Chapter 2: The Brain

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Chapter 2: The Brain
2015-03-06 22:42:28
NPTE: Chapter 2
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  1. Cerebral Hemispheres (telencephalon)
    • Convolutions of gray matter composed of gyri (crests) and sulci (fissures)
    • Paired hemispheres, consist of 6 lobes on each side (frontal, parietal, temporal, occipital, insular, limbic)
  2. Cerebral Hemispheres: Fissures and Sulci
    • Lateral central fissure (fissure of Sylvius): separates temporal lobe from frontal and parietal lobes
    • Longitudinal cerebral fissure: separates the two hemispheres
    • Central sulcus: separates the frontal lobe from the parietal lobe
  3. Frontal Lobe
    • Precentral gyrus: primary motor cortex for voluntary muscle activation
    • Prefrontal cortex: controls emotions and judgements
    • Broca's area: controls motor aspects of speech
  4. Parietal Lobe
    • Postcentral gyrus: primary sensory cortex for integration of sensation
    • Receives fibers conveying touch, proprioception, pain, and temperature sensation from opposite side of body
  5. Temoral Lobe
    • Primary auditory cortex: receives/processes auditory stimuli
    • Associative auditory cortex: processes auditory stimuli
    • Wernicke's area: language comprehension
  6. Occipital Lobe
    • Primary visual cortex: receives/processes visual stimuli
    • Visual association cortex: processes visual stimuli
  7. Insula
    • Deep within lateral sulcus
    • Associated with visceral functions
  8. Limbic System: Components
    • Limbic lobe (cingulate, parahippocampal, and subcallosal gyri)
    • Hippocampal formation
    • Amygdaloid nucleus
    • Hypothalamus
    • Anterior nucleus of thalamus
  9. Limbic System: Functions
    • Phylogenetically oldest part of the brain
    • Concerned with instincts and emotions contributing to preservation of the individual
    • Basic functions = feeding, aggression, emotions, and endocrine aspects of sexual response
  10. White Matter
    Myelinated nerve fibers located centrally
  11. White Matter: Transverse (Commissural) Fibers
    • Interconnect the two hemispheres
    • Including the corpus callosum (the largest), anterior commissure, and hippocampal commissure
  12. White Matter: Projection Fibers
    Connect cerebral hemispheres with other portions of the brain and spinal cord
  13. White Matter: Association Fibers
    • Connect different portions of the cerebral hemispheres
    • Allows cortex to function as integrated whole
  14. Basal Ganglia: Definition
    • Masses of gray matter deep within cerebral hemispheres
    • Forms an associated motor system (extrapyramidal system) wither other nuclei in the subthalamus and midbrain
  15. Basal Ganglia: Components
    • Striatum (caudate nucleus, neucleus accumbens, putamen)
    • Globus pallidus (internus and externus)
    • Subthalamic nucleus
    • Substantia nigra (compact part, reticular part)
    • Lenticular nucleus = putamen and globus pallidus
  16. Multiple Circuits in the Basal Ganglia
    • Oculomotor circuit (caudate loop)
    • Motor loop (putamen loop)
    • Limbic circuit
  17. Basal Ganglia: Oculomotor Circuit (Caudate Loop)
    • Originates in frontal and supplementary motor eye fields
    • Projects to caudate
    • Functions with saccadic eye movements
  18. Basal Ganglia: Motor Loop (Putamen Loop)
    • Originates in precentral motor and postcentral somatosensory areas
    • Projects to and excites putamen neurons
    • Putamen cells - inhibit globes pallid us neurons --> boosts activity in ventral lateral nucleus and supplemental motor area
    • Functions to scale amplitude and velocity of movements
    • Reinforces selected pattern, suppresses conflicting patterns
    • Preparatory for movement (i.e. motor set, anticipatory movement)
  19. Basal Ganglia: Limbic Circuit
    • Originates in prefrontal and limbic areas of cortex
    • To BG
    • To prefrontal cortex
    • Functions to organize behaviors (executive functions, problem solving, motivation) and for procedural learning
  20. Diencephalon
    • Thalamus
    • Subthalamus
    • Hypothalamus
    • Epithalamus
  21. Thalamus: Sensory Nuclei
    • Integrate and relay sensory info from body, face, retina, cochlea, and taste receptors to cerebral cortex and subcortical regions
    • Smell (olfaction) is the exception
  22. Thalamus: Motor Nuclei
    Relay motor information from cerebellum and globes pallidus to precentral motor cortex
  23. Thalamus: Other Nuclei
    Assist in integration of visceral and somatic functions
  24. Subthalamus
    Involved in control of several functional pathways for sensory, motor, and reticular function
  25. Hypothalamus
    • Integrates and controls function of ANS and neuroendocrine system
    • Maintains body homeostasis → regulates body temp, eating, water balance, anterior pituitary function/sexual behavior, and emotion
  26. Epithalamus: Habenular Nuclei
    Integrate olfactory, visceral, and somatic afferent pathways
  27. Epithalamus: Pineal Gland
    • Secretes hormones that influence pituitary gland and several other organs
    • Influences circadian rhythm
  28. Brainstem
    • Midbrain
    • Pons
    • Medulla
  29. Midbrain (Mesencephalon)
    • Connects pons to cerebrum
    • Superior peduncle connects midbrain to cerebellum
    • Contains cerebral peduncles (2 lateral halves) → each divided into anterior part or basis (crus cerebra and substantia nigra) and a posterior part (tegmentum)
  30. Midbrain: Tegmentum
    • Contains ll ascending tracts and some descending tracts
    • Red nucleus receives fibers from cerebellum
    • Is origin for rubrospinal tract
    • Important for coordination
    • Contains CN nuclei (oculomotor and trochlear)
  31. Midbrain: Substantia Nigra
    • Large motor nucleus
    • Connects basal ganglia and cortex
    • Important in motor control and muscle tone
  32. Midbrain: Superior and Inferior Colliculus
    • Superior: important relay station for vision and visual reflexes 
    • Inferior: important relay station for hearing and auditory reflexes
  33. Midbrain: Periaqueductal Gray
    Contains endorphin-producing cells (important for suppression of pain) and descending autonomic tracts
  34. Pons
    • Connects the medulla oblongata to the midbrain
    • Allows passage of important ascending and descending tracts
    • Anterior basal part, midline raphe nuclei, and tegmentum
  35. Pons: Anterior Basal Part
    Acts as a bridge to cerebellum (middle cerebellar peduncle)
  36. Pons: Midline Raphe Nuclei
    Project widely and are important for modulating pain and controlling arousal
  37. Pons: Tegmentum
    Contains several important cranial nerve nuclei:

    • Abducens
    • Trigeminal
    • Facial
    • Vestibulocochlear
  38. Medulla Oblongata
    • Connects spinal cord with pons
    • Contain relay nuclei of dorsal column (gracilis and cuneatus) → fibers cross to give rise to medial lemniscus
    • Corticospinal tracts cross (decussate) in pyramids
    • Contains several important cranial nuclei (hypoglossal, dorsal nucleus of vagus and vestibulocochlear) 
    • Contains important centers for vital functions (cardiac, respiratory, and vasomotor centers)
  39. Medulla Oblongata: Inferior Cerebellar Peduncle
    Relays dorsal spinocerebellar tract to cerebellum
  40. Medulla Oblongata: Medial Longitudinal Fasciculus
    • Arises from vestibular nuclei
    • Extends throughout brainstem and upper cervical spinal cord
    • Important for control of head movement and gaze stabilization (vestibular-ocular reflex)
  41. Medulla Oblongata: Olivary Nuclear Complex
    • Connects cerebellum to brainstem 
    • Important for voluntary movement control
  42. Cerebellum
    • Located behind dorsal pons and medulla in posterior fossa
    • Joined to brainstem by 3 pairs of peduncles: superior, middle, and inferior 

    • Comprises:
    • 3 hemispheres and midline vermis
    • Cerebellar cortex
    • Underlying white matter
    • 4 paired deep nuclei
  43. Achicerebellum (Flocculonodular Lobe)
    • Connects with vestibular system 
    • Concerned with equilibrium and regulation of muscle tone
    • Helps coordinate vestibulo-ocular reflex
  44. Paleocerebellum (Rostral Cerebellum, Anterior Lobe)
    • A.K.A. Spinocerebellum
    • Receives input from proprioceptive pathways
    • Concerned with modifying muscle tone and synergistic actions of muscles
    • Important in maintenance of posture and voluntary movement control
  45. Neocerebellum (Cerebellar Hemisphere, Posterior Lobe)
    • A.K.A. Pontocerebellum
    • Receives input from corticopontocerebellar tracts and olivocerebellar fibers
    • Concerned with smooth coordination of voluntary movements
    • Ensures accurate force, direction, and extent of movement 
    • Important for motor learning, sequencing of movements, and visually triggered movements 
    • May have role in assisting cognitive function and  mental imagery