Chapter 12 cont

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Chapter 12 (cont)
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Diencephalon

• 3. Hypothalamus
• Autonomic control center
• Body temperature regulation
• Regulates feelings of hunger and satiety
• Regulates sleep and the sleep cycle
• Involved with perception of pleasure, fear, rage

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Hypothalamus

• Regulates water balance
• Produces ADH and oxytocin
• Releases hormones that controls secretion of
  hormones by the anterior pituitary

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Brain Stem

• Consists of 3 regions midbrain, pons, and
  medulla oblongata
• Controls automatic behaviors necessary for
  survival
• Provides the pathway for tracts between higher
  and lower neuro centers
• Associated with 10 of the 12 pairs (III-XII) of
  cranial nerves

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Brain Stem Midbrain

• Located between the diencephalon and the pons
• Midbrain structures include
• Cerebral peduncles two bulging structures that
  contain descending motor tracts
• Various nuclei
• Corpora quadrigemina
• Visual reflex cneter
• Startle reflex
• Red nucleus

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Midbrain Nuclei

• Corpora quadrigemina four domelike protrusions
  of the dorsal midbrain
• Superior colliculi visual reflex centers
• Inferior colliculi auditory relay centers
• Nuclei that control cranial nerves III
  (oculomotor) and IV (trochlear)
• Red nucleus largest nucleus of the reticular
  formation red nuclei are relay nuclei for some
  descending motor pathways

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Brain Stem Pons

• Bulging brainstem region between the midbrain and
  the medulla oblongata
• Forms part of the anterior wall of the fourth
  ventricle
• Fibers of the pons
• Connect higher brain centers and lower brain
  centers
• Relay impulses between the motor cortex and the
  cerebellum
• Nuclei

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Brain Stem Pons

• Origin of cranial nerves V (trigeminal), VI
  (abducens), and VII (facial)
• Contains nuclei of the reticular formation

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Brain Stem Medulla Oblongata

• Most inferior part of the brain stem
• Pyramids two longitudinal ridges formed by
  corticospinal tracts
• Decussation of the pyramids crossover points of
  the corticospinal tracts

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Brain Stem Medulla Oblongata

• Cardiovascular control center adjusts force and
  rate of heart contraction and blood vessel
  diameter to regulate blood pressure
• Respiratory centers along with pons control
  rate and depth of breathing
• Other centers regulate vomiting, hiccupping,
  swallowing, coughing, sneezing
• Cranial nerves IX - XII are associated with the
  medulla

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Cerebellum

• Located dorsal to the pons and medulla
• Protrudes under the occipital lobes of the
  cerebrum
• Makes up 11 of the brains mass
• Provides precise timing and appropriate patterns
  of skeletal muscle contraction
• Cerebellar activity occurs subconsciously

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Cerebellum

• Two bilaterally symmetrical hemispheres connected
  medially by the vermis
• Folia transversely oriented gyri
• Each hemisphere has three lobes anterior,
  posterior, and flocculonodular
• Neural arrangement gray matter cortex, internal
  white matter, scattered nuclei
• Arbor vitae distinctive treelike pattern of the
  cerebellar white matter

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Cerebellar Processing

• Cerebellum receives impulses of the intent to
  initiate voluntary muscle contraction
• Proprioceptors and visual signals inform the
  cerebellum of the bodys condition
• Cerebellar cortex calculates the best way to
  perform a movement
• A blueprint of coordinated movement is sent to
  the cerebral motor cortex

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Functional Brain Systems

• Networks of neurons working together and spanning
  wide areas of the brain
• The two systems are
• Limbic system
• Reticular formation

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Limbic System

• The emotional or affective brain
• Group of structures located on medial aspect of
  each cerebral hemisphere and diencephalon
• Interactions with higher and lower brain regions
  allow us to respond to environmental stimuli.
• Assesses danger and elicits the fear response

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Limbic System

• The emotional or affective brain
• Group of structures located on medial aspect of
  each cerebral hemisphere and diencephalon
• Interactions with higher and lower brain regions
  allow us to respond to environmental stimuli.
• Assesses danger and elicits the fear response

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Reticular Formation

• Extends through the central core of the brain
  stem.
• Provides a continuous stream of stimuli to
  cerebral cortex, keeping it alert

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Protection of the Brain

• Brain is protected by
• Bone
• Membranes
• Cerebralspinal fluid
• Blood brain barrier

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Meninges

• 3 connective tissue membranes external to the CNS
• Dura Mater leathery, tough outer layer
• Arachnoid mater middle layer
• Pia mater delicate connective tissue richly
  invested with tiny blood vessels

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Cerebrospinal Fluid

• CSF reduces brain weight by 97
• Protects brain and spinal cord from trauma
• Helps nourish brain
• Produced by choroid plexuses in ventricles
• Total adult CSF volume ½ cup (150 ml)
• Replaced every 8 hours

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Blood-brain Barrier

• Protective mechanism that helps maintain a stable
  environment for brain
• Nutrients like glucose, fats, O2, CO2 some
  electrolytes diffuse through
• Metabolic wastes, proteins, toxins, most drugs
  are denied entry
• Absent at hypothalamus