Ch 15: Brain and Cranial NervesCh 15: Brain and Cranial Nerves Discuss the organization of the brain, Discuss the organization of the brain,

including the major structures and their including the major structures and their functionsfunctions

Describe the meninges of the spinal cord and Describe the meninges of the spinal cord and brain, and integrate the formation and flow of brain, and integrate the formation and flow of CSF with this information.CSF with this information.

Describe the structures that constitute the Describe the structures that constitute the BBB and their functionsBBB and their functions

Review the cranial nerves, again giving a Review the cranial nerves, again giving a

brief function of each.brief function of each.

Major Brain Subdivisions Major Brain Subdivisions

Telencephalon (= Cerebrum)Telencephalon (= Cerebrum)

Diencephalon Diencephalon (Thalamus and hypothalamus)(Thalamus and hypothalamus)

MesencephalonMesencephalon

Metencephalon Metencephalon (Pons and cerebellum)(Pons and cerebellum)

Myelencephalon (= Medulla Myelencephalon (= Medulla oblongata)oblongata)

Brainstem

Gray & White Matter OrganizationGray & White Matter Organization

In In brain stem brain stem similar similar to spinal cord (to spinal cord (nuclei nuclei around ventricles, tracts around ventricles, tracts on outside)on outside)

In In cerebrumcerebrum and and cerebellumcerebellum: white : white matter covered matter covered with layer of neural with layer of neural cortex (grey)cortex (grey)

Cranial MeningesCranial Meninges1. 1. Dura materDura mater - strong, "tough mother" - strong, "tough mother"

a. falx cerebri a. falx cerebri b. falx cerebelli b. falx cerebelli c. tentorum cerebelli c. tentorum cerebelli

2. 2. ArachnoidArachnoid - spidery, - spidery, holds blood vesselsholds blood vessels

3. 3. Pia materPia mater - "delicate - "delicate mother"mother"

Arachnoid granulations: This is where the CSF produced in the choroid plexuses of the ventricles and which has circulated into the subarachnoid space is reabsorbed.

Longitudinal fissure

Four VentriclesFour VentriclesCSF filled chambersCSF filled chambers

Communicating with central canal of spinal cordCommunicating with central canal of spinal cord

Lined by ependymal cells

CSF: Cerebro-Spinal Fluid Formation in ventricles by specialized ependymal cells of Formation in ventricles by specialized ependymal cells of

choroid plexuseschoroid plexuses (~500 mL/day; total volume ~ 150 mL)(~500 mL/day; total volume ~ 150 mL)

FunctionsFunctions– transport medium, in transport medium, in – shock absorption shock absorption – buoyancybuoyancy (floats the brain)(floats the brain)

CSF circulation: Ventricles → central canal → subarachnoid CSF circulation: Ventricles → central canal → subarachnoid spacespace

Reabsorption into circulation via Reabsorption into circulation via arachnoid granulationsarachnoid granulations into into superior sagittal sinus. superior sagittal sinus.

Fig 15.6

Blood Brain Barrier (BBB)Blood Brain Barrier (BBB)

what is it?what is it?

3 areas in brain don’t have BBB3 areas in brain don’t have BBB

1.1. portion of hypothalamus portion of hypothalamus

2.2. pineal gland (in diencephalon) pineal gland (in diencephalon)

3.3. choroid plexuschoroid plexus

Two hemispheres Two hemispheres separated by separated by longitudinal longitudinal fissurefissure

Gyrus (gyri) separated by sulcus (sulci)Gyrus (gyri) separated by sulcus (sulci)

Major lobes named Major lobes named after overlaying bonesafter overlaying bones

CerebrumCerebrum

Cerebral Hemispheres . . .Cerebral Hemispheres . . .

. . have functional regions (motor, sensory and association areas)

. . . have some functional differences (in spite of anatomical resemblance) → Lateralization of cortical functioning

. . . receive information and generate commands for opposite side of body

Cerebral Cortex and Central White MatterCerebral Cortex and Central White Matter

Gray surface (cortex) with white tracts internallyGray surface (cortex) with white tracts internally

CommissuresCommissures – connect corresponding gyri of the – connect corresponding gyri of the two hemispheres two hemispheres 1) corpus callosum1) corpus callosum2) anterior commissure2) anterior commissure

Projection tracts (fibers)Projection tracts (fibers) – connect more or less – connect more or less verticallyvertically

Association tracts (fibers)Association tracts (fibers) – connect one gyrus to – connect one gyrus to another in the same hemisphereanother in the same hemisphere

Basal (or cerebral) NucleiBasal (or cerebral) NucleiMisnomer: basal ganglia

Gray matter internal to the cerebral cortex, below floor of lateral ventricles.

Function: modulate motor output from the cerebral cortex. Subconscious control of skeletal muscle tone and coordination of learned movement patterns.

Parkinson's disease is caused by the loss of at least 80% of the dopaminergic neurons in basal nuclei and substantia nigra (resting tremor)

Fig 15.11

DiencephalonDiencephalon

Epithalamus Pineal gland - produces melatonin, sets diurnal cycles

Thalamus (~12 nuclei)

Hypothalamus Just superior to optic chiasma Infundibulum - connects to pituitary gland

Some functions:Control of autonomic nervous system Coordination of nervous and endocrine systems Secretion of hormones - ADH and oxytocin

Mesencephalon)Mesencephalon)= Midbrain = Midbrain

Corpora quadrigemina Corpora quadrigemina = 2 pairs of sensory nuclei= 2 pairs of sensory nuclei1.1. Superior colliculi Superior colliculi (relay station for visual information)2.2. Inferior colliculi Inferior colliculi (relay station for auditory informationinformation

Substantia nigra - regulates motor outputSubstantia nigra - regulates motor output

Cerebral peduncles - ascending and descending Cerebral peduncles - ascending and descending tracts to thalamustracts to thalamus

Nuclei of ori for CN III and IVNuclei of ori for CN III and IV

Metencephalon: Metencephalon: CerebellumCerebellum

Hemispheres and lobes

Cortex -gray surface with folia - fine ridges and sulci - grooves between the ridges

Purkinje cells , axons of which become arbor vitae (white matter) in center

Regulation of posture and balance

Metencephalon: PonsMetencephalon: PonsMyelencephalon: Medulla oblongataMyelencephalon: Medulla oblongata

Mostly ascending and descending Mostly ascending and descending tractstracts

Nuclei of ori for many cranial nervesNuclei of ori for many cranial nerves

Location of autonomic nuclei involved in respiratory and

cardiovascular control

Relay stations for Relay stations for sensory sensory and and motor neurons motor neurons

Cranial NervesCranial Nerves Twelve pairs:Twelve pairs:

– 2 attach to forebrain 2 attach to forebrain (Telen- & (Telen- & Diencephalon)Diencephalon)

– 10 attach to 10 attach to brainstembrainstem

(Mes-, Met- and Myelencephalon)(Mes-, Met- and Myelencephalon)

Names relate toNames relate to appearance or function appearance or function

Classification ?Classification ?

Olfactory Nerve (= CN or N I)Olfactory Nerve (= CN or N I)

1º function?1º function?

Origin?Origin?

Destination? _____________(By way of Destination? _____________(By way of cribiform plate of ethmoidcribiform plate of ethmoid))

Only CN directly attached to CerebrumOnly CN directly attached to Cerebrum

Optic Nerve (N II)Optic Nerve (N II)

1º fu?1º fu?

ori?ori?

dest? - dest? - by way of by way of optic foramen optic foramen of sphenoid to of sphenoid to Diencephalon Diencephalon (optic chiasma) (optic chiasma) and to and to occipital lobeoccipital lobe

Oculomotor (N III)Oculomotor (N III)

C: Motor C: Motor

O: MesencephalonO: Mesencephalon

D: Somatic motor to superior, inferior, medial D: Somatic motor to superior, inferior, medial recti and inferior oblique; visceral motor to recti and inferior oblique; visceral motor to intrinsic eye musclesintrinsic eye muscles

by way of superior orbital fissure by way of superior orbital fissure

Trochlear (N IV)Trochlear (N IV)

C: Motor C: Motor

O: MesencephalonO: Mesencephalon

D: superior obliqueD: superior oblique

by way of superior orbital fissureby way of superior orbital fissure

Trigeminal (N V)Trigeminal (N V)

C: Mixed C: Mixed three major branchesthree major branches

1. ophthalmic (sensory)1. ophthalmic (sensory)2. Maxillary (sensory)2. Maxillary (sensory)3. Mandibular (mixed)3. Mandibular (mixed)

O: face / nuclei of ponsO: face / nuclei of pons

D: sensory nuclei in pons / muscles of masticationD: sensory nuclei in pons / muscles of mastication

AbducensAbducens(CN VI)(CN VI)

C: Motor O: PonsD: Runs lateral rectus eye muscle

Facial (N VII)Facial (N VII)

C: Mixed C: Mixed

O: sensory from taste receptors of O: sensory from taste receptors of anterior 2/3 of tongue / motor from pons anterior 2/3 of tongue / motor from pons

D: Sensory to sensory nuclei of pons / D: Sensory to sensory nuclei of pons / motor muscles of facial expression, motor muscles of facial expression, visceral motor to tear gland.visceral motor to tear gland.

Vestibulocochlear (N VIII)Vestibulocochlear (N VIII)

CO ?D

Glossopharyngeal (CN IX)Glossopharyngeal (CN IX)

C: mixed

O: sensory from posterior 1/3 of tongue / motor from medulla oblongata

D: medulla / muscles for swallowing, parotid gland

Vagus (N X)Vagus (N X)

C: Mixed C: Mixed

O: O: Sensation from pharyngeal area and Sensation from pharyngeal area and outer earouter ear / motor from medulla / motor from medulla

D: D: Sensory to medullaSensory to medulla / / visceral motor visceral motor to thoracic and abdominal to thoracic and abdominal cavities and their organs. cavities and their organs. Major Major motor pathway for ANSmotor pathway for ANS

Accessory (N XI)Accessory (N XI) and and C: Motor C: Motor O: Motor nuclei of medulla O: Motor nuclei of medulla and spinal cordand spinal cordD: Swallowing, trapezius & scm musclesD: Swallowing, trapezius & scm muscles

Hypoglossal (N XII)Hypoglossal (N XII)C: Motor C: Motor O: Motor nuclei of medulla O: Motor nuclei of medulla D: Tongue musculatureD: Tongue musculature

Mnemonic

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