I. INTRODUCTION TO NEUROSCIENCE

1 1 INTRODUCTION TO NEUROSCIENCETHE NERVOUS SYSTEM (NS) CONSISTS OF Peripheral Nervous System (PNS)o Divided into Autonomic and Somatic Nervous 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 theBrain), and all 31 pairs of Spinal Nerves. Central Nervous System (CNS)o Contains Brain and Spinal NERVOUS SYSTEM (PNS)2 -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 lastinter-neuronal synapse of an autonomic nerve is in a peripheral AUTONOMIC NERVOUS SYSTEMC onsists of Sensory and Motor Neurons and their Axons that communicate the CNS with internal organs,muscles and Reflex: Autonomic efferent fibers can be initiated in response to different types of afferentsignals: Visceral Afferent Fibers: Transmission of visceral pressure, stretch, and Cell bodies of these sensory neurons are located in the sensory ganglia of CN VII, IX, and Enteroreceptors are specialized fibers to transmit these visceral signals.

2 Somatic Afferent Fibers: Transmition of Temperature, pain, and light. Cognitive Input from higher learning centers: Perceived threats, anxiety, excitement, and sexual arousalcan all influence autonomic motor OriginCRANIO-SACRAL: CN III, VII,IX, X, and the Pelvic SplanchnicNervesTHORACO-LUMBARP reganglion Axon:Postganglionic AxonLong Preganglion Axon and shortpostganglionic Axon; Ratio isnearly 1:1, yielding discrete effectsShort Preganglionic Axon andlong postganglionic axon; ratio is1:many, yielding diffuse of Upper Cell BodiesBrainstem nuclei and sacralsegmentsIntermediolateral segments ofthe thoracolumbar spinal cordLocation of InterneuronalGangliaIn or very near the target organParavertebral and PrevertebralGanglia, far away from targetorgansPrinciple NeurotransmitterAcetylcholineNorepinephr ineOther Neurotransmitters foundVasoactive Intestinal Peptide(VIP), which results in synthesis ofNO ------> vasodilationNeuropeptide YSomatostatinEnkephalinsPrinciple NeurotransmitterReceptors at target organs:Muscarinic acetylcholinereceptors, at the end Muscarinic Autoreceptorson the postganglionic terminal,providing feedback inhibition forrelease of Ach.

3 -Adrenergic Receptors (cAMPsecondary pathway) -Adrenergic Receptors(IP3/DAG secondary pathway)Neurotransmitter InactivationAcetylcholinesterase is theprimary wayReuptake is the primary methodof getting rid of ReflexMiosis: constriction of pupil is areflex to lightAccommodation: Initiated byafferent signals from optic nerve ------> Contract ciliary muscle ------>increase natural curvature of lens ------> focus for near visionLacrimation via Facial Dilation: Radialsmooth muscle of pupil contractsCiliary Muscle RelaxationThese neurons for these reflexescome from Superior CervicalGanglion ------> Carotid PlexusDigestive ReflexSalivation via ChordaTympani (VII) andLingual (IX)General increase in GI smoothmuscle toneLiver promotion of glycogenesisSalivation via sympathetics fromexternal carotid plexusGeneral Relaxation of GI smoothmuscle toneLiver induction of glycogenolysisand gluconeogenesisAnal Sphincter contractionRespiratory ReflexBronchoconstrictionVagal innervation of smoothmuscle in trachea and ReflexDecrease heart rate by vagalinnervation SA nodeIncrease heart rate by innervationof SA NodeIncrease heart contractilitySexual ReflexPenile Erection vasodilationinvolved NO and possible VIPE jaculation4 NERVOUS SYSTEM Pathway of sympathetic spinal nerves out of the spinal cord.

4 O From spinal cord, the dorsal root and ventral root of each sympathetic nerve join to form the WhiteCommunicating The White Communicating Ramus goes to the paravertebral Ganglia, on either side of the 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 chainto 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 It is innervated by sympathetic preganglionics, which have come by way of the celiac ganglion, butthey didn t synapse It is sympathetic cholinergic, with nicotinic ganglionic acetylcholine receptors.

5 ADRENERGIC RECEPTORS:o Beta Receptors: Activated by Isoproterenolo Alpha Receptors: Activated by PhenylephrineGANGLIONIC 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 PLEXUS: Autonomic postganglionics are unmyelinated. Near the target organ they divide toform a meshwork-like web called a Varicosity: The autonomic axon becomes wider near the 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 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 Supersensitivity: As a compensatory mechanism, a target loses autonomic innervation; itbecomes hypersensitive to said neurotransmitter.

6 Hypersensitivity due to increased synthesis of neuroreceptors. SYMPATHETIC LESIONS:o Preganglionic Lesion: Not so much hypersensitivity at Postganglion Lesion: Pronounced Hypersensitivity because there is no longer a way forneurotransmitter reuptake to occur!!FIVE WAYS TO AUTONOMICALLY REGULATE END-ORGAN ACTIVITY Antagonistic Effects on the same organ: Sympathetic and Parasympathetic have same Heart, Respiratory Passageso Urinary Bladdero Gut5 Antagonistic Effects through opposing organs: Sympathetic and Parasympathetic innervate differenttargets to achieve antagonistic 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.

7 Loss of this function (drooping eyelids) is calledPtosis, a component of lost sympathetic innervation, or Horner s Syndrome. Ecocrine Sweat Glands are cholinergic sympathetic. They are present all over and are responsiblefor thermoregulation. Apocrine Glands = Sebaceous Sweat Glands. Mainly in axilla. They receive adrenergic ERECTION: Parasympathetic vasodilation of penile arteries to yield erection. Sympathetic constriction of vas deferens and seminal vesicles for 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 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 Lateral Ventricles: Filled with cerebrospinal Basal Ganglia: Important role in modulating motor activity and emotional tone.

8 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 Pons (Metencephalon): Associated with CN V, VI, VII, and part of CN 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 DIVISIONS OF THE BRAINPRE-CENTRAL GYRUS - Cerebral Cortex in front of the Central Sulcus: FRONTAL LOBES - Responsible for effecting voluntary motor activities, and foresight and GYRUS - The other cerebrocortical lobes (SENSORY LOBES) are responsible for oneor another sensory PARIETAL LOBES - Primary Somatosensory Cortex (Touch).

9 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 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 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.

10 Corticobulbar Fiber System: Influences the head and neck via the four cranial nerves that provideparasympathetic motor innervation to the head and beck NERVESN erveCNSourceBranchesMotorSensoryNotesOlf actoryIFilaments ofthe bipolarolfactoryepithelial cellsconstitute theOlfactory orderOlfactorynerve cellbodies locatedin the olfactorybulbNoneSmell (SVA)Multipleolfactoryfilaments passthrough thecribriformplate to exit the7 cranialfossa andsynapse in theolfactory bulb;the olfactorytract carries thesignal from thebulb toolfactorycortex of theforebrainOpticIIGanglion layerof the retina tothe (SSA)The course ofthe optic nerveis: through theoptic canal tothe opticchiasma, thenthe optic tractto the lateralgeniculatebody and opticradiationOculomotorIIIO culomotornuclei of themidbrain(extraocularmuscles);accessor yoculomotornucleus(nucleus ofEdinger-Westphal -preganglionicpara-sympathetic)Superior br.