14-1 Central Nervous System overview of the brain meninges, ventricles, cerebrospinal fluid and blood supply hindbrain and midbrain forebrain integrative

14-1

Central Nervous System• overview of the brain

• meninges, ventricles, cerebrospinal fluid and blood supply

• hindbrain and midbrain

• forebrain

• integrative functions

• the cranial nerves

Figure 14.1a

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Frontal lobe

Occipital lobe

Central sulcus

Longitudinal fissure

Parietal lobe

(a) Superior view

Cerebralhemispheres

14-2

Introduction to the Nervous System• Aristotle thought brain was ‘radiator’ to cool blood

• Hippocrates was more accurate, “from the brain only, arises our pleasures, joys, laughter, and jests, as well as our sorrows, pains, griefs, and tears”

• cessation of brain activity - clinical criterion of death

• evolution of the central nervous system shows spinal cord very little changed while brain has changed a great deal.– greatest growth in areas of vision, memory, and motor

control of the prehensile hand.

14-3

Embryonic Development• nervous system develops from ectoderm

– outermost tissue layer of the embryo

• by fourth week, creates a hollow channel – neural tube• The neural tube exhibits three anterior dilations (primary

vesicles)– forebrain (prosencephalon)– midbrain (mesencephalon)– hindbrain (rhombencephalon)

• by fifth week, it subdivides into five secondary vesicles– forebrain divides into two of them

• telencephalon – becomes cerebral hemispheres• diencephalon – has optic vesicles that becomes retina of the eye

– midbrain remains undivided and remains• mesencephalon

– hind brain divides into two vesicles• metencephalon• myelencephalon

14-4

Embryonic Brain DevelopmentCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Diencephalon

Mesencephalon

Telencephalon

Forebrain

Pons

CerebellumMetencephalon

Spinal cord

Hindbrain

Telencephalon

Optic vesicle

Diencephalon

Metencephalon

Myelencephalon

Spinal cord

Rhombencephalon

Mesencephalon

Prosencephalon

(a) 4 weeks (b) 5 weeks

(c) Fully developed

Midbrain

Myelencephalon(medulla oblongata)

• 4th week– forebrain– midbrain– hindbrain

• 5th week– telencephalon– diencephalon– mesencephalon– metencephalon– myelencephalon Figure 14.4

14-5

Major Brain Portions

• three major portions of the brain - cerebrum, cerebellum, brainstem– cerebrum is 83% of brain volume;

cerebral hemispheres, gyri and sulci, longitudinal fissure, corpus callosum

– cerebellum contains 50% of the neurons; second largest brain region, located in posterior cranial fossa

– brainstem the portion of the brain that remains if the cerebrum and cerebellum are removed; diencephalon, midbrain, pons, and medulla oblongata

Figure 14.1b

Brainstem

Cerebellum

Cerebrum

Spinal cord

Rostral Caudal

Central sulcus

Lateral sulcus

Gyri

(b) Lateral view

Temporal lobe


14-6

Cerebrum • longitudinal fissure – deep

groove that separates cerebral hemispheres

• gyri - thick folds

• sulci - shallow grooves

• corpus callosum – thick nerve bundle at bottom of longitudinal fissure that connects hemispheres

Figure 14.1a


Frontal lobe

Occipital lobe

Central sulcus


Parietal lobe

(a) Superior view

Cerebralhemispheres

14-7

Cerebellum

• occupies posterior cranial fossa

• marked by gyri, sulci, and fissures

• about 10% of brain volume

• contains over 50% of brain neurons

Figure 14.1b

Brainstem

Cerebellum

Cerebrum

Spinal cord

Rostral Caudal

Central sulcus

Lateral sulcus

Gyri

(b) Lateral view

Temporal lobe


14-8

Brainstem

• brainstem – what remains of the brain if the cerebrum and cerebellum are removed

• major components

– diencephalon

– midbrain

– pons

– medulla oblongata

Figure 14.1b

Brainstem

Cerebellum

Cerebrum

Spinal cord

Rostral Caudal

Central sulcus

Lateral sulcus

Gyri

(b) Lateral view

Temporal lobe


14-9

Median Section of the Brain

Figure 14.2a


leaves

Thalamus

Hypothalamus

Frontal lobe

Corpus callosum

Cingulate gyrus

Optic chiasm

Pituitary gland

Mammillary body

Midbrain

Pons

Central sulcus

Parietal lobe

Parieto–occipital sulcus

Occipital lobe

Pineal gland

Habenula

Posterior commissure

Cerebral aqueduct

Fourth ventricle

Cerebellum

(a)

EpithalamusAnteriorcommissure

Temporal lobe

Medullaoblongata

14-10

Median Section of Cadaver Brain

Figure 14.2b


Corpus callosum

Cingulate gyrus

Lateral ventricle

Thalamus

Hypothalamus

Midbrain

Cerebellum

Fourth ventriclePons

(b)

Choroid plexus

Pineal gland

Occipital lobe

Parieto–occipitalsulcus

Posteriorcommissure

© The McGraw-Hill Companies, Inc./Dennis Strete, photographer

Medullaoblongata

14-11

Gray Matter, White Matter, and Meninges

• gray matter – the seat of neuron cell bodies, dendrites, and synapses and forms surface layer, cortex, over cerebrum and cerebellum

• white matter - bundles of axons that lies deep to cortical gray matter, opposite relationship in the spinal cord

• meninges – three connective tissue membranes that envelop the brain– lies between the nervous tissue and bone– as in spinal cord, they are the dura mater, arachnoid mater, and the

pia mater– protect the brain and provide structural framework for its arteries and veins

14-12

Ventricles and Cerebrospinal Fluid• ventricles – four internal chambers within the brain

– two lateral ventricles – one in each cerebral hemisphere • interventricular foramen - a tiny pore that connects to third ventricle

– third ventricle - single narrow medial space beneath corpus callosum

• cerebral aqueduct runs through midbrain and connects third to fourth ventricle

– fourth ventricle – small triangular chamber between pons and cerebellum

• connects to central canal runs down through spinal cord

• choroid plexus – spongy mass of blood capillaries on the floor of each ventricle

• ependyma – neuroglia that lines the ventricles and covers choroid plexus– produces cerebrospinal fluid

14-13

Brain Ventricles

Figure 14.6 a-b

Lateral ventricles

Central canal

Lateral aperture

Fourth ventricle

Third ventricle

Median aperture

(a) Lateral view

Caudal

Interventricularforamen

Cerebralaqueduct

Rostral

Lateral ventricle

Third ventricle

Cerebrum

Lateral aperture

Fourth ventricle

Median aperture

(b) Anterior view

Interventricularforamen

Cerebralaqueduct


14-14

Cerebrospinal Fluid (CSF)• cerebrospinal fluid (CSF) – clear, colorless liquid that fills the ventricles

and canals of CNS– bathes its external surface

• buoyancy– allows brain to attain considerable size without being impaired by its

own weight– if it rested heavily on floor of cranium, the pressure would kill the

nervous tissue

• protection– protects the brain from striking the cranium when the head is jolted– shaken child syndrome and concussions do occur from severe

jolting

• chemical stability– flow of CSF rinses away metabolic wastes from nervous tissue and

homeostatically regulates its chemical environment

14-15

Blood Supply to the Brain

• brain is only 2% of the adult body weight, and receives 15% of the blood

– 750 mL/min

• brain barrier system – strictly regulates what substances can get from the bloodstream into the tissue fluid of the brain

• two points of entry must be guarded:– blood capillaries throughout the brain tissue– capillaries of the choroid plexus

• blood-brain barrier - protects blood capillaries throughout brain tissue– astrocytes reach out and contact capillaries with their perivascular feet– endothelial cells can exclude harmful substances from passing to the brain

tissue while allowing necessary ones to pass

Cerebrum

• cerebrum – largest and most conspicuous part of the human brain– seat of sensory perception, memory, thought, judgment, and

voluntary motor actions

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leaves

Thalamus

Hypothalamus

Frontal lobe

Corpus callosum

Cingulate gyrus

Optic chiasm

Pituitary gland

Mammillary body

Midbrain

Pons

Central sulcus

Parietal lobe


Occipital lobe

Pineal gland

Habenula


Cerebral aqueduct

Fourth ventricle

Cerebellum

(a)


Temporal lobe

Medullaoblongata

Figure 14.2a

14-17

Cerebrum - Gross Anatomy

• two cerebral hemispheres divided by longitudinal fissure– connected by white fibrous tract the corpus callosum

– gyri and sulci – increases amount of cortex in the cranial cavity

– gyri increases surface area for information processing capability

– some sulci divide each hemisphere into five lobes named for the cranial bones that overly them

Frontal lobe

Occipital lobe

Central sulcus


Parietal lobe

(a) Superior view

Cerebralhemispheres

Figure 14.1a,b

Brainstem

Cerebellum

Cerebrum

Spinal cord

Rostral Caudal

Central sulcus

Lateral sulcus

Gyri

(b) Lateral view

Temporal lobe


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• frontal lobe– voluntary motor functions – motivation, foresight, planning,

memory, mood, emotion, social judgment, and aggression

• parietal lobe– receives and integrates general

sensory information, taste and some visual processing

• occipital lobe– primary visual center of brain

• temporal lobe– areas for hearing, smell, learning,

memory, and some aspects of vision and emotion

• insula (hidden by other regions)– understanding spoken language,

taste and sensory information from visceral receptors

Functions of Cerebrum - Lobes

Figure 14.13


Postcentral gyrus

Occipital lobe

Temporal lobe

Lateral sulcus

Frontal lobe Parietal lobe

Insula

Rostral Caudal

Centralsulcus

Precentralgyrus

14-19

Functional Regions of Cerebral Cortex

Wernicke area

Broca area

Primary motorcortex

Motor associationarea

Prefrontalcortex

Olfactoryassociationarea

Primary somestheticcortex

Somestheticassociation area

Primary gustatorycortex

Visual associationarea

Primaryvisual cortex

Primaryauditory cortex

Auditoryassociation area

Figure 14.21


14-20

Cerebral White MatterCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Association tracts

Frontal lobe

Corpus callosum

Temporal lobe

(a) Sagittal section

Projection tracts

Parietal lobe

Occipital lobe


Corpus callosum

Basal nuclei

Cerebral peduncle

Projection tracts

Decussation in pyramids

Commissuralta tracts

Lateral ventricle

Thalamus

Third ventricle

Mammillary body

pons

Pyramid

Medulla oblongata

(b) Frontal sectionFigure 14.14

14-21

Cerebral Cortex• neural integration is carried

out in the gray matter of the cerebrum

• cerebral gray matter found in three places– cerebral cortex– basal nuclei– limbic system

• cerebral cortex – layer covering the surface of the hemispheres– only 2 – 3 mm thick– cortex constitutes about 40% of

the mass of the brain– contains 14 – 16 billion neurons


I

II

III

IV

V

VI

Cortical surface

Stellate cells

Small pyramidalcells

Large pyramidalcells

Whitematter

Figure 14.15

14-22

Cerebral Cortex– contains two principal types of

neurons• stellate cells

– have spheroid somas with dendrites projecting in all directions

– receive sensory input and process information on a local level

• pyramidal cells– tall, and conical, with apex

toward the brain surface– a thick dendrite with many

branches with small, knobby dendritic spines

– include the output neurons of the cerebrum

– only neurons that leave the cortex and connect with other parts of the CNS

• neocortex – six layered tissue that constitutes about 90% of the human cerebral cortex

– relatively recent in evolutionary origin


I

II

III

IV

V

VI

Cortical surface

Stellate cells

Small pyramidalcells

Large pyramidalcells

Whitematter

Figure 14.15

14-23

Cerebral Lateralization• cerebral lateralization – the difference in the structure and function of

the cerebral hemispheres

• left hemisphere - categorical hemisphere– specialized for spoken and written language– sequential and analytical reasoning (math and science)– breaks information into fragments and analyzes it in a linear way

• right hemisphere - representational hemisphere– perceives information in a more integrated holistic way – seat of imagination and insight– musical and artistic skill– perception of patterns and spatial relationships– comparison of sights, sounds, smells, and taste

• highly correlated with handedness – left hemisphere is the categorical one in 96% of right-handed people

• right hemisphere in 4%

– left handed people – right hemisphere is categorical in 15% and left in 70%

• lateralization develops with age– males exhibit more lateralization than females and suffer more functional loss

when one hemisphere is damaged

14-24

Cerebral LateralizationCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

leaves

Olfaction, left nasal cavity

Memory for shapes

Left hand motor control

Musical ability

Intuitive, nonverbal thought

Vision, left fieldVision, right field

Speech

Verbal memory

Olfaction, right nasal cavity

Left hemisphere Right hemisphere

Posterior

Anterior

(Limited languagecomprehension, mute)

Feeling shapes withleft hand

Hearing nonvocal sounds(left ear advantage)

Superior recognition offaces and spatialrelationships

Right handmotor control

Feeling shapeswith right hand

Hearing vocal sounds(right ear advantage)

Rational, symbolicthought

Superior languagecomprehension

Figure 14.26

14-25

The Forebrain

Diencephalon

Mesencephalon

TelencephalonForebrain

Pons

CerebellumMetencephalon

Spinal cord

Hindbrain

(c) Fully developed

Midbrain

Myelencephalon(medulla oblongata)


• forebrain consists of :

– the diencephalon• encloses the third

ventricle

• most rostral part of the brainstem

• has three major embryonic derivatives

– thalamus– hypothalamus– epithalamus

– the telencephalon• develops chiefly into the

cerebrum

Figure 14.4c

14-26

Diencephalon: Thalamus

• thalamus – ovoid mass on each side of the brain perched at the superior end of the brainstem beneath the cerebral hemispheres

– constitutes about four-fifths of the diencephalon– two thalami are joined medially by a narrow intermediate mass– composed of at least 23 nuclei – we will consider five major functional groups– the “gateway to the cerebral cortex” – nearly all input to the cerebrum passes by way of

synapses in the thalamic nuclei, filters information on its way to cerebral cortex– plays key role in motor control by relaying signals from cerebellum to cerebrum and

providing feedback loops between the cerebral cortex and the basal nuclei– involved in the memory and emotional functions of the limbic system – a complex of

structures that include some cerebral cortex of the temporal and frontal lobes and some of the anterior thalamic nuclei


leaves

(a) Thalamus

Anterior group

Medial group

Ventral group

Lateral group

Posterior group

Lateral geniculate nucleus

Medial geniculate nucleus

Thalamic Nuclei

Part of limbic system;memory and emotion

Emotional output to prefrontalcortex; awareness of emotions

Somesthetic output topostcentral gyrus; signalsfrom cerebellum and basalnuclei to motor areas of cortex

Somesthetic output toassociation areas of cortex;contributes to emotional functionof limbic system

Relay of visual signals tooccipital lobe (via lateralgeniculate nucleus) and auditorysignals to temporal lobe (viamedial geniculate nucleus)

Figure 14.12a

14-27

• hypothalamus – forms part of the walls and floor of the third ventricle

• extends anteriorly to optic chiasm and posteriorly to the paired mammillary bodies

• each mammillary body contains three or four mammillary nuclei– relay signals from the limbic

system to the thalamus

• infundibulum – a stalk that attaches the pituitary gland to the hypothalamus

• major control center of autonomic nervous system and endocrine system– plays essential roll in homeostatic

regulation of all body systems

Diencephalon: Hypothalamus

Figure 14.2a

leaves

Thalamus

Hypothalamus

Frontal lobe

Corpus callosum

Cingulate gyrus

Optic chiasm

Pituitary gland

Mammillary body

Midbrain

Pons

Central sulcus

Parietal lobe


Occipital lobe

Pineal gland

Habenula


Cerebral aqueduct

Fourth ventricle

Cerebellum

(a)


Temporal lobe

Medullaoblongata


14-28

• functions of hypothalamic nuclei– hormone secretion

• controls anterior pituitary• regulates growth, metabolism, reproduction ,and

stress responses– autonomic effects

• major integrating center for the autonomic nervous system

• influences heart rate, blood pressure, gastrointestinal secretions and motility, and others

– thermoregulation• hypothalamic thermostat monitors body

temperature• activates heat-loss center when temp is too high• activates heat-promoting center when temp is

too low– food and water intake

• hunger and satiety centers monitor blood glucose and amino acid levels

– produce sensations of hunger and satiety• thirst center monitors osmolarity of the blood

– rhythm of sleep and waking• controls 24 hour circadian rhythm of activity

– memory• -mammillary nuclei receive signals from

hippocampus– emotional behavior

• anger, aggression, fear, pleasure, and contentment

Diencephalon: Hypothalamus

Figure 14.2a

leaves

Thalamus

Hypothalamus

Frontal lobe

Corpus callosum

Cingulate gyrus

Optic chiasm

Pituitary gland

Mammillary body

Midbrain

Pons

Central sulcus

Parietal lobe


Occipital lobe

Pineal gland

Habenula


Cerebral aqueduct

Fourth ventricle

Cerebellum

(a)


Temporal lobe

Medullaoblongata


Diencephalon: Epithalamus

• epithalamus – very small mass of tissue composed of:– pineal gland – endocrine gland

– habenula – relay from the limbic system to the midbrain

– thin roof over the third ventricle

14-29


leaves

Thalamus

Hypothalamus

Frontal lobe

Corpus callosum

Cingulate gyrus

Optic chiasm

Pituitary gland

Mammillary body

Midbrain

Pons

Central sulcus

Parietal lobe


Occipital lobe

Pineal gland

Habenula


Cerebral aqueduct

Fourth ventricle

Cerebellum

(a)


Temporal lobe

Medullaoblongata

Figure 14.2a

14-30

Cerebellum

• the largest part of the hindbrain and the second largest part of the brain as a whole

• consists of right and left cerebellar hemispheres connected by vermis

• cortex of gray matter with folds (folia) and four deep nuclei in each hemisphere

• contains more than half of all brain neurons, about 100 billion– granule cells and Purkinje cells synapse on deep nuclei

• white matter branching pattern is called arbor vitae


leaves

(b) Superior view

Folia

Anterior

Posterior

Anterior lobe

Vermis

Posterior lobe

Cerebellarhemisphere

Figure 14.11b

14-31

Cerebellum

• cerebellar peduncles – three pairs of stalks that connect the cerebellum to the brainstem– inferior peduncles – connected to medulla oblongata

• most spinal input enters the cerebellum through inferior peduncle

– middle peduncles – connected to the pons• most input from the rest of the brain enters by way of middle peduncle

– superior peduncles – connected to the midbrain• carries cerebellar output

• consist of thick bundles of nerve fibers that carry signals to and from the cerebellum


Superior colliculus


Pineal glandInferior colliculus

Mammillary bodyMidbrain

Cerebral aqueduct

Oculomotor nerve

Pons

Fourth ventricle

Medulla oblongata

Gray matter

(a) Median section

White matter(arbor vitae)

Figure 14.11a

14-32

Cerebellum Functions• monitors muscle contractions and aids in motor

coordination

• evaluation of sensory input– comparing textures without looking at them– spatial perception and comprehension of different views of 3D

objects belonging to the same object

• timekeeping center– predicting movement of objects– helps predict how much the eyes must move in order to

compensate for head movements and remain fixed on an object

• hearing– distinguish pitch and similar sounding words

• planning and scheduling tasks

• lesions may result in emotional overreactions and trouble with impulse control

14-33

Midbrain

• mesencephalon becomes one mature brain structure, the midbrain

– short segment of brainstem that connects the hindbrain to the forebrain

14-34

Midbrain -- Cross SectionCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

leaves

TegmentumCerebral peduncle:

Cerebral crus

TectumSuperior colliculus

Cerebral aqueduct

Medial geniculate nucleusReticular formation Central gray matter

Oculomotor nucleusMedial lemniscus

Red nucleus

Substantia nigra

Oculomotor nerve (III)

Posterior

Anterior

(a) Midbrain

(a) Midbrain

(c) Medulla

(b) Pons

Figure 14.9a

14-35

Pons• ascending sensory tracts

• descending motor tracts

• pathways in and out of cerebellum

• cranial nerves V, VI, VII, and VIII– sensory roles – hearing, equilibrium, taste, facial

sensations

– motor roles – eye movement, facial expressions, chewing, swallowing, urination, and secretion of saliva and tears

• reticular formation in pons contains additional nuclei concerned with:– sleep, respiration, and posture

14-36

Pons

Figure 14.2a


leaves

Thalamus

Hypothalamus

Frontal lobe

Corpus callosum

Cingulate gyrus

Optic chiasm

Pituitary gland

Mammillary body

Midbrain

Pons

Central sulcus

Parietal lobe


Occipital lobe

Pineal gland

Habenula


Cerebral aqueduct

Fourth ventricle

Cerebellum

(a)


Temporal lobe

Medullaoblongata

• metencephalon - develops into the pons and cerebellum

• pons – anterior bulge in brainstem, rostral to medulla

• cerebral peduncles – connect cerebellum to pons and midbrain

14-37

Hindbrain - Medulla Oblongata

• cardiac center – adjusts rate and force of heart

• vasomotor center – adjusts blood vessel diameter

• respiratory centers – control rate and depth of breathing

• reflex centers – for coughing, sneezing, gagging, swallowing,

vomiting, salivation, sweating, movements of tongue and head

14-38

Medulla Oblongata

• pyramids contain descending fibers called corticospinal tracts– carry motor signals to skeletal muscles

• inferior olivary nucleus – relay center for signals to cerebellum• reticular formation - loose network of nuclei extending throughout

the medulla, pons and midbrain– contains cardiac, vasomotor & respiratory centers

Figure 14.9c


Hypoglossal nerve

Medial lemniscusTectospinal tract

NucleusTract

Gracile nucleus

Cuneate nucleus

Olive

Pyramids of medullaCorticospinal tract

Trigeminal nerve:

Fourth ventricle

Reticular formation

(c) Medulla oblongata

(a) Midbrain

(c) Medulla

(b) Pons

Posterior spinocerebellartract

Nucleus ofvagus nerve

Inferior olivarynucleus

Nucleus ofhypoglossal nerve

14-39

Higher Brain Functions• higher brain functions - sleep, memory,

cognition, emotion, sensation, motor control, and language

• involve interactions between cerebral cortex and basal nuclei, brainstem and cerebellum

• functions of the brain do not have easily defined anatomical boundaries

• integrative functions of the brain focuses mainly on the cerebrum, but involves combined action of multiple brain levels

14-40

Brain Waves

• alpha waves 8 – 13 Hz– awake and resting with eyes closed and mind wandering– suppressed when eyes open or performing a mental task

• beta waves 14 – 30 Hz– eyes open and performing mental tasks– accentuated during mental activity and sensory stimulation

• theta waves 4 – 7 Hz– drowsy or sleeping adults – if awake and under emotional stress

• delta waves high amplitude, less than 3.5 Hz– deep sleep in adults

14-41

Sleep• sleep occurs in cycles called circadian rhythms

– events that reoccur at intervals of about 24 hours

• sleep - temporary state of unconsciousness from which one can awaken when stimulated– characterized by stereotyped posture

• lying down with eyes closed

– sleep paralysis - inhibition of muscular activity– resembles unconsciousness but can be aroused by sensory stimulation– coma or hibernation – states of prolonged unconsciousness where

individuals cannot be aroused from those states by sensory stimulation

• restorative effect– brain glycogen and ATP levels increase in non-REM sleep– memories strengthened in REM sleep

• synaptic connections reinforced

14-42

Four Stages of Sleep• Stage 1

– feel drowsy, close our eyes, begin to relax– often feel drifting sensation, easily awakened if stimulated– alpha waves dominate EEG

• Stage 2– pass into light sleep– EEG declines in frequency but increases in amplitude– exhibits sleep spindles – high spikes resulting from interactions between neurons

of the thalamus and cerebral cortex

• Stage 3– moderate to deep sleep– about 20 minutes after stage 1– theta and delta waves appear– muscles relax and vital signs (body temperature, blood pressure, heart and

respiratory rate) fall

• Stage 4– called slow-wave-sleep (SWS) – EEG dominated by low-frequency, high amplitude

delta waves– muscles now very relaxed, vital signs at their lowest, and we become more difficult to

awaken

14-43

Rhythm of Sleep• about five times a night, a sleeper backtracks from stage 3 or 4 to

stage 2– exhibits bouts of rapid eye movement (REM) sleep, eyes oscillate

back and forth

– also called paradoxical sleep, because EEG resembles the waking state, but sleeper is harder to arouse than any other stage

– vital signs increase, brain uses more oxygen than when awake

– sleep paralysis stronger to prevent sleeper from acting out their dreams

• dreams occur in both REM and non-REM sleep– REM tend to be longer and more vivid

• parasympathetic nervous system active during REM sleep– causing constriction of the pupils

– erection of the penis and clitoris

14-44

Sleep Stages

Figure 14.19


0

0 1 2 3 4 5 6 7 8

10

Awake

Awake

Stage 1

Stage 2

Stage 3

Stage 4

EE

G s

tag

es

20 30 40Time (min)

Time (hr)

(a) One sleep cycle

(b) Typical 8-hour sleep period

Sta

ge

50 60 70

REM REM REMREMREM

Sleep spindles

Stage 1Drowsy

Stage 2Light sleep

Stage 3Moderate todeep sleep

Stage 4Deepest sleep

REMsleep

14-45

Cognition• cognition – the range of mental processes by which we

acquire and use knowledge– such as sensory perception, thought, reasoning, judgment, memory,

imagination, and intuition

• association areas of cerebral cortex has above functions – constitutes about 75% of all brain tissue

• studies of patients with brain lesions, cancer, stroke, and trauma yield information on cognition– parietal lobe association area – perceiving stimuli

• contralateral neglect syndrome – unaware of objects on opposite side of their body

– temporal lobe association area – identifying stimuli• agnosia – inability to recognize, identify, and name familiar objects• prosopagnosia – person cannot remember familiar faces

– frontal lobe association area – planning our responses and personality – inability to execute appropriate behavior

14-46

Memory• information management requires

– learning – acquiring new information– memory – information storage and retrieval– forgetting – eliminating trivial information; as important as remembering

• amnesia – defects in declarative memory – inability to describe past events

• procedural memory – ability to tie your shoes– anterograde amnesia – unable to store new information– retrograde amnesia – cannot recall things they knew before the injury

• hippocampus – important memory-forming center– does not store memories– organizes sensory and cognitive information into a unified long-term memory– memory consolidation – the process of “teaching the cerebral cortex” until a long-term

memory is established– long-term memories are stored in various areas of the cerebral cortex– vocabulary and memory of familiar faces stored in superior temporal lobe– memories of one’s plans and social roles stored in the prefrontal cortex

• cerebellum – helps learn motor skills

• amygdala - emotional memory

14-47

Emotion• emotional feelings and memories are interactions between prefrontal

cortex and diencephalon

• prefrontal cortex - seat of judgment, intent, and control over expression of emotions

• feelings come from hypothalamus and amygdala– nuclei generate feelings of fear or love

• amygdala receives input from sensory systems– role in food intake, sexual behavior, and drawing attention to novel stimuli– one output goes to hypothalamus influencing somatic and visceral motor

systems• heart races, raises blood pressure, makes hair stand on end, induce vomiting

– other output to prefrontal cortex important in controlling expression of emotions

• ability to express love, control anger, or overcome fear

• behavior shaped by learned associations between stimuli, our responses to them, and the reward or punishment that results

14-48

Sensation• primary sensory cortex - sites

where sensory input is first received and one becomes conscious of the stimulus

• association areas nearby to sensory areas that process and interpret that sensory information

– primary visual cortex is bordered by visual association area which interprets and makes cognitive sense of visual stimuli

– multimodal association areas – receive input from multiple senses and integrate this into an overall perception of our surroundings

Anterior

Posterior

(a)

Precentralgyrus

Centralsulcus

Postcentralgyrus Parietal

lobe

Frontallobe

Occipitallobe


Figure 14.22a

14-49

Special Senses• special senses – limited to the head and employ relatively complex sense

organs• primary cortices and association areas listed below• vision

– visual primary cortex in far posterior region of the occipital lobe– visual association area – anterior and occupies all the remaining occipital lobe

• much of inferior temporal lobe deals with facial recognition and other familiar objects

• hearing– primary auditory cortex in the superior region of the temporal lobe and insula– auditory association area – temporal lobe deep and inferior to primary auditory cortex

• recognizes spoken words, a familiar piece of music, or a voice on the phone

• equilibrium– signals for balance and sense of motion project mainly to the cerebellum and

several brainstem nuclei concerned with head and eye movements and visceral functions

– association cortex in the roof of the lateral sulcus near the lower end of the central sulcus

• seat of consciousness of our body movements and orientation in space

• taste and smell– gustatory (taste) signals received by primary gustatory cortex in inferior end of the

postcentral gyrus of the parietal lobe and anterior region of insula– olfactory (smell) signals received by the primary olfactory cortex in the medial

surface of the temporal love and inferior surface of the frontal lobe

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Motor Control• basal nuclei

– determines the onset and cessation of intentional movements• repetitive hip and shoulder movements in walking

– highly practiced, learned behaviors that one carries out with little thought• writing, typing, driving a car

– lies in a feedback circuit from the cerebrum to the basal nuclei to the thalamus and back to the cerebrum

• cerebellum– highly important in motor coordination– aids in learning motor skills– maintains muscle tone and posture– smoothes muscle contraction – coordinates eye and body movements– coordinates the motions of different joints with each other– ataxia – clumsy, awkward gait

14-51

Input and Output to CerebellumCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Cerebrum

Cerebrum

Motor cortex

Cerebellum

Cerebellum

Brainstem

Brainstem

Inner ear

Eye

Reticular formation

Muscle and joint proprioceptors

(a) Input to cerebellum (b) Output from cerebellum

Spinocerebellartracts of spinal cord

Reticulospinaland vestibulospinaltracts of spinal cord

Limb and posturalmuscles

Figure 14.24

14-52

Language• language include several abilities: reading, writing,

speaking, and understanding words assigned to different regions of the cerebral cortex

• Wernicke area– permits recognition of spoken and written language and creates

plan of speech– when we intend to speak, Wernicke area formulates phases

according to learned rules of grammar– transmits plan of speech to Broca area

• Broca area – generates motor program for the muscles of the larynx, tongue,

cheeks and lips – transmits program to primary motor cortex for commands to the

lower motor neurons that supply relevant muscles

• Affective language area lesions produce aprosody - flat emotionless speech

14-53

Language CentersCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

leavesPrecentral gyrus

Anterior Posterior

Speech center ofprimary motor cortex

Primary auditorycortex(in lateral sulcus)

Postcentralgyrus

Angulargyrus

Primaryvisual cortex

Wernickearea

Brocaarea

Figure 14.25

14-54

Cranial Nerves

• the brain must communicate with the rest of the body

– most of the input and output travels by way of the spinal cord

– 12 pairs of cranial nerves arise from the base of the brain

– exit the cranium through foramina

– lead to muscles and sense organs located mainly in the head and neck

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Spinal Cord, Spinal Nerves, and Somatic Reflexes

• spinal cord

• spinal nerves

• somatic reflexes

Figure 13.1b


Spinal cord

Spinal nerve rootlets

Spinal nerve

Subarachnoid space

Posterior median sulcus

Posterior root ganglion

Rib

Dura materArachnoid mater

Epidural space

(b)

Vertebra (cut)

13-56

Functions of the Spinal Cord• conduction

– bundles of fibers passing information up and down spinal cord, connecting different levels of the trunk with each other and with the brain

• locomotion– walking involves repetitive, coordinated actions of several muscle

groups– central pattern generators are pools of neurons providing control

of flexors and extensors that cause alternating movements of the lower limbs

• reflexes– involuntary, stereotyped responses to stimuli

• withdrawal of hand from pain

– involves brain, spinal cord and peripheral nerves

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Cross-Sectional Anatomy of the Spinal Cord

• central area of gray matter shaped like a butterfly and surrounded by white matter in 3 columns

• gray matter - neuron cell bodies with little myelin– site of information processing – synaptic integration

• white matter – abundantly myelinated axons– carry signals from one part of the CNS to another


Gray matter: White matter:

Anterior median fissure

(b) Spinal cord and meninges (thoracic)

Posterior hornLateral columnGray commissureAnterior column

Central canal

Posterior column

Posterior root ganglion

Spinal nerve

Lateral horn

Anterior horn

Pia materArachnoid mater

Meninges:

Dura mater (dural sheath)

Posterior root of spinal nerve

Posteriormedian sulcus

Anterior rootof spinal nerve

(c) Lumbar spinal cordc: Sarah Werning

Figure 13.2b & c

13-58

Ascending Tracts

• ascending tracts carry sensory signals up the spinal cord

• sensory signals travel across three neurons from origin in receptors to the destination in the sensory areas of the brain

– first order neurons – detect stimulus and transmit signal to spinal cord or brainstem

– second order neurons – continues to the thalamus at the upper end of the brainstem

– third order neurons – carries the signal the rest of the way to the sensory region of the cerebral cortex

13-59

Descending Tracts

• descending tracts - carry motor signals down the brainstem and spinal cord

• involves two neurons

– upper motor neuron originate in cerebral cortex or brainstem and terminates on a lower motor neuron

– lower motor neuron in brainstem or spinal cord

• axon of lower motor neuron leads the rest of the way to the muscle or other target organ

13-60

Classification of Nerve Fibers

• sensory (afferent) nerves– carry signals from sensory

receptors to the CNS

• motor (efferent) nerves– carry signals from CNS to

muscles and glands

• mixed nerves – consists of both afferent and

efferent fibers– conduct signals in two directions

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Immediate Memory• immediate memory – the ability to hold

something in your thoughts for just a few seconds– essential for reading ability

• feel for the flow of events (sense of the present)

• our memory of what just happened “echoes” in our minds for a few seconds– reverberating circuits

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Short-Term or Working Memory• short-term memory (STM) - lasts from a few

seconds to several hours– quickly forgotten if distracted – calling a phone number we just looked up– reverberating circuits

• facilitation causes memory to last longer– tetanic stimulation – rapid arrival of repetitive signals

at a synapse • causes Ca2+ accumulation and postsynaptic cell more likely to

fire

– post-tetanic potentiation - to jog a memory• Ca2+ level in synaptic knob stays elevated• little stimulation needed to recover memory

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Long-Term Memory• types of long-term memory

– declarative - retention of events that you can put into words

– procedural - retention of motor skills

• physical remodeling of synapses– new branching of axons or dendrites

• molecular changes - long-term potentiation– changes in receptors and other features increases

transmission across “experienced” synapses– effect is longer-lasting

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Alzheimer Disease• 100,000 deaths/year

– 11% of population over 65; 47% by age 85

• memory loss for recent events, moody, combative, lose ability to talk, walk, and eat

• show deficiencies of acetylcholine (ACh) and nerve growth factor (NGF)

• diagnosis confirmed at autopsy– atrophy of gyri (folds) in cerebral cortex

– neurofibrillary tangles and senile plaques

– formation of beta-amyloid protein from breakdown product of plasma membranes

• genetics implicated

• treatment - halt beta-amyloid production– research halted due to serious side effects

– Give NGF or cholinesterase inhibitors

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Alzheimer Disease Effects

Figure 12.31a Figure 12.31b


(a)

Shrunkengyri

Wide sulci

Custom Medical Stock Photo, Inc.


(b)

Senile plaque

Neurons withneurofibrillarytangles

© Simon Fraser/Photo Researchers, Inc.

12-66

Parkinson Disease• progressive loss of motor function beginning in 50’s or 60’s -

no recovery– degeneration of dopamine-releasing neurons

• dopamine normally prevents excessive activity in motor centers (basal nuclei)

• involuntary muscle contractions– pill-rolling motion, facial rigidity, slurred speech, – illegible handwriting, slow gait

• treatment - drugs and physical therapy– dopamine precursor (L-dopa) crosses brain barrier – bad side effects

on heart & liver– MAO inhibitor slows neural degeneration– surgical technique to relieve tremors

Documents

14-1 Central Nervous System overview of the brain meninges, ventricles, cerebrospinal fluid and blood supply hindbrain and midbrain forebrain integrative