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Principal Parts of the BrainPrincipal Parts of the Brain

CerebrumCerebrum DiencephalonDiencephalon

thalamus & thalamus & hypothalamushypothalamus

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Chapter 14Chapter 14The Brain and Cranial NervesThe Brain and Cranial Nerves

Largest organ in the body at almost 3 lb.Largest organ in the body at almost 3 lb. Brain functions in sensations, memory, emotions, decision making, behaviorBrain functions in sensations, memory, emotions, decision making, behavior

CerebellumCerebellum BrainstemBrainstem

medulla, pons & midbrainmedulla, pons & midbrain

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Protective Coverings of the Protective Coverings of the BrainBrain

Bone, meninges & Bone, meninges & fluidfluid

Meninges same as Meninges same as around the spinal around the spinal cordcord dura materdura mater arachnoid materarachnoid mater pia materpia mater

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Blood Supply to BrainBlood Supply to Brain Arterial blood supply is branches from circle of Arterial blood supply is branches from circle of

Willis on base of brain (page 699)Willis on base of brain (page 699) Vessels on surface of brain----penetrate tissueVessels on surface of brain----penetrate tissue Uses 20% of our bodies oxygen & glucose Uses 20% of our bodies oxygen & glucose

needsneeds blood flow to an area increases with activity in that blood flow to an area increases with activity in that

areaarea deprivation of O2 for 4 min does permanent injurydeprivation of O2 for 4 min does permanent injury

at that time, lysosome release enzymesat that time, lysosome release enzymes

Blood-brain barrier (BBB)Blood-brain barrier (BBB) protects cells from some toxins and pathogensprotects cells from some toxins and pathogens

proteins & antibiotics can not pass but alcohol & proteins & antibiotics can not pass but alcohol & anesthetics doanesthetics do

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Cerebrospinal Fluid (CSF)Cerebrospinal Fluid (CSF)

80-150 ml (3-5oz)80-150 ml (3-5oz) Clear liquid containing glucose, proteins, Clear liquid containing glucose, proteins,

& ions& ions FunctionsFunctions

mechanical protection mechanical protection floats brain & softens impact with bony wallsfloats brain & softens impact with bony walls

chemical protectionchemical protection optimal ionic concentrations for action potentialsoptimal ionic concentrations for action potentials

circulationcirculation nutrients and waste products to and from nutrients and waste products to and from

bloodstreambloodstream

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Drainage of CSF from Drainage of CSF from VentriclesVentricles

One median aperture & two lateral apertures One median aperture & two lateral apertures allow CSF to exit from the interior of the brainallow CSF to exit from the interior of the brain

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Reabsorption of CSFReabsorption of CSF

Reabsorbed through arachnoid villiReabsorbed through arachnoid villi grapelike clusters of arachnoid penetrate dural venous sinusgrapelike clusters of arachnoid penetrate dural venous sinus

20 ml/hour reabsorption rate = same as production 20 ml/hour reabsorption rate = same as production raterate

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HydrocephalusHydrocephalus Blockage of drainage of CSF (tumor, Blockage of drainage of CSF (tumor,

inflammation, developmental inflammation, developmental malformation, meningitis, hemorrhage or malformation, meningitis, hemorrhage or injuryinjury

Continued production cause an increase in Continued production cause an increase in pressure --- hydrocephaluspressure --- hydrocephalus

In newborn or fetus, the fontanels allow In newborn or fetus, the fontanels allow this internal pressure to cause expansion this internal pressure to cause expansion of the skull and damage to the brain of the skull and damage to the brain tissuetissue

Neurosurgeon implants a drain shunting Neurosurgeon implants a drain shunting the CSF to the veins of the neck or the the CSF to the veins of the neck or the abdomenabdomen

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Medulla OblongataMedulla Oblongata Continuation of spinal cordContinuation of spinal cord Nuclei of 5 cranial nervesNuclei of 5 cranial nerves Cardiovascular centerCardiovascular center

force & rate of heart beatforce & rate of heart beat diameter of blood vesselsdiameter of blood vessels

Respiratory centerRespiratory center medullary rhythmicity area sets basic rhythm of medullary rhythmicity area sets basic rhythm of

breathingbreathing Information in & out of cerebellumInformation in & out of cerebellum Reflex centers for coughing, sneezing, Reflex centers for coughing, sneezing,

swallowing etcswallowing etc

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XII = Hypoglossal NerveXII = Hypoglossal Nerve

Controls muscles of Controls muscles of tongue during tongue during speech and speech and swallowingswallowing

Injury deviates Injury deviates tongue to injured tongue to injured side when side when protrudedprotruded

Mixed, primarily Mixed, primarily motormotor

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X = Vagus NerveX = Vagus Nerve

Receives Receives sensations from sensations from viscera viscera

Controls cardiac Controls cardiac muscle and smooth muscle and smooth muscle of the muscle of the visceraviscera

Controls secretion Controls secretion of digestive fluidsof digestive fluids

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IX = Glossopharyngeal NerveIX = Glossopharyngeal Nerve

Stylopharyngeus Stylopharyngeus m. (lifts throat m. (lifts throat during swallowing)during swallowing)

Secretions of Secretions of parotid glandparotid gland

Somatic Somatic sensations & taste sensations & taste on posterior 1/3 of on posterior 1/3 of tonguetongue

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Injury to the MedullaInjury to the Medulla

Hard blow to the back of the head may be fatalHard blow to the back of the head may be fatal Cranial nerve malfunctions on same side as injury;Cranial nerve malfunctions on same side as injury;

loss of sensation or paralysis of throat or tongue; loss of sensation or paralysis of throat or tongue; irregularities in breathing and heart rhythmirregularities in breathing and heart rhythm

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PonsPons

One inch longOne inch long White fiber tracts White fiber tracts

ascend and ascend and descenddescend

Pneumotaxic & Pneumotaxic & apneustic areas apneustic areas help control help control breathingbreathing

Middle cerebellar Middle cerebellar peduncles carry peduncles carry sensory info to the sensory info to the cerebellumcerebellum

Cranial nerves 5 Cranial nerves 5 thru 7thru 7

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VII = Facial NerveVII = Facial Nerve

Motor portionMotor portion facial musclesfacial muscles salivary & nasal salivary & nasal

and oral mucous and oral mucous glands & tearsglands & tears

Sensory portionSensory portion taste buds on taste buds on

anterior 2/3’s of anterior 2/3’s of tonguetongue

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MidbrainMidbrain

One inch in One inch in lengthlength

Extends from Extends from pons to pons to diencephalondiencephalon

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CerebellumCerebellum

2 cerebellar hemispheres and vermis (central area)2 cerebellar hemispheres and vermis (central area) FunctionFunction

correct voluntary muscle contraction and posture based on correct voluntary muscle contraction and posture based on sensory data from body about actual movementssensory data from body about actual movements

sense of equilibriumsense of equilibrium

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ThalamusThalamus

1 inch long mass of gray mater in each half of brain 1 inch long mass of gray mater in each half of brain (connected across the 3rd ventricle by intermediate (connected across the 3rd ventricle by intermediate mass)mass)

Relay station for sensory information on way to cortexRelay station for sensory information on way to cortex Crude perception of some sensationsCrude perception of some sensations

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Thalamic NucleiThalamic Nuclei

Nuclei have different rolesNuclei have different roles relays auditory and visual impulses, taste and relays auditory and visual impulses, taste and

somatic sensations somatic sensations receives impulses from cerebellum or basal gangliareceives impulses from cerebellum or basal ganglia anterior nucleus concerned with emotions, memory anterior nucleus concerned with emotions, memory

and acquisition of knowledge (cognition)and acquisition of knowledge (cognition)

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HypothalamusHypothalamus

Dozen or so nuclei in 4 major regions Dozen or so nuclei in 4 major regions mammillary bodies are relay station for olfactory reflexes;mammillary bodies are relay station for olfactory reflexes;

infundibulum suspends the pituitary glandinfundibulum suspends the pituitary gland Major regulator of homeostasisMajor regulator of homeostasis

receives somatic and visceral input, taste, smell & hearing receives somatic and visceral input, taste, smell & hearing information; monitors osmotic pressure, temperature of bloodinformation; monitors osmotic pressure, temperature of blood

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Functions of HypothalamusFunctions of Hypothalamus Controls and integrates activities of the ANS Controls and integrates activities of the ANS

which regulates smooth, cardiac muscle and which regulates smooth, cardiac muscle and glandsglands

Synthesizes regulatory hormones that control Synthesizes regulatory hormones that control the anterior pituitarythe anterior pituitary

Contains cell bodies of axons that end in Contains cell bodies of axons that end in posterior pituitary where they secrete hormonesposterior pituitary where they secrete hormones

Regulates rage, aggression, pain, pleasure & Regulates rage, aggression, pain, pleasure & arousalarousal

Feeding, thirst & satiety centersFeeding, thirst & satiety centers Controls body temperatureControls body temperature Regulates daily patterns of sleepRegulates daily patterns of sleep

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EpithalamusEpithalamus

Pineal glandPineal gland endocrine gland the endocrine gland the

size of small peasize of small pea secretes melatonin secretes melatonin

during darknessduring darkness promotes promotes

sleepiness & sets sleepiness & sets biological clockbiological clock

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Subthalamus & CVOSubthalamus & CVO Circumventricular organsCircumventricular organs

sites of entry of HIV virus into brain sites of entry of HIV virus into brain (dementia)(dementia)

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CerebrumCerebrum (Cerebral Hemispheres) (Cerebral Hemispheres)

Cerebral cortex is gray matterCerebral cortex is gray matteroverlying white matteroverlying white matter 2-4 mm thick containing billions2-4 mm thick containing billions

of cellsof cells grew so quickly formed foldsgrew so quickly formed folds

(gyri) and grooves (sulci or fissures)(gyri) and grooves (sulci or fissures) Longitudinal fissure separates left Longitudinal fissure separates left

& right cerebral hemispheres& right cerebral hemispheres Corpus callosum is band of white matter Corpus callosum is band of white matter

connecting left and right cerebral connecting left and right cerebral hemisphereshemispheres

Each hemisphere is subdivided into 4 lobesEach hemisphere is subdivided into 4 lobes

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Lobes and Lobes and FissuresFissures

Longitudinal fissure (green)Longitudinal fissure (green) Frontal lobeFrontal lobe Central sulcus (yellow)Central sulcus (yellow)

precentral & postcentral precentral & postcentral gyrusgyrus

Parietal lobeParietal lobe Parieto-occipital sulcusParieto-occipital sulcus Occipital lobeOccipital lobe Lateral sulcus (blue)Lateral sulcus (blue) Temporal lobeTemporal lobe InsulaInsula

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Basal GangliaBasal Ganglia

Control large automatic movements of skeletal Control large automatic movements of skeletal musclesmuscles

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Limbic SystemLimbic System

Emotional brain--intense pleasure & intense Emotional brain--intense pleasure & intense painpain

Strong emotions increase efficiency of memoryStrong emotions increase efficiency of memory

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Brain InjuriesBrain Injuries Causes of damageCauses of damage

displacement or distortion of tissue at impactdisplacement or distortion of tissue at impact increased intracranial pressureincreased intracranial pressure infectionsinfections free radical damage after ischemiafree radical damage after ischemia

Concussion---temporary loss of consciousnessConcussion---temporary loss of consciousness headache, drowsiness, confusion, lack of headache, drowsiness, confusion, lack of

concentrationconcentration Contusion--bruising of brain (less than 5 min Contusion--bruising of brain (less than 5 min

unconsciousness but blood in CSF)unconsciousness but blood in CSF) Laceration--tearing of brain (fracture or bullet)Laceration--tearing of brain (fracture or bullet)

increased intracranial pressure from hematomaincreased intracranial pressure from hematoma

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AphasiaAphasia Language areas are located in the left Language areas are located in the left

cerebral hemisphere of most peoplecerebral hemisphere of most people Inability to use or comprehend words = Inability to use or comprehend words =

aphasiaaphasia nonfluent aphasia = inability to properly form nonfluent aphasia = inability to properly form

wordswords know what want to say but can not speak know what want to say but can not speak damage to Broca’s speech areadamage to Broca’s speech area

fluent aphasia = faulty understanding of fluent aphasia = faulty understanding of spoken or written wordsspoken or written words

faulty understanding of spoken or written wordsfaulty understanding of spoken or written words word deafness = an inability to understand spoken wordsword deafness = an inability to understand spoken words word blindness = an inability to understand written wordsword blindness = an inability to understand written words

damage to common integrative area or auditory damage to common integrative area or auditory association areaassociation area

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Hemispheric LateralizationHemispheric Lateralization Functional Functional

specialization of each specialization of each hemisphere more hemisphere more pronounced in menpronounced in men

Females have larger Females have larger connections between connections between 2 sides2 sides

Damage to left side Damage to left side produces aphasiaproduces aphasia

Damage to same Damage to same area on right side area on right side produces speech produces speech with little emotional with little emotional inflectioninflection

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Electroencephalogram (EEG)Electroencephalogram (EEG) Brain waves are millions Brain waves are millions

of nerve action of nerve action potentials in cerebral potentials in cerebral cortexcortex diagnosis of brain diagnosis of brain

disorders (epilepsy)disorders (epilepsy) brain death (absence of brain death (absence of

activity in 2 EEGs 24 activity in 2 EEGs 24 hours apart)hours apart)

Alpha -- awake & restingAlpha -- awake & resting Beta -- mental activityBeta -- mental activity Theta -- emotional Theta -- emotional

stressstress Delta -- deep sleepDelta -- deep sleep

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II -- Optic NerveII -- Optic Nerve

Connects to retina Connects to retina supplying visionsupplying vision

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I -- Olfactory NerveI -- Olfactory Nerve

Extends from Extends from olfactory olfactory mucosa of nasal mucosa of nasal cavity to cavity to olfactory bulbolfactory bulb

Sense of smellSense of smell

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Dorsal View of Neural GrooveDorsal View of Neural Groove

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Aging & the Nervous SystemAging & the Nervous System Years 1 to 2Years 1 to 2

rapid increase in size due to increase in size of rapid increase in size due to increase in size of neurons, growth of neuroglia, myelination & neurons, growth of neuroglia, myelination & development of dendritic branchesdevelopment of dendritic branches

Early adulthood until deathEarly adulthood until death brain weight declines until only 93% by age 80brain weight declines until only 93% by age 80 number of synaptic contacts declinesnumber of synaptic contacts declines processing of information diminishesprocessing of information diminishes conduction velocity decreasesconduction velocity decreases voluntary motor movements slow downvoluntary motor movements slow down reflexes slow downreflexes slow down

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Cerebrovascular Accident Cerebrovascular Accident (CVA)(CVA)

Third leading cause of death after heart Third leading cause of death after heart attacks and cancerattacks and cancer

2 types of strokes2 types of strokes ischemic due to decreased blood flowischemic due to decreased blood flow hemorrhagic due to rupture of blood vesselhemorrhagic due to rupture of blood vessel

Risk factorsRisk factors high blood pressure, high cholesterol, heart high blood pressure, high cholesterol, heart

disease, diabetes, smoking, obesity, alcoholdisease, diabetes, smoking, obesity, alcohol Tissue plasminogen activator (t-PA) Tissue plasminogen activator (t-PA)

used within 3 hours of onset will used within 3 hours of onset will decrease permanent disabilitydecrease permanent disability

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Transient Ischemic Attack Transient Ischemic Attack (TIA)(TIA)

Episode of temporary cerebral dysfunctionEpisode of temporary cerebral dysfunction CauseCause

impaired blood flow to the brainimpaired blood flow to the brain SymptomsSymptoms

dizziness, slurred speech, numbness, paralysis dizziness, slurred speech, numbness, paralysis on one side, double visionon one side, double vision

reach maximum intensity almost immediatelyreach maximum intensity almost immediately persists for 5-10 minutes & leaves no deficitspersists for 5-10 minutes & leaves no deficits

Treatment is aspirin or anticoagulants; Treatment is aspirin or anticoagulants; artery bypass grafting or carotid artery bypass grafting or carotid endarterectomyendarterectomy

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Alzheimer Disease (AD)Alzheimer Disease (AD) Dementia = loss of reasoning, ability to Dementia = loss of reasoning, ability to

read, write, talk, eat & walkread, write, talk, eat & walk Afflicts 11% of population over 65Afflicts 11% of population over 65 Loss of neurons that release acetylcholineLoss of neurons that release acetylcholine Plaques of abnormal proteins outside Plaques of abnormal proteins outside

neuronsneurons Tangled protein filaments within neuronsTangled protein filaments within neurons Risk factors -- head injury, heredityRisk factors -- head injury, heredity Beneficial effects of estrogen, vitamin E, Beneficial effects of estrogen, vitamin E,

ibuprofen & ginko bilobaibuprofen & ginko biloba