesubmandibulargland and thesublingualgland

Abducens VIPons:abducensnucleus

None GSE: lateralrectus m. None

Passes throughthe superiororbital fissure

Facial VII Pons andmedulla:nucleussolitarius ofmedulla vianervousintermedius(SVA sensoryroot) fromgeniculateganglion;superiorsalivatorynucleus (GVEpreganglionicpara-sympathetic) ofpons via nervusintermedius;facial motornucleus of ponsvia motor root

Greaterpetrosal n.(Pre-ganglionicpara-sympathetic topterygo-palatineganglion, Post-ganglionic par-asympathetictravels withbrs. ofmaxillarydivision of V).Chordatympani (SVAtaste fromanterior 2/3 ofthe tongue;pre-ganglionicpara-sympathetic tothe sub-mandibularganglion, post-ganglionicpara-sympathetic tothe sub-mandibular andsublingualglands).Nerve tostapedius.Posteriorauricular n.Intraparotidplexus withtemporal,zygomatic,buccal,marginalmandibular &cervical brs.

Stapedius m,stylohyoidm, posteriorbelly ofdigastric m,muscles offacialexpression;secretomotorto lacrimal,sub-mandibular,sublingual,and mucousglands of thenasal andoral cavities

Taste (SVA)from theanterior 2/3of thetongue; partof the skin ofthe externalauditorymeatus

Exits theposteriorcranial fossaby passing intothe internalacousticmeatus, goesthrough thefacial canal;motor tomuscles offacialexpressionexits the skullat thestylomastoidforamen


Vestibulo-cochlear VIII

Pons &medulla:vestibularnuclei from thevestibularganglion of thesemicircularducts; cochlearnuclei in theinferiorcerebellarpeduncle

Divides withinthe temporalbone intovestibular andcochlear parts

None

Vestibular:balance/proprioception(SSA);cochlear:hearing(SSA)

Auditorynerve; passesinto theinternalauditorymeatus

Glosso-pharyngeal IX

Medulla: spinaltrigeminalnucleus fromthe superiorganglion(GVA);nucleussolitarius fromthe inferiorganglion(SVA); nucleusambiguus(GVA);inferiorsalivatorynucleus (GVE -preganglionicpara-sympathetic)

Tympanicnerve to thetympanicplexus andlesser petrosaln., carotidsinus n., stylo-pharyngeusbrs.,pharyngeal brs.

GSE: stylo-pharyngeus;GVE:secretomotorto the parotidgland (pre-ganglionicpara-sympatheticvia thetympanic n.to the lesserpetrosal n. tothe oticganglion;post-ganglionicpara-sympatheticvia theauriculo-temporal n.)

GVA:carotid body,carotid sinus,pharynx,middle ear;GSA: skin ofthe externalear; SVA:taste fromthe posterior1/3 of thetongue

Exits theposteriorcranial fossaby passingthrough thejugularforamen.It maypenetrate thestylo-pharyngeus m.

Vagus X

Medulla:dorsal motornucleus (GVEpreganglionicparasympathetic); inferiorganglion(GVA);nucleusambiguus(SVE);superiorganglion(GSA); inferiorganglion(SVA)

Auricular br.,pharyngeal br.,superiorlaryngeal,superior andinferiorcervicalcardiac brs.,recurrentlaryngeal n.,thoraciccardiac brs.,brs. to thepulmonaryplexus, brs. tothe esophagealplexus, anteriorand posteriorvagal trunks

SVE:intrinsicmuscles ofthe larynx,pharynx(exceptstylo-pharyngeus),and palate(excepttensor velipalatini);GVE:smoothmuscle of therespiratorytree & gut(proximal tothe left colicflexure),heart;

GSA: skin ofthe externalauditorymeatus;GVA:viscera ofhead, neck,thorax &abdomenproximal tothe left colicflexure;SVA: tastefrom theepiglottis

Passes throughthe jugularforamen to exitthe posteriorcranial fossa;vagus means"wanderer" inreference to itsextensivedistribution tothe bodycavities


secretomotor: mucousglands of thelarynx,respiratorytree, pharynxand gut;secretomotorto digestiveglands

Accessory XI

Cranial root:medulla -nucleusambiguous.Spinal root:spinal nucleusof the uppercervical spinalcord

None

GSE: sterno-cleidomastoid andtrapeziusmm.

None

Spinal rootenters cranialcavity bypassingthrough theforamenmagnum.Exits skull bypassingthrough thejugularforamen.Accessory n. ismotor only; thesubtrapezialplexus ofnerves receivesproprioceptivefibers: for thesternocleido-mastoid m.From theventral primaryrami of spinalnn. C2 and C3for trapeziusvia ventralprimary ramiof C3 and C4

Hypoglossal XII Medulla:hypoglossalnucleus

No namedbranches.Branches of theventral primaryramus of spinalnerve C1 arecarried by thisnerve and arenot consideredto be branchesof thehypoglossalnerve

Intrinsic andextrinsicmuscles ofthe tongue(except thepalato-glossus m.)

None Exits theposteriorcranial fossaby passingthrough thehypoglossalcanal; thesuperior root ofthe ansacervicalistravels with thehypoglossal n.for a shortdistance


CRANIAL NERVE NUCLEI

CN NUCLEUS LOCATION

Spinal Trigeminal Nucleus (V) Medulla: It’s right next to the Inferior Cerebellar Peduncle

Pons: It’s right next to the Middle Cerebellar Peduncle

Spinal Trigeminal Tract (V) Throughout the Brainstem

Lateral to the Spinal Trigeminal Nucleus

Hypoglossal Nucleus (XII) Closed Medulla

Dorsal to the MLF, Central in the internal arcuate decussation

Dorsal Motor Nucleus (X) Early Open Medulla

Dorsolateral to Hypoglossal Nucleus, in Central Grey

Solitary Tract and Nucleus (IX,X)

Early Open Medulla

The Tract is a dark spot in the Reticular Formation

Nucleus Ambiguus (IX, X, XI) Early Open Medulla

Laterally in the Reticular Formation, near the Inferior CerebellarPeduncle

Spinal Vestibular Nucleus (VIII) Open Medulla

It’s more pigmented; located just medial to inferior CerebellaPeduncle, on dorsal surface.

Medial Vestibular Nucleus (VIII) Open Medulla

It’s less pigmented; medial to Spinal Vestibular Nucleus

Dorsal Cochlear Nucleus (VIII) Open Medulla

Lateral to Inferior Cerebellar Peduncle, just proximal to nerve


Ventral Cochlear Nucleus (VIII) Open Medulla

Almost in the nerve

COCHLEAR NERVE (VIII) Open Medulla

It exits lateral to the Inferior Cerebellar Peduncle

Facial Nucleus (VII) Pontomedullary Junction

Floor of the Fourth Ventricle, just lateral to Abducens Nucleus

FACIAL NERVE (VII) Pontomedullary Junction

It can be seen crossing the Reticular Formation on right side, andcoursing more laterally through Pons

Abducens Nucleus (VI) Pons

Very dorsal surface of Pons; floor of the fourth ventricle medially

ABDUCENS NERVE (VI) Pons

Can be seen coursing medially through Pons

Main Sensory Trigeminal Nucleus(V)

Pons

Right next to Middle Cerebellar Peduncle

Motor Trigeminal Nucleus (V) Pons

Just medial to Main Sensory of V

Mesencephalic TrigeminalNucleus (V)

Pons

Right below the Superior Cerebellar Peduncle

TRIGEMINAL NERVE (V) Pons (caudal Pons)

Can be seen exiting off the CN-V Nuclei, near the MCP

TROCHLEAR NERVE (IV) Pontomesencephalic Junction (After MCP)

It can be seen exiting dorsally

Trochlear Nucleus (IV) Mesencephalon (Inferior Colliculus)

Central Gray, above MLF

Oculomotor Nucleus (III) Mesencephalon (Superior Colliculus)

Central Gray, inside the “V” of the MLF

Edinger-Westphal Nucleus (III) Mesencephalon (Superior Colliculus)

Central Gray, directly dorsal to Oculomotor Nucleus

OCULOMOTOR NERVE (III) Mesencephalon (Rostrum)

Can be seen coursing between Red Nuclei, and exiting out ofInterpeduncular Fossa

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