MIDTERM NEUROANATOMY

• Cerebrum


  • Largest part of the brain
  • Divided into two hemispheres (right & left)
  • Each hemisphere is further divided into lobes

  
• Corpus callosum


  Mass of white matter which connects the two hemispheres of the cerebrum
• Central sulcus of Rolando


  Most important line to remember in order to know the different parts of the cerebrum
• Central sulcus of Rolando

  • Does not transect the lateral fissure
  • Fissure must originate from the top
• Lobes of the cerebrum

  • Frontal lobe
  • Parietal lobe
  • Occipital lobe
  • Temporal lobe
  • Insula

  
• Frontal lobe


  Motor area & seat of mental activities

  
• Parietal lobe


  Somesthetic area (sensory)
• Occipital lobe


  Visual center
• Temporal lobe


  Hearing center
• Insula


  Considered as the 5th lobe in neuroanatomy

  
• Function of the cerebrum

  • Sensation - perceives sensory information
  • Motor - commands skilled movements
  • Emotions - provides awareness of emotions
  • Higher mental functions - necessary for memory, thinking, language ability, etc.
• Areas of the cerebrum

  • Anatomical areas - lobes
  • Functional areas - Brodmann's classification
• Cerebral gray matter


  Composed of neuronal cell bodies

  
• Cerebral cortex


  Outermost layer of gray matter making up the superficial aspect of the cerebrum

  
• Basal nuclei


  Large masses of gray matter embedded in the white matter of the cerebrum
• Cerebral white matter


  • Composed of both myelinated & non-myelinated fibers
  • Central core of the hemispheres that appear white due to myelin

  
• Fibers of the white matter

  • Association fibers - connects various cortical regions within the same hemisphere
  • Commissural fibers - connects areas of cortex in one hemisphere with corresponding areas of the opposite hemisphere
  • Projection fibers - connects cortex with subcortical areas (other parts of the brain) as well as brainstem & spinal cord
• Cerebral features


  • Gyrus (plural: gyri) - elevated ridges
  • Sulcus (plural: sulci) - small grooves dividing the gyri
  • Fissure (plural: fissures) - deep grooves which generally divide large regions/lobes of the brain

  
• Longitudinal fissure


  Divides the two cerebral hemispheres
• Transverse fissure


  Separates the cerebrum from the cerebellum
• Sylvian/lateral fissure


  Divides the temporal lobe from the frontal & parietal lobes
• Central sulcus of Rolando


  Separates the parietal from frontal lobe
• Parieto-occipital fissure


  Separates the parietal lobe from the occipital lobe
• Primary cortical areas


  Small portion of the cortex with a generally symmetrical function

  
• Primary cortical areas


  • Primary motor area
  • Primary somatosensory areas
  • Primary areas for vision, hearing, taste, and smell

  
• Association areas


  • Usually adjacent to the primary areas
  • For higher processing
• Functions of the association areas

  • Plan, integrate, and initiate motor activity
  • Integrate & interpret sensory information
• Brodmann's classification (areas)


  Korbinian Brodmann (1909) divided the brain into different functional areas according to: cytoarchitectural structure (histology) & organization of neurons

  
• Important Brodmann areas


  • BA 3, 1, 2 - Primary somatosensory cortex
  • BA 4 - Primary motor cortex
  • BA 5 - Somatosensory association cortex
  • BA 6 - Premotor cortex & supplementary motor cortex
  • BA 8 - Includes frontal eye fields
  • BA 9 - Dorsolateral prefrontal cortex
  • BA 10 - Anterior prefrontal cortex
  • BA 17 - Primary visual cortex (V1)
  • BA 18 - Secondary visual cortex (V2)
  • BA 19 - Associative visual cortex (V3, V4, and V5)
  • BA 22 - Superior temporal gyrus (caudal part is usually considered to contain the Wernicke's area)
  • BA 39 - Angular gyrus (considered by some to be part of the Wernicke's area)
  • BA 40 - Supramarginal gyrus (considered by some to be part of the Wernicke's area)
  • BA 41 & 42 - Auditory cortex
  • BA 43 - Primary gustatory cortex
  • BA 44 - Pars opercularis (part of the inferior frontal gyrus and part of the Broca's area)
  • BA 45 - Pars triangularis (part of the inferior frontal gyrus and part of the Broca's area)

  
• Parts of the frontal lobe

  • Precentral gyrus
  • Superior frontal gyrus
  • Middle frontal gyrus
  • Inferior frontal gyrus - Pars orbitalis, Pars triangularis, Pars opercularis
  • Orbital gyrus
  • Paracentral lobule
  • Marginal sulcus

  
• Primary motor area (BA 4)

  • Located in the precentral gyrus & at the anterior part of the paracentral lobule
  • Contributes to the corticospinal tract
  • Controls contralateral movements of voluntary muscles
• Isolated ipsilateral movements do not occur in the primary motor area, although bilateral movements can occur for extraocular muscles, muscles of the upper part of the face, tongue, mandible, larynx, and pharynx
• Motor homunculus of the precentral gyrus


  Shows which portion of the precentral gyrus is concerned with which parts of the body; it also represents the magnitude of control

  
• Premotor cortex (BA 6)


  • Also known as the secondary motor area
  • Located anterior to the precentral gyrus
  • Controls proximal & axial muscles
  • Stores programs of motor activity of the primary cortex

  
• Supplementary motor cortex (BA 6)

  • Part of BA 6 found on the medial surface of the hemisphere
  • Located anterior to the paracentral lobule
  • Programs complex motor sequences
  • Coordinates bilateral movements

  
• Frontal eye fields (parts of BA 6, 8, and 9)

  • Located in the posterior part of the middle frontal gyrus
  • Causes conjugate movements of the eye (especially toward the opposite side)
  • Controls voluntary scanning movements of the eye and is independent of visual stimuli
• Prefrontal cortex (BA 9, 10, 11, and 12)


  • Areas of higher cortical function
  • Makeup of one's personality
  • Regulation of one's depth of feeling
  • Determining of one's initiative & judgement

  
• Broca's area (BA 44 and 45)

  • Motor speech area
  • Located at the opercular & triangular parts of the inferior frontal gyrus
  • Responsible for the formation of words
  • When damaged, it is associated with expressive or motor aphasia
• Cingulate gyrus


  • Gyrus immediately above the corpus callosum
  • Modulates emotional aspects of behavior

  
• Orbitofrontal cortex


  • Located between the superior frontal gyrus & inferior rostral sulcus
  • Site of frontal lobotomies