Anatomy of the brain


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Anatomy of the brain

  2. 2. • Total surface area of thecerebral cortex = 2,500cm2 (2.5 square feet).• In order to fit it in theskull, it is crumpled up.• The weight of the brain innormal young adultsranges from 1050 g to1800 gAn Overview
  3. 3. Although the two halves may look aliketheir functions are very differentAn Overviewbrain can be divided into three main parts1. The rhombencephalon orhindbrain-medulla oblongata ormyelencephalon-metencephalonPonsCerebellum2. The mesencephalon or midbrain3. The prosencephalon or forebrain-Diencephalonlarge thalamusthe much smallerhypothalamus,-Telencephalon -two cerebralhemispheresfive main parts or lobes: lobus frontalis, lobusparietalis, lobus temporalis, lobus occipitalis andlobus limbicus
  4. 4. What is a brain made of?• A neuron is a nerve cell.• The brain is made up of approximately 100 billionneurons.• Neurons have specialized projections calleddendrites and axons.• Dendrites bring information to the cell body andaxons take information away from the cell body.• The axon of a motor neuron in the spinal cordthat innervates a muscle in the foot can beabout 3 feet in length.• They are separated by small gap called asynapse• Total number of synapses in cerebral cortex isabout 60 trillion. This is equal to about a half-billion synapses per cubic millimeter.
  5. 5. • There are 10-50 times as many Glia cells asneurons.What is a brain made of?There several types of glial cells;Insulate the neurons (myelin) OligodendrocytesNourish and support the neurons AstrocytesProduce Spinal Fluid Ependymal CellsRemove debris Microglia• In addition to each neuron, there are 50 times asmany glial cells, and many blood vessels filling thespace between them.• The neurons make up less than 8% of the cells inthe brain• The majority of the remaining cells are called“Glia”, which means glue.
  6. 6. Glial Cells
  7. 7. Coverings of the BrainDura
  8. 8. Arachnoid• The Arachnoid is like a sheet of cellophanethat is draped over the brain.• There is a space between the Arachnoid and the brain called the subarachnoidspace.• In this space is the spinal fluid and the blood vessels
  9. 9. Pia• The Pia is a single layer of cells that coat the brainsurface, much like linoleum on a floorThe arrowsoutline thespace betweenthe arachnoid and pia;the subarachnoid space
  10. 10. Dural Partitions• In a few regions, the dura creates large partitions, separating large parts of thebrain
  11. 11. The Cerebrum: Features• Sulci – Small grooves dividing the gyri– Central Sulcus – Divides the FrontalLobe from the Parietal Lobe• Longitudinal Fissure – Divides the two Cerebral Hemispheres• Transverse Fissure – Separates the Cerebrum from theCerebellum• Sylvian/Lateral Fissure – Divides the Temporal Lobe from theFrontal and Parietal Lobes• Gyri – Elevated ridges “winding” aroundthe brain.• Fissures – Deep grooves, generallydividing large regions/lobes of the brain
  12. 12. The CerebrumGrey matter is composed of cellbodies of the neuronsWhite matter is the axons and dendritesof the neurons – bundles of “cables”connecting regions of the brain andspinal cord.Deep within the brain are large clusters of neuron cell bodiescalled nuclei or ganglia. They are also grey matter
  13. 13. The CerebrumOccasionally, the Insula is considered the fifth lobe. It is located deep to the Temporal Lobe.TransverseFissureSylvian/LateralFissureCentral Sulcus
  14. 14. The Cerebrum: Frontal Lobe• The Frontal Lobe of the brain is located deep to theFrontal Bone of the skull.• It plays an integral role in the following functions oractions:- Memory Formation- Emotions- Decision Making/Reasoning- Personality
  15. 15. The Cerebrum: Frontal Lobe• Primary Motor Cortex (Precentral Gyrus)– Cortical site involved with controlling movements of the body.• Broca’s Area – Controls facialneurons, speech, and languagecomprehension.Located on Left Frontal Lobe.Broca’s Aphasia – Results in theability to comprehend speech, butthe decreased motor ability (orinability) to speak and form words.• Olfactory Bulb - Cranial Nerve I,Responsible for sensation of Smell
  16. 16. The Cerebrum: Parietal Lobe• The Parietal Lobe of the brain is located deep to theParietal Bone of the skull.• It plays a major role in the following functions oractions:1. Senses and integrates sensation(s)2. Spatial awareness and perception(Proprioception - Awareness of body/ body parts inspace and in relation to each other)
  17. 17. Parietal Lobe: Cortical Regions• Primary Somatosensory Cortex (Postcentral Gyrus)– Site involved with processing of tactile and proprioceptive information.• Somatosensory Association Cortex- Assists with the integration andinterpretation of sensations relative to bodyposition and orientation in space. May assistwith visuo-motor coordination.• Primary Gustatory Cortex– Primary site involved with the interpretationof the sensation of Taste.
  18. 18. The Cerebrum: Occipital Lobe• The Occipital Lobe of the Brain is located deep to theOccipital Bone of the Skull.• Its primary function is the processing, integration,interpretation, etc. of VISION and visual stimuli.
  19. 19. Occipital Lobe: Cortical Regions• Primary Visual Cortex – This is the primary area of the brain responsible forsight -recognition of size, color, light, motion, dimensions, etc.• Visual Association Area –Interprets information acquiredthrough the primary visual cortex.
  20. 20. The Cerebrum: Temporal Lobe• The Temporal Lobes are located on the sides of thebrain, deep to the Temporal Bones of the skull.• They play an integral role in the following functions:- Hearing- Organization/Comprehension of language- Information Retrieval (Memory and MemoryFormation)
  21. 21. Temporal Lobe: Cortical Regions• Primary Auditory Cortex – Responsible for hearing• Primary Olfactory Cortex –Interprets the sense of smell once itreaches the cortex via the olfactorybulbs. (Not visible on the superficialcortex)• Wernicke’s Area – Languagecomprehension.Located on the Left Temporal Lobe.Wernicke’s Aphasia – Languagecomprehension is inhibited. Wordsand sentences are not clearlyunderstood, and sentence formationmay be inhibited or non-sensical.
  22. 22. HOMUNCULUSThis graphic representation of the regions of the Primary Motor Cortexand Primary Sensory Cortex is one example of a HOMUNCULUS:
  23. 23. Connectivity
  24. 24. • Arcuate Fasciculus - A white matter tract that connects Broca’s Area andWernicke’s Area through the Temporal, Parietal and Frontal Lobes.Allows for coordinated, comprehensible speech.•Damage may result in: Conduction Aphasia- Where auditory comprehension and speech articulation arepreserved, but people find it difficult to repeat heard speech.Connectivity
  25. 25. • In the individual person, speech depends on the integrityof specific cortical areas that usually lie only in onehemisphere• It is normally the left one in right-handed persons.• In left-handed persons, it may be the right or the lefthemisphereDominant Hemisphere
  26. 26. Dominant Hemisphere
  27. 27. Internal Capsule
  28. 28. • Deep within the cerebral hemispheres, large grey masses of nervescells called nuclei, form components of the basal ganglia• 4 basal ganglia• The caudate nucleus• The putamen• The Globus pallidus (paleostriatum)• The amygdala (oldest of the BG- archistriatum)Basal GangliaLentiform nucleusCorpusstriatum• Amygdala located ventral to corpusstriatum in medial part of temporallobe, receives olfactory inputs butplays no role in olfactory perception.• Pathological processes includeabnormal involuntary movement(dyskinesia) and significantalterations of muscle tone
  29. 29. • The thalamus involved in the relay and distribution of most but not allsensory and motor signals to specific regions of the cerebral cortexThalamus• The relay nuclei in turn supply theprimary and secondary sensory areasof the cerebral cortex.• Sensory signals generated in all typesof receptors are projected via complexpathways to specific relay nuclei in thethalamus.
  30. 30. • It controls major endocrine functions by secreting hormones (i.e. oxytocinand vasopressin) that induce smooth muscle contractions of reproductive,digestive and excretory systems)Hypothalamus• Specific regions of the hypothalamus arealso involved with the control ofsympathetic and parasympatheticsactivities, temperature regulation, foodintake, reproductive cycle, emotionalexpression and behaviour.• The hypothalamus lies below the thalamus in the walls and floor of the thirdventricle
  31. 31. • The brainstem comprises the medulla oblongata, the pons and themidbrainBrain stem• The midbrain lies above pons containingmajor motor supply to the muscles controllingeye movements.• The medulla transmits all signals betweenthe spinal cord and the higher part of thebrain, also governs mechanisms such asheartbeat, blood pressure and breathing• The pons lies above the medulla, associatedwith sensation and movement of the face
  32. 32. • It lies behind the pons and medulla oblongata and fills the greater part ofthe base of skullCerebellum• The cerebellum serves as a sort ofregulator and coordinator of nerve impulsesbetween the brain and the muscles.• It influences upon equilibrium, muscle toneand the coordination of voluntary motorfunction.• It connected to midbrain, pons and medulla viasuperior pedunclesmiddle pedunclesinferior peduncles• It contains a pair of lateral lobes (hemispheres) and midline vermis
  33. 33. Brain Circulation• Although the brain comprisesonly about 2% of the bodyweight it uses about 20% ofthe bodys blood supply andconsumes 15-20% of theoxygen• The human brain contains around400 miles of blood vessels.
  34. 34. Brain Circulation
  35. 35. Brain Circulation
  36. 36. Brain Circulation
  37. 37. Brain Circulation: Venous System
  38. 38. Brain Circulation: Venous System
  39. 39. The VentriclesThe ventricles are cavities in our brains, where most of thecerebrospinal fluid (CFS) is made is made.
  40. 40. The Ventricles
  41. 41. Cerebrospinal FluidCSF• CSF is actively secretedby the brain. CSF isconstantly being made,circulates and isreabsorbed into the bloodstream.• Total volume of cerebrospinalfluid = 125-150 ml• The entire volume ofcerebrospinal fluid turnsover 3 to 4 times per day• CSF is made at a rate ofabout 30cc per hour• The CSF resides in thesubarachnoid space
  42. 42. Thank You