THE BRAIN

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THE BRAIN

• Structure Function

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THE BRAIN

• most complex organ
• controls everything that we do, say feel
• without it we would only react without knowing or
  experiencing events
• enables the mind
• allows us to see, hear, remember, think, feel,
  speak dream

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Embryonic Development

• nervous system develops from ectoderm
• by week 3 neuroectoderm develops?thickens forming
  neural plate
• plate gives rise to all neurons glial cells of
  nervous system
• plate sinks forming neural groove with raised
  neural folds along each side
• neural folds fuse forming a hollow tube- neural
  tube which contains a fluid filled
  cavity-neurocoel

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Embryonic Development

• by week 4 tube has 3 primary vesicles
• Prosencephalon-forebrain
• Mesencephalon-midbrain
• Rhombencephalon-hindbrain

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Embryonic Development

• week 5-primary vesicles become 5 secondary
  vesicles
• Prosencephalon? telencephalon diencephalon
• midbrain does not divide
• rhombencephalon ?metencephalon myelencephalon

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Ventricles

• neurocoel expands forming ventricles
• each hemisphere has a lateral ventricle
• 3rd ventricle is in diencephalon
• lateral ventricles communicate with the 3rd via
  interventricular foramen or foramen of Munro
• mesencephalic aqueduct connects 3rd ventricle
  with 4th which extends into medulla oblongata
• 4th ventricle narrows becoming continuous with
  central canal of spinal cord
• ventricles are filled with cerebral spinal fluid
  (CSF)

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Protection Support

• cranial bones
• cranial meninges
• dura mater
• Arachnoid
• pia mater
• cerebral Spinal Fluid
• blood-brain barrier

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Meninges

• outer most-dura mater
• has an outer-endosteal layer fused to periosteum
  of cranial bones an inner fibrous layer or
  meningeal layer
• arachnoid meninge
• in contact with inner layer of dura mater
• pia mater-innermost
• sticks to brain surface
• extends into every fold of brain

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Dural Folds

• dura mater extensions
• hold brain in position
• falx cerebri
• between cerebral hemispheres in longitudinal
  fissure
• tentorium cerebelli
• separates cerebellar hemispheres from cerebrum
• falx cerebelli
• divides cerebellar hemispheres

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Cerebral Spinal Fluid

• CSF surrounds bathes all exposed surfaces of
  CNS
• cushions CNS from jolts shocks
• supports brain which actually floats in CSF
• transports nutrients, chemical messengers waste
  products
• changes in CSF denote changes in function of CNS
• forms in choroid plexus of the ventricles

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Blood Supply

• to meet high demands for oxygen glucose-
  extensive circulatory supply
• arterial blood reaches brain through internal
  carotid vertebal arteries
• venous flow leaves via internal jugular veins

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Blood-Brain Barrier

• isolates CNS from general circulation
• blood carries substances that might be harmful to
  brain
• due to tight junctions between endothelial cells
  lining capillaries of CNS
• prevent diffusion of materials between adjacent
  cells
• only lipid soluble compounds can diffuse across
  membranes into brain spinal cord
• waste products ions must pass through channels
• restricted permeability depends on
• astrocytes
• secrete chemicals
• that control permeability

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Brain Structure

• internal parts rolled up to fit into the skull
• fit a large amount of material into a small space
• biological history of brain is like an
  archeological dig
• deeper you go?older structures are found
• older parts are more apt to include basic
  mechanisms for survival

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Brain Divisions

• Brainstem
• Cerebellum
• Diencephalon
• Cerebrum

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BRAIN STEM

• begins where spinal cord enters skull swells
• Medulla oblongata
• Pons
• Midbrain

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MEDULLA

• regulates autonomic functions
• breathing, heartbeat, blood pressure digestion
  or vegetative processes
• cross over point where nerves come in cross to
  opposite side-decussation
• groups of nuclei
• cardiovascular center adjusts heart rate blood
  flow through peripheral tissues
• respiratory rhythmicity centers set basic pace
  for respiratory movements
• Sensory or motor nuclei of cranial nerves, VIII,
  IX, X, XI, XII provide motor commands to muscles
  of neck, pharynx back
• Nucleus gracilis nucleus cuneatus pass sensory
  information to thalamus

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PONS

• connects cerebellum to brain stem
• nuclei for somatic visceral motor control
• cranial nerves V, VI, VII, VIII
• innervates jaw face muscles, eye muscles and
  organs of vestibular sense
• contains nuclei for control of respiration
• apneustic pneumotaxic centers
• modify activity of respiratory rhythmicity
  centers of medulla

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Midbrain

• connects hindbrain forebrain
• contains cerebral aqueduct
• gives rise to cranial nerves that control eye
  movements

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Midbrain

• corpora quadrigemina
• tectum or roof houses 2
• superior inferior colliculi
• Superior colliculi
• receive visual information
• control reflexes related to vision
• Inferior colliculi
• receive auditory sensations
• control reflexes in relation to sound

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Midbrain

• red nucleus substantia nigra are found on each
  side of midbrain
• red nucleus
• contains numerous blood vessels
• receives information from cerebrum cerebellum
• issues subconscious motor commands affecting
  background muscle tone and limb position
• substantia nigra
• inhibits activity of cerebral nuclei by
  releasing dopamine
• cerebral peduncles
• descending nerve fiber bundles
• project to cerebellum via pons
• carry voluntary motor commands from the primary
  motor cortex

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Reticular Formation

• loosely organized area of gray matter running
  vertically through all levels of brainstem
• Ascending part-Reticular Activating System (RAS)
• altertness attention
• sleep
• consciousness
• habituation
• process by which brain learns to ignore
  repetitive stimuli while remaining sensitive to
  others
• damaged-coma

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Cerebellum

• extends from rear of brainstem
• right left cerebellar hemispheres
• connected by vermis
• each hemisphere has slender folds or
  pleating-folia

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Cerebellar Lobes

• Anterior lobe
• Posterior lobe
• govern subconscious aspects of skeletal muscle
  movement
• Flocculonodular lobe
• contributes to equilibrium balance
• Arbor viking or tree of life
• white matter

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Cerebellum

• connects to brainstem by three cerebellar
  peduncles
• automatic processing center
• responsible for adjusting ongoing movements by
  comparing arriving sensations sensations
  experienced previously
• adjusts postural muscles
• coordinates rapid, automatic adjustments that
  maintain balance and equilibrium
• responsible for coordination of voluntary
  movements
• allows you to walk straight by monitoring
  proprioceptive, visual, tactile, balance
  auditory sensations
• responsible for programming fine tuning
  movements controlled at conscious subconscious
  levels
• refines learned movement patterns or learned
  motor responses
• driving a car, playing a musical instrument or
  any activity performed nearly unconsciously

A cerebral peduncle
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Diencephalon

• links cerebrum with brainstem
• integrates conscious unconscious sensory
  information motor commands
• three major parts
• Thalamus
• Hypothalamus
• Epithalamus

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Thalamus

• top of brainstem
• relay station
• receives information from all senses, except
  smell
• routes them to higher brain regions
• acts as a filter by passing on only small amounts
  of arriving information
• coordinates activities of cerebral nuclei
  cerebral cortex
• important in motor control by relaying signals
  from cerebellum to cerebrum

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Thalamus

• anterior nuclei
• part of limbic system
• primitive brain area effecting motivation
  emotion
• medial nuclei
• conscious awareness of emotional states
• connect emotional centers in hypothalamus with
  frontal lobes
• ventral nuclei
• relay information from basal nuclei of cerebrum
  cerebellum to somatic motor areas of cerebral
  cortex
• relay information regarding touch, pressure, pain
  and temperature to sensory areas of cerebral
  cortex
• posterior nuclei
• lateral geniculate nucleus
• receives visual information from optic tract
• medial geniculate nucleus
• relays auditory information to cerebral cortex

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Hypothalamus

• below thalamus
• connected to pituitary gland by infundibulum
• maintenance functions
• regulates hunger, thirst, hormone production,
  body temperature sexual behavior
• controls by triggering autonomic nervous system
  by monitoring hormone levels in blood

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Hypothalamic Nuclei

• endocrine gland
• ADH or antidiuretic hormone
• produced by supraoptic nucleus
• restricts water loss at kidneys
• Oxytoxin
• made by paraventricular nucleus
• stimulates smooth muscle contractions in uterus
• produces emotions behavior drives such as
  hunger, thirst, and sexual desire
• coordinates voluntary autonomic functions,
  preparing body for emergencies
• regulates body temperature via preoptic area
• controls circadian rhythms by suprachiasmatic
  nucleus

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Epithalamus

• Roof
• houses pineal gland
• secretes melatonin
• day/night cycles
• habenular nuclei
• emotional response to odors

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Cerebrum

• most visible largest part of brain-80 of
  brains weight
• right left cerebral hemispheres
• extensive cerebral hemispheres make mammals
  different from other vertebrates
• releases species from genetic control increases
  adaptability

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Functions

• conscious thoughts
• higher functions
• processes somatic sensory
• processes motor information
• ultimate control information processing center
• responsible for conscious thought, sensations,
  intellect, memory complex movements

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Cerebrum

• surface is highly convoluted
• increases surface area
• cortex forms elongated ridges-gyri
• separated by deep depressions-sulci or deeper
  grooves-fissures
• covered by a neural or cerebral cortex
• superficial layer of gray matter composed of
  interconnected neural cells, pyramidal cells,
  stellate cells, 6 layers thick (1/8th inch)
• contains 30 billion nerve cells

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Hemispheres

• hemisperes are divided by longitudinal fissure
• connected by corpus callosum

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Hemisphere Lobes

• each hemipshere divided into 4 lobes made
  distinct by gyri
• named for bone each covers
• central sulcus separates frontal lobe from
  parietal lobe
• lateral sulcus separates frontal lobe from
  temporal lobe
• parieto-occipital sulcus separates parietal lobe
  from occipital lobe

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Lobe Functions

• Frontal lobes
• executive centers
• Parietal lobes
• spatial relationships\
• pre post central gyri
• movement sensations
• Occipital lobes
• sight
• Temporal lobes
• hearing

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Cerebral White Matter

• most of volume of cerebrum
• fibers form bundles or tracts
• Projection
• Commissural
• Association

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Association Fibers

• interconnect neural cortex in one hemisphere
• shorter fibers-arcuate
• curve in an arc from one gyrus to another
• longer fibers-fasciculi
• longitudinal fasciculi
• connect frontal lobe to other lobes in same
  hemisphere

ARCUATE FIBER
Longitudinal Fasciculi
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Commissural Fibers

• Interconnect gyri between cerebral hemispheres
• Corpus Callosum
• thick white band
• provides way for cerebral hemispheres to
  communicate
• Anterior Commissure

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Projection Fibers

• link cerebral cortex to lower parts of CNS
• entire collection of projective fibers is
  internal capsule

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Gray Matter of Brain

• cell bodies
• cerebral cortex
• basal nuclei
• limbic system

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Basal Nuclei

• masses of gray matter embedded in white matter
• globus pallidus
• Putamen
• Together form lentiform nucleus
• caudate nucleus
• all three corpus striatum

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Corpus Striatum

• monitor activities occurring at subconscious
  level
• help initiate terminate movements cognitive
• subconscious control of skeletal muscle tone
• coordination of learned movement patterns
• once motion is underway basal nuclei provide
  basic pattern rhythm for movement

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Basal ganglia
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Limbic System

• Amygdala
• Hippocampus

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Amygdala

• Fear
• Applies emotional significance to people things

AMYGDALA
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Hippocampus

• Memory functions
• Making memories
• Retrieval of memories

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Cerebral Cortex

• covers hemispheres of brain
• 2-3mm thick
• 6 layers
• neocortex
• two main neurons
• Stellate cells
• receive process information locally
• Pyramidal cells
• output neuron
• transmits signals to other parts of CNS

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Functions of Cerebral Cortex

• higher brain functions
• Sleep
• Memory
• Cognition
• Emotion
• Sensation
• Motor control
• Language

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Functional Organization of Cerebral Cortex

• functions not responsibility of just one brain
  area
• cortex is arranged according to function
• Sensory areas
• receive sensory information
• involved in perception
• conscious awareness of sensation
• Motor areas
• control execution of voluntary movements.
• Association areas
• deal with complex, integrative functions
• memory, emotions, reasons, personality
  intelligence

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Location of Functions in Cerebral Hemispheres

• primary motor cortex
• arch shaped region at back of frontal lobes
  running from one ear to other across top of brain
  
• stimulate area? specific muscles contract on
  opposite side of stimulation site
• controls voluntary movements

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Primary Sensory Cortex

• located behind motor cortex at front of parietal
  lobes
• post central gyrus
• stimulation produces sensations of being touched
  on specific parts of body
• more sensitive body part? more area of sensory
  cortex is allotted to it

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Other Sensory Areas

• Primary visual area
• occipital lobes
• Primary auditory area
• temporal lobes
• Primary olfactory area
• medial surface of temporal lobe inferior
  surface of frontal lobe
• Primary gustatory area
• temporal lobe
• base of post central gyrus

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Primary Motor Cortex

• mapped 1950s
• Forester Penfield
• Precentral gyrus
• body parts that need precise control such as
  fingers mouths had greater amount of cortical
  space
• seen on a homunculus

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Brocas Area

• located in frontal lobe
• controls motor cortex?speech produced

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Association Areas

• identification of functions for the sensory
  motor areas of brain leaves ¾ of cerebral
  cortex with nothing to do
• when these areas are stimulated?no observable
  responses
• areas not dormant
• do not use 10 of our brains
• these areas represent association areas

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Association Areas

• responsible for integrating information
• associate sensory inputs with stored memories
• important in cognition or thinking

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Association Areas

• Somatosensory association area
• posterior to primary somatosensory area
• receives information from primary somatosensory
  area, thalamus other parts of the brain
• lets us determine exact shape texture of an
  object just by feeling it
• stores memory and lets us recognize objects by
  touching them
• Auditory association area
• monitor sensory activity in auditory cortex
• Visual association area
• monitor patterns of activity in visual cortex
  interpret results
• Wernickes area- posterior language area
• left temporal parietal lobes
• interprets meaning of speech by recognizing
  spoken words
• Frontal lobe association area-premotor cortex
• personality, intellect complex learning

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Association Areas

• facial recognition area (fusiform)
• inferior temporal lobe
• receives information from visual association area
  
• allows us to store information about faces
  recognize individuals by their faces
• primary isolated to right hemisphere
• orbitofrontal cortex
• lateral part of frontal lobe
• receives information from primary olfactory area
• allows us to identify odors
• frontal eye field area (between 4, 5 8)
• frontal lobe
• controls voluntary scanning movements

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Association Area Comparison
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Hemispheric Lateralization

• right left cerebral hemispheres are not paired
• have different functions
• Specialized
• Left
• Speech
• Reasoning
• Math and scientific skills

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RIGHT HEMISPHERE

• analyzes sensory information
• relates body to sensory environment identifies
  faces
• understands simple requests perceives objects
• superior in drawing faces, perceiving
  differences, perceiving emotions expressing
  emotion on left side of face
• important in understanding emotional context of
  conversations

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