The Brain and Cranial Nerves
An Introduction to the Organization of the
Brain
Major regions and landmarks
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Six regions in the adult brain
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Cerebrum
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Diencephalon
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Mesencephalon
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Pons
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Cerebellum
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Medulla oblongata
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Brain contains extensive areas of neural cortex
• Layer
of gray matter on the surface of the cerebellum and cerebrum
Embryology of the brain
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Brain forms from three swellings at the tip of the
developing neural tube
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Prosencephalon
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Forms the telencephalon and eventually the cerebrum and
diencephalon
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Mesencephalon
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Rhombencephalon
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Forms the metencephalon (cerebellum and pons) and
myelencephalon (medulla oblongata)
Ventricles of the brain
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Central passageway of the brain enlarges to form
ventricles
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Contain cerebrospinal fluid (CSF)
Protection and Support of the Brain
The cranial meninges
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Continuous with the three layers of the spinal cord
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Folds of dura mater help stabilize the position of the
brain
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Falx cerebri
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Tentorium cerebelli
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Falx cerebelli
Cerebrospinal fluid (CSF)
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CSF cushions delicate neural structures
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Supports the brain
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Transports nutrients, chemical messengers, and waste
products
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Pathway of CSF
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Produced at the Choroid plexus,
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Travels through the lateral and medial apertures to the
subarachnoid space,
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Diffuses across the arachnoid granulations into the
superior sagittal sinus
Blood supply to the brain
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Blood brain barrier isolates neural tissue from general
circulation
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Incomplete barrier in areas
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Parts of the hypothalamus
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Pituitary gland
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Pineal gland
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Choroid plexus
The Medulla Oblongata
Medulla oblongata
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Connects the brain with the spinal cord
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Contains relay stations and reflex centers
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Olivary nuclei
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Cardiovascular and respiratory rhythmicity centers
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Reticular formation begins in the medulla oblongata and
extends into more superior portions of the brainstem
The Pons
The pons contains
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Sensory and motor nuclei for four cranial nerves
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Nuclei that help control respiration
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Nuclei and tracts linking the cerebellum with the brain
stem, cerebrum and spinal cord
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Ascending, descending and transverse tracts
The Cerebellum
The cerebellum
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Adjusts postural muscles and tunes on-going movements
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Cerebellar hemispheres
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Anterior and posterior lobes
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Vermis
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Flocculonodular lobe
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Superior, middle and inferior cerebellar peduncles link
cerebellum with brain stem, diencephalon, cerebrum, and spinal cord
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Interconnects the two cerebellar hemispheres
The Mesencephalon
The mesencephalon
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The tectum (roof) contains the corpora quadrigemina
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Superior and
inferior colliculi
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The mesencephalon contains many nuclei
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Red nucleus
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Substantia nigra
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Cerebral peduncles
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RAS headquarters
The Diencephalon
The diencephalon is composed of
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Epithalamus
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Hypothalamus
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Thalamus
The thalamus
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Final relay point for ascending sensory information
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Coordinates the activities of the cerebral cortex and
basal nuclei
The hypothalamus
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Controls somatic motor activities at the subconscious
level
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Controls autonomic function
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Coordinates activities of the endocrine and nervous
systems
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Secretes hormones
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Produces emotions and behavioral drives
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Coordinates voluntary and autonomic functions
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Regulates body temperature
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Coordinates circadian cycles of activity
The Limbic System
The limbic system or motivational system includes
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Amygdaloid body
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Cingulated gyrus
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Parahippocampal gyrus
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Hippocampus
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Fornix
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Functions of the limbic system involved emotions and
behavioral drives
The Cerebrum
The cerebral cortex
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Surface contains gyri and sulci or fissures
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Longitudinal fissure separates two cerebral hemispheres
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Central sulcus separates frontal and parietal lobes
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Temporal and occipital lobes also bounded by sulci
White matter of the cerebrum
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Contains association fibers
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Commissural fibers
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Projection fibers
The basal nuclei
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Caudate nucleus
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Globus pallidus
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Putamen
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Control muscle tone and coordinate learned movement
patterns
Motor and sensory areas of the cortex
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Primary motor cortex of the precentral gyrus directs
voluntary movements
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Primary sensory cortex of the postcentral gyrus
receives somatic sensory information
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Touch
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Pressure
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Pain
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Taste
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Temperature
Association areas
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Control our ability to understand sensory information
and coordinate a response
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Somatic sensory association area
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Visual association area
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Somatic motor association area
general interpretive and speech areas
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General interpretive area
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Receives information from all sensory areas
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Present only in left hemisphere
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Speech center
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Regulates patterns of breathing and vocalization
cortex functions and hemispheric differences
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Prefrontal cortex
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Coordinates information from secondary and special
association areas
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Performs abstract intellectual functions
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Hemispheric differences
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Left hemisphere typically contains general interpretive
and speech centers and is responsible for language based skills
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Right hemisphere is typically responsible for spatial
relationships and analyses
Electroencephalogram (EEG)
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Measures brain activity
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Alpha waves = healthy resting adult
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Beta waves = concentrating adult
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Theta waves = normal children
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Delta waves = normal during sleep
Focus: Cranial Nerves
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12 pairs of cranial nerves
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Each attaches to the ventrolateral surface of the
brainstem near the associated sensory or motor nuclei
The
Brain and Cranial Nerves
Olfactory nerves (I)
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Carry sensory information responsible for the sense of
smell
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Synapse within the olfactory bulb
cranial nerves II, III, IV
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Optic nerves (II)
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Carry visual information from special sensory receptors
in the eyes
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Occulomotor nerves (III)
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Primary source of innervation for 4 of the extraocular
muscles
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Trochlear nerves (IV)
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Innervate the superior oblique muscles
cranial nerves V, VI, VII
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Trigeminal nerves (V)
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Missed nerves with ophthalmic, maxillary and mandibular
branches
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Abducens nerve (VI)
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Innervates the lateral rectus muscles
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Facial nerves (VII)
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Mixed nerves that control muscles of the face and scalp
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Provide pressure sensations over the face
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Receive taste information from the tongue
cranial nerves VIII, IX
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Vestibulocochlear nerves (VIII)
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Vestibular branch monitors balance, position and
movement
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Cochlear branch monitors hearing
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Glossopharyngeal nerves (IX)
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Mixed nerves that innervate the tongue and pharynx
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Control the action of swallowing
cranial nerves X
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Vagus nerves (X)
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Mixed nerves
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Vital to the autonomic control of visceral function
cranial nerves XI, XII
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Accessory nerves (XI)
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Internal branches
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Innervate voluntary swallowing muscles of the soft
palate and pharynx
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External branches
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Control muscles associates with the pectoral girdle
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Hypoglossal nerves (XII)
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Provide voluntary motor control over tongue movement
Cranial Reflexes
Cranial reflexes
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Involve sensory and motor fibers of cranial nerves