Central Nervous System: The Brain

• Anatomy of the Brain

Cerebral Hemispheres

Diencephalon

Brain Stem

Cerebellum

• Protection of the CNS

Meninges

Cerebrospinal Fluid

Blood-Brain Barrier

Brain Dysfunction

Regions of the Brain Cerebrum

• Integration, speech, language, emotion, memory, learning, consciousness, behavior

Diencephalon

• Sorting sensory input, homeostasis, biological clock

Brain stem

• Coordination of movement, homeostasis, conduction of info to higher centers

Cerebellum

• Error checking of perceptual, cognitive, and motor responses, coordination, motor learning (hand-eye coordination, balance)

Figure 12.3d

Cerebellum

Diencephalon

Cerebralhemisphere

(d) Birth

Brain stem• Midbrain• Pons• Medullaoblongata

Cerebral Hemispheres (2 Cerebra)

Paired (left and right) superior parts of the brain

The surface is made of ridges (gyri), grooves (sulci), and deep grooves (fissures)

Fissures divide cerebrum into lobes

• Frontal lobe

• Parietal lobe

• Occipital lobe

• Temporal lobe

Transverse cerebral fissure

Longitudinal fissure

Figure 12.6c

Parietallobe

Frontal lobe

Right cerebralhemisphere

Occipitallobe

Left cerebralhemisphere

Cerebral veinsand arteriescovered byarachnoidmater

Longitudinalfissure

Posterior(c)

Anterior

Central sulcus

Functional Areas of the Cerebral Cortex The three types of functional areas are:

• Motor areas —control voluntary movement

• Sensory areas —conscious awareness of sensation

• Association areas —integrate diverse information

Conscious behavior involves the entire cortex

Motor Areas

Primary (somatic) motor cortex

• Allows conscious control of precise, skilled, voluntary movements

Other motor areas include the Broca’s area (speech) and the frontal eye field (vision)

Figure 12.8a

Gustatory cortex(in insula)

Primary motor cortex

Working memoryfor spatial tasksExecutive area fortask managementWorking memory forobject-recall tasks Solving complex,multitask problems

(a) Lateral view, left cerebral hemisphere

Motor areas in red/orange

Prefrontal cortex

Sensory areas and relatedassociation areas

Central sulcus

Primary somatosensorycortexSomatosensoryassociation cortex

Somaticsensation

Taste

Wernicke’s area(outlined by dashes)

Primary visualcortexVisualassociation area

Vision

Auditoryassociation areaPrimaryauditory cortex

Hearing

Primary motor cortex Motor association cortex Primary sensory cortex

Sensory association cortex Multimodal association cortex

Sensory Areas

Primary somatosensory cortex

Somatosensory association cortex

Visual areas

Auditory areas

Motor and Sensory Areas of the Cerebral Cortex

Homunculous Diagrams

Figure 12.8a

Gustatory cortex(in insula)

Primary motor cortex

Working memoryfor spatial tasksExecutive area fortask managementWorking memory forobject-recall tasks Solving complex,multitask problems

(a) Lateral view, left cerebral hemisphere

Motor areas in red/orange

Prefrontal cortex

Sensory areas and relatedassociation areas

Central sulcus

Primary somatosensorycortexSomatosensoryassociation cortex

Somaticsensation

Taste

Wernicke’s area(outlined by dashes) handles articulation of unfamiliar words

Primary visualcortexVisualassociation area

Vision

Auditoryassociation areaPrimaryauditory cortex

Hearing

Primary motor cortex Motor association cortex Primary sensory cortex

Sensory association cortex Multimodal association cortex

Broca’s Area effects how words are articulated in speech (left lob only)

Left cerebral hemisphere is the “language brain”Right cerebral hemisphere is the “abstract, conceptual, and spatial brain”

Motor and Sensory Areas of the Cerebral Cortex

Homunculous Diagrams

Corpus callosum

Posterior commissure

Anteriorcommissure

Pituitary gland

Medulla oblongata

Spinal cord

Association fibers (interneurons) connect regions of the same hemisphere together (white matter)Commissural fibers

connect the two hemispheres to each other

Cerebral hemisphereInterthalamic

adhesion(intermediatemass of thalamus)

Projection fibers connect the cortex to lower brain structures and the spinal cord, eg. afferent and efferent tracts.

Neuron Cell Body Names and Locations

Clusters of cell bodies Bundles of nerve fibers (neuronal processes)

CNS Nuclei Tracts White matter -dense myelinated fibers

Gray matter- unmyelinated fibers and cell bodies

PNS Ganglia Nerves

(bundles of axons)

Layers of the Cerebrum Gray matter

• Outer layer

• Composed mostly of neuron cell bodies (nuclei)

White matter

• Fiber tracts found deep to the gray matter

• Example: corpus callosum connects hemispheres

Figure 12.4

CerebrumCerebellum

Migratorypattern ofneurons

Cortex ofgray matterInner graymatter

Gray matter

Outer whitematter

Central cavity

Central cavity

Inner gray matter

Gray matter

Outer white matter

Central cavity

Inner gray matter

Outer white matter

Region of cerebellum

Brain stem

Spinal cord

Layers of the Cerebrum Basal nuclei – internal islands of gray matter (cell

bodies) where processing occurs to modify motor instructions from primary motor cortex

•Influence muscular control

•Help regulate attention and cognition

•Regulate intensity of slow or stereotyped movements

•Inhibit antagonistic and unnecessary movements

Central Nervous System: The Brain

• Anatomy of the Brain

Cerebral Hemispheres

Diencephalon

Brain Stem

Cerebellum

• Protection of the CNS

Meninges

Cerebrospinal Fluid

Blood-Brain Barrier

Brain Dysfunction

Diencephalon: Three Parts• Thalamus

Surrounds the third ventricle

The relay station for sensory impulses (sense of expectation)

Transfers impulses to the correct part of the cortex for localization and interpretation

• Hypothalamus Under the thalamus

Important autonomic nervous system center

o Helps regulate body temperature

o Controls water balance

o Regulates metabolism

An important part of the limbic system (thirst, appetite, sex, pain, pleasure)

The pituitary gland is attached to the hypothalamus

Epithalamus Forms the roof of the third ventricle

Houses the pineal body (an endocrine gland)

Includes the choroid plexus – forms cerebrospinal fluid

Central Nervous System: The Brain

• Anatomy of the Brain

Cerebral Hemispheres

Diencephalon

Brain Stem

Cerebellum

• Protection of the CNS

Meninges

Cerebrospinal Fluid

Blood-Brain Barrier

Brain Dysfunction

Brain Stem Routing for ascending and descending tracts and basal nuclei

for cranial nerves controlling breathing and blood pressure

Midbrain

Midbrain• Contains cerebral aqueduct connecting third and fourth ventricles.• Divides into 2 fiber tracts called cerebral peducles• Has posteriorly/dorsally oriented four nuclei for vision and hearing reflexes (corpora quadrigemina)

Pons• "Bridge" with nuclei to control breathing and passage of fiber tracts

Medulla oblongata• Fiber tract with nuclei regulating heart rate, blood pressure, breathing, swelling, vomiting (autonomic functions)

Figure 12.15b

View (b)

Crus cerebri ofcerebral peduncles (midbrain)

InfundibulumPituitary gland

Trigeminal nerve (V)

Abducens nerve (VI)

Facial nerve (VII)

Vagus nerve (X)

Accessory nerve (XI)

Hypoglossal nerve (XII)

Pons

(b) Left lateral view

Glossopharyngeal nerve (IX)

Diencephalon

Brainstem

Thalamus

Hypothalamus

Midbrain

Pons

Medullaoblongata

Thalamus

Superior colliculusInferior colliculusTrochlear nerve (IV)

Superior cerebellar peduncle

Middle cerebellar peduncle

Inferior cerebellar peduncle

Vestibulocochlear nerve (VIII)Olive

Figure 12.14

Frontal lobeOlfactory bulb(synapse point ofcranial nerve I)Optic chiasmaOptic nerve (II)Optic tractMammillary body

Pons

MedullaoblongataCerebellum

Temporal lobe

Spinal cord

Midbrain

Central Nervous System: The Brain

• Anatomy of the Brain

Cerebral Hemispheres

Diencephalon

Brain Stem

Cerebellum

• Protection of the CNS

Meninges

Cerebrospinal Fluid

Blood-Brain Barrier

Brain Dysfunction

Cerebellum: Two hemispheres

Control of balance, equilibrium, timing of muscle activity, coordination: the "automatic pilot" or coordinating center

Regions of the Brain

Cerebrum (2 hemispheres)

• Integration, memory, learning

Diencephalon

• Sorting signals and homeostasis, day/night cycles, endocrine control

Brain stem

• Heart rate, blood pressure,breathing, conduction of messages

Cerebellum

• Motor coordination and balance

Central Nervous System: The Brain

• Anatomy of the Brain

Cerebral Hemispheres

Diencephalon

Brain Stem

Cerebellum

• Protection of the CNS

Meninges

Cerebrospinal Fluid

Blood-Brain Barrier

Brain Dysfunction

Meninges: Dura mater, arachnoid, & pia mater

Falx cerebri

periosteal layer

meningeal layer

Subarachnoid space with CSF

dura mater = "tough mother"

archnoid = "spidery"

pia mater = "delicate mother"Singular: menixPlural: meninges

Central Nervous System: The Brain

• Anatomy of the Brain

Cerebral Hemispheres

Diencephalon

Brain Stem

Cerebellum

• Protection of the CNS

Meninges

Cerebrospinal Fluid and Ventricles

Blood-Brain Barrier

Brain Dysfunction

Cerebrospinal Fluid (CSF) Composition

• Watery solution with constant volumne

• Less protein and different ion concentrations than plasma

Functions

• Gives buoyancy to the CNS organs

• Protects the CNS from blows and other trauma

• Nourishes the brain and carries chemical signals

Production at choroid plexi

• Produce CSF at a constant rate hanging from the roof of each ventricle

• Ependymal cells use ion pumps to control the composition of the CSF and help cleanse CSF by removing wastes

Figure 12.5

Anterior horn

Interventricularforamen

Inferiorhorn

Lateralaperture

(b) Left lateral view

Lateral ventricle

Septum pellucidum

Third ventricle

Cerebral aqueduct

(a) Anterior view

Fourth ventricleCentral canal

Inferior horn

Posteriorhorn

MedianapertureLateralaperture

Ventricles of the Brain

Ventricles and Location of the Cerebrospinal Fluid

Medial aperture (of Magendie) and lateral apertures to subarachnoid

space

Cerebralspinal fluid flow movie

Interventricular foramen

Blood Brain Barrier

Includes the least permeable capillaries of the body

Excludes many potentially harmful substances

Useless against some substances

• Fats and fat soluble molecules

• Respiratory gases

• Alcohol

• Nicotine

• Anesthesia

Central Nervous System: The Brain

• Anatomy of the Brain

Cerebral Hemispheres

Diencephalon

Brain Stem

Cerebellum

• Protection of the CNS

Meninges

Cerebrospinal Fluid

Blood-Brain Barrier

Brain Dysfunction

The Twelve Cranial Nerves (I-V) I Olfactory nerve – purely sensory for smell; ask

patient to identify oil of cloves and vanilla

II Optic nerve – purely sensory for vision; observe eye, test patient with eye chart

III Oculomotor nerve – mostly motor fibers to eye muscles, some proprioreceptive afferents; examine pupil size and reflex, ability to follow objects with the eye

IV Trochlear – mostly motor fibers to extrinsic eye muscles; test patient’s ability to follow objects with eye

V Trigeminal nerve – 3 divisions:

• Opthalmic (tested by corneal reflex) carrying sensory for skin of anterior scalp, eyelid, nose

• Maxillary (tested with pain, touch temperature using safety pin) carrying sensory from nasal cavity, palate, upper lip, cheek

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The Twelve Cranial Nerves (Vi-XIII) VI Abducens nerve – motor fibers to eye muscles

(lateral rectus); test by having patient follow object side-to-side

VII Facial nerve – sensory for taste; motor fibers to the face (test with ability to taste sweet salt, sour, bitter and close eyes, smile, whistle, make tears); five major branches: temporal, zygomatic, buccal, mandibular, cervical

VIII Vestibulocochlear nerve – sensory for balance (semicircular canals) and hearing; test with air and bone conduction with tuning fork

IX Glossopharyngeal nerve – sensory for taste and touch, pressure, pain from posterior tongue; motor fibers to the swallowing muscles in pharynx; test for gag and swallowing reflex, cough, taste, uvula position

X Vagus nerves – sensory (including aortic arch baroreceptors, respiration) and motor fibers for pharynx, larynx, and viscera (heart rate, breathing, digestive activity); test by gag, swallowing reflexes

XI Accessory nerve – mostly motor fibers to neck and upper back (trapezius, sternocleidomastoid); test for head rotation strength and shrugging against resistance

XII Hypoglossal nerve – mostly motor fibers to tongue allowing food manipulation; test by tongue protraction and retraction)

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Diseases of the Brain

Parkinson's Disease Degeneration of the dopamine-

releasing neurons of the substantia nigra: causes tremors, loss of co-ordination

Huntington's Chorea A fatal hereditary disorder caused by

accumulation of the protein huntingtin that leads to degeneration of the basal nuclei and cerebral cortex: causes jerky movements

Alzheimer's Disease A progressive degenerative disease of

the brain that results in dementia

Traumatic Brain Injuries

Concussion

edema

blood at arrows

7 month old baby having siezures(probably a victim of child abuse)

Cerebral edema Contusion

Cerebrovascular Accident (CVA): Stroke

Computed tomography (CT) scan showinghemhorrage in right thalamus

• Blood circulation is blocked and brain tissue dies, e.g., blockage of a cerebral artery by a blood clot

• Typically leads to hemiplegia, or sensory and speed deficits

Transient ischemic attacks (TIAs)

Temporary episodes of reversible cerebral ischemia

Central Nervous System: The Brain

• Anatomy of the Brain

Cerebral Hemispheres

Diencephalon

Brain Stem

Cerebellum

• Protection of the CNS

Meninges

Cerebrospinal Fluid

Blood-Brain Barrier

Brain Dysfunction