Chapter 19 The Brain and Cranial Nerves - PowerPoint PPT Presentation

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Chapter 19 The Brain and Cranial Nerves

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Title: Chapter 19 The Brain and Cranial Nerves


1
Chapter 19The Brain and Cranial Nerves
  • Brain functions in sensations, memory, emotions,
    decision making, behavior

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3
Principal Parts of the Brain
  • Cerebrum
  • Diencephalon
  • thalamus hypothalamus
  • Cerebellum
  • Brainstem
  • medulla, pons midbrain

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Protective Coverings of the Brain
  • Bone, meninges fluid
  • Meninges same as around the spinal cord
  • dura mater
  • arachnoid mater
  • pia mater

6
Blood Supply to Brain
  • Arterial blood supply is branches from circle of
    Willis on base of brain 99)
  • Vessels on surface of brain----penetrate tissue
  • Uses 20 of our bodies oxygen glucose needs
  • blood flow to an area increases with activity in
    that area
  • deprivation of O2 for 4 min does permanent injury
  • at that time, lysosome release enzymes
  • Blood-brain barrier (BBB)
  • protects cells from some toxins and pathogens
  • proteins antibiotics can not pass but alcohol
    anesthetics do
  • tight junctions seal together epithelial cells,
    continuous basement membrane, astrocyte processes
    covering capillaries

7
Cerebrospinal Fluid (CSF)
  • 80-150 ml (3-5oz)
  • Clear liquid containing glucose, proteins, ions
  • Functions
  • mechanical protection
  • floats brain softens impact with bony walls
  • chemical protection
  • optimal ionic concentrations for action
    potentials
  • circulation
  • nutrients and waste products to and from
    bloodstream

8
Origin of CSF
  • Choroid plexus capillaries covered by
    ependymal cells
  • 2 lateral ventricles, one within each cerebral
    hemisphere
  • roof of 3rd ventricle
  • fourth ventricle

9
Drainage of CSF from Ventricles
  • One median aperture two lateral apertures allow
    CSF to exit from the interior of the brain

10
Flow of Cerebrospinal Fluid
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Reabsorption of CSF
  • Reabsorbed through arachnoid villi
  • grapelike clusters of arachnoid penetrate dural
    venous sinus
  • 20 ml/hour reabsorption rate same as production
    rate

13
Medulla Oblongata
  • Continuation of spinal cord
  • Ascending sensory tracts
  • Descending motor tracts
  • Nuclei of 5 cranial nerves
  • Cardiovascular center
  • force rate of heart beat
  • diameter of blood vessels
  • Respiratory center
  • medullary rhythmicity area sets basic rhythm of
    breathing
  • Information in out of cerebellum
  • Reflex centers for coughing, sneezing, swallowing
    etc

14
Ventral Surface of Medulla Oblongata
Olive olivary nucleus neurons send input to
cerebellum proprioceptive signals gives precision
to movements
  • Ventral surface bulge
  • large motor tract
  • pyramids
  • left cortex controls right muscles

15
Dorsal Surface of Medulla Oblongata
  • Nucleus gracilis nucleus cuneatus sensory
    neurons
  • relay information to thalamus on opposite side of
    brain
  • 5 cranial nerves arise from medulla -- 8 thru 12

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Injury to the Medulla
  • Hard blow to the back of the head may be fatal
  • Cranial nerve malfunctions on same side as
    injuryloss of sensation or paralysis of throat
    or tongue irregularities in breathing and heart
    rhythm

18
Pons
  • One inch long
  • White fiber tracts ascend and descend
  • Pneumotaxic apneustic areas help control
    breathing
  • Middle cerebellar peduncles carry sensory info to
    the cerebellum
  • Cranial nerves 5 thru 7

19
Midbrain
  • One inch in length
  • Extends from pons to diencephalon
  • Cerebral aqueduct connects 3rd ventricle above to
    4th ventricle below

20
Midbrain in Section
  • Cerebral peduncles---clusters of motor sensory
    fibers
  • Substantia nigra---helps controls subconscious
    muscle activity
  • Red nucleus-- rich blood supply iron-containing
    pigment
  • cortex cerebellum coordinate muscular movements
    by sending information here from the cortex and
    cerebellum

21
Cerebellum
  • 2 cerebellar hemispheres and vermis (central
    area)
  • Function
  • correct voluntary muscle contraction and posture
    based on sensory data from body about actual
    movements
  • sense of equilibrium

22
Cerebellum
  • Transverse fissure between cerebellum cerebrum
  • Cerebellar cortex (folia) central nuclei are
    grey matter
  • Arbor vitae tree of life white matter

23
Cerebellar Peduncles
  • Superior, middle inferior peduncles attach to
    brainstem
  • inferior carries sensory information from spinal
    cord
  • middle carries sensory fibers from cerebral
    cortex basal ganglia
  • superior carries motor fibers that extend to
    motor control areas

24
Diencephalon Surrounds 3rd Ventricle
  • Surrounds 3rd ventricle
  • Superior part of walls is thalamus
  • Inferior part of walls floor is hypothalamus

25
Thalamus
  • 1 inch long mass of gray mater in each half of
    brain (connected across the 3rd ventricle by
    intermediate mass)
  • Relay station for sensory information on way to
    cortex
  • Crude perception of some sensations

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Thalamic Nuclei
  • Nuclei have different roles
  • relays auditory and visual impulses, taste and
    somatic sensations
  • receives impulses from cerebellum or basal
    ganglia
  • anterior nucleus concerned with emotions, memory
    and acquisition of knowledge (cognition)

28
Hypothalamus
  • Dozen or so nuclei in 4 major regions
  • mammillary bodies are relay station for olfactory
    reflexesinfundibulum suspends the pituitary
    gland
  • Major regulator of homeostasis
  • receives somatic and visceral input, taste, smell
    hearing information monitors osmotic pressure,
    temperature of blood

29
Functions of Hypothalamus
  • Controls and integrates activities of the ANS
    which regulates smooth, cardiac muscle and glands
  • Synthesizes regulatory hormones that control the
    anterior pituitary
  • Contains cell bodies of axons that end in
    posterior pituitary where they secrete hormones
  • Regulates rage, aggression, pain, pleasure
    arousal
  • Feeding, thirst satiety centers
  • Controls body temperature
  • Regulates daily patterns of sleep

30
Reticular Formation
  • Scattered nuclei in medulla, pons midbrain
  • Reticular activating system
  • alerts cerebral cortex to sensory signals (sound
    of alarm, flash light, smoke or intruder) to
    awaken from sleep
  • maintains consciousness helps keep you awake
    with stimuli from ears, eyes, skin and muscles
  • Motor function is involvement with maintaining
    muscle tone

31
Cerebrum (Cerebral Hemispheres)
  • Cerebral cortex is gray matteroverlying white
    matter
  • 2-4 mm thick containing billionsof cells
  • grew so quickly formed folds(gyri) and grooves
    (sulci or fissures)
  • Longitudinal fissure separates left right
    cerebral hemispheres
  • Corpus callosum is band of white matter
    connecting left and right cerebral hemispheres
  • Each hemisphere is subdivided into 4 lobes

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Lobes and Fissures
  • Longitudinal fissure (green)
  • Frontal lobe
  • Central sulcus (yellow)
  • precentral postcentral gyrus
  • Parietal lobe
  • Parieto-occipital sulcus
  • Occipital lobe
  • Lateral sulcus (blue)
  • Temporal lobe
  • Insula

34
Insula within Lateral Fissure
35
Cerebral White Matter
  • Association fibers between gyri in same
    hemisphere
  • Commissural fibers from one hemisphere to other
  • Projection fibers form descending ascending
    tracts

36
Basal Ganglia
  • Connections to red nucleus, substantia nigra
    subthalamus
  • Input output with cerebral cortex, thalamus
    hypothalamus
  • Control large automatic movements of skeletal
    muscles

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39
Limbic System
  • Emotional brain--intense pleasure intense pain
  • Strong emotions increase efficiency of memory

40
Functional organization of the cerebral cortex
41
Sensory Areas of Cerebral Cortex
  • Receive sensory information from the thalamus
  • Primary somatosensory area postcentral gyrus
    1,2,3
  • Primary visual area 17
  • Primary auditory area 41 42
  • Primary gustatory area 43

42
Motor Areas of Cerebral Cortex
  • Voluntary motor initiation
  • Primary motor area 4 precentral gyrus
  • controls voluntary contractions of skeletal
    muscles on other side
  • Motor speech area 44 Brocas area
  • production of speech -- control of tongue airway

43
Association Areas of Cerebral Cortex
  • Somatosensory area 5 7 (integrate
    interpret)
  • Visual association area 18 19 (recognize
    evaluate)
  • Auditory association area(Wernickes) 22(words
    become speech)
  • Gnostic area 5,7,39 40 (integrate all senses
    respond)
  • Premotor area 6 (learned skilled movements such
    as typing)
  • Frontal eye field 8 (scanning eye movements such
    as phone book)

44
Hemispheric Lateralization
  • Functional specialization of each hemisphere more
    pronounced in men
  • Females have larger connections between 2 sides
  • Damage to left side produces aphasia
  • Damage to same area on right side produces speech
    with little emotional inflection

45
I -- Olfactory Nerve
Cranial Nerves
  • Extends from olfactory mucosa of nasal cavity to
    olfactory bulb
  • Sense of smell

46
II -- Optic Nerve
  • Connects to retina supplying vision

47
III Oculomotor Nerve
  • Levator palpebrae raises eyelid (ptosis)
  • 4 extrinsic eye muscles
  • 2 intrinsic eye muscles
  • accomodation for near vision (changing shape of
    lens during reading)
  • constriction of pupil

48
IV Trochlear Nerve
  • Superior oblique eye muscle

49
V Trigeminal Nerve
  • Motor portion
  • muscles of mastication
  • Sensory portion
  • touch, pain, temperature receptors of the face
  • ophthalmic branch
  • maxillary branch
  • mandibular branch

50
VI Abducens Nerve
  • Lateral rectus eye muscle

51
VII Facial Nerve
  • Motor portion
  • facial muscles
  • salivary nasal and oral mucous glands tears
  • Sensory portion
  • taste buds on anterior 2/3s of tongue

52
VIII Vestibulocochlear Nerve
  • Cochlear branch begins in medulla
  • receptors in cochlea
  • hearing
  • if damaged deafness or tinnitus (ringing) is
    produced
  • Vestibular branch begins in pons
  • receptors in vestibular apparatus
  • sense of balance
  • vertigo (feeling of rotation)
  • ataxia (lack of coordination)

53
IX Glossopharyngeal Nerve
  • Stylopharyngeus m. (lifts throat during
    swallowing)
  • Secretions of parotid gland
  • Somatic sensations taste on posterior 1/3 of
    tongue

54
X Vagus Nerve
  • Receives sensations from viscera
  • Controls cardiac muscle and smooth muscle of the
    viscera
  • Controls secretion of digestive fluids

55
XI Spinal Accessory Nerve
  • Cranial portion
  • arises medulla
  • skeletal mm of throat soft palate
  • Spinal portion
  • arises cervical spinal cord
  • sternocleidomastoid and trapezius mm.

56
XII Hypoglossal Nerve
  • Controls muscles of tongue during speech and
    swallowing
  • Injury deviates tongue to injured side when
    protruded
  • Mixed, primarily motor
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