Neuroanatomy Midterms

• Cerebral Cortex


  Brain's outermost layer of nerve cell tissue, composed of neurons supported by glial cells, made up of lipoproteins and cholesterol-type of cells, also called the gray matter
• Cerebral Cortex


  • Forms a complete covering of the cerebral hemisphere
  • Consists of a mixture of nerve cells, nerve fibers, neuroglia, and blood vessels
  • Only way in and out is through Internal Capsule
• Role of Cerebral Cortex


  Overall in command of the nervous system, can overrule any other part of nervous system, origin of all voluntary movement, for all conscious awareness
• Origin of Cerebral Cortex

  From neuroectodermal cells, formed prosencephalon, divided into two telencephalon, matured into two cerebral hemisphere, made up of gray matter arranged in gyri with sulci that give a big surface area
• Nerve Fibers in Cerebral Cortex

  • Arranged both radially and tangentially
  • Radial fibers run at right angles to the cortical surface, include afferent entering projection, association, and commissural fibers
  • Tangential fibers run parallel to the cortical surface, includes axons of horizontal and stellate cells and collateral branches of pyramidal and fusiform cells

  
• Layers of Cerebral Cortex

  • Molecular Layer
  • External Granular Layer
  • External Pyramidal Layer
  • Internal Granular Layer
  • Internal Pyramidal Layer
  • Multiform or Fusiform Layer
• Layers of Cerebral Cortex

  • Layers are divided by type, density and arrangement of cells for descriptive purposes
  • Molecular layer is the most superficial layer consisting mainly of a dense network of tangentially oriented nerve fibers
  • External Granular layer contains large numbers of small pyramidal cells and stellate cells
  • External Pyramidal layer is composed of pyramidal cells, whose cell body size increases from the superficial to the deeper borders of the layer
  • Internal Granular layer is composed of closely packed stellate cells
  • Internal Pyramidal layer contains very large and medium-size pyramidal cells
  • Multiform or Fusiform layer majority of the cells are fusiform, but many are modified pyramidal cells
• Neurons in Cerebral Cortex

  • Pyramidal Neurons (Betz cells & Meynert cells)
  • Stellate Neurons (form intracortical connections)
  • Fusiform Neurons (enter deep white matter)
  • Neurons of Martinotti (connect layers upward)
  • Neurons of Cajal (run horizontal in the first layer)

  
• Association Fibers


  Intracortical fibers that only transmit and originate from the same cortical hemisphere and end up in the same hemisphere
• Commissural Fibers


  Intercortical fibers that connect one cerebral hemisphere to the other, largest is the Corpus Callosum
• Projection Fibers


  Start in the cortex and transmit down to the other parts of the nervous systems, are long fibers
• Cortical Structure Variations


  • Heterotypical areas where the basic six layers cannot be recognized, can be described as granular and agranular type
  • Homotypical areas where the basic six layers can be recognized
• Lobes of the Cerebral Cortex

  • Frontal Lobe
  • Parietal Lobe
  • Occipital Lobe
  • Temporal Lobe
  • Limbic Lobe
• Functions of Frontal Lobe

  Brodmann's Area 4 & 6 are the origin of all voluntary movement, Prefrontal Lobe Area 9, 10, 11, 12 are for proper response to stimuli
• Motor Area of Frontal Lobe

  • Area 4 (Primary Motor Area) forms a motor homunculus in the precentral gyrus and brings out the command/movement through the corticospinal tract
  • Area 6 & 8 (Supplementary Motor Area) are the motor planning area for movement of the contralateral limbs
  • Area 44 (Broca's Area) is for expression of speech on the dominant hemisphere
• Pre-Frontal Lobe


  Also part of the Limbic Lobe, makes up the individual's personality, Brodmann's Area 9, 10, 11, 12 are responsible for appropriate response to stimuli
• Functions of Parietal Lobe


  Receive, collect, process and interpret general sensory stimuli (excluding vision, hearing, taste)
• Functions of Occipital Lobe


  Receive, collect, process and interpret visual stimuli
• Functions of Temporal Lobe


  Receive, collect, process and interpret auditory stimuli, stores all the memory in the inferior temporal gyrus
• Limbic Lobe


  Scattered diffusely throughout the brain, core of our emotions and responses, includes structures like prefrontal lobe, amygdala, cingulate gyrus, nucleus basalis of Meynert, parahippocampus, hippocampus, insula of Reille
• 3 Neurons for the Receiving Lobes

  Primary Area collects and receives data, Association Area processes and interprets data, Integration Area integrates the data

  
• General Sensation is processed in the Primary Somat Area of the Cerebral Cortex
• Sulcus


  It runs parallel to the posterior ramus of the lateral sulcus which divide the lobe into 3 (superior, middle, inferior temporal gyri)
• Temporal gyri


  • Superior Temporal Gyrus
  • Middle Temporal Gyrus
  • Inferior Temporal Gyrus
• The sulcus is continued onto the inferior surface of the hemisphere
• Limbic lobe


  • Scattered diffusely throughout the brain
  • Core of our emotions & responses
• Structures of the limbic lobe

  • Prefrontal lobe
  • Amygdala
  • Cingulate gyrus
  • Nucleus Basalis of Meynert
  • Parahippocampus
  • Hippocampus
  • Insula of Reille
• 3 neurons for the receiving lobes

  • Primary Area - collect & receive data
  • Association Area - data is processed & interpreted
  • Integration Area - to integrate the data

  
• Areas of general sensation

  • Primary Somathestetic Area (Areas 3,1,2)
  • Somathestetic Association Area (Area 5 & 7)
• The larger the area, the more complex the movement is = you need more neuronal areas/neurons to create more complex movement
• Prefrontal Lobotomy is a treatment for aggressive patients done by inserting a probe from the nostrils into the cribriform plate and ablate the prefrontal lobe = no more aggression
• Areas of vision


  • Primary Visual Area (Area 17)
  • Visual Association Area (Areas 18 & 19)
  • Integration Area (Areas 39 & 40)
• Areas of audition/hearing


  • Primary Auditory Area (Area 41 & 42)
  • Auditory Association Area (Area 22)
  • Integration Area (Area 39 & 40)
  • Wernicke's Area
• Taste area


  • Situated at the lower end of the postcentral gyrus in the superior wall of the lateral sulcus and in the adjoining area of the insula (BRODMANN AREA 43)
  • Ascending fibers from the nucleus solitarius probably ascend to the ventral posteromedial nucleus of the thalamus where they synapse on neurons that send fibers to the cortex
• Vestibular area


  • Situated near the part of the postcentral gyrus concerned with the sensations of the face
  • Lies opposite the auditory area in the superior temporal gyrus
  • Concerned with appreciation of the positions and movements of the head in space
  • Through its nerve connections, movement of the eyes and the muscles of the trunk and limbs are influenced in the maintenance of posture
• Insula


  • Buried within the lateral sulcus and forms its floor
  • Posterior part is Granular, Anterior part is Agranular
  • Important for planning or coordinating the articulatory movements necessary for speech
• Association cortex


  • Forms only a small part of the total surface area
  • Primary sensory area with their granular cortex
  • Primary motor area with their agranular cortex
  • Remaining areas have all 6 cellular layers also known as the homotypical cortex
  • Homotypical cortex is classically known as the association areas, although precisely what they associate is not known
  • Now become apparent that these areas of the cortex have multiple inputs & outputs and are very much concerned with behavior, discrimination, and interpretation of sensory experiences
  • 3 main association areas: Prefrontal, Anterior Temporal, and Posterior Parietal
• Prefrontal cortex


  • Capable of associating experiences that are necessary for the production of abstract ideas, judgment, emotional feeling, and personality
  • Destruction of the prefrontal region does not produce any marked loss of intelligence
• Anterior temporal cortex


  • Plays a role in the storage of previous sensory experiences
  • Stimulation may cause the individual to recall objects seen or music heard in the past
• Posterior parietal cortex


  • Visual information from the posterior occipital cortex and the sensory input of touch and pressure and propioception from the anterior parietal cortex is integrated into concepts of size, form and texture (this ability is also known as STEREOGNOSIS)
  • A conscious appreciation of the body image is also assembled in this area