Central Nervous System: The Brain

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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

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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)

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Cerebral hemisphere
Diencephalon
Cerebellum
Brain stem
Midbrain
Pons
Medullaoblongata

(d) Birth
Figure 12.3d
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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)

Longitudinal fissure
Transverse cerebral fissure

• Fissures divide cerebrum into lobes
• Frontal lobe
• Parietal lobe
• Occipital lobe
• Temporal lobe

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Anterior
Longitudinal fissure
Frontal lobe
Central sulcus
Cerebral veins and arteries covered
by arachnoid mater
Parietal lobe
Right cerebral hemisphere
Left cerebral hemisphere
Occipital lobe
Posterior
(c)
Figure 12.6c
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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

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Motor Areas

• Primary (somatic) motor cortex
• Allows conscious control of precise, skilled,
  voluntary movements
• Other motor areas include the Brocas area
  (speech) and the frontal eye field (vision)

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Motor areas in red/orange
Sensory areas and related association areas
Central sulcus
Primary motor cortex
Primary somatosensory cortex
Somatic sensation
Somatosensory association cortex
Gustatory cortex (in insula)
Taste
Prefrontal cortex
Wernickes area (outlined by dashes)
Working memory for spatial tasks
Executive area for task management
Primary visual cortex
Working memory for object-recall tasks
Vision
Visual association area
Solving complex, multitask problems
Auditory association area
Hearing
Primary auditory cortex
(a) Lateral view, left cerebral hemisphere
Motor association cortex
Primary sensory cortex
Primary motor cortex
Sensory association cortex
Multimodal association cortex
Figure 12.8a
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Sensory Areas

• Primary somatosensory cortex
• Somatosensory association cortex
• Visual areas
• Auditory areas

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Motor and Sensory Areas of the Cerebral Cortex
Homunculous Diagrams
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Motor areas in red/orange
Sensory areas and related association areas
Central sulcus
Primary motor cortex
Primary somatosensory cortex
Somatic sensation
Somatosensory association cortex
Gustatory cortex (in insula)
Taste
Prefrontal cortex
Wernickes area (outlined by dashes) handles
articulation of unfamiliar words
Working memory for spatial tasks
Executive area for task management
Primary visual cortex
Working memory for object-recall tasks
Vision
Visual association area
Solving complex, multitask problems
Brocas Area effects how words are articulated in
speech (left lob only)
Auditory association area
Hearing
Primary auditory cortex
(a) Lateral view, left cerebral hemisphere
Motor association cortex
Primary sensory cortex
Primary motor cortex
Sensory association cortex
Multimodal association cortex
Left cerebral hemisphere is the language
brain Right cerebral hemisphere is the
abstract, conceptual, and spatial brain
Figure 12.8a
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Motor and Sensory Areas of the Cerebral Cortex
Homunculous Diagrams
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Association fibers (interneurons) connect regions
of the same hemisphere together (white matter)
Commissural fibers connect the two hemispheres to
each other
Cerebral hemisphere
Projection fibers connect the cortex to lower
brain structures and the spinal cord, eg.
afferent and efferent tracts.
Interthalamic adhesion (intermediate mass of
thalamus)
Corpus callosum
Posterior commissure
Anterior commissure
Pituitary gland
Medulla oblongata
Spinal cord
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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)
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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

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Cortex of gray matter
Central cavity
Migratory pattern of neurons
Inner gray matter
Outer white matter
Cerebrum
Cerebellum
Gray matter
Region of cerebellum
Central cavity
Inner gray matter
Outer white matter
Gray matter
Brain stem
Central cavity
Outer white matter
Inner gray matter
Spinal cord
Figure 12.4
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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

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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

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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

• Epithalamus
• Forms the roof of the third ventricle
• Houses the pineal body (an endocrine gland)
• Includes the choroid plexus forms cerebrospinal
  fluid

• Hypothalamus
• Under the thalamus
• Important autonomic nervous system center
• Helps regulate body temperature
• Controls water balance
• Regulates metabolism
• An important part of the limbic system (thirst,
  appetite, sex, pain, pleasure)
• The pituitary gland is attached to the
  hypothalamus

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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

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Brain Stem

• Routing for ascending and descending tracts
  and basal nuclei for cranial nerves controlling
  breathing and blood pressure

• 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)

Midbrain

• 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)

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Crus cerebri of cerebral peduncles (midbrain)
Thalamus
View (b)
Infundibulum
Superior colliculus
Pituitary gland
Inferior colliculus
Trochlear nerve (IV)
Trigeminal nerve (V)
Superior cerebellar peduncle
Pons
Middle cerebellar peduncle
Facial nerve (VII)
Inferior cerebellar peduncle
Abducens nerve (VI)
Vestibulocochlear nerve (VIII)
Glossopharyngeal nerve (IX)
Olive
Hypoglossal nerve (XII)
Thalamus
Vagus nerve (X)
Diencephalon
Hypothalamus
Midbrain
Accessory nerve (XI)
Pons
Brainstem
Medulla oblongata
(b) Left lateral view
Figure 12.15b
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Frontal lobe
Olfactory bulb (synapse point of cranial nerve I)
Optic chiasma
Optic nerve (II)
Optic tract
Mammillary body
Midbrain
Pons
Temporal lobe
Medulla oblongata
Cerebellum
Spinal cord
Figure 12.14
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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

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

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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

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Meninges Dura mater, arachnoid, pia mater
periosteal layer meningeal layer
Subarachnoid space with CSF
Falx cerebri
dura mater "tough mother" archnoid
"spidery" pia mater "delicate mother"
Singular menix Plural meninges
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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

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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

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Ventricles of the Brain
Lateral ventricle
Septum pellucidum
Anterior horn
Posterior horn
Inferior horn
Interventricular foramen
Lateral aperture
Median aperture
Third ventricle
Inferior horn
Lateral aperture
Cerebral aqueduct
Fourth ventricle
Central canal
(b) Left lateral view
(a) Anterior view
Figure 12.5
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Ventricles and Location of the Cerebrospinal Fluid
Interventricular foramen
Medial aperture (of Magendie) and lateral
apertures to subarachnoid space
Cerebralspinal fluid flow movie
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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

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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

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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 patients 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
• Mandibular (test by teeth clenching, move jaw)
  carrying sensory from lower teeth, masseter,
  temporalis

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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

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Traumatic Brain Injuries

• Concussion

• Cerebral edema

• Contusion

edema
blood at arrows
7 month old baby having siezures (probably a
victim of child abuse)
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Cerebrovascular Accident (CVA) Stroke

• 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

Computed tomography (CT) scan showing hemhorrage
in right thalamus
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Transient ischemic attacks (TIAs)
Temporary episodes of reversible cerebral ischemia
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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