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Chapter 14. The Brain and Cranial Nerves. An Introduction to the Brain and Cranial Nerves. The Adult Human Brain Ranges from 750 cc to 2100 cc Contains almost 97% of the body’s neural tissue Average weight about 1.4 kg (3 lb). The Brain. Six Regions of the Brain Cerebrum Cerebellum

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Chapter 14


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chapter 14

Chapter 14

The Brain and Cranial Nerves

an introduction to the brain and cranial nerves
An Introduction to the Brain and Cranial Nerves
  • The Adult Human Brain
    • Ranges from 750 cc to 2100 cc
    • Contains almost 97% of the body’s neural tissue
    • Average weight about 1.4 kg (3 lb)
the brain
The Brain
  • Six Regions of the Brain
    • Cerebrum
    • Cerebellum
    • Diencephalon
    • Mesencephalon
    • Pons
    • Medulla oblongata
the brain1
The Brain
  • Cerebrum
    • Largest part of brain
    • Controls higher mental functions
    • Divided into left and right cerebral hemispheres
    • Surface layer of gray matter (neural cortex)
the brain2
The Brain
  • Cerebrum
    • Neural cortex
      • Also called cerebral cortex
      • Folded surface increases surface area
      • Elevated ridges (gyri)
      • Shallow depressions (sulci)
      • Deep grooves (fissures)
the brain3
The Brain
  • Cerebellum
    • Second largest part of brain
    • Coordinates repetitive body movements
    • Two hemispheres
    • Covered with cerebellar cortex
the brain4
The Brain
  • Diencephalon
    • Located under cerebrum and cerebellum
    • Links cerebrum with brain stem
    • Three divisions
      • Left thalamus
      • Right thalamus
      • Hypothalamus
the brain5
The Brain
  • Diencephalon
    • Thalamus
      • Relays and processes sensory information
    • Hypothalamus
      • Hormone production
      • Emotion
      • Autonomic function
    • Pituitary gland
      • Major endocrine gland
      • Connected to hypothalamus
      • Via infundibulum (stalk)
      • Interfaces nervous and endocrine systems
the brain6
The Brain
  • The Brain Stem
    • Processes information between
      • Spinal cord and cerebrum or cerebellum
    • Includes
      • Mesencephalon
      • Pons
      • Medulla oblongata
the brain7
The Brain
  • The Brain Stem
    • Mesencephalon
      • Also called midbrain
      • Processes sight, sound, and associated reflexes
      • Maintains consciousness
    • Pons
      • Connects cerebellum to brain stem
      • Is involved in somatic and visceral motor control
the brain8
The Brain
  • The Brain Stem
    • Medulla oblongata
      • Connects brain to spinal cord
      • Relays information
      • Regulates autonomic functions:
        • heart rate, blood pressure, and digestion
the brain9
The Brain

Figure 14–1 An Introduction to Brain Structures and Functions.

the brain10
The Brain
  • Embryological Development
    • Determines organization of brain structures
    • Neural tube
      • Origin of brain
      • Enlarges into three primary brain vesicles
        • prosencephalon
        • mesencephalon
        • rhombencephalon
the brain11
The Brain
  • Five Secondary Brain Vesicles
    • Telencephalon
    • Diencephalon
    • Mesencephalon
    • Metencephalon
    • Myelencephalon
the brain12
The Brain
  • Origins of Brain Structures
  • Diencephalon and mesencephalon persist
    • Telencephalon:
      • Becomes cerebrum
    • Metencephalon
      • Forms cerebellum and pons
    • Myelencephalon
      • Becomes medulla oblongata
the brain14
The Brain
  • Ventricles of the Brain
    • Origins of ventricles
      • Neural tube encloses neurocoel
      • Neurocoel expands to form chambers (ventricles) lined with ependymal cells
    • Each cerebral hemisphere contains one large lateral ventricle
      • Separated by a thin medial partition (septum pellucidum)
the brain15
The Brain
  • Ventricles of the Brain
    • Third ventricle
      • Ventricle of the diencephalon
      • Lateral ventricles communicate with third ventricle:
        • via interventricular foramen (foramen of Monro)
the brain16
The Brain
  • Ventricles of the Brain
    • Fourth ventricle
      • Extends into medulla oblongata
      • Becomes continuous with central canal of the spinal cord
      • Connects with third ventricle:
        • via narrow canal in mesencephalon
        • aqueduct of midbrain
the brain17
The Brain

Figure 14–2 Ventricles of the Brain.

the brain18
The Brain
  • The brain is a large, delicate mass of neural tissue containing internal passageways and chambers filled with cerebrospinal fluid
  • Each of the six major brain regions has specific functions
  • Ascending from the medulla oblongata to the cerebrum, brain functions become more complex and variable
  • Conscious thought and intelligence are produced in the neural cortex of the cerebral hemispheres
brain protection and support
Brain Protection and Support
  • Physical protection
    • Bones of the cranium
    • Cranial meninges
    • Cerebrospinal fluid
  • Biochemical isolation
    • Blood–brain barrier
brain protection and support1
Brain Protection and Support
  • The Cranial Meninges
    • Have three layers:
      • Dura mater
      • Arachnoid mater
      • Pia mater
    • Are continuous with spinal meninges
    • Protect the brain from cranial trauma
brain protection and support2
Brain Protection and Support
  • The Cranial Meninges
    • Dura mater
      • Inner fibrous layer (meningeal layer)
      • Outer fibrous layer (endosteal layer) fused to periosteum
      • Venous sinuses between two layers
    • Arachnoid mater
      • Covers brain
      • Contacts epithelial layer of dura mater
      • Subarachnoid space: between arachnoid mater and pia mater
    • Pia mater
      • Attached to brain surface by astrocytes
brain protection and support3
Brain Protection and Support
  • Dural Folds
    • Folded inner layer of dura mater
    • Extend into cranial cavity
    • Stabilize and support brain
    • Contain collecting veins (dural sinuses)
    • Falx cerebri, tentorium cerebelli, and falx cerebelli
brain protection and support4
Brain Protection and Support
  • Dural Folds
    • Falx cerebri
      • Projects between the cerebral hemispheres
      • Contains superior sagittal sinus and inferior sagittal sinus
    • Tentorium cerebelli
      • Separates cerebellum and cerebrum
      • Contains transverse sinus
    • Falx cerebelli
      • Divides cerebellar hemispheres below the tentorium cerebelli
brain protection and support5
Brain Protection and Support

Figure 14–3a The Relationship among the Brain, Cranium, and Meninges.

brain protection and support6
Brain Protection and Support

Figure 14–3b The Relationship among the Brain, Cranium, and Meninges.

brain protection and support7
Brain Protection and Support
  • Cerebrospinal Fluid (CSF)
    • Surrounds all exposed surfaces of CNS
    • Interchanges with interstitial fluid of brain
    • Functions of CSF
      • Cushions delicate neural structures
      • Supports brain
      • Transports nutrients, chemical messengers, and waste products
brain protection and support8
Brain Protection and Support
  • Cerebrospinal Fluid (CSF)
    • Choroid plexus
      • Specialized ependymal cells and capillaries:
        • secrete CSF into ventricles
        • remove waste products from CSF
        • adjust composition of CSF
      • Produces about 500 mL of CSF/day
brain protection and support9
Brain Protection and Support
  • Cerebrospinal Fluid (CSF)
    • CSF circulates
      • From choroid plexus
      • Through ventricles
      • To central canal of spinal cord
      • Into subarachnoid spacearound the brain, spinal cord, and cauda equina
brain protection and support10
Brain Protection and Support
  • Cerebrospinal Fluid (CSF)
    • CSF in subarachnoid space
      • Arachnoid villi:
        • extensions of subarachnoid space
        • extend through dura mater to superior sagittal sinus
      • Arachnoid granulations:
        • large clusters of villi
        • absorb CSF into venous circulation
brain protection and support11
Brain Protection and Support

Figure 14–4 The Formation and Circulation of Cerebrospinal Fluid.

brain protection and support12
Brain Protection and Support

Figure 14–4a The Formation and Circulation of Cerebrospinal Fluid.

brain protection and support13
Brain Protection and Support

Figure 14–4b The Formation and Circulation of Cerebrospinal Fluid.

brain protection and support14
Brain Protection and Support
  • Blood Supply to the Brain
    • Supplies nutrients and oxygen to brain
    • Delivered by internal carotidarteries and vertebral arteries
    • Removed from dural sinuses by internal jugular veins
brain protection and support15
Brain Protection and Support

Figure 21–22 Arteries of the Neck and Head.

brain protection and support16
Brain Protection and Support

Figure 21–23 Arteries of the Brain.

brain protection and support17
Brain Protection and Support

Figure 21–28 Major Veins of the Head, Neck, and Brain.

brain protection and support18
Brain Protection and Support

Figure 21–28 Major Veins of the Head, Neck, and Brain.

brain protection and support19
Brain Protection and Support
  • Cerebrovascular Disease
    • Disorders interfere with blood circulation to brain
    • Stroke or cerebrovascular accident (CVA)
      • Shuts off blood to portion of brain
      • Neurons die
brain protection and support20
Brain Protection and Support
  • Blood–Brain Barrier
    • Isolates CNS neural tissue from general circulation
    • Formed by network of tight junctions
    • Between endothelial cells of CNS capillaries
    • Lipid-soluble compounds (O2, CO2), steroids, and prostaglandins diffuse into interstitial fluid of brain and spinal cord
    • Astrocytes control blood–brain barrier by releasing chemicals that control permeability of endothelium
brain protection and support21
Brain Protection and Support
  • Blood–CSF Barrier
    • Formed by special ependymal cells
    • Surround capillaries of choroid plexus
    • Limits movement of compounds transferred
    • Allows chemical composition of blood and CSF to differ
brain protection and support22
Brain Protection and Support
  • Four Breaks in the BBB
    • Portions of hypothalamus
      • Secrete hypothalamic hormones
    • Posterior lobe of pituitary gland
      • Secretes hormones ADH and oxytocin
    • Pineal glands
      • Pineal secretions
    • Choroid plexus
      • Where special ependymal cells maintain blood–CSF barrier
brain protection and support23
Brain Protection and Support
  • Meninges stabilize brain in cranial cavity
  • Cerebrospinal fluid protects against sudden movement
  • CSF provides nutrients and removes wastes
  • Blood–brain barrier and blood–CSF barrier
    • Selectively isolate brain from chemicals in blood that might disrupt neural function
the medulla oblongata
The Medulla Oblongata
  • The Medulla Oblongata
    • Allows brain and spinal cord to communicate
    • Coordinates complex autonomic reflexes
    • Controls visceral functions
    • Nuclei in the Medulla
      • Autonomic nuclei: control visceral activities
      • Sensory and motor nuclei: of cranial nerves
      • Relay stations: along sensory and motor pathways
the medulla oblongata1
The Medulla Oblongata

Figure 14–5a The Diencephalon and Brain Stem.

the medulla oblongata2
The Medulla Oblongata

Figure 14–5b The Diencephalon and Brain Stem.

the medulla oblongata3
The Medulla Oblongata

Figure 14–5c The Diencephalon and Brain Stem.

the medulla oblongata4
The Medulla Oblongata
  • The Medulla Oblongata
    • Includes three groups of nuclei
      • Autonomic nuclei
      • Sensory and motor nuclei of cranial nerves
      • Relay stations along sensory and motor pathways
the medulla oblongata5
The Medulla Oblongata
  • Autonomic Nuclei of the Medulla Oblongata
    • Reticular formation
      • Gray matter with embedded nuclei
      • Regulates autonomic functions
    • Reflex centers
      • Control peripheral systems:
        • cardiovascular centers:
          • cardiac center
          • control blood flow through peripheral tissues
        • respiratory rhythmicity centers

sets pace for respiratory movements

the medulla oblongata6
The Medulla Oblongata
  • Sensory and Motor Nuclei of the Medulla Oblongata
      • Associated with 5 of 12 cranial nerves (VIII, IX, X, XI, XII)
the medulla oblongata7
The Medulla Oblongata
  • Relay Stations of the Medulla Oblongata
    • Nucleus gracilis and nucleus cuneatus
      • Pass somatic sensory information to thalamus
    • Solitary nucleus
      • Receives visceral sensory information
    • Olivary nuclei (olives)
      • Relay information about somatic motor commands
the medulla oblongata8
The Medulla Oblongata

Figure 14–6a The Medulla Oblongata and Pons.

the medulla oblongata9
The Medulla Oblongata

Figure 14–6b The Medulla Oblongata and Pons.

the pons
The Pons
  • The Pons
    • Links cerebellum with mesencephalon, diencephalon, cerebrum, and spinal cord
    • Sensory and motor nuclei of cranial nerves V, VI, VII, VIII
the pons1
The Pons
  • The Pons
    • Nuclei involved with respiration
      • Apneustic center and pneumotaxic center:
        • modify respiratory rhythmicity center activity
    • Nuclei and tracts
      • Process and relay information to and from cerebellum
      • Ascending, descending, and transverse tracts:
        • transverse fibers (axons):
          • link nuclei of pons with opposite cerebellar hemisphere
the pons2
The Pons

Figure 14–6a The Medulla Oblongata and Pons.

the pons3
The Pons

Figure 14–6b The Medulla Oblongata and Pons.

the pons4
The Pons

Figure 14–6c The Medulla Oblongata and Pons.

the cerebellum
The Cerebellum
  • Functions of the Cerebellum
    • Adjusts postural muscles
    • Fine-tunes conscious and subconscious movements
the cerebellum1
The Cerebellum
  • Structures of the Cerebellum
    • Folia
      • Surface of cerebellum
      • Highly folded neural cortex
    • Anterior and posterior lobes
      • Separated by primary fissure
    • Cerebellar hemispheres:
      • Separated at midline by vermis
    • Vermis
      • Narrow band of cortex
    • Flocculonodular lobe
      • Below fourth ventricle
the cerebellum2
The Cerebellum
  • Structures of the Cerebellum
    • Purkinje cells
      • Large, branched cells
      • Found in cerebellar cortex
      • Receive input from up to 200,000 synapses
    • Arbor vitae
      • Highly branched, internal white matter of cerebellum
      • Cerebellar nuclei: embedded in arbor vitae:
        • relay information to Purkinje cells
the cerebellum3
The Cerebellum
  • Structures of the Cerebellum
    • The peduncles
      • Tracts link cerebellum with brain stem, cerebrum, and spinal cord:
        • superior cerebellar peduncles
        • middle cerebellar peduncles
        • inferior cerebellar peduncles
the cerebellum4
The Cerebellum
  • Disorders of the Cerebellum
    • Ataxia
      • Damage from trauma or stroke
      • Intoxication (temporary impairment)
      • Disturbs muscle coordination
the cerebellum5
The Cerebellum

Figure 14–7a The Cerebellum.

the cerebellum6
The Cerebellum

Figure 14–7b The Cerebellum.

the mesencephalon
The Mesencephalon
  • Structures of the Mesencephalon
    • Tectum
      • Two pairs of sensory nuclei (corpora quadrigemina):
        • superior colliculus (visual)
        • inferior colliculus (auditory)
    • Tegmentum
      • Red nucleus (many blood vessels)
      • Substantia nigra (pigmented gray matter)
the mesencephalon1
The Mesencephalon
  • Structures of the Mesencephalon
    • Cerebral peduncles
      • Nerve fiber bundles on ventrolateral surfaces
      • Contain:
        • descending fibers to cerebellum
        • motor command fibers
the mesencephalon2
The Mesencephalon

Figure 14–8a The Mesencephalon.

the mesencephalon3
The Mesencephalon

Figure 14–8b The Mesencephalon.

the diencephalon
The Diencephalon
  • Integrates sensory information and motor commands
  • Thalamus, epithalamus, and hypothalamus
    • The pineal gland
      • Found in posterior epithalamus
      • Secretes hormone melatonin
the diencephalon1
The Diencephalon
  • The Thalamus
    • Filters ascending sensory information for primary sensory cortex
    • Relays information between basal nuclei and cerebral cortex
    • The third ventricle
      • Separates left thalamus and right thalamus
      • Interthalamic adhesion (or intermediate mass):
        • projection of gray matter
        • extends into ventricle from each side
the diencephalon2
The Diencephalon
  • The Thalamus
    • Thalamic nuclei
      • Are rounded masses that form thalamus
      • Relay sensory information to basal nuclei and cerebral cortex
the diencephalon3
The Diencephalon
  • Five Groups of Thalamic Nuclei
    • Anterior group
      • Anterior nuclei
      • Part of limbic system (emotions)
    • Medial group
      • Provides awareness of emotional states
    • Ventral group
      • Relays sensory information
the diencephalon4
The Diencephalon
  • Five Groups of Thalamic Nuclei
    • Posterior group
      • Pulvinar nucleus (sensory)
      • Lateral geniculate nucleus (visual)
      • Medial geniculate nucleus (auditory)
    • Lateral group
      • Affects emotional states
      • Integrates sensory information
the diencephalon5
The Diencephalon

Figure 14–9 The Thalamus.

the diencephalon6
The Diencephalon

Figure 14–9a The Thalamus.

the diencephalon7
The Diencephalon

Figure 14–9b The Thalamus.

the diencephalon8
The Diencephalon

[INSERT Table. 14.5]

the diencephalon9
The Diencephalon
  • The Hypothalamus
    • Mamillary bodies
      • Process olfactory and other sensory information
      • Control reflex eating movements
    • Infundibulum
      • A narrow stalk
      • Connects hypothalamus to pituitary gland
    • Tuberal area
      • Located between the infundibulum and mamillary bodies
      • Helps control pituitary gland function
the diencephalon10
The Diencephalon

Figure 14–10a The Hypothalamus in Sagittal Section.

the diencephalon11
The Diencephalon

Figure 14–10b The Hypothalamus in Sagittal Section.

the diencephalon12
The Diencephalon
  • Eight Functions of the Hypothalamus
    • Provides subconscious control of skeletal muscle
    • Controls autonomic function
    • Coordinates activities of nervous and endocrine systems
    • Secretes hormones
      • Antidiuretic hormone (ADH) by supraoptic nucleus
      • Oxytocin (OT; OXT) by paraventricular nucleus
the diencephalon13
The Diencephalon
  • Eight Functions of the Hypothalamus
    • Produces emotions and behavioral drives
      • The feeding center (hunger)
      • The thirst center (thirst)
    • Coordinates voluntary and autonomic functions
    • Regulates body temperature
      • Preoptic area of hypothalamus
    • Controls circadian rhythms (day–night cycles)
      • Suprachiasmatic nucleus