THE BRAINTHE BRAIN

Chapter 14Chapter 14

Brain Basics:Brain Basics:

100 billion neurons in the adult brain100 billion neurons in the adult brain 1000 billion neuroglia1000 billion neuroglia adult brain weighs almost 3 lbsadult brain weighs almost 3 lbs 4 basic parts of the brain:4 basic parts of the brain:

– Brain stemBrain stem– CerebellumCerebellum– DiencephalonDiencephalon– CerebrumCerebrum

4 Parts of the Brain4 Parts of the Brain --brain stembrain stem *continuous with the spinal cord*continuous with the spinal cord *medulla oblongata*medulla oblongata *pons*pons *midbrain*midbrain --cerebellumcerebellum --diencephalondiencephalon *thalamus*thalamus *hypothalamus*hypothalamus --cerebrumcerebrum *largest part*largest part *2 hemispheres*2 hemispheres

COVERINGS OF THE BRAIN:COVERINGS OF THE BRAIN:

Meninges: Meninges: dura mater = dura mater = outer layerouter layer arachnoidarachnoid = middle layer = middle layer pia materpia mater =inner layer =inner layer

Fig. 14-3a, top, p. 456

Fig. 14-3, p. 456

BRAIN BLOOD FLOW AND THE BRAIN BLOOD FLOW AND THE BLOOD BRAIN BARRIERBLOOD BRAIN BARRIER

Basics:Basics: Blood supply to the brain is mainly from Blood supply to the brain is mainly from

the cerebral arterial circle –or the circle the cerebral arterial circle –or the circle of Willis at the base of the brain.of Willis at the base of the brain.

Brain is 2% of body weight but Brain is 2% of body weight but consumes 20% of oxygen and glucose consumes 20% of oxygen and glucose used at rest.used at rest.

Brain metabolizes glucose using Brain metabolizes glucose using oxidative respiration to generate ATPoxidative respiration to generate ATP

And…..And….. There is a corresponding increase in There is a corresponding increase in

blood supply when there is a localized blood supply when there is a localized increase in brain activityincrease in brain activity

An interruption of blood flow can An interruption of blood flow can cause unconsciousness, 1-2 minutes cause unconsciousness, 1-2 minutes can impair neuronal function, 4 can impair neuronal function, 4 minutes can result in permanent injuryminutes can result in permanent injury

No glucose is stored in the brain so it No glucose is stored in the brain so it must be continually suppliedmust be continually supplied

Ventricles of the Brain and CSFVentricles of the Brain and CSF

Ventricles:Ventricles: There are 4 ventricles filled with CSFThere are 4 ventricles filled with CSF

-2 lateral, one in each cerebral hemisphere-2 lateral, one in each cerebral hemisphere*separated by the *separated by the septum septum

pellucidumpellucidum-Third ventricle-Third ventricle

*narrow cavity superior to the *narrow cavity superior to the hypothalamushypothalamus

-Fourth ventricle-Fourth ventricle*between the brain stem and the *between the brain stem and the

cerebellumcerebellum

Fig. 14-2a, p. 454

CSF –Cerebral Spinal FluidCSF –Cerebral Spinal Fluid

Clear, colorless liquidClear, colorless liquid Carries oxygen, glucose proteins, lactic Carries oxygen, glucose proteins, lactic

acid, urea, cations (Na+, K+ , Ca2+, acid, urea, cations (Na+, K+ , Ca2+, Mg2+) and anions (Cl- and HCO3-) and Mg2+) and anions (Cl- and HCO3-) and some white blood cellssome white blood cells

Circulates continually through the super-Circulates continually through the super-arachnoid space and around the brain arachnoid space and around the brain and spinal cordand spinal cord

Total volume: 80-150 mLTotal volume: 80-150 mL

Contributes to homeostasis in 3 Contributes to homeostasis in 3 waysways

mechanical protection –shock absorber, mechanical protection –shock absorber, the brain “floats” the brain “floats”

chemical protection –optimal chemical chemical protection –optimal chemical environment for accurate neuronal environment for accurate neuronal signalingsignaling

Circulation –medium for exchange of Circulation –medium for exchange of nutrients and wastes between blood and nutrients and wastes between blood and nervous tissuenervous tissue

Fig. 14-2b, p. 454

THE BRAIN STEMTHE BRAIN STEM Basics:Basics: Between spinal cord and diencephalonBetween spinal cord and diencephalon Reticula formationReticula formation -netlike gray and white matter-netlike gray and white matter -extends through the brain stem-extends through the brain stem -RAS -RAS Reticular activating systemReticular activating system *awakening from sleep*awakening from sleep *maintaining level of consciousness*maintaining level of consciousness *arouses cerebral cortex in response to *arouses cerebral cortex in response to

stimulistimuli *maintains muscle tone*maintains muscle tone

Fig. 14-1, part 2, p. 453

3 parts of the brain stem:3 parts of the brain stem: 1. Medulla Oblongata1. Medulla Oblongata

– continuation of the upper part of the spinal continuation of the upper part of the spinal cordcord

– begins at the foramen magnum and extends begins at the foramen magnum and extends to the pons -3 cmto the pons -3 cm

– pyramids –anterior aspectpyramids –anterior aspect-formed by largest motor tracts from spinal -formed by largest motor tracts from spinal cordcord

-conspicuous external bulges-conspicuous external bulges-cross over each other –-cross over each other –decussation decussation of pyramidsof pyramids

inferior olivary nucleusinferior olivary nucleus (oval shaped swelling (oval shaped swelling (olive) -relay stations to the thalamus(olive) -relay stations to the thalamus

-nucleus gracilis --nucleus gracilis --nucleus cuneatus-nucleus cuneatus

Autonomic Nuclei Autonomic Nuclei -regulation of vital -regulation of vital functionsfunctions

-reflex centers receive inputs from cranial nerves, -reflex centers receive inputs from cranial nerves, brain stem, and cerebral cortexbrain stem, and cerebral cortex

-adjust activities of peripheral systems-adjust activities of peripheral systems cardiovascular centerscardiovascular centers -cardiac-cardiac -vasomotor-vasomotor respiratory rhythmicity centersrespiratory rhythmicity centers -activity regulated by the pons-activity regulated by the pons

Fig. 14-5b, p. 460

Fig. 14-5a, p. 460

2. Pons (bridge)2. Pons (bridge)

-nuclei -control breathing with -nuclei -control breathing with medullamedulla

pneumatoaxic areapneumatoaxic areaapneustic areaapneustic area

1. nuclei for cranial nerves1. nuclei for cranial nervesTrigeminal (V)Trigeminal (V)

-mixed-mixed-largest cranial nerve-largest cranial nerve-somatosensory info for head and -somatosensory info for head and

neckneck-motor for chewing-motor for chewing-Trigeminal neuralgia (-Trigeminal neuralgia (Tic Tic

Douloureux)Douloureux) affects CVaffects CVAbducens (VI)Abducens (VI)

-motor-motor-eye movements-eye movements

More……More……– Facial (VII)Facial (VII)

-mixed-mixed -taste, secretion of saliva, tears, -taste, secretion of saliva, tears,

muscles for facial expressionmuscles for facial expression --Bell’s palsyBell’s palsy- inflammation of CVII- inflammation of CVII

– Vestibulocochlear (VIII)Vestibulocochlear (VIII) -special sensory-special sensory -balance and equilibrium-balance and equilibrium

Cranial NervesCranial Nerves

To help you remember the cranial nerves:To help you remember the cranial nerves: On occasion, our trusty truck acts funny—On occasion, our trusty truck acts funny—

very good vehicle any how.very good vehicle any how. 1. Olfactory, 2. optic, 3. oculomotor, 1. Olfactory, 2. optic, 3. oculomotor, 4. trochlear, 5. trigeminal, 6. abducens, 4. trochlear, 5. trigeminal, 6. abducens, 7. facial, 8. vestibulocochlear, 7. facial, 8. vestibulocochlear, 9. glossopharangeal, 10. vagus, 9. glossopharangeal, 10. vagus, 11. accessory, 12. hypoglossal11. accessory, 12. hypoglossal

3. Midbrain (or mesencephalon)3. Midbrain (or mesencephalon)

reflex centersreflex centers

– superior colliculisuperior colliculi

-movement of eyes, head, and neck -movement of eyes, head, and neck in in response to visual and other stimuliresponse to visual and other stimuli

– Inferior colliculiInferior colliculi

-movement of head and trunk in -movement of head and trunk in response to auditory stimuliresponse to auditory stimuli

2. Specialized nuclei2. Specialized nuclei

a. Substantia nigraa. Substantia nigra-subconscious muscle activities-subconscious muscle activities

-fluidity of movement-fluidity of movement

-secretes dopamine-secretes dopamine

--Parkinson’s disease- Parkinson’s disease-

decrease in dopamine secreting cellsdecrease in dopamine secreting cells

b. red nucleib. red nuclei -control of skeletal muscle tone-control of skeletal muscle tone

Fig. 14-1, part 1, p. 453

CEREBELLUMCEREBELLUMBasics:Basics:

Second largest part of the brainSecond largest part of the brainShape is like a butterflyShape is like a butterfly

Vermis =central constrictionVermis =central constrictionCerebellar hemispheresCerebellar hemispheres

-anterior and posterior lobe-anterior and posterior lobe*govern subconscious movements of *govern subconscious movements of skeletal musclesskeletal muscles

-Flocculonodular lobe -Flocculonodular lobe *inferior surface*inferior surface*sense of equilibrium*sense of equilibrium

Fig. 14-7a, left, p. 463

Main functions:Main functions:

-compares intended movements with -compares intended movements with what is actually happeningwhat is actually happening

-coordinates complex, skilled -coordinates complex, skilled movementsmovements

-regulates posture and balance-regulates posture and balance Affected by drugs and traumaAffected by drugs and trauma -alcohol affects cerebellum causing -alcohol affects cerebellum causing

ataxiaataxia

DIENCEPHALONDIENCEPHALON1. Thalamus –2 halves1. Thalamus –2 halves

– 80% of diencephalon –3 cm long80% of diencephalon –3 cm long– principal relay station for sensory impulsesprincipal relay station for sensory impulses– ““the secretary”the secretary”– sends sensory input to cerebral cortexsends sensory input to cerebral cortex– assorted nuclei and their roles:assorted nuclei and their roles:

--medial geniculate nucleusmedial geniculate nucleus –auditory –auditory --lateral geniculate nucleuslateral geniculate nucleus -visual -visual --ventral posterior nucleus ventral posterior nucleus -taste, touch, -taste, touch,

pressure, vibration, temperature, painpressure, vibration, temperature, pain --anterior nucleusanterior nucleus -emotions and memory -emotions and memory functions in cognition and awarenessfunctions in cognition and awareness

Fig. 14-8b, p. 465

2. Hypothalamus2. HypothalamusSmall, inferior to thalamus (in position)Small, inferior to thalamus (in position)

4 major regions:4 major regions:

1. mammillary region1. mammillary region-mammillary bodies -mammillary bodies -relay stations for reflexes related -relay stations for reflexes related to sense of smellto sense of smell

2. tuberal region2. tuberal region-widest part-widest part

3. infindibulum connects hypothalamus 3. infindibulum connects hypothalamus with the pituitary glandwith the pituitary gland

-supraoptic region-supraoptic region-superior to optic chiasm (where -superior to optic chiasm (where

optic optic nerves cross)nerves cross)-contains suprachiasmatic nucleus-contains suprachiasmatic nucleus

4. preoptic region4. preoptic region-contains medial and lateral -contains medial and lateral preoptic preoptic

nucleinuclei-regulates certain autonomic -regulates certain autonomic

activitiesactivities

Fig. 14-10b, p. 467

Functions:Functions:

major regulator of homeostasismajor regulator of homeostasis

a. Control of ANSa. Control of ANS

-axons from hypothalamus to -axons from hypothalamus to parasympathetic and parasympathetic and

sympatheticsympathetic

-regulates visceral activities -regulates visceral activities

-regulates heart rate-regulates heart rate

Controls Pituitary gland Controls Pituitary gland (master gland)(master gland)

-hypothalamic regulating hormones-hypothalamic regulating hormones

*stimulate or inhibit secretion of *stimulate or inhibit secretion of hormones from the anterior pituitaryhormones from the anterior pituitary

-axons from paraventricular and -axons from paraventricular and supraoptic nuclei supraoptic nuclei

*nerve cell bodies make oxytocin *nerve cell bodies make oxytocin and and ADH which are transported and ADH which are transported and stored stored in the posterior pituitaryin the posterior pituitary

Regulation of emotional and Regulation of emotional and behavioral patternsbehavioral patterns

-works with the limbic system-works with the limbic system

*rage*rage

*aggression *aggression

*pain *pain

*pleasure*pleasure

*behavior patterns related to sexual *behavior patterns related to sexual arrousalarrousal

And……And……

*Feeding center –hunger*Feeding center –hunger

*Satiety center –fullness*Satiety center –fullness

*Thirst center *Thirst center

––cells stimulated by rising cells stimulated by rising osmotic pressureosmotic pressure

-sensation of thirst-sensation of thirst

Control of Body TemperatureControl of Body Temperature

*monitors blood temperature*monitors blood temperature

*promotes cooling or warming up*promotes cooling or warming up

– Regulation of circadian rhythms Regulation of circadian rhythms and states of consciousnessand states of consciousness

*sleep patterns of circadian rhythm*sleep patterns of circadian rhythm

3. Epithalamus3. Epithalamus –superior and posterior to thalamus–superior and posterior to thalamus

pineal glandpineal gland

-pea size-pea size

-secretes -secretes melatoninmelatonin

-may promote sleepiness-may promote sleepiness

-may set biological clock-may set biological clock

habenular nucleihabenular nuclei

-olfaction-olfaction

-emotional responses to odors-emotional responses to odors

CEREBRUMCEREBRUM

- bulk of the brain- bulk of the brain Geographic basics of the Cerebrum:Geographic basics of the Cerebrum: Cerebral cortex is the 2-4 mm layer of gray Cerebral cortex is the 2-4 mm layer of gray

matter on the surface of the cerebrum –billions matter on the surface of the cerebrum –billions of neuronsof neurons

Cerebral white matter is underneathCerebral white matter is underneath Folds or convolutions of the cerebrum are due Folds or convolutions of the cerebrum are due

to the rapid growth of gray matter during to the rapid growth of gray matter during development which is faster than white matterdevelopment which is faster than white matter

Fissures are the deepest groovesFissures are the deepest grooves

Fig. 14-12c, p. 471

Sulci the shallower groovesSulci the shallower grooves Longitudinal fissure separates Longitudinal fissure separates

the right and left cerebral the right and left cerebral hemisphereshemispheres

Corpus callosum connects the Corpus callosum connects the two hemispheres –nerve nettwo hemispheres –nerve net

Cerebrum divided into lobes Cerebrum divided into lobes named for the bones that lie over named for the bones that lie over them.them.

Lobes of the CerebrumLobes of the Cerebrum --FrontalFrontal -central sulcus-central sulcus --parietalparietal -pre-central gyrus –in front of the central -pre-central gyrus –in front of the central

sulcus- sulcus- motor areamotor area -post-central gyrus –primary -post-central gyrus –primary somatosensory somatosensory

areaarea -Lateral cerebral sulcus-Lateral cerebral sulcus --Temporal lobeTemporal lobe -parieto-occipital sulcus-parieto-occipital sulcus --occipital lobeoccipital lobe --insulainsula (deep within the lateral cerebral fissure) (deep within the lateral cerebral fissure)

Fig. 14-9a, p. 466

Fig. 14-12b, p. 471

BASAL GANGLIABASAL GANGLIA

Function:Function:

-receive input from and -receive input from and provide output to:provide output to:

-cerebral cortex-cerebral cortex

-thalamus-thalamus

-hypothalamus-hypothalamus

Structures includedStructures included:: (paired nuclei)(paired nuclei)

--corpus striatumcorpus striatum -largest nuclei-largest nuclei -includes:-includes: 1. -1. -caudate nucleuscaudate nucleus

*autonomic movement of skeletal muscles*autonomic movement of skeletal muscles 2. -2. -lentiform nucleuslentiform nucleus (2 parts) (2 parts) **putamenputamen (lateral part) (lateral part)

- autonomic movement of skeletal muscles- autonomic movement of skeletal muscles-swinging of arms while walking, laughing-swinging of arms while walking, laughing

**globus pallidusglobus pallidus (medial) (medial)-muscle tone for specific body movements-muscle tone for specific body movements

Huntington’s DiseaseHuntington’s Disease Genetic Disease –dominant geneGenetic Disease –dominant gene Affects the basal gangliaAffects the basal ganglia Progresses slowly over a period of 20 yearsProgresses slowly over a period of 20 years Affects the coordination (chorea) controlled by Affects the coordination (chorea) controlled by

the basal ganglia and the cortex involved in the basal ganglia and the cortex involved in memory and thoughtmemory and thought

Unsteady gait, lack of coordination, impaired Unsteady gait, lack of coordination, impaired reasoning and memory.reasoning and memory.

Abnormal protein -HuntingtinAbnormal protein -Huntingtin Killed Woodie GuthrieKilled Woodie Guthrie

Parkinson’s Disease

Etiology: idiopathic (most do not know), head trauma, MDMA

Cells of sustantia nigra no longer make dopamine Symptoms

– Tremor –(pill rolling)– Slowed movement (bradykinesia)– Muscle rigidity– Loss of facial expression– mumbling

treatment

Levadopa Dopamine agonists (magnify the effects of

dopamine. MAO B inhibitors -inhibit MAO type B in the

breakdown of dopamine COMT –break down the enzyme that breaks

down levadopa Anticholinergics -for tremors

Limbic SystemLimbic System

Functional groupingFunctional grouping The emotional brainThe emotional brain HippocampusHippocampus ParahippocampusParahippocampus AmygdolaAmygdola hypothalamushypothalamus Important in learningImportant in learning

AmygdolaAmygdola

acts as an interface between the acts as an interface between the cerebrum, sensory systems, and limbic cerebrum, sensory systems, and limbic systemsystem

Encircles upper part of the brain stem Encircles upper part of the brain stem and the corpus callosumand the corpus callosum

Hippocampus along with portions of the Hippocampus along with portions of the cerebrum functions in memorycerebrum functions in memory

Primative brain –life altering memoriesPrimative brain –life altering memories– Emotional context of memories.Emotional context of memories.

Fig. 14-11a, p. 469

Fig. 14-11b, p. 469

CEREBRAL CORTEX AND ASSOCITATION AREAS

Sensory Areas Primary somatosensory (PSSA) Posterior to the central sulcus In postcentral gyrus of each parietal lobe Receives input from sensory receptors for

touch, pain, proprioception, temperature Function of PSSA is to localize the part of the

body receiving the impulse (Thalamus generalizes)

Body parts are not represented in proportion to their size

Fig. 14-13, p. 472

Primary visual (PVA)

medial surface of the occipital lobe

Optic nerve (C II) terminates at the geniculate nucleus of the thalamus

Thalamus relays information to the PVA

Primary Auditory (PAA)

superior part of the temporal lobe near the lateral cerebral sulcus

interprets basic characteristics of sound like pitch and rhythm

Primary Gustatory (PGA)base of the postcentral gyrus, superior to

the lateral cerebral sulcus in parietal cortexTaste

Primary Olfactory (POA)in temporal lobe on the medial aspect (not

visible)smell

Motor Areas:

Primary Motor precentral gyrus of the frontal lobe voluntary contractions of specific muscle

groups controls muscles on opposite side of the

body body parts are not represented in

proportion to their size

Broca’s Area –Speech

in 97% of people on left frontal lobe superior to the lateral cerebral sulcus

production of speech

ASSOCIATION AREAS: Basics:

– interpret incoming data – may incorporate a motor response– analyze, recognize, and act on sensory

inputs– multiple inputs and outputs– independent of the primary sensory

and motor areas– functions are complex

Prefrontal cortex: anterior portions of the frontal lobes most complicated cortical region of all involved with intellect complex learning abilities (cognition) production of abstract ideas, judgment reasoning, planning, concern for others and

conscience matures slowly (anywhere from late teens to

early 20’s depending on the source) dependent on positive an negative feedback

from the social environment linked to the limbic system

lesions in this area (tumors) cause mental and personality disorders

prefrontal lobotomy- severs the connections to the prefrontal cortex

used in the 1930s-1950s to treat severe mental illness

patients became less anxious cure worse than the disease patients developed personality

disorders, lack of judgment or loss of initiative, even epilepsy

Somatosensory Association Area

just posterior to and receives input from the primary somatosensory area, thalamus

functions to integrate and interpret sensations

perceive relationship of one body part to another, shapes and textures without seeing, orientation of objects

stores memories of sensory experiences

Fig. 15-5a, p. 504

Visual Association Area

occipital lobe relates present and past visual

experiences essential for recognizing and

evaluating visual images

Common Integrative Area (General Interpretive Area)

Sometimes called the Gnostic area bordered by somatosensory, visual, and

auditory integrates sensory interpretations from

association areas and impulse from other areas

transmits signals to other parts of the brain based on the input

usually only found in the left hemisphere

Also….. appears to be storage site for

complex memories associated with sensation

integrates all incoming signals into a single thought or understanding of the situation

assessment set to prefrontal cortex which adds emotional overtones and makes the appropriate response

And…… example –drop a bottle of acid –overall

message of danger supersedes visual crash of bottle, sound of shattering glass, smell of acid, burning on skin

Research indicates that the gnostic area and prefrontal cortex work together to assemble new experiences into logical constructs or “stories” based on past experiences

Not objective –based on past experience Storytelling may be a part of the hardware of

mental processing! injury to this area can result in the ability to

interpret any information -“imbecility”

Premotor Area

immediately anterior to the primary motor area

learned motor activities of a complex and sequential nature

generates nerve impulses that cause specific groups of muscles to contract in specific sequences

memory bank for sequential movement

Fig. 15-9, p. 510

Visceral Association area:

the cortex of the insulamay be involved in conscious

perception of visceral sensations (upset stomach, full bladder)

Frontal Eye Field

frontal cortex scanning movements of eyes,

like reading voluntary not always categorized as an

association area

Auditory Association Area

inferior and posterior to the primary auditory area in temporal cortex

determines if sound is speech, music, or noise

Fig. 14-15a, p. 475

Language Areas Cortical regions involved in language

occur in both hemispheres neurons from Broca’s area pass to

premotor cortex impulses from premotor area

coordinate the movements of the mouth, tongue etc. to form speech

impulses also control breathing muscles to coordinate the mechanics of speech through the vocal cords

Fig. 14-16, p. 477

Wernicke’s Area interprets the meaning of speech translates words into thoughts the dictionary PET scans indicate it also may be

involved in sounding out words right hemisphere adds emotional context

to the word “wet” and the speech region comparable to Broca’s area adds inflection and tone to the speech

language comprehension occurs in the prefrontal cortex

Clinical Correlation:

Aphasia: inability to use or comprehend words

Broca’s area damage: nonfluent aphasia, know what they want to say but are not able to articulate or form words

Integrative area or auditory association areas –fluent aphasia- faulty understanding of spoken or written words –strings of words that have no meaning

HEMISPHERIC LATERALIZATION

Functional asymmetry of the 2 cerebral hemispheres

Anatomical differences– Wernicke’s area is 50% larger on the left

side in 66% of individuals– appears at 30 weeks of gestation in the

fetus– Broca’s area is on the left in 97% of

individuals

Functional differences 1. Right side controls left side of the body and left

side controls the right side of the body 2. In most individuals the left hemisphere is

considered dominant or the categorical hemisphere:-responsible for language based skills

*reading*writing*speech

*use and understanding of sign language -analytical tasks

*mathematical calculations*logical decision making

Right Hemisphere important analyzing sensory information and

relates the body to the sensory environment:

*identify familiar objects by touch, smell, sight, taste, or feel

*face recognition*understanding of 3 dimensional relationships*analysis of the emotional context of a

conversation-Difference is less pronounced

in females, perhaps due to larger white matter tracts communicating between both hemispheres

Interesting addendum:

96% of right handed people are left brain dominant

9% of the human population is left handed, 70% of the left handed population are left brain dominant, 15% are right brain dominant, and the other 15% show no specialization.

BRAIN WAVES: Electroencephalogram –EEG –detects brain

waves 4 types of normal brain waves:

Alpha waves:-rhythmic waves-8-13 cycles / sec (hertz)-awake or resting with eyes closed

Beta waves:-generally appear when nervous

system is active such as sensory input and mental activity

-14-30 hertz

And…….Theta waves:

-children and adults experiencing emotional stress

-4-7 hertz-may occur in brain disorders

Delta waves:-1-5 hertz-occur in deep sleep in adults-normal in awake infants-appearance in an awake adult

indicates brain damage

Fig. 14-17abcd, p. 479

Sleep

State of altered consciousness Exact trigger for sleep is unknown A chemical involved is adenosine

– Produced during high ATP usage– Binds to A1 receptors and inhibits RAS pathway– Caffeine and theophylline work by binding these

receptors instead.– Different levels of sleep and REM and non REM

Dreams: most during REM sleep Sleep paralysis: can occur if you

wake during REM sleep Sleepwalking occurs during stage 4

of nREM sleep

Fig. 16-14, p. 540

Sleep Disorders

Insomnia: can’t sleep Narcolepsy: REM sleep is not inhibited

during waking hours and individual has involuntary periods (about 15 min.) of sleep during the day

Sleep Apnea: Individuals have periods of not breathing during sleep (10 + seconds).

Learning and Memory

Learning= acquiring new knowledge Memory = knowledge is retained over time. Plasticity = change associated with learning.

Parts of the brain associated with memory are: association areas of all the lobes fo the brain, limbic system (especially the hippocampus and the amygdala), diencephalon.

Types of Memory

Short term memory: information held for a brief amount of time

Long term memory: more permanent memory –can be retrieved after months or years.

Memory consolidation: repeated retrieval of information (rehearsal) that results in reinforcement of memory

Long Term Potentiation

Long lasting increase in strength of synapse response following stimulation.

Especially in the hippocampus Neurotransmitter is Glutamate Involves NMDA-Glutamate receptors Nitric oxide is released from the post

synaptic neuron and results in long term potentiation.

Fig. 16-13, p. 538

Clinical correlations:

anencephaly –absence of skull and cerebral

hemispheres -neural folds fail to fuse rostrally -child is totally vegetative: unable to see,

hear or process sensory input -no voluntary movement

spina bifida –

-incomplete formation of the vertebral arches -typically involves lumbo-sacral region -variable: *involves one or two vertebrae with no neural

problems *severe (inferior spinal cord is rendered

functionless) Folic acid supplementation during pregnancy

is helpful in preventing both these conditions

Cerebral Palsy:

temporary lack of oxygen during birth and other conditions such as smoking, drug exposure, rubella

neuromuscular disability –voluntary muscles poorly controlled or paralyzed due to brain damage

spastic, speech difficulties, motor difficulties 50% have seizures 50% mentally retarded 33% some degree of deafness does not get worse over time, but not reversible largest single cause of crippling in children

Traumatic Brain Injuries:

Concussion -slight brain injury following blow to the head

or sudden stopping of a moving head -most common brain injury -symptoms are relatively mild -dizzy, see stars, lose consciousness -headache, drowsiness, lack of concentration -confusion, or post-traumatic amnesia -no permanent neurological damage

Contusion

-bruising of the brain due to trauma -leakage of blood from microscopic vessels -pia mater may be torn -blood may leak into subarachnoid space -frontal lobe most commonly affected -loss of consciousness (brief) -loss of reflexes, transient cessation of

repieraton and decreased BP –stabilize within a few seconds

Laceration

-tear of the brain -usually from skull fractur or gunshot wound -rupture of large blood vessels -bleeding into brain and subarachnoid space -cerebral hematoma, swells against brain

tissue -increase in intracranial pressure

HOMEOSTATIC IMBALANCES:

Stroke (CVA cerebrovascular accident): Persistent neurological symptoms resulting

from the destruction of brain tissue Causes: intracerebral hemorrhage, emboli,

atherosclerosis of the cerebral arteries Plasminogen activator- drug used to open

blocked blood vessels in brain Should be administered within 3 hours of the

onset of the CVA Only works if the CVA is due to a blood clot Can decrease disability by 50%

Coma

Damage to the RAS State of deep unconsciousness Person cannot be aroused Different stages Light stage –brain stem and spinal reflexes

active Deepest stage –cardiac and respiratory

reflexes lost = death

Transient Ischemic Attack (TIA)

Temporary cerebral dysfunction caused by impaired blood flow to the brain

Symptoms include dizziness, weakness, numbness, paralysis, headache, slurred speech, drooping of one side of the face, etc.

Sudden onset, persists no more than 24 hours, leaves no persistent neurological deficits

33% of patients who experience a TIA will have a CVA within 5 years

Treatment involves aspirin, and anticoagulants as well as cerebral artery bypass grafting and others.

Other CLINICAL CORRELATIONS:

1. Alzheimer disease (AD) Affects 5 % of the population between 65 and

74 years -not part of normal aging. ½ the people over 85 years. Loss of reason and ability to care for oneself Loss of interest in surroundings Loss of long term memories Mental emptiness Loss of bodily functions

Distinct structural abnormalities

-decreased brain weight -cortical atrophy -subcortical atrophy (hippocampus,

amygdala, basal nuclei) -senile plaques –hallmark of AD *contain amyloid deposits *kill neurons where they are

deposited -neurobrillary tangles

Treatment:

Ach precursorsAchE inhibitorsother

Dementiageneralized term for senility

Forgetfulness Untidiness Confusion Restlessness Lethargy Errors in judgment Impaired new memory storage Long-term memory mostly unaffected

. Epilepsy

Primary Etiology –idiopathic Secondary-

-trauma-neoplasm-infection-cerebrovascular disease-brain lesion

More common in children 1% of population can result in brain cell loss

many types of seizures-partial

-generalized

*Grand mal –generalized Tonic –clonic

*Petit Mal –absence seizures

Treatments -anticonvulsant mechanisms *increase GABA -valium -barbiturates -Depakote

Pain Analgesics: drugs that relieve pain Pain Sensation:

– Nociceptors –receptors for pain– Stimulated by prostaglandins, kinins

Aspirin and other NSAIDs interrupt synthesis of protaglandins

– Substance P =neurotransmitter for pain2 types of pain

fast pain -acute or shapeslow pain -c fibers, develops over tim

Endorphins enkephlins neuromodulate substance P

Substance Abuse Abuse: self-administered use of any drug in a

manner that deviates from the approved medical or social patterns within a given culture

Some evidence for genetic predisposition Substance dependence

-tolerance –need more for the same effect-withdrawal- characteristic syndrome for withdrawal from the substance*physical dependence-abnormal

behavior and autonomic symptoms that occur upon the withdrawal of

the drug*psychological dependence- dysphoria and intense

craving upon withdrawal from the drug

Categories of Drugs

Hallucinogens– Marijuana– LSD– PCP

Stimulants– Amphetamines– Cocaine– Caffeine– Nicotine

And….. Depressants

– Alcohol– Barbiturates– Methaqualone– Diazepam, Librium

Narcotics– Morphine– Heroin– Methadone– Codeine

Drug Mechanisms

-Psychostimulants *(cocaine, amphetamines)*euphoric effects due to

activation of mesolimbic DA system-Hallucinogens

*activation of one type of 5HT receptors

-Cannabinoids*activation of cannabinoid

receptors-Nicotine

*activation of nicotine receptors-Caffeine

*activation of adenosine receptors

-Opioid*complex!*euphoria through modulation

of the mesolimbic DA transmission

Just to clarify…

Mesolimbic: nucleus accumbens, olefactory tubercle, and projections to the cortex

Types of circutsTypes of circuts

DivergentDivergent ConvergentConvergent SerialSerial ParallelParallel ReverberationReverberation

Neuronal Circuits Nerves are organized into networks. Networks distribute the impulse in different

manners to suit different needs.

1. simple series 2. diverging –one fiber stimulates many

– -can be motor impulse – -can be a sensory impulse being distributed to

many parts of the brain

And…. 3. Converging

-many neurons stimulate one neuron.-Effective in stimulating or inhibiting since you have multiple inputs. Complex motor skills.

4. Reverberating circuit circuit branches back to re-stimulate the pathway. Short term memory, waking up.

5. Parallel circuit-one neuron branches into parallel branches that all reach a final neuron.-mathematical calculations.

Fig. 13-13, p. 438