Chapter 11 Brain Anatomy

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Chapter 11Brain Anatomy Functions
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Meninges

• Membranes surrounding CNS
• Protect CNS
• Three layers
• Dura mater
• Outer layer
• Adheres to cranial bones
• Tough

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Meninges

• Arachnoid mater
• Thin, weblike
• Pia mater
• Inner layer
• Adhere directly to brain
• Very thin
• Fibrous and vascular

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Meninges

• Spinal Cord
• Same three layers
• Provides protection

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Ventricles

• Interconnected cavities
• Within cerebral hemispheres and brain stem
• Continuous with central canal of spinal cord
• Filled with cerebrospinal fluid (CSF)

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Ventricles

• Lateral ventricles
• Third ventricle
• Fourth ventricle
• Cerebral aqueduct

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Ventricles
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Cerebrospinal Fluid

• Secreted by choroid plexus
• Circulates in ventricles, central canal of
  spinal cord, and subarachnoid space
• Completely surrounds brain and spinal cord
  between the meninges

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Cerebrospinal Fluid

• Clear liquid
• 80-150 ml in CNS
• Contains proteins, glucose, and salts
• Nutritive and protective
• Shock absorber
• Helps maintain stable ion concentrations in CNS

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Spinal Cord

• Slender column of nervous tissue continuous with
  brain
• Extends downward through vertebral canal
• Begins at level of foramen magnum terminates
  near first second lumbar

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Cross Section of Spinal Cord
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Functions of Spinal Cord

• Center for spinal reflexes

• Conduit for nerve impulses to and from the brain

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Reflex Arcs
Reflexes automatic, subconscious responses to
stimuli within or outside the body
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Brain
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Brain

• Functions
• Interprets sensations
• Determines perception
• Stores memory
• Reasoning
• Makes decisions
• Coordinates muscular movements
• Regulates visceral activities
• Determines personality

• Major Parts
• Cerebrum
• Two hemispheres
• Basal nuclei
• Diencephalon
• Brainstem
• Cerebellum

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Brain
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Brain Development

• Three Major Vesicles
• Forebrain
• Midbrain
• Hindbrain

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Brain Development
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Cerebrum

• Looks like cap of a mushroom
• Spread over diencephalon
• 7/8 total mass
• Fills most of cranium

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Clinical Application Cerebrum

• Result from displacement distortion of neurons
  at the moment of impact
• Concussion
• Abrupt but temporary loss of consciousness
  following a blow to the head or the sudden
  stopping of a moving head
• No visible bruising but post traumatic amnesia
  may occur

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Clinical Application Cerebrum

• Contusion
• Visible bruising of the brain due to trauma and
  blood leaking from microscopic vessels
• Pia mater is torn
• Results in unconsciousness for several minutes to
  many hours

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Clinical Application Cerebrum

• Laceration
• Tearing of the brain, usually from skull
  fractures or gunshot wound
• Large blood vessels bleed into the brain and can
  cause cerebral hematoma, and increase cranial
  pressure

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Lobes of Cerebral Hemispheres

• Name of lobe corresponds with name of cranial
  bone
• Frontal
• Parietal
• Temporal
• Occipital
• Insula

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Functions of the Cerebrum

• Interpreting impulses
• Initiating voluntary movements
• Storing information as memory
• Retrieving stored information
• Reasoning
• Seat of intelligence and personality

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Functional Regions of Cerebral Cortex
Cerebral Cortex thin layer of gray matter that
constitutes the outermost portion of cerebrum
contains 75 of all neurons in nervous system
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Structure of Cerebrum

• Cerebral Cortex
• Surface of cerebrum
• Convolutions
• Folds in cerebrum
• Bumps or gyri
• Sulci
• Shallow grooves
• Fissures
• Deep grooves

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Structure of Cerebrum

• Corpus callosum
• Connects cerebral hemispheres
• Longitudinal fissure
• Separates hemispheres
• Transverse fissure
• Separates cerebrum from cerebellum

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Sensory Areas

• Cutaneous Sensory Area
• Parietal lobe
• Interprets sensations on skin

• Visual Area
• Medial Occipital lobe
• Interprets vision

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Sensory Areas

• Primary Gustatory
• Taste
• Near bases of the central sulci
• Primary Olfactory
  
• Smell
• Arise from centers deep within the cerebrum

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Sensory Areas

• Auditory Area
• Superior part of temporal lobe near lateral
  cerebral sulcus
• Interprets hearing

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Sensory Areas
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Association Areas

• Regions that are not primary motor or primary
  sensory areas
• Widespread throughout the cerebral cortex
• Analyze and interpret sensory experiences
• Provide memory, reasoning, verbalization,
  judgment, emotions

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Association Areas

• Frontal Lobe Association Areas
• Concentrating
• Planning
• Complex problem solving

• Temporal Lobe Association Areas
• Interpret complex sensory
• experiences
• Store memories of visual scenes,
• music, and complex patterns

• Parietal Lobe Association Areas
• Understanding speech
• Choosing words to express thought

• Occipital Lobe Association Areas
• Analyze and combine visual images with other
  sensory experiences

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Hemisphere Dominance

• The left hemisphere is dominant is most
  individuals

• Nondominant hemisphere controls
• Nonverbal tasks
• Motor tasks
• Understanding and interpreting musical and
  visual patterns
• Provides emotional and intuitive thought
  processes

• Dominant hemisphere controls
• Speech
• Writing
• Reading
• Verbal skills
• Analytical skills
• Computational skills

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Hemisphere Differences

• Anatomical
• Frontal lobe of left hemisphere is smaller
• Left handed people
• Right parietal and occipital lobes are narrower

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Hemisphere Differences

• Right Hemisphere
• Left handed
• Music and artistic awareness
• Space and patter perception
• imagination

• Left Hemisphere
• Right handed
• Numerical and scientific skills
• Sign language and reasoning

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Memory

• Short Term
• Working memory
• Closed neuronal circuit
• Circuit is stimulated over and over
• When impulse flow ceases, memory does also
• Unless it enters long-term memory via memory
  consolidation

• Long Term
• Changes structure or function of neurons
• Enhances synaptic transmission

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Motor Areas

• Primary Motor Areas
• frontal lobes
• control voluntary muscles

• Brocas Area
• anterior to primary motor cortex
• usually in left hemisphere
• controls muscles needed for speech

• Frontal Eye Field
• above Brocas area
• controls voluntary movements of eyes and eyelids

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Motor Areas
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Functions of the Cerebral Lobes
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Diencephalon

• Between cerebral hemispheres and above the
  brainstem
• Surrounds third ventricle

• Thalamus
• Hypothalamus
• Optic tracts
• Optic chiasma
• Infundibulum
• Posterior pituitary
• Mammillary bodies
• Pineal gland

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Diencephalon

• Thalamus
• Oval structure above midbrain
• Gateway for sensory impulses heading to cerebral
  cortex
• Receives all sensory impulses (except smell)
• Channels impulses to appropriate part of
  cerebral cortex for interpretation
• Interpretation of pain, temperature, and pressure

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Diencephalon

• Hypothalamus
• Small portion inferior to thalamus
• Protected by sella turcica
• Maintains homeostasis by regulating visceral
  activities
• Water concentrations
• Hormone concentrations
• Blood temperature
• Links nervous and endocrine systems

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Diencephalon

• Homeostatic functions
• Regulates autonomic nervous system
• Reception integration of sensory impulses from
  viscera
• Mind over body (stress--heart rate increases)
• Rage aggression
• Regulates body temperature
• Regulates food intake (hunger full feelings)
• Thirst
• Sleep patterns

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Diencephalon
Limbic System

• Consists of
• portions of frontal lobe
• portions of temporal lobe
• hypothalamus
• thalamus
• basal nuclei
• other deep nuclei

• Functions
• controls emotions
• produces feelings
• interprets sensory impulses

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Brain Stem

• Three Parts
• Midbrain
• Pons
• Medulla Oblongata

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Midbrain

• Mesencephalon
• Between diencephalon and pons
• Contains bundles of fibers that join lower parts
  of brainstem and spinal cord with higher part of
  brain

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Midbrain

• Cerebral aqueduct
• Connects 3rd 4th ventricles of brain
• Cerebral peduncles bundles of nerve fibers
• Motor pathway between cerebrum lower parts of
  nervous system
• Corpora quadrigemina centers for visual and
  auditory reflexes

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Pons

• Rounded bulge on underside of brainstem
• Between medulla oblongata and midbrain
• Helps regulate rate and depth of breathing
• Relays nerve impulses to and from medulla
  oblongata and cerebellum

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Medulla Oblongata

• Enlarged continuation of spinal cord
• Conducts ascending and descending impulses
  between brain and spinal cord
• Contains 3 reflex centers
• Cardiac
• Heart rate force of contraction
• Vasomotor
• Controls diameter of blood vessels
• Respiratory
• Controls breathing patterns

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Medulla Oblongata

• Contains various nonvital reflex control centers
• Coughing
• Sneezing
• Swallowing
• Vomiting

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Medulla Oblongata

• Reticular Formation
• Complex network of nerve fibers scattered
  throughout the brain stem
• Extends into the diencephalon
• Connects to centers of hypothalamus, basal
  nuclei, cerebellum, and cerebrum
• Filters incoming sensory information
• Arouses cerebral cortex into state of wakefulness

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Cerebellum

• Inferior to occipital lobes
• Posterior to pons and medulla oblongata
• Two hemispheres
• Vermis connects hemispheres
• Cerebellar cortex
• Gray matter on surface
• Arbor vitae
• White matter inside
• Tree-like pattern
• Cerebellar peduncles
• nerve fiber tracts

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Cerebellum

• Dentate nucleus
• Largest nucleus in cerebellum
• Integrates sensory information concerning
  position of body parts
• Coordinates skeletal muscle activity
• Maintains posture

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Cerebellum

• Damage results in
• Lack of muscle control
• Change of speech pattern
• Severe dizziness
• Disturbances of gait (walking)

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Life-Span Changes

• Brain cells begin to die before birth
• Over average lifetime, brain shrinks 10
• Most cell death occurs in temporal lobes
• By age 90, frontal cortex has lost half its
  neurons
• Number of dendritic branches decreases
• Decreased levels of neurotransmitters
• Fading memory
• Slowed responses and reflexes
• Increased risk of falling
• Changes in sleep patterns that result in fewer
  sleeping hours

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Clinical Application
Cerebral Injuries and Abnormalities

• Cerebral Palsy
• Motor impairment at birth
• Caused by blocked cerebral blood vessels during
  development
• Seizures
• Learning disabilities

• Cerebrovascular Accident
• Stroke
• Sudden interruption in blood flow
• Brain tissues die