BIOLOGY 2401 ANATOMY

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BIOLOGY 2401ANATOMY PHYSIOLOGYPART ICHAPTER
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• The Brain and the Cranial Nerves

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REGIONS AND ORGANIZATION OF THE BRAIN

• The basic parts of the brain are as follows
• The cerebrum
• The diencephalon
• The brain stem
• The cerebellum
• The brain is organized into groupings of cell
  bodies (the gray matter) and fibers (the white
  matter).
• The cerebrum the cerebellum contain gray matter
  on the outer edges w/white matter below this
  surface.
• While the diencephalon brain stem are filled
  with internal pockets of gray matter w/white
  matter around them

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THE CEREBRAL HEMISPHERES

• More than 80 of brains weight is the cerebrum.
• The cerebrum is divided into different regions by
  fissures sulci (singular, sulcus)
• The upfoldings are called gyri.
• There are four major lobes or areas on each
  hemisphere
• The frontal lobe
• The parietal lobe
• The occipital lobe
• The temporal lobe

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VIEW OF THE CEREBRUM
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Other parts

• The diencephalon
• The thalamus
• The hypothalamus
• The epithalamus
• The brain stem
• The midbrain
• The pons
• The medulla oblongata
• The cerebellum

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PROTECTION OF THE BRAIN

• The brain spinal cord are a very delicate set
  of organs which are easily damaged by pressure or
  blows.
• The CNS is protected by a set of structures
• The cranium spinal column vertebrae
• The meninges
• The cerebrospinal fluid
• The blood brain barrier

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THE MENINGES

• The meninges are a set of 3 connective tissue
  layers that surround the brain and spinal cord.
• The dura mater toughest outermost
• The arachnoid mater middle layer containing
  most major blood vessels and cerebrospinal fluid.
• The pia mater inner most layer with fine blood
  vessels.

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VIEW OF THE MENINGES
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CEREBROSPINAL FLUID

• CSF is found within and all around the brain to
  protect it and make it more buoyant.
• CSF is produced from blood plasma.

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VENTRICLES OF THE BRAIN
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CRANIAL NERVES

• 12 major nerves leave the brain before the spinal
  cord
• These are part of the Peripheral Nervous System
  (PNS)
• They are numbered I-XII

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CRANIAL NERVES

• I. Olfactory
• II. Optic
• III. Oculomotor
• IV. Trochlear
• V. Trigeminal
• Ophthalmic
• Maxillary
• Mandibular
• VI. Abducens

• VII. Facial
• VIII. Vestibulocochlear
• IX. Glossopharyngeal
• X. Vagus
• XI. Accessory
• XII. Hypoglossal

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Cranial Nerve I Olfactory

• Functions solely by carrying afferent impulses
  for the sense of smell

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Cranial Nerve II Optic

• Arises from the retina of the eye
• Functions solely for vision
• Exits through optic canal

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Cranial Nerve III Oculomotor

• Functions in raising the eyelid, directing the
  eyeball, constricting the iris, and controlling
  lens shape
• Exits through superior orbital fissure

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Cranial Nerve IV Trochlear

• Primarily a motor nerve that directs the eyeball,
  
• Exits through the superior orbital fissure

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Cranial Nerve V Trigeminal

• Composed of 3 divisions ophthalmic (V1),
  maxillary (V2), and mandibular (V3)
• Fibers run via the superior orbital fissure (V1),
  the foramen rotundum (V2), and the foramen ovale
  (V3)
• Conveys sensory impulses from various areas of
  the face (V1) and (V2), and supplies motor fibers
  (V3) for mastication

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Cranial Nerve V Trigeminal
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Cranial Nerve VI Abducens

• Fibers enter the orbit via the superior orbital
  fissure
• Primarily a motor nerve innervating the lateral
  rectus muscle (abducts the eye)
• Exits through the superior orbital fissure

Figure VI from Table 13.2
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Cranial Nerve VII Facial

• Motor functions include facial expression, and
  the transmittal of autonomic impulses to lacrimal
  and salivary glands
• Sensory function is taste from the anterior
  two-thirds of the tongue
• Exits through the internal acoustic meatus and
  the stylomastoid foramen

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Cranial Nerve VII Facial
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Cranial Nerve VIII Vestibulocochlear

• Sensory fibers arise from the hearing and
  equilibrium apparatus of the inner ear
• Two divisions cochlear (hearing) and vestibular
  (balance)
• Exits through the internal acoustic meatus

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Cranial Nerve IX Glossopharyngeal

• Mixed nerve with motor sensory functions
• Motor innervates part of tongue pharynx, and
  provides motor fibers to the parotid salivary
  gland
• Sensory fibers conduct taste and general
  sensory impulses from the tongue and pharynx
• Exits through the jugular foramen

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Cranial Nerve X Vagus

• The only cranial nerve that extends beyond the
  head and neck the wanderer
• The vagus is a mixed nerve
• Most motor fibers are parasympathetic fibers to
  the heart, lungs, and visceral organs
• Its sensory function is in taste
• Exits through the jugular foramen

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Cranial Nerve X Vagus
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Cranial Nerve XI Accessory

• Primarily a motor nerve
• Supplies fibers to the larynx, pharynx, soft
  palate
• Innervates the trapezius and sternocleidomastoid,
  which move the head and neck
• Exits through the jugular foramen

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Cranial Nerve XI Accessory
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Cranial Nerve XII Hypoglossal

• Innervates muscles of the tongue, which
  contribute to swallowing and speech
• Exits through the hypoglossal canal

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Practice Questions
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• Which of the following cranial nerves is not
  involved with the eye?   
• Oculomotor 
• Trochlear 
• Optic 
• Abducens 
• Trigeminal

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• Which of the following cranial nerves is purely
  sensory?   
• Accessory 
• Vagus 
• Trigeminal 
• Optic 
• Hypoglossal

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• Which of the following cranial nerves has a name
  that means "the wanderer"?   
• Vestibulocochlear 
• Glossopharyngeal 
• Trochlear 
• Trigeminal 
• Vagus

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• Cranial nerves are formed by fusion of sensory
  and motor roots.  True False

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•  Nerves are either sensory or motor but not
  both.  True False

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• The cranial nerves serve structures only in the
  head and neck.  True False