Anatomy Ch 14

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Anatomy Ch 14
2010-12-06 13:22:17
Anatomy Brain Cranial Nerves

Note on chapter 14 the brain and cranial nerves
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  1. Four major parts of the brain
    1. Brain Stem- continuous with the spinal cord and consists of the medulla oblongata, pons, and midrain

    2. Cerebellum - posterior to the brain stem

    3. Diencephalon - consists of the thalamus, hypothalamus, and epithalamus

    4. Cerebrum - largest part of the brain
  2. Protective coverings of the brain
    Cranial meninges - continuous with the spinal cord, have the same basic structure

    • 1.Dura mater:- two-layered sheet in the brain made of fibrous connective tissue
    • -periosteal layer: more superficial layer, attaches to the internal surface of the skull bones (periosteum)
    • -meningeal layer: deeper layer; forms true external covering of the brain, continuous with dura mater of the spinal cord
    • two layers are fused except at dural sinuses - NO EPIDURAL SPACE

    2. Arachnoid mater - forms knoblike projections called arachnoid villi that project superiorly through dura mater into dural sinuses and act as valves that allow CSF to pass from subarachnoid space into dural blood sinuses

    3. Pia mater - highly vascularized, clings tightly to the brain surface, following its contours
  3. Three extensions of dura mater that separate parts of the brain
    1. Falx cerebri - separates the two hemispheres (sides) of the brain

    2. Falx cerebelli - separates the two hemisphere of the cerebellum

    3. tentorium cerebelli - separates the cerebrum from the cerebellum
  4. Brain blood flow and the blood brain barrier
    • -Internal carotid and vertebral arteries supply brain with blood
    • - Internal jugular veins return blood from the head to the heart
    • - Brain demands 20% of oxygen and glucose in the body (even at rest)
    • - Blood brain barrier prevents unwanted substances from reaching the brain tissue
    • 1. Facilitated by tight junctions between capillary cells and also by astrocytes
    • 2. thick basement membrane
  5. Cerebrospinal fluid - CSF
    • clear liquid containing oxygen, glucose, proteins, and ions
    • Funcions:
    • 1. Mechanical and chemical protection
    • - brain floats and softens impact with body walls of the cranium
    • - maintains accurate ionic balance necessary for proper neural conduction
    • 2. Circulation - transport of nutrients, chemical messengers, and wasted to and from the blood system

    • Ventricles - four CSF- filled cavities within the brain
    • 1) Lateral ventricles - located in each hemisphere of the cerebrum - separated by a thin membrane called the septum pellucidum
    • 2) Third ventricle - narrow cavity along the midline superior to the hypothalamus and between the right and left halves of the thalamus

    3) Fourth ventricle - lies between the brain stem and the cerebellum
  6. choroid plexuses
    networks of blood capillaries in the walls of the ventricles that produce CSF

    Each plexus consists of a layer of ependymal cells covered by pia mater. CSF is continually made through filtration of blood plasma through the ependymal cells into the ventricles.
  7. interventricular foramina
    aqueduct of the midbrain (cerebral aqueduct)
    median aperture
    lateral aperture
    arachnoid villus
    superior sagittal sinus
    • CSF is produced by choroid plexuses in the lateral ventricles and flows to the:
    • interventricular foramina - connections form lateral ventricles to the third ventricle

    aqueduct of the midbrain (cerebral aqueduct) - passes through the midbrain and connects the third and fourth ventricle

    median aperture - connects the fourth ventricle to the central canal of the spinal cord

    lateral aperture - openings on each side of the fourth ventricle that allow fluid to flow in the subarachnoid space

    arachnoid villus - fingerlike projections of the arachnoid mater that project into the sinuses - reabsorbes the CSF in the blood

    sinus - spaces between the layers of dura mater that circulate CSF

    superior sagittal sinus - a thin wall vein that runs down the middle of the brain
  8. hydrocephalus
    when excess CSF accumulates in the ventricles, the CSF pressure rises - can damage brain
  9. Three parts of the brain stem
    • 1. Medulla oblingata
    • 2. Pons
    • 3. midbrain
  10. Medulla Oblongata
    • - continuous with the spinal cord
    • - all sensory (ascending) and motor (decending) tracts run through the white matter of the medulla
  11. Pyramids
    decussation of the pyramids
    white matter bulges on the anterior of the medulla - formed by the large corticospinal tracts that pass from the cerebrum to the spinal cord - control voluntary movement of the limbs and trunk

    • decussation of the pyramids - just superior to the junction of the medulla with the spinal cord, 90% of the axons in the left pyramid cross to the right and 90% of the axons in the right pyramid cross to the left
    • -explains why each side of the brain controls voluntary movement on the opposite side of the body
  12. Nuclei of the medulla oblongata
    cardiovascular center
    medullary rythmicity area
    • -collection of neuronal cell bodies in the medulla (grey matter)
    • - control vital body functions and reflexes such as breathing, heart rate, blood flow, swallowing, coughing, sneezing, vomiting, hiccupping

    cardiovascular center - nuclei in the medulla that regulates rate and force of the heartbeat and the diameter of the blood vessels - medulla modifies heart rate based on activity

    medullary rythmicity area of the respiratory center - nuclei in the medulla that adjusts the basic rhythm of breathing
  13. Pons
    nuclei in the pons:
    pontine nuclei
    pneumotaxic area
    apneustic area
    • bridge between all major regions of the brain
    • -contains sensory and motor tracts and nuclei
    • - relay center for signals traveling to and from the cerebellum

    pontine nuclei - relay into from the cerebrum to the cerebellum

    pneumotaxic area of the respiratory center - short shallow breaths

    apneustic area of the respiratory center - deep long breaths
  14. Midbrain - also called the mesencephalon
    nuclei of the midbrain:
    superior colliculi
    inferior colliculi - startle reflex
    substantia nigra - dopamine
    Red nuclei
    • - highest portion of the brain stem
    • - cerebral aqueduct passes through the midbrain (connects third and fourth ventricles)
    • - extends from pons to diencephalon
    • - contain both nuclei and tracts

    • cerebral peduncles - anterior of the midbrain contains paired bundles of axons
    • - rope-like extensions of midbrain
    • - contains tracts (white matter)
    • - conducts impulses between midbrain and cerebrum

    • Tectum - roof - posterior part of the midbrain - contains four rounded elevations
    • -superior colliculi - nuclei that function in controlling reflex movements of the eyes
    • - inferior colliculi- nuclei that function in controlling reflex movements of the head, neck, and trunk in response to auditory stimuli - the startle reflex - response to loud noise

    substantia nigra - nuclei of the midbrain - large and darkly pigmented -contains neurons that release dopamine - help control subconscious activity (loss of these neurons is associated with Parkinsons)

    Red nuclei - rich blood supply and iron-containing pigment in their neuronal cell bodies - function in coordination of muscular movement
  15. reticular formation
    reticular activating system - RAS
    • -spans the entire brain stem
    • - netlike arragement of widely interspersed clusters of neuronal cell bodies (grey matter) interspersed with small bundles of myelinated axons (white matter)
    • - neurons within the reticular formation have both sensory and motor functions

    • reticular activating system - RAS - helps maintain consciousness and functions during awakening from sleep (ascending function) - sensitive to lights and sounds but not smell - fire alarms
    • - helps maintain muscle tone - descending function
  16. cerebellum
    transverse fissure
    cerebellar hemispheres
    cerebellar cortex
    arbor vitae
    cerebellar peduncles
    Functions of cerebellum:
    • -second largest part of the brain
    • - highly folded surface to increase surface area of grey matter cortex - allow for greater number of neurons

    transverse fissure - deep groove that separates the cerebellum from the cerebrum

    vermis - worm - the central area of the cerebellum - body of butterfly

    cerebellar hemispheres - wings - lateral lobes of the butterfly

    cerebellar cortex - superficial layer of the cerebellum that consists of grey matter in a series of folds called FOLIA (leaves).

    • arbor vitae - the tree of life - white matter tracts that are deep to the grey matter folia

    cerebellar peduncles - three pairs of white matter bundles that attach the cerebellum to the brain stem

    • functuions:
    • - coordinates and controls voluntary muscular movement, posture and balance
    • - Fine-tunes precise movements in conjunction with the cerebrum
    • - may also function in cognition and language processing
  17. Parts of the Diencephalon
    • 1. thalamus
    • 2. hypothalamus
    • 3. epithalamus
    • 4. subthalamus

    • - surrounds the third ventricle
  18. thalamus
    intermediate mass
    functions of thalamic nuclei
    • -major part of diencephalon - paired oval masses
    • - relay center for most sensory signals going into the cerebrum

    intermediate mass - bridge of grey matter joins the left and right halves of the thalamus

    • functions:
    • - emotions, regulation of alertness, memory, learning, cognition
    • - crude perception of painful, thermal, and pressure sensations
    • - funnels virtually all ascending signals to the cerebral bortex
  19. Hypothalamus
    mamillary bodies
    • -triangular area
    • - inferior to the thalamus

    has inferior extension called the INFUNDIBULUM that connect the hypothalamus to the PITUITARY GLAND (looks like a bean at the end of a white stalk)

    • mammillary bodies - two, small, rounded projections that serve as relay stations for reflexes related to sense of smell
  20. circadian rythms
    patters of biological activity that occur on a circadian cycle (24 hour cycle)
  21. Functions of the hypothalamic nuclei
    • nuclei in hypothalamus (in the diencephalon):
    • 1. controls ANS
    • 2. Produce hormones
    • 3. Regulates emotion and behavior
    • 4. Controls eating reflexes (swallowing, licking) and feelings of hunger and thirst
    • 5. Regulates body temperature
    • 6. Controls circadian rhythm
  22. Epithalamus
    • - pink area at the top of the third ventrical
    • - superior and posterior to the thalamus
    • - contains pineal gland - part of the endocrine system because it secretes the hormone Melatonin which promotes sleepiness and helps set the body's biological clock
    • - contain habenular nuclei - involved in olfaction and memory - emotional responses to odors
  23. subthalamus
    • - immediately inferior to the thalamus
    • - functions in conjunction with other brain structures to control body movements
  24. The Cerebrum
    parts of the cerebrum
    the "seat of intelligence" - give is the ability to read, write, and speak

    • 1. cerebral cortex
    • 2. an internal region of cerebral white matter
    • 3. gray matter nuclei deep within the white matter
  25. Cerebral cortex
    gyri (gyrus)
    sulci (silcus)
    longitudinal fissure
    cerebral hemisphere
    corpus collosum
    cortex = rind or bark

    - regions of grey matter that form the outer rind of the the cerebrum

    gyri (plural) - also called convolutions -the folds of the cortical regions - during embryonic development the grey matter of the cortex grow faster than the white matter below causing it to roll and fold upon itself

    sulci (plural) - shallow grooves between folds of the cortex

    fissure - deep grooves between folds of the cortex

    longitudinal fissure - most prominent fissure - separates the cerebrum into right and left halves called the cerebral hemispheres

    • corpus collosum - connects the cerebral hemispheres - band of white matter containing axons that extend between the hemispheres
  26. lobes of the cerebrum
    - named after the bones that cover them

    • 1. Frontal
    • 2. Parietal
    • 3. Temporal
    • 4. Occipital
  27. Cerebrum:
    central sulcus
    lateral cerebral sulcus
    parieto-occipital sulcus
    precentral gyrus
    postcentral gyrus
    central sulcus - separates the frontal and parietal lobe

    lateral cerebral sulcus - separates the frontal and temporal lobes

    parieto-occipital sulcus - separates the parietal and occipital lobes

    precentral gyrus - the gyrus (singular) anterior to the central sulcus - contains the primary motor area of the cerebral cortex

    postcentral gyrus - posterior to the central sulcus - contains primary somatosensory area of the cerebral cortex (pain center)

    insula - cannot be seen at surface - lies within the lateral cerebral sulcus
  28. cerebral white matter
    Three types of white matter tracts
    • cerebral white matter - located in interior of cerebrum
    • -contains both myelinated and unmyelinated axons in three tracts

    1. Association tracts - local - run between gyri of the same hemisphere

    • 2. Commissural tracts - crossing over - run from gyri of one cerebral hemisphere to gyri of the other cerebral hemisphere
    • --Corpus callosum - (200 million axons) - connects cerebral hemispheres
    • --Anterior and posterior commissure

    3. Projections tracts - info up & down - links cerebrum to diencephalon, brain stem, and spinal cord
  29. Basal Ganglia
    3 nuclei of basal ganglia
    3 nuclei (masses of grey matter) deep in each cerebral hemisphere (called ganglia even though in CNS)

    • 1. Globus pallidus
    • 2. putamen
    • 3. caudate nucleus

    • functions:
    • -regulating the initiation and termination of movements
    • -help initiate and terminate cognitive functions
    • -with limbic system, help regulate emotional behaviors
  30. Limbic system
    olifactory bulb
    • limbic system - emotional center
    • -consists of nuclei and tacts in regions of the cerebrum, diencephalon, and mesencephalon
    • -establishes emotional states

    • important parts:
    • hippocampus - functions in memory storage and retrieval
    • amygdala - rage - stimulation of amygdala causes rage
    • olifactory bulb - flattened bodies of the olefactory pathway that rest on the cribiform plate

    Phineas Gage - railway worker - limbic system damaged
  31. Sensory areas of the cerebral cortex
    Primary somatosensory area
    • -receives and interprets sensory impulses
    • -used in perception - the conscious awareness of a sensation

    primary somatosensory area - posterior to the central sulcus in the postcentral gyrus - receives info on touch, position, itching, tickle, thermal sensations
  32. Motor areas of the cerebral cortex
    Primary motor area
    Broca's speech area
    -control execution of voluntary movements

    • Primary motor area - located in precentral gyrus
    • -controls voluntary contractions of skeletal muscles

    • Broca's speech area - located in frontal lobe
    • - mechanical ability to speak - coordinates respiratory muscles and muscles of the tongue, cheeks,and lips
  33. Association areas of the cerebral cortex
    Werniche's area
    common integrative area
    prefronal cortex
    premotor area
    frontal eye field area
    - interpret incoming data from different areas and deal with complex integrative functions such as memory, emotions, reasoning, will, judgement, personality traits, and intelligence

    • Wernicke's area (posterior language) - area in the left temporal and parietal lobes
    • - interprets the meaning of speech and recognizing spoken words

    common integrative area - integrates sensory interpretations from the association areas and transmits signals for the appropriate response to interpretations

    prefrontal cortex - anterior frontal lobe - personalty, intellect, complex learning abilities, recall of information, initiative, judgement, foresight, reasoning, conscience

    premotor area - immediately anterior to the primary motor area (motor area of cerebral cortex) -remembers and generates nerve impulses for learned motor activities of a complex and sequential nature - wirting your name

    frontal eye field area - in the frontal cortex - controls voluntary scanning movements of the eye - reading
  34. aphasia
    inability to use or comprehend words caused by injury to language areas of cerebral cortex

    Broca's area - damage results in inability to form words

    Werniche's area - damage results in faulty understanding of spoken or written words - strings of words with no meaning
  35. hemispheric laterilization
    -specific functions centered in one of the two hemispheres

    • Left Hemisphere - controls right side of the body
    • -involved in language, math, logic, science

    • Right Hemisphere - controls left side of body
    • -involved in musical and artistic awareness
  36. brain waves
    4 types of brain waves
    brain waves - refers to all nerve impulses collectively

    EEG - electroencephalogram - detects electrical signals generated by the brain

    • 1. Alpha waves - normal when awake - disappear when asleep
    • 2. Beta waves - appear during mental activity
    • 3. Theta waves - normal in children and adults experiencing emotional stress - occur in many brain disorders
    • 4. Delta waves - normal in awake infants and sleeping adults - indicate brain damage if appear when adult is awake
  37. Cranial nerves
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    -12 pairs of nerves that connect directly to the brain

    -located on the ventrolateral surface of the brain

    - names indicate structure innervated and principle function

    - classified as either sensory, motor, or mixed (both)

  38. Classification of cranial nerves

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