Functional Brain SystemFunctional Brain System

Networks of neurons working together and Networks of neurons working together and spanning wide areas of the brainspanning wide areas of the brain

The two systems are:The two systems are: Limbic systemLimbic system Reticular formationReticular formation

Limbic SystemLimbic System

Structures located on the medial aspects of Structures located on the medial aspects of cerebral hemispheres and diencephaloncerebral hemispheres and diencephalon

Includes the rhinencephalon, amygdala, Includes the rhinencephalon, amygdala, hypothalamus, and anterior nucleus of the hypothalamus, and anterior nucleus of the thalamusthalamus

Limbic SystemLimbic System

Parts especially important in emotions:Parts especially important in emotions: Amygdala – deals with anger, danger, and fear Amygdala – deals with anger, danger, and fear

responsesresponses Cingulate gyrus – plays a role in expressing Cingulate gyrus – plays a role in expressing

emotions via gestures, and resolves mental conflictemotions via gestures, and resolves mental conflict Puts emotional responses to odors – e.g., Puts emotional responses to odors – e.g.,

skunks smell badskunks smell bad

Limbic SystemLimbic System

Figure 12.18

Limbic System: Emotion and Limbic System: Emotion and CognitionCognition

The limbic system interacts with the prefrontal The limbic system interacts with the prefrontal lobes, therefore:lobes, therefore: One can react emotionally to conscious One can react emotionally to conscious

understandingsunderstandings One is consciously aware of emotion in one’s lifeOne is consciously aware of emotion in one’s life

Hippocampal structures – convert new Hippocampal structures – convert new information into long-term memoriesinformation into long-term memories

Reticular FormationReticular Formation

Composed of three broad columns along the Composed of three broad columns along the length of the brain stemlength of the brain stem Raphe nucleiRaphe nuclei Medial (large cell) groupMedial (large cell) group Lateral (small cell) groupLateral (small cell) group

Has far-flung axonal connections with Has far-flung axonal connections with hypothalamus, thalamus, cerebellum, and hypothalamus, thalamus, cerebellum, and spinal cordspinal cord

Reticular FormationReticular Formation

Figure 12.19

Reticular Formation: RAS and Reticular Formation: RAS and Motor FunctionMotor Function

RAS – RAS – RReticular eticular AActivating ctivating SSystem ystem Sends impulses to the cerebral cortex to keep it Sends impulses to the cerebral cortex to keep it

conscious and alertconscious and alert Filters out repetitive and weak stimuliFilters out repetitive and weak stimuli

Motor functionMotor function Helps control coarse motor movementsHelps control coarse motor movements Autonomic centers regulate visceral motor Autonomic centers regulate visceral motor

functions – e.g., vasomotor, cardiac, and functions – e.g., vasomotor, cardiac, and respiratory centersrespiratory centers

Brain WavesBrain Waves Normal brain function involves continuous Normal brain function involves continuous

electrical activityelectrical activity An electroencephalogram (EEG) records this An electroencephalogram (EEG) records this

activityactivity Patterns of neuronal electrical activity recorded Patterns of neuronal electrical activity recorded

are called brain wavesare called brain waves Each person’s brain waves are uniqueEach person’s brain waves are unique Continuous train of peaks and troughsContinuous train of peaks and troughs Wave frequency is expressed in Hertz (Hz)Wave frequency is expressed in Hertz (Hz)

Types of Brain WavesTypes of Brain Waves Alpha waves – regular and rhythmic, low-Alpha waves – regular and rhythmic, low-

amplitude, slow, synchronous waves indicating amplitude, slow, synchronous waves indicating an “idling” brainan “idling” brain

Beta waves – rhythmic, more irregular waves Beta waves – rhythmic, more irregular waves occurring during the awake and mentally alert occurring during the awake and mentally alert statestate

Theta waves – more irregular than alpha Theta waves – more irregular than alpha waves; common in children but abnormal in waves; common in children but abnormal in adultsadults

Delta waves – high-amplitude waves seen in Delta waves – high-amplitude waves seen in deep sleep and when reticular activating deep sleep and when reticular activating system is dampedsystem is damped

Types of Brain WavesTypes of Brain Waves

Figure 12.20b

Brain Waves: State of the BrainBrain Waves: State of the Brain

Change with age, sensory stimuli, brain Change with age, sensory stimuli, brain disease, and the chemical state of the bodydisease, and the chemical state of the body

EEGs used to diagnose and localize brain EEGs used to diagnose and localize brain lesions, tumors, infarcts, infections, abscesses, lesions, tumors, infarcts, infections, abscesses, and epileptic lesionsand epileptic lesions

A flat EEG (no electrical activity) is clinical A flat EEG (no electrical activity) is clinical evidence of deathevidence of death

EpilepsyEpilepsy

A victim of epilepsy may lose consciousness, A victim of epilepsy may lose consciousness, fall stiffly, and have uncontrollable jerking, fall stiffly, and have uncontrollable jerking, characteristic of epileptic seizurecharacteristic of epileptic seizure

Epilepsy is not associated with, nor does it Epilepsy is not associated with, nor does it cause, intellectual impairmentscause, intellectual impairments

Epilepsy occurs in 1% of the populationEpilepsy occurs in 1% of the population

Epileptic SeizuresEpileptic Seizures

Absence seizures, or petit mal – mild seizures Absence seizures, or petit mal – mild seizures seen in young children where the expression seen in young children where the expression goes blankgoes blank

Grand mal seizures – victim loses Grand mal seizures – victim loses consciousness, bones are often broken due to consciousness, bones are often broken due to intense convulsions, loss of bowel and bladder intense convulsions, loss of bowel and bladder control, and severe biting of the tonguecontrol, and severe biting of the tongue

Control of EpilepsyControl of Epilepsy

Epilepsy can usually be controlled with Epilepsy can usually be controlled with anticonvulsive drugsanticonvulsive drugs

Valproic acid, a nonsedating drug, enhances Valproic acid, a nonsedating drug, enhances GABA and is a drug of choiceGABA and is a drug of choice

Vagus nerve stimulators can be implanted Vagus nerve stimulators can be implanted under the skin of the chest and can keep under the skin of the chest and can keep electrical activity of the brain from becoming electrical activity of the brain from becoming chaoticchaotic

ConsciousnessConsciousness

Encompasses perception of sensation, Encompasses perception of sensation, voluntary initiation and control of movement, voluntary initiation and control of movement, and capabilities associated with higher mental and capabilities associated with higher mental processingprocessing

Involves simultaneous activity of large areas Involves simultaneous activity of large areas of the cerebral cortexof the cerebral cortex

Is superimposed on other types of neural Is superimposed on other types of neural activityactivity

ConsciousnessConsciousness

Is holistic and totally interconnectedIs holistic and totally interconnected Clinical consciousness is defined on a Clinical consciousness is defined on a

continuum that grades levels of behavior – continuum that grades levels of behavior – alertness, drowsiness, stupor, comaalertness, drowsiness, stupor, coma

Types of SleepTypes of Sleep

There are two major types of sleep:There are two major types of sleep: Non-rapid eye movement (NREM)Non-rapid eye movement (NREM) Rapid eye movement (REM)Rapid eye movement (REM)

One passes through four stages of NREM One passes through four stages of NREM during the first 30-45 minutes of sleepduring the first 30-45 minutes of sleep

REM sleep occurs after the fourth NREM REM sleep occurs after the fourth NREM stage has been achievedstage has been achieved

Types and Stages of Sleep: Types and Stages of Sleep: NREMNREM

NREM stages include:NREM stages include: Stage 1 – eyes are closed and relaxation begins; the Stage 1 – eyes are closed and relaxation begins; the

EEG shows alpha waves; one can be easily arousedEEG shows alpha waves; one can be easily aroused Stage 2 – EEG pattern is irregular with sleep spindles Stage 2 – EEG pattern is irregular with sleep spindles

(high-voltage wave bursts); arousal is more difficult(high-voltage wave bursts); arousal is more difficult Stage 3 – sleep deepens; theta and delta waves appear; Stage 3 – sleep deepens; theta and delta waves appear;

vital signs decline; dreaming is commonvital signs decline; dreaming is common Stage 4 – EEG pattern is dominated by delta waves; Stage 4 – EEG pattern is dominated by delta waves;

skeletal muscles are relaxed; arousal is difficultskeletal muscles are relaxed; arousal is difficult

Types and Stages of Sleep: REMTypes and Stages of Sleep: REM

Characteristics of REM sleep Characteristics of REM sleep EEG pattern reverts through the NREM stages to EEG pattern reverts through the NREM stages to

the stage 1 patternthe stage 1 pattern Vital signs increaseVital signs increase Skeletal muscles (except ocular muscles) are Skeletal muscles (except ocular muscles) are

inhibitedinhibited Most dreaming takes placeMost dreaming takes place

SleepSleep

Figure 12.21a.1

SleepSleep

Figure 12.21a.2

Sleep PatternsSleep Patterns

Alternating cycles of sleep and wakefulness Alternating cycles of sleep and wakefulness reflect a natural circadian rhythmreflect a natural circadian rhythm

Although RAS activity declines in sleep, sleep Although RAS activity declines in sleep, sleep is more than turning off RASis more than turning off RAS

The brain is actively guided into sleepThe brain is actively guided into sleep The suprachiasmatic and preoptic nuclei of the The suprachiasmatic and preoptic nuclei of the

hypothalamus regulate the sleep cyclehypothalamus regulate the sleep cycle A typical sleep pattern alternates between A typical sleep pattern alternates between

REM and NREM sleepREM and NREM sleep

Importance of SleepImportance of Sleep

Slow-wave sleep is presumed to be the Slow-wave sleep is presumed to be the restorative stagerestorative stage

Those deprived of REM sleep become moody Those deprived of REM sleep become moody and depressedand depressed

REM sleep may be a reverse learning process REM sleep may be a reverse learning process where superfluous information is purged from where superfluous information is purged from the brainthe brain

Daily sleep requirements decline with ageDaily sleep requirements decline with age

Sleep DisordersSleep Disorders

Narcolepsy – lapsing abruptly into sleep from Narcolepsy – lapsing abruptly into sleep from the awake statethe awake state

Insomnia – chronic inability to obtain the Insomnia – chronic inability to obtain the amount or quality of sleep neededamount or quality of sleep needed

Sleep apnea – temporary cessation of Sleep apnea – temporary cessation of breathing during sleepbreathing during sleep

MemoryMemory

Memory is the storage and retrieval of Memory is the storage and retrieval of informationinformation

The three principles of memory are:The three principles of memory are: Storage – occurs in stages and is continually Storage – occurs in stages and is continually

changingchanging Processing – accomplished by the hippocampus Processing – accomplished by the hippocampus

and surrounding structures and surrounding structures Memory traces – chemical or structural changes Memory traces – chemical or structural changes

that encode memorythat encode memory

Memory ProcessingMemory Processing

Figure 12.22

Stages of MemoryStages of Memory

The two stages of memory are short-term The two stages of memory are short-term memory and long-term memorymemory and long-term memory

Short-term memory (STM, or working memory) Short-term memory (STM, or working memory) – a fleeting memory of the events that – a fleeting memory of the events that continually happencontinually happen

STM lasts seconds to hours and is limited to 7 STM lasts seconds to hours and is limited to 7 or 8 pieces of informationor 8 pieces of information

Long-term memory (LTM) has limitless Long-term memory (LTM) has limitless capacitycapacity

Transfer from STM to LTMTransfer from STM to LTM Factors that effect transfer of memory from Factors that effect transfer of memory from

STM to LTM include:STM to LTM include: Emotional state – we learn best when we are alert, Emotional state – we learn best when we are alert,

motivated, and arousedmotivated, and aroused Rehearsal – repeating or rehearsing material Rehearsal – repeating or rehearsing material

enhances memoryenhances memory Association – associating new information with old Association – associating new information with old

memories in LTM enhances memorymemories in LTM enhances memory Automatic memory – subconscious information Automatic memory – subconscious information

stored in LTMstored in LTM

Categories of MemoryCategories of Memory

The two categories of memory are fact The two categories of memory are fact memory and skill memorymemory and skill memory

Fact (declarative) memory: Fact (declarative) memory: Entails learning explicit informationEntails learning explicit information Is related to our conscious thoughts and our Is related to our conscious thoughts and our

language abilitylanguage ability Is stored with the context in which it was learnedIs stored with the context in which it was learned

Skill MemorySkill Memory

Skill memory is less conscious than fact Skill memory is less conscious than fact memory and involves motor activitymemory and involves motor activity

It is acquired through practiceIt is acquired through practice Skill memories do not retain the context in Skill memories do not retain the context in

which they were learnedwhich they were learned

Structures Involved in Fact Structures Involved in Fact MemoryMemory

Fact memory involves the following brain Fact memory involves the following brain areas:areas: Hippocampus and the amygdala, both limbic Hippocampus and the amygdala, both limbic

system structuressystem structures Specific areas of the thalamus and hypothalamus Specific areas of the thalamus and hypothalamus

of the diencephalonof the diencephalon Ventromedial prefrontal cortex and the basal Ventromedial prefrontal cortex and the basal

forebrainforebrain

Structures Involved in Skill Structures Involved in Skill MemoryMemory

Skill memory involves:Skill memory involves: Corpus striatum – mediates the automatic Corpus striatum – mediates the automatic

connections between a stimulus and a motor connections between a stimulus and a motor responseresponse

Portion of the brain receiving the stimulus Portion of the brain receiving the stimulus Premotor and motor cortexPremotor and motor cortex

Mechanisms of MemoryMechanisms of Memory Neuronal RNA content is alteredNeuronal RNA content is altered Dendritic spines change shapeDendritic spines change shape Extracellular proteins are deposited at synapses Extracellular proteins are deposited at synapses

involved in LTMinvolved in LTM Number and size of presynaptic terminals may Number and size of presynaptic terminals may

increaseincrease More neurotransmitter is released by More neurotransmitter is released by

presynaptic neuronspresynaptic neurons New hippocampal neurons appearNew hippocampal neurons appear

Mechanisms of MemoryMechanisms of Memory

Long-term potentiation (LTP) is involved and Long-term potentiation (LTP) is involved and is mediated by NMDA receptorsis mediated by NMDA receptors

Synaptic events involve the binding of brain-Synaptic events involve the binding of brain-derived neurotropic factor (BDNF)derived neurotropic factor (BDNF)

BDNF is involved with NaBDNF is involved with Na++, Ca, Ca2+2+, and Mg, and Mg2+2+ influence at synapsesinfluence at synapses

Proposed Memory CircuitsProposed Memory Circuits

Figure 12.23

Protection of the BrainProtection of the Brain

The brain is protected by bone, meninges, and The brain is protected by bone, meninges, and cerebrospinal fluidcerebrospinal fluid

Harmful substances are shielded from the Harmful substances are shielded from the brain by the blood-brain barrierbrain by the blood-brain barrier

MeningesMeninges

Three connective tissue membranes lie Three connective tissue membranes lie external to the CNS – dura mater, arachnoid external to the CNS – dura mater, arachnoid mater, and pia matermater, and pia mater

Functions of the meningesFunctions of the meninges Cover and protect the CNSCover and protect the CNS Protect blood vessels and enclose venous sinusesProtect blood vessels and enclose venous sinuses Contain cerebrospinal fluid (CSF)Contain cerebrospinal fluid (CSF) Form partitions within the skullForm partitions within the skull

MeningesMeninges

Figure 12.24a

Dura MaterDura Mater

Leathery, strong meninx composed of two Leathery, strong meninx composed of two fibrous connective tissue layers fibrous connective tissue layers

The two layers separate in certain areas and The two layers separate in certain areas and form dural sinusesform dural sinuses

Dura MaterDura Mater

Three dural septa extend inward and limit Three dural septa extend inward and limit excessive movement of the brainexcessive movement of the brain Falx cerebri – fold that dips into the longitudinal Falx cerebri – fold that dips into the longitudinal

fissurefissure Falx cerebelli – runs along the vermis of the Falx cerebelli – runs along the vermis of the

cerebellumcerebellum Tentorium cerebelli – horizontal dural fold extends Tentorium cerebelli – horizontal dural fold extends

into the transverse fissureinto the transverse fissure

Dura MaterDura Mater

Figure 12.25

Arachnoid MaterArachnoid Mater

The middle meninx, which forms a loose brain The middle meninx, which forms a loose brain coveringcovering

It is separated from the dura mater by the It is separated from the dura mater by the subdural spacesubdural space

Beneath the arachnoid is a wide subarachnoid Beneath the arachnoid is a wide subarachnoid space filled with CSF and large blood vesselsspace filled with CSF and large blood vessels

Arachnoid villi protrude superiorly and permit Arachnoid villi protrude superiorly and permit CSF to be absorbed into venous bloodCSF to be absorbed into venous blood

Arachnoid MaterArachnoid Mater

Figure 12.24a

Pia MaterPia Mater

Deep meninx composed of delicate connective Deep meninx composed of delicate connective tissue that clings tightly to the braintissue that clings tightly to the brain

Cerebrospinal Fluid (CSF)Cerebrospinal Fluid (CSF)

Watery solution similar in composition to Watery solution similar in composition to blood plasmablood plasma

Contains less protein and different ion Contains less protein and different ion concentrations than plasmaconcentrations than plasma

Forms a liquid cushion that gives buoyancy to Forms a liquid cushion that gives buoyancy to the CNS organsthe CNS organs

Cerebrospinal Fluid (CSF)Cerebrospinal Fluid (CSF)

Prevents the brain from crushing under its own Prevents the brain from crushing under its own weightweight

Protects the CNS from blows and other traumaProtects the CNS from blows and other trauma Nourishes the brain and carries chemical Nourishes the brain and carries chemical

signals throughout itsignals throughout it

Circulation of CSFCirculation of CSF

Figure 12.26b

Choroid PlexusesChoroid Plexuses

Clusters of capillaries that form tissue fluid Clusters of capillaries that form tissue fluid filters, which hang from the roof of each filters, which hang from the roof of each ventricleventricle

Have ion pumps that allow them to alter ion Have ion pumps that allow them to alter ion concentrations of the CSFconcentrations of the CSF

Help cleanse CSF by removing wastesHelp cleanse CSF by removing wastes

Choroid PlexusesChoroid Plexuses

Figure 12.26a

Blood-Brain BarrierBlood-Brain Barrier

Protective mechanism that helps maintain a Protective mechanism that helps maintain a stable environment for the brainstable environment for the brain

Bloodborne substances are separated from Bloodborne substances are separated from neurons by:neurons by: Continuous endothelium of capillary wallsContinuous endothelium of capillary walls Relatively thick basal laminaRelatively thick basal lamina Bulbous feet of astrocytesBulbous feet of astrocytes

Blood-Brain Barrier: FunctionsBlood-Brain Barrier: Functions

Selective barrier that allows nutrients to pass Selective barrier that allows nutrients to pass freelyfreely

Is ineffective against substances that can diffuse Is ineffective against substances that can diffuse through plasma membranesthrough plasma membranes

Absent in some areas (vomiting center and the Absent in some areas (vomiting center and the hypothalamus), allowing these areas to monitor hypothalamus), allowing these areas to monitor the chemical composition of the bloodthe chemical composition of the blood

Stress increases the ability of chemicals to pass Stress increases the ability of chemicals to pass through the blood-brain barrierthrough the blood-brain barrier

Cerebrovascular Accidents (Strokes)Cerebrovascular Accidents (Strokes)

Caused when blood circulation to the brain is Caused when blood circulation to the brain is blocked and brain tissue diesblocked and brain tissue dies

Most commonly caused by blockage of a Most commonly caused by blockage of a cerebral arterycerebral artery

Other causes include compression of the brain Other causes include compression of the brain by hemorrhage or edema, and atherosclerosisby hemorrhage or edema, and atherosclerosis

Transient ischemic attacks (TIAs) – temporary Transient ischemic attacks (TIAs) – temporary episodes of reversible cerebral ischemiaepisodes of reversible cerebral ischemia

Tissue plasminogen activator (TPA) is the only Tissue plasminogen activator (TPA) is the only approved treatment for strokeapproved treatment for stroke

Degenerative Brain DisordersDegenerative Brain Disorders

Alzheimer’s disease – a progressive degenerative Alzheimer’s disease – a progressive degenerative disease of the brain that results in dementiadisease of the brain that results in dementia

Parkinson’s disease – degeneration of the Parkinson’s disease – degeneration of the dopamine-releasing neurons of the substantia dopamine-releasing neurons of the substantia nigranigra

Huntington’s disease – a fatal hereditary disorder Huntington’s disease – a fatal hereditary disorder caused by accumulation of the protein huntingtin caused by accumulation of the protein huntingtin that leads to degeneration of the basal nucleithat leads to degeneration of the basal nuclei

Embryonic Development of the Embryonic Development of the Spinal CordSpinal Cord

Develops from caudal portion of neural tubeDevelops from caudal portion of neural tube By week 6, there are two clusters of By week 6, there are two clusters of

neuroblasts:neuroblasts: Alar plate – will become interneuronsAlar plate – will become interneurons Basal plate – will become motor neuronsBasal plate – will become motor neurons

Neural crest cells form the dorsal root gangliaNeural crest cells form the dorsal root ganglia

Embryonic Development of the Embryonic Development of the Spinal CordSpinal Cord

Figure 12.28