Brain and Cranial Nerves

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Brain and Cranial Nerves

• Bio 40B
• Dr. Kandula

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Brain

• Part of CNS
• Found in dorsal body cavity
• Continuous with spinal cord at foramen magnum
• The development and uniqueness of brain makes
  humans superior to other animals

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Brain

• Enclosed and protected by the cranium and
  three membranes called meninges
• Dura Mater
• Arachnoid Mater
• Pia Mater

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Meninges of Brain
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Meninges

• Three membranes that surround and protect the
  brain
• Dura mater
• outermost tough fibrous membrane
• Made up of 2 layers outer periosteal layer is
  attached to cranium inner layer surrounds brain

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Meninges of the Brain

• There are 3 inward folds of dura mater
• Falx cerebri Goes into longitudinal fissure
  separating two cerebral hemispheres
• Falx cerebelli Separates the 2 hemispheres of
  cerebellum
• Tentorium cerebelli Separates cerebrum from
  cerebellum

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Meninges

• Arachnoid lies deep to dura mater and is
  separated from it by subdural space, this space
  contains small amounts of interstitial fluid. The
  arachnoid is an avascular layer.
• Pia mater lies deep to the arachnoid layer and is
  separated from it by the subarachnoid space. The
  subarachnoid space contains cerebrospinal fluid.
  The pia mater is tightly attached to surface of
  brain.

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Brain

• Made up of 4 parts
• The four parts include
• cerebral hemispheres,
• diencephalon,
• brainstem and
• cerebellum.

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Sectional view of Brain
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Brain

• In humans the cerebrum is the most prominent part
  and makes up 70 of the brain

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Cerebrum

• Separated into two hemispheres by longitudinal
  fissure
• Falx cerebri found in fissure
• Corpus callosum (white matter fibers) connects
  two hemispheres at base of fissure

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Cerebrum

• Gyri (pl) or gyrus (sing) are ridges
• Sulci (pl) or sulcus (sing) are shallow grooves
• central sulcus,
• parieto-occipital sulcus,
• lateral sulcus
• Fissures are deeper grooves
• longitudinal fissure
• transverse fissure

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Superior view of Brain
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Cerebrum

• Cortex Thin outer edge of gray matter (neuron
  cell bodies)
• Thick central core of white matter (axons)
• Four lobes
• Parietal receives sensory info
• Frontal voluntary motor
• Occipital vision
• temporal hearing, taste

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Cerebrum

• Important gyri
• Precentral gyrus primary motor area, ie. all
  impulses for voluntary muscular activities
  originate here.
• Postcentral gyrus primary sensory area, ie.,
  all general senses information perceived here

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Functional areas to know Primary motor, primary
somatosensory, somatosensory association, vision,
hearing
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Diencephalon and Brain stem
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Diencephalon

• Thalamus
• Mostly gray matter
• Relays sensory info to cerebrum
• Hypothalamus
• master gland of body
• Controls hormones, temp, emotion, thirst
• Maintains homeostasis
• Controls ANS functions
• 3. Epithalamus has pineal gland to control
  day/night cycles.

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Brain Stem

• Medulla oblongata
• White matter of motor and sensory neurons
• This is where neurons cross to opposite side of
  body - pyramids
• Breathing and heart control
• Pons meansbridge
• Bridge between medulla and midbrain
• Also contains breathing center/helps regulate
  breathing
• Midbrain
• Corpora quadrigemina,( superior and inferior
  colliculi) controls reflexes associated with
  hearing and vision
• cerebral aqueduct (with CSF)

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Cerebellum
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Cerebellum

• Also has 2 hemispheres connected by a body called
  vermis
• Function coordination, balance and equilibrium
• Folds of gray matter? folia
• White matter arrangement characteristic and
  called arbor vitae

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Cerebrospinal Fluid (CSF)

• Function cushion/protect brain and spinal cord
• Made by the ependymal cells of choroid plexuses
  (small capillaries in the ventricles)
• Circulates through subarachoid space and the four
  ventricles
• Finally, CSF drains out the arachnoid villi back
  into the blood circulation

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Circulation of CSF
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4 Ventricles of brain with cerebrospinal fluid
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Circulation of CSF

• Lateral ventricles ? foramen of Munro ? third
  ventricle ? cerebral aqueduct ? fourth ventricle
  ? central canal of spinal cord or
• subarachnoid space surrounding brain and
  spinal cord

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Cranial nerves
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Cranial nerves

• Part of the peripheral nervous system
• 12 pairs that mostly control head and neck
• Nerves contain motor neurons, sensory neurons, or
  mixed
• See handout

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Number Name Innervation Type Function
I Olfactory Temporal lobe of brain sensory Smell
II Optic Occipital lobe of brain sensory Vision
III Occulomotor Eye muscles and ciliary body mixed Movement of eyeball
IV Trochlear Superior oblique muscle of eye mixed Movement of eyeball
V Trigeminal touchpaintemperature to the face motor division of the nerve supplies the muscles of mastication mixed Touch on face mastication
VI Abducens supply a muscle called the lateral rectus muscle that moves the eye outward. mixed Movement of eyeball
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Number Name Innervation Type Action
VII Facial motor portion supplies all the facial musculature/ sensory portion, taste to the anterior two-thirds of the tongue secretory to the lacrimal gland and salivary glands mixed facial musculature, taste, and tears saliva secretion
VIII Auditory Temporal lobe of brain sensory Hearing and equilibrium
IX Glossopharyngeal Pharynx, tongue and salivary glands mixed TASTE POSTERIOR 1/3 TONGUE, SALIVATION, SWALLOWING
X Vagus Pharynx heart, respiratory tract, GIT, mixed GASTRIC PANCREATIC SECRETIONS, GI MOVEMENT, CARDIAC, RESPIRATORY AND VISCERAL REFLEX
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Number Name Innervation Type Action
XI Spinal Accessory Muscles of neck and shoulder mixed MUSCLE MOVEMENT (sternocleidomastoid, trapezius) AND VISCERAL REFLEX
XII Hypoglossal Tongue muscles mixed Tongue movement