ANATOMY CH 13 CENTRAL NERVOUS SYSTEM

brain stem, cerebellum, diencephalon, cerebrum

• 4 major regions of the brain

ventricles

• fluid filled cavities of the brain → cerebrospinal fluid

• lined with ependymal cells

• continuous with each other and central canal of spinal cord

lateral ventricles

• two horseshoe shaped ventricles in cerebral hemisphere

  • bent from cerebral hemispheres

third ventricle

• ventricle that lies in diencephalon

• connected with lateral ventricles via INTERVENTRICULAR FORAMEN

cerebral aqueduct

• connects 3rd and 4th ventricles

fourth ventricle

• ventricle that lies in hindbrain

• connects to the central canal of spinal cord

choroid plexus

• creates cerebrospinal fluid

  • blood filtrate

grey matter

• nonmyelinated neurons and cell bodies

white matter

• myelinated and nonmyelinated axons

outer layer of grey matter, inner layer of white matter

• the cerebrum and cerebellum’s distribution of grey and white matter

  • NUCLEI— inner grey matter

outer layer of white matter, inner layer of grey matter

• brain stem and spinal cord’s distribution of grey and white matter

  • brain stem has nuclei (additional inner grey matter)

brainstem

• structure

  • midbrain

  • pons

  • medulla oblongata

• function

  • passageway for all fiber tracts (white matter) between cerebrum and spinal cord

  • 10 cranial nerves attach to it

  • automatic survival functions; breathing, BP, heart rate

  • reflexes for sound and vision

medulla oblongata

• continuous with spinal cord

• anterior to 4th ventricle

• most caudal part of brain stem

  • pyramids

  • inferior cerebellar peduncles

  • olives

  • reticular formation

  • CNs VIII, IX, X, and XII

pyramids

• ventral surface of medulla oblongata

• carries voluntary motor output to spinal cord

• DECUSSATION— crossing over of motor tracts

cerebellar peduncles

• major fiber tracts and brain nuclei

• inferior nerve fibers connects medulla/pons and cerebellum

  • also superior and middle that connect to midbrain

• fibers to and from the cerebellum are IPSILATERAL

  • run to and from the same side of the body

olives (inferior olivary nucleus)

• lateral medulla oblongata

• nucleus that relays proprioception (spacial position) info to the cerebellum

vestibular nuclear complex, cochlear nuclei

• medullary brain nuclei associated with

  • vestibulocochlear CN VII

nucleus ambiguus

• medullary brain nucleus associated with

  • glossopharyngeal CN IX and vagus CN X

• motor nucleus on left lateral medulla oblongata

solitary nucleus

• medullary brain nucleus associated with

  • glossopharyngeal CN IX and vagus CN X

• sensory nucleus on left posterior medulla oblongata

dorsal motor nucleus

• medullary brain nucleus associated with

  • vagus CN X

• motor nucleus of chest and throat

hypoglossal nucleus

• medullary brain nucleus associated with

  • hypoglossal CN XII

• motor nucleus on right side posterior medulla oblongata

reticular formation

• core/middle of medulla oblongata

• nuclei that coordinate reflexes and autonomic functions

  • cardiac center

  • vasomotor center— dilate/contract blood vessels

  • medullary respirator center

  • hiccupping, sneezing, swallowing, coughing

pons

• brainstem

• bridge between midbrain and medulla oblongata

  • pyramidal motor tracts

  • cerebellar peduncles

  • pontine nuclei

  • CNs V, VI, and VII

pyramidal motor tracts

• pons

• motor tracts that come from cerebral cortex

pontine nuclei

• nuclei of the pons

• connects portions of cerebral cortex to cerebellum

cerebellar peduncles

• pons

• axons going to cerebellum

midbrain

• superior portion of the brainstem

• lies between diencephalon and pons

• connects brainstem to regions of CNS

  • cerebral aqueduct

  • cerebral peduncles

  • substantia nigra

  • red nucleus

  • periaqueductal grey matter

  • corpora quadrigemina

  • CNs III and IV

cerebral peduncles

• ventral surface of midbrain

  • PYRAMIDAL (corticospinal) TRACTS

  • SUPERIOR CEREBELLAR PEDUNCLES

    • tracts that connect midbrain to cerebellum

substantia nigra

• pigmented nucleus of the midbrain

• neuron cell bodies containing melanin

• functionally linked to basal ganglia nuclei

• controls voluntary movement

red nucleus

• pigmented nucleus of the midbrian

• lies deep to the substantia nigra

• rich blood supply

• works with cerebellum to coordinate flexion of limbs

periaqueductal grey matter

• midbrain but part of reticular formation

• surrounds cerebral aqueduct

  • involved in fight or flight

  • manages (mediates) response to visceral pain

• contains the nuclei for oculomotor CN III and trochlear IV

  • eye movement

corpora quadrigemina

• largest nuclei in the midbrain

• divided into

  • SUPERIOR COLLICULI— visual reflexes

  • INFERIOR COLLICULI— auditory reflexes

cerebellum

• brain region dorsal to the pons and medulla

• structure

  • two cerebellar hemispheres (left and right)

    • connected by vermus

  • anterior, posterior, and flocculonodular lobes

  • surface folia and deeper fissures that subdivide lobes

• function

  • smoothing and coordinating body movements

  • maintain equilibrium

cortex

• region of cerebellum

• external grey matter

arbor vitae

• region of cerebellum

• internal white matter

deep cerebellar nuclei

• region of cerebellum

• deep situated grey matter

function of the cerebellum

• coordinates movement

  • cortex recieves info on equilibrium, movements of body, and motor information from cerebral cortex

  • recieves info from motor cortex → compares intended movement with body position → sends instructions back to cerebral cortex to adjust and fine tune motor commands

• higher cognitive functions

  • motor memory; learning motor skills

  • cognition; language, problem solving, task planning

diencephalon

• central core region of the brain

• surrounded by cerebral hemispheres

• borders the third ventricle

• primarily composed of gray matter

  • thalamus

  • hypothalamus

  • epithalamus

thalamus

• 80% of diencephalon

• forms superolateral walls of third ventricle

• every part of the CNS communicating with cerebral cortex relays signals through major nuclei

  • sends axons to regions of the cerebral cortex

• afferent impulses (incoming sensory message) converge here, synapse in at least one of its nuclei

• organizes, amplifies, or tones down signals, relay station

hypothalamus

• diencephalon

• between optic chiasm and mammilary bodies

• pituitary gland projects inferiorly

• dozen nuclei

• main visceral control center of the body

  • controls ANS, emotional responses, body temp, hunger/thirst, motivation/reward, sleep wake, endocrine system, and forms memory

epithalamus

• diencephalon

• tiny group of nuclei

• forms part of third ventricle’s “roof”

• pineal gland

  • secretes melatonin under influence of hypothalamus

  • aids in control of circadian rhythm

cerebrum

• 83% of brain mass

  • fissures

    • transverse and longitudinal

  • sulci

  • gyri

central sulcus

• cerebrum

• separates frontal and parietal lobes

  • precentral gyrus— motor cortex

  • postcentral gyrus— somatosensory cortex

parieto-occipital sulcus

• cerebrum

• separates occipital lobe from parietal lobe

lateral sulcus

• cerebrum

• separates temporal lobe from parietal and frontal lobe

insula

• cerebrum

• “lobe” deep within lateral sulcus

frontal lobe

• cerebral cortex

  • voluntary movement— primary motor cortex

  • planning movement— premotor cortex

  • eye movement— frontal eye field

  • speech production— broca’s area

  • executive cognitive functions— anterior association area

  • emotional response— limbic association area

parietal lobe

• cerebral cortex

  • general somatic sensation— somatosensory cortex and association area

  • spatial awareness of objects, sounds, and body parts—posterior association area

  • understanding speech— wernicke’s area

occipital lobe

• cerebral cortex

  • visual cortex and association areas

temporal lobe

• cerebral cortex

  • hearing— auditory cortex and association areas

  • smell— olfactory cortex

  • object identification— posterior association area

  • emotional response/memory— limbic association area

insula

• cerebral cortex

  • taste— gustatory cortex

cerebral cortex

• outermost region of cerebrum

• grey matter

  • neuron cell bodies, dendrites, short axons

• 40% of brain mass

• folds in cortex make it 3x the size

• BRODMANN AREAS

  • 47 structurally distinct areas

• conscious mind

  • distinct motor and sensory functions; memory and language spread over wide area

• can be separated into functional regions

  • sensory areas

  • motor areas

  • association areas (interpretation)

sensory area

• each major sense has one in cerebral cortex

  • in parietal, temporal, and occipital lobes

• each sense also has a primary sensory cortex

primary somatosensory cortex

• sensory area located in postcentral gyrus

• conscious awareness of general somatic senses

  • spacial discrimination— locating a stimulus

• contralateral— cerebral hemispheres receive sensory input from opposite side of the body

primary visual cortex

• sensory area deep within calcarine sulcus— medial occipital lobe

• largest of all sensory areas

• receives visual information from retina first

  • contralateral

visual association area

• sensory area that surrounds the primary visual cortex in the occipital lobe

• continues processing of visual information

  • color, form, movement

  • complex visual processing extends into temporal and parietal lobes

primary auditory cortex

• sensory area on superior edge of temporal lobe

• conscious awareness of sound/hearing

• sound waves excite receptors in inner ear → impulses transmitted to primary auditory cortex

auditory association area

• sensory area posterior to primary auditory cortex

• permits evaluation of different sounds

vestibular cortex

• sensory area in cortex of insula

• responsible for conscious awareness of balance sense

gustatory cortex

• sensory area in the insula

• involved in conscious awareness of taste stimuli

olfactory cortex

• sensory area rostral to diencephalon

  • RHINENCEPHALON— “nose brain”

• olfactory nerves transmit impulses here; conscious awareness of smell

  • piriform cortex— venterolateral region of frontal lobe

  • olfactory tracts

  • olfactory bulbs

visceral sensory areas

• sensory areas within the lateral sulcus on the insula

• recieves general sensory input

  • pain

  • pressure

  • hunger

motor areas

• cerebral cortex

• plans and initiates voluntary motor functions

  • premotor cortex

  • primary motor cortex

  • frontal eye field

  • broca’s area

• all in posterior frontal lobe

premotor cortex

• motor area anterior to the motor cortex in the precentral gyrus

• controls more complex movements

  • recieves processed sensory information— visual, auditory, and general somatic sensory

• controls voluntary actions dependent on sensory feedback

• involved in planning movements

primary motor cortex

• motor area in the precentral gyrus

• controls motor functions

• SOMATOTROPY

  • body is represented spatially in primary motor cortex

  • correspondence of a specific area of the body to a specific point in CNS

pyramidal cells

• large neurons of primary motor cortex

• specific cells control specific areas of the body

• face and hand muscles are controlled by many cells

corticospinal tracts

• descend through brainstem and spinal cord

• axons of pyramidal neurons signal motor neurons in spinal cord to control skilled movements

• contralateral— pyramidal axons cross over to opposite side of the brain

frontal eye field

• motor area anterior to the premotor cortex

• controls voluntary movement of the eyes

  • especially when moving eyes to follow a moving target

broca’s area

• motor area in the left medial frontal lobe

• manages speech production

  • connected to language comprehension areas in posterior association area

• corresponding region in the right cerebral hemisphere controls emotional overtones to spoken words

multimodal association areas

• receives and integrates input from multiple regions of the cerebral cortex

  • sensory information recieved by primary sensory cortex

  • information relayed to sensory association area

  • recieves input in parallel from multiple sensory areas

  • makes associations between kinds of sensory information

  • enacts motor plan

• 3 association areas

  • posterior association area

  • anterior association area

  • limbic association area

posterior association area

• multimodal association area at interface of visual, auditory, and somatosensory association areas

• integrates sensory information into unified perception

  • allows awareness of spatial location of body

• related to language comprehension and speech

• multiple language areas in left cerebral cortex

  • wernicke’s area

• areas in right cerebral hemisphere

  • creative interpretation of words

  • emotional overtones of speech

wernicke’s area

• part of posterior association area in left cerebral cortex

• speech comprehension

• coordination of auditory and visual aspects of language

• initiation of word articulation

• recognition of sound sequences

anterior association area

• multimodal association area in prefrontal cortex

• recieves information from posterior sensory association area

• integrates information with past experience

• initiates and plans motor movements

• has links to limbic system

• complex thinking, processing ideas, impulse control, empathy, etc.

• last part of brain to mature

limbic association area

• multimodal association area in the medial side of frontal lobe

• involved with memory and emotions

  • integrates sensory and motor behaviors

  • aids in formation of memory

  • processes emotions

cerebral white matter (tracts)

• axonal fibers of the cerebrum are myelinated and bundled into tracts

• different areas of the cerebral cortex communicate with each other, brainstem, and spinal cord

• type of tracts

  • commissural fibers

  • association fibers

  • projection fibers

commissural fibers

• type of tract (cerebral white matter)

• allows communication between the two cerebral hemispheres

  • CORPUS CALLOSUM— largest commissure

association fibers

• type of tract (cerebral white matter)

• connects different parts of the same hemisphere

  • ex. parts of wernicke’s and broca’s areas are connected by association fibers

projection fibers

• type of tract (cerebral white matter)

• runs vertically, either

  • DESCENDS from cerebral cortex to more caudal parts of CNS, ex corticospinal (pyrimidal) tract

  • ASCENDS to the cortex from lower regions

cerebrum nuclei

• deep grey matter

  • basal nuclei/basal ganglia

  • basal forebrain nuclei

  • claustrum

  • amygdaloid body

basal ganglia nuclei

• group of nuclei deep within the cerebral white matter

• formed from

  • caudate nucleus— arches over thalamus

  • putamen

  • globus pallidus

• influenced by substantia nigra

• cooperates with cerebral cortex in complex calculating and controlling of movement

  • start stop and regulate intensity of voluntary movements

  • select appropriate muscles and inhibit others

  • estimate passage of time

• degenerative conditions produce dyskinesia

  • Parkinson’s, Huntington’s

limbic system

• functional brain system

  • cerebrum— cingulate gyrus, septal nuclei, part of amygdaloid body, hippocampal formation

  • diencephalon— anterior thalamic nuclei, hypothalamus

  • fornix and other tracts link limbic system together

cingulate gyrus

• cerebral component of limbic system

• superior to corpus callosum

• mediates emotional and visceral responses to sensory input (pain is unpleasant)

hippocampal formation

• cerebral component of limbic system

  • hippocampus and parahippocampal gyrus

• critical in memory formation and retrieval

amygdaloid body (amygdala)

• cerebral component of limbic system

• contains key brain nuclei for processing fear

• stimulates appropriate sympathetic response

• forms emotional memory

reticular formation

• functional brain system

• runs through central core of brain stem

• consciousness and arousal

  • RETICULAR ACTIVATING SYSTEM

• neurons have long branching axons that project to widely separated regions

  • thalamus

  • cerebellum

  • spinal cord

reticular activating system

• maintains consciousness and alertness

• functions in sleep and arousal from sleep

• malfunctions in people with narcolepsy

protection of the brain

• skull

• meninges

• cerebrospinal fluid

• blood brain barrier

meninges

• structure

  • dura mater

  • arachnoid mater

  • pia mater

• function

  • covers and protects the CNS

  • enclose and protect vessels that supply the CNS

  • contains cerebrospinal fluid between pia and arachnoid maters

dura mater

• meninge

• in spinal cord

  • single layer surrounding spinal cord

  • spinal dural sheath

  • external to it is the epidural space

• in brain

  • strongest of the meninges

  • periosteal layer— attaches to skull

  • meningeal layer— forms true ext. covering of brain

  • fused layers except for DURAL VENOUS SINUSES

    • blood filled, collects blood from the brain, conducts to internal jugular veins

    • largest sinus is the SUPERIOR SAGGITAL SINUS

  • extends inward to subdivide cranial cavity and limit movement of brain

    • falx cerebri— longitudinal fissure, falx cerebelli, tentorium cerebelli

arachnoid mater

• meninge

• in spinal cord

  • lies deep to dura mater

  • SUBARACHNOID SPACE below L1/L2, where a spinal tap is taken

• in brain

  • SUBDURAL SPACE— between arachnoid and dura mater

  • SUBARACHNOID SPACE— deep, weblike threads that hoid it to lower meninge, filled with CSF, contains largest blood vessels supplying brain

  • ARACHNOID GRANULATIONS— project through dura mater to allow CSF to pass into dural blood sinuses above

pia mater

• meninge

• in spinal cord

  • extends to coccyx

  • delicate CT

  • DENTICULATE LIGAMENTS— lateral extensions that anchor the spinal cord

• in brain

  • made of delicate CT

  • richly vascularized with fine blood vessels

  • clings to and follows surface of the brain

cerebrospinal fluid

• fills subarachnoid space, ventricles, cerebral aqueduct, central canal of spinal cord

• provides protection for brain and spinal cord

  • liquid cushion, resists compressive forces

  • brain floats in this liquid

  • nourishes brain and spinal cord

  • removes wastes

  • carries chemical signals between parts of the CNS

choroid plexus

• located in all four ventricles

• composed of ependymal cells and capillaries

• forms cerebrospinal fluid

  • arises from blood

blood brain barrier

• prevents most blood borne toxins from entering the brain

  • impermeable capillaries (tight junctions)

  • astrocytes surrounding capillaries

• not an absolute barrier

  • allows lipid soluable substances— oxygen and CO2

  • allows passage of alcohol, nicotine, and anesthetics

spinal cord functions

• spinal nerves— involved in sensory and motor innervation inferior to the head

• ascending and descending tracts— provides two-way conduction pathway for signals between body and brain

• sensory and motor synapse in grey matter— provides major center for reflexes

spinal cord

• runs through vertebral canal of the vertebral column

  • extends from foramen magnum (occipital bone) to vertebra L1/L2

• 31 pairs of spinal nerves attach through dorsal and ventral nerve routes

  • named based on where they are in vertebral column

• features

  • conus medullaris

  • filum terminale

  • cervical and lumbar enlargements

  • cauda equina

  • spinal cord segments

  • dorsal medial sulcus

  • ventral median fissure

conus medullaris

• inferior end of the spinal cord at L1/L2

filum terminale

• long filament of CT extending from conus medullaris

• attaches to coccyx inferiorly

• anchors spinal cord in place

cervical and lumbar enlargements

• where nerves for upper and lower limbs arise

cauda equina

• collection of spinal nerve roots