Objectives - Nervous System • distinguish the central nervous system from the peripheral nervous system

• define the autonomic nervous system in terms of its location and function

• distinguish between afferent, interneuron (association), and efferent neurons/systems

• what are the sensory modalities?

• in the central nervous system, what is meant by the terms: nucleus, lamina, tract, and projection?

• distinguish between contralateral and ipsilateral projections and decussations

• - which is most common

• what is the difference between a ganglion and a nucleus?

• what are ventricles of the brain? - how do they form? - how are they connected?

• -with what are they filled?

• what is cortex? what is a gyrus? - a sulcus? - a fissure?

• what is the basic difference in organization between the brain and spinal cord?

• how does gray matter differ from white matter?

• how do fiber tracts maintain anatomical distinction of function, modality, and somatopic organization

• where are afferent systems localized in the brain? - in the spinal cord?

• where are efferent systems localized in the brain? - in the spinal cord?

• what is a dermatome?

• what is a reflex arc?

• define funiculus and fasciculus

• what is the location of primary efferent neurons? - of primary afferent neurons?

• know the cranial nerves, their locations, and their functions

• why are there enlargements in the cervical and lumbosacral regions of the spinal cord?

• what are the brachial and lumbosacral plexuses?

Objectives (continued) - Nervous System • what sorts of organs and tissues are innervated by the autonomic nervous system?

• is the autonomic nervous system voluntary or involuntary?

• does the autonomic nervous system include afferents and efferents?

• what are the differences in sympathetic and parasympathetic nervous system:

• locations

• functions

• neurotransmitters

• length of preganglionic and postganglionic fibers?

• what are the characteristics of nervous tissue?

• how is a nerve impulse transmitted along a cell? - between cells?

• what are the functions of the dendrite, cell body, axon, and synapse

• distinguish neurons from neuroglia

• what are neurotransmitters? - where are they formed? - where are they stored? - where do they work?

• how many different neurotransmitters can a single neuron produce? - to how many different neurotransmitters can a single neuron respond?

• describe the three meninges, the falx cerebri, falx cerebelli, and tentorium cerebelli

• what are the arterial blood supplies to the brain?

• what is the Circle of Willis?

• what is the path of blood flow through the venous sinuses?

• what is the result of denervation on muscles?

Nervous System Central Nervous System (CNS) – brain and spinal cord, includes cell bodies of all neurons except Dorsal Root Ganglia and ganglia or plexuses of the Autonomic Nervous System Peripheral Nervous System (PNS) – consists of cell process (axons and dendrites) that make up nerves that travel to and from organs Afferent – sensory Efferent – motor Interneuron Autonomic Nervous System (ANS) – involuntary, innervates viscera, smooth muscle, glands, considered to be part of the peripheral nervous system but preganglionic neurons are all located in the CNS, authors disagree whether visceral afferents should be considered part of the ANS includes two antagonistic components:

Parasympathetic Nervous System – craniosacral Sympathetic Nervous System – thoracolumbar

General Organization of the Central Nervous System

Gray Matter – cell bodies, (generally) superficial in brain, deep in spinal cord White Matter –fiber tracts (cell processes), superficial in spinal cord, deep in

brain Levels of neuronal organization Diffuse – least sophisticated, neurons of like kind spread out in a matrix of

white matter, e.g., pontine reticular formation Nuclei – neurons of like kind grouped in discrete clusters, e.g., basal ganglia Laminated Cortex – most sophisticated, neurons of different types and

connections, layered in stereotyped fashion regardless of specific function, much like a computer chip, e.g., cerebral cortex

White matter Fasciculus – fiber tract Projection – where information is sent by a fiber tract Ipsilateral projection – to same side of body Contralateral projection – to opposite side of body Decussation – point at which contralateral projections cross the midsagittal

Brain In early development, the central nervous system begins as a tube formed by infolding of [neur]ectoderm along the dorsal midsagittal plane Encephalization is the expansion of the cranial end of the neural tube, into three parts:

Prosencephalon – forebrain Mesencephalon – midbrain Rhombencephalon – hindbrain

Subsequent development divides two of these parts further

Prosencephalon Telencephalon (paired right and left) Diencephalon

Mesencephalon Rhombencephalon

Metencephalon Myelencephalon

Ventricles of the Brain Lateral (paired) paired, in forebrain, curve along with caudate nucleus and fornix around lenticular nuclei, internal capsule and thalamus Foramen of Monroe (paired) Third Ventricle midline, between right and left diencephalon Cerebral Aqueduct Fourth Ventricle midline, between cerebellum and brainstem Central Canal of Spinal Cord

Ventricles of the Brain

Outline of Brain Organization Forebrain Telencephalon

Cerebrum laminated cortex, deep nuclei and association tracts; sensation, voluntary motor, olfaction, vision, hearing, emotions, memory, language, associations

Terms relating to cerebral cortex

Sulcus or Fissure – groove between gyri or cleft between hemispheres or lobes, e.g., central sulcus, lateral fissure

Gyrus – convex region between sulci, e.g., precentral and postcentral gyri Lobe – functional regions corresponding roughly to overlying bones

Outline of Brain Organization Forebrain Telencephalon

Cerebrum Cortical Areas:

prefrontal association, memory, emotion frontal Broca's area – efferent (left lateral cerebral dominance) precentral gyrus central sulcus postcentral gyrus parietal Wernicke's area – afferent (left lateral cerebral dominance) lateral sulcus temporal Wernicke's area – afferent audition, memory, emotion occipital vision

Cerebral Cortex

The “Humunculus” – somatotopic map on precentral and postcentral gyri

Outline of Brain Organization Forebrain Telencephalon Basal Ganglia deep nuclei routine repetitive motor tasks

caudate nucleus, paired, ventral to lateral ventricles

lenticular nuclei (= corpus striatum) lateral to thalamus

Basal Ganglia within telencephalon

coronal lateral

transverse

Basal Ganglia relay to cerebral cortex

Outline of Brain Organization Forebrain Telencephalon and Diencephalon Limbic System emotions, memory, language, associations amygdala, hippocampus, fornix, etc.

Limbic System within telencephalon

Outline of Brain Organization Forebrain Diencephalon

Thalamus paired, walnut-shaped, lateral to 3rd ventricle, medial to basal ganglia relay and processing between spinal cord and cerebrum

Hypothalamus thin-walled, hollow, cone shaped,

enclosing inferior portion of 3rd ventricle, master of ANS

vegetative functions Hypophysis (pituitary) endocrine

Outline of Brain Organization Midbrain - Mesencephalon Tectum (“roof” above Cerebral Aqueduct)

Superior and Inferior Colliculi (Corpora Quadrigemina) visual and auditory spatial reflexes

Tegmentum (“floor” beneath Cerebral Aqueduct)

Oculomotor Complex (nuclei of oculomotor nerve) Cerebral Peduncles (fiber tracts) deep nuclei (i.e., Red Nucleus and Substantia Nigra - relay between Cerebrum and Cerebellum coordinating movement)

Outline of Brain Organization

Hindbrain - Rhombencephalon Metencephalon Cerebellum layered cortex and deep nuclei, motor coordination (tuning by inhibition) Pons cerebellar decussation and pontine reticular formation

Outline of Brain Organization

Hindbrain - Rhombencephalon Myelencephalon Medulla Oblongata similar to spinal cord, cranial nerve nuclei, tracts and decussations, vegetative functions (sleep/wakefulness, vomite center, vestibular and cochlear nuclei, vagal nuclei)

Cranial Nerves

Cranial Nerves left lateral view (brainstem +)

Cranial Nerve Nuclei

Spinal Cord Horns – gray matter, dorsal (afferent), ventral (efferent), lateral (autonomic) Funiculus (pl. funiculi) – fiber tracts, dorsal, lateral (paired), ventral Conus Medullaris –most inferior part of spinal cord, between vertebrae T12 and L2 Filum Terminale – filament extending from conus to sacrum Cauda Equina – spinal nerves contained within dura matter and vertebral canal extending inferior to conus medullaris

Conus Medullaris Filum Terminale Cauda Equina

Key Efferent Tracts Corticospinal or Pyramidal Tracts (Ventral and Lateral) – primary

voluntary motor pathway Rubrospinal Tract – voluntary somatomotor from Red Nucleus Tectospinal Tract – somatomotor to cervical levels from Tectum Vestibulospinal Tract – postural somatomotor from Vestibular

Nuclei Reticulospinal Tract – visceral motor from Pontine Reticular

Formation

Key Afferent Tracts Dorsal Column/Medial Lemniscus – somatosensory, fine touch Spinothalamic Tracts (Ventral and Lateral) – somatosensory, pain

and temperature Spinocerebellar Tracts (Dorsal and Ventral) – somatosensory,

proprioception

Spinal Tracts functional and somatotopic organization

Cervical and Lumbosacral enlargements increased number of 1o motoneurons (pyramidal cells) in the ventral horn associated with the brachial and lumbosacral plexuses that serve the limbs

Lateral Corticospinal (Pyramidal) Tract voluntary somatomotor contralateral projection

Dorsal Columns/Medial Lemniscus general somatosensory fine touch, pressure, vibration contralateral projection

Lateral Spinothalamic System somatosensory pain, temperature contralateral projection

Dermatomes

Dermatomes

Sympathetic Nerve

Visceral Afferent Nerve (blue)

Parasympathetic Nerves

Bulbus Oculi - Eye

In part, an extension of the central nervous system

transverse section through head of embryo

Tunics (Layers) of the Eye Fibrous Tunic – outermost, includes the cornea and schlera Vascular Tunic or Uvea– middle pigmented layer, includes the iris, ciliary body, and choroid Nervous Tunic – innermost, sensory, the retina

Layers of the Eye

Cavities of the Eye Anterior Chamber – between cornea and iris, contains aqueous humor – a secretion of epithelial cells Posterior Chamber – between iris and lens, ciliary body, and suspensory ligament Vitreous Cavity – occupies posterior ~4/5’s of eye, between lens and ciliary body anteriorly and retina posteriorly

Layers of the Eye

Diatropic (Refractory) Media of the Eye Cornea – anterior 1/6th of fibrous tunic, transparent, avascular Aqueous Humor – secreted by epithelium lining anterior and posterior chambers; drained by trabecular meshwork/sinus venosus schlerae Lens – mostly crystallin protein in capsule, biconvex, avascular, flexible, suspended and stretched by suspensory ligament and ciliary body Vitreous Body – occupies posterior ~4/5’s of eye, between lens and ciliary body anteriorly and retina posteriorly, mostly water, some salts and albumin protein

Layers of the Eye

Crystallin

Eye – key terms Conjunctiva – thin epithelium covering cornea and interior of palpebrae

Cornea – anterior-most transparent layer of eye

Limbus – junction of cornea and schlera

Iris – pigmented muscular layer separating anterior and posterior chambers, affects adaptation

Uvea – vascular tunic, alternatively pigmented posterior surface of iris

Pupil – aperture in iris

Lens – biconvex, mostly composed of crystallin protein

Choroid – vascular pigmented membrane of posterior ~4/5’s of eye

Ciliary Body – includes ciliaris muscle, affecting accommodation of lens

Zonula Ciliaris – includes Suspensory Ligament of lens, originating from ciliary body

Trabecular Meshwork and Sinus Venosus Schlerae (Canal of Schlemm) – drain aqueous humor from anterior chamber

Macula Lutea/Fovea Centralis – area of greatest visual acuity and color vision

Optic Disc/Blind Spot – point of entry of optic nerve to retina

Ora Serrata – jagged union of retina and choroid

Hyaloid Canal – lymph-filled vestige of passage of vessels through vitreous body to embryonic lens

Autonomic Innervation of Intrinsic Ocular Muscles

Parasympathetic Preganglionic axons from oculomotor nerve synapse in ciliary ganglion in orbit innervates sphincter pupillae of iris, ciliary muscle

Sympathetic Preganglionic axons synapse in superior cervical ganglion; postganglionic axons enter cranial cavity via carotid canal innervates dilator pupillae of iris (dark adaptation), levator palpebrae superioris (both voluntary and involuntary)

Lacrimal Gland

located in superior lateral portion of orbit, in lacrimal fossa of orbital plate of frontal bone

Lacrimal Gland Innervation

Parasympathetic Preganglionic axons from facial nerve synapse in pterygopalatine (sphenopalatine) ganglion; postanglionic axons ultimately join the lacrimal branch of the ophthalmic nerve (nV3) in orbit

Sympathetic Preganglionic axons synapse in superior cervical ganglion; postganglionic axons ultimately travel alongside parasympathetic axons through pterygopalatine ganglion but without synapsing ←Sympathetic Chain Ganglion

←Common Carotid Artery

Hindbrain

Spinal

Cord

Meibomian or Tarsal Glands

located in internal side of superior palbebra with many tiny ducts produce lipid-rich secretions (also with many proteins) exocrine, holocrine

Ear External Ear ends at Tympanic Membrane Middle Ear ends at Fenestra Ovale and Fenestra Rotundum Inner Ear

External Ear pinna or auricle external auditory meatus

Middle Ear auditory ossicles (lateral to medial)

Malleus – begins at tympanic membrane, dampened by Tensor Tympani muscle (innervation by Trigeminal nerve)

Incus – unites Malleus and Stapes Stapes – basal plate covers Fenestra Ovale, dampened by Stapedius

muscle (innervation by Facial nerve)

Associated features

Pharyngotympanic tube Mastoid air cells Chorda Tympani

Middle Ear – Autonomic nerves to and from orbit and tongue http://www.yourarticlelibrary.com/ear/ear-useful-notes-on-human-ear-13270-words/9691/

Inner Ear Bony Labyrinth – filled with Perilymph (cerebrospinal fluid) continuous

with Subarachnoid Space via Perilymphatic Duct Membranous Labyrinth – filled with Endolymph; Endolymphatic Duct

and Sac

http://www.yourarticlelibrary.com/ear/ear-useful-notes-on-human-ear-13270-words/9691/

Sensory Regions Membranous Labyrinth (in black) Ampullae of semicircular canals Maculae of Utricle and Saccule Organ of Corti of Cochlea

Inner Ear Vestibular System – vestibular special sense Vestibule – large space of bony labyrinth Otolith Organs – divisions of membranous labyrinth; kinocilia (modified

cilia) and stereocilia (modified microvilli) of hair cells embedded in CaCO3 crystals

Utricle – gravity and horizontal linear acceleration Saccule – gravity and vertical linear acceleration

Semicircular Canals (3) – angular acceleration kino/sterocilia embedded in gelatinous cupula

http://www.yourarticlelibrary.com/ear/ear-useful-notes-on-human-ear-13270-words/9691/

Inner Ear Cochlear System – auditory special sense Cochlea – winds 2 ¾ times around Modiolus; three canals

Scala Vestibuli – division of bony labyrinth; continuous with fenestra ovalis via vestibule; continuous with Scala Tympani via Helicotrema

Scala Media – division of membranous labyrinth; separated from

Scala Vestibuli by Reisner’s Membrane; separated from Scala Tympani by Basilar Membrane; includes Organ of Corti; continuous with Saccule via Ductus Reuniens

Organ of Corti – sensory organ; rests on Basilar Membrane; stereocilia embedded in Tectorial Membrane

Scala Tympani – division of bony labyrinth; continuous with Scala

Vestibuli via Helicotrema; continuous with Fenestra Rotundum via Vestibule

Pathway of sound waves

External auditory meatus

Tympanic membrane

Malleus

Incus

Stapes

Scala Vestibuli Scala Media

Scala Tympani

Pathway of Sound Waves Schematic! (Vestibule omitted)

http://www.yourarticlelibrary.com/ear/ear-useful-notes-on-human-ear-13270-words/9691/