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THE BRAIN

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THE BRAIN Structure & Function ... say & feel without it we would only react without knowing or experiencing events enables the mind allows us to see, hear, remember ... – PowerPoint PPT presentation

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Title: THE BRAIN


1
THE BRAIN
  • Structure Function

2
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

3
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

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

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

6
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)

7
Protection Support
  • cranial bones
  • cranial meninges
  • dura mater
  • Arachnoid
  • pia mater
  • cerebral Spinal Fluid
  • blood-brain barrier

8
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

9
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

10
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

11
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

12
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

13
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

14
Brain Divisions
  • Brainstem
  • Cerebellum
  • Diencephalon
  • Cerebrum

15
BRAIN STEM
  • begins where spinal cord enters skull swells
  • Medulla oblongata
  • Pons
  • Midbrain

16
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

17
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

18
Midbrain
  • connects hindbrain forebrain
  • contains cerebral aqueduct
  • gives rise to cranial nerves that control eye
    movements

19
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

20
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

21
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

22
Cerebellum
  • extends from rear of brainstem
  • right left cerebellar hemispheres
  • connected by vermis
  • each hemisphere has slender folds or
    pleating-folia

23
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

24
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
25
Diencephalon
  • links cerebrum with brainstem
  • integrates conscious unconscious sensory
    information motor commands
  • three major parts
  • Thalamus
  • Hypothalamus
  • Epithalamus

26
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

27
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

28
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

29
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

30
Epithalamus
  • Roof
  • houses pineal gland
  • secretes melatonin
  • day/night cycles
  • habenular nuclei
  • emotional response to odors

31
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

32
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

33
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

34
Hemispheres
  • hemisperes are divided by longitudinal fissure
  • connected by corpus callosum

35
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

36
Lobe Functions
  • Frontal lobes
  • executive centers
  • Parietal lobes
  • spatial relationships\
  • pre post central gyri
  • movement sensations
  • Occipital lobes
  • sight
  • Temporal lobes
  • hearing

37
Cerebral White Matter
  • most of volume of cerebrum
  • fibers form bundles or tracts
  • Projection
  • Commissural
  • Association

38
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
39
Commissural Fibers
  • Interconnect gyri between cerebral hemispheres
  • Corpus Callosum
  • thick white band
  • provides way for cerebral hemispheres to
    communicate
  • Anterior Commissure

40
Projection Fibers
  • link cerebral cortex to lower parts of CNS
  • entire collection of projective fibers is
    internal capsule

41
Gray Matter of Brain
  • cell bodies
  • cerebral cortex
  • basal nuclei
  • limbic system

42
Basal Nuclei
  • masses of gray matter embedded in white matter
  • globus pallidus
  • Putamen
  • Together form lentiform nucleus
  • caudate nucleus
  • all three corpus striatum

43
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

44
Basal ganglia
45
Limbic System
  • Amygdala
  • Hippocampus

46
Amygdala
  • Fear
  • Applies emotional significance to people things

AMYGDALA
47
Hippocampus
  • Memory functions
  • Making memories
  • Retrieval of memories

48
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

49
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50
Functions of Cerebral Cortex
  • higher brain functions
  • Sleep
  • Memory
  • Cognition
  • Emotion
  • Sensation
  • Motor control
  • Language

51
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

52
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

53
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

54
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

55
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

56
Brocas Area
  • located in frontal lobe
  • controls motor cortex?speech produced

57
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

58
Association Areas
  • responsible for integrating information
  • associate sensory inputs with stored memories
  • important in cognition or thinking

59
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

60
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

61
Association Area Comparison
62
Hemispheric Lateralization
  • right left cerebral hemispheres are not paired
  • have different functions
  • Specialized
  • Left
  • Speech
  • Reasoning
  • Math and scientific skills

63
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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