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Brain

Brain. Chapter 14. General Information. Wt= 2% of body weight 25 billion neurons (45,000/min made before birth!) 20% of bl. circ thru brain/min Consumes 20% of O 2 at rest Bl. delivered by 4 arteries Some molecules diffuse easily into brain;ex. O2, glucose, aa

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Brain

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  1. Brain Chapter 14

  2. General Information • Wt= 2% of body weight • 25 billion neurons (45,000/min made before birth!) • 20% of bl. circ thru brain/min • Consumes 20% of O2 at rest • Bl. delivered by 4 arteries • Some molecules diffuse easily into brain;ex. O2, glucose, aa • Some molecules are blocked by bl. brain barrier

  3. Protection of Brain • Meninges (meninx= sing.) • Dura mater – contains dura folds, tough -subdural space • Arachnoid membrane- spider web like -subarachnoid space • Pia mater – highly vascular

  4. Cerebrospinal Fluid- plate 120 • Shock absorber • In subarchnoid space, ventricles in brain, and central canal of spinal cord • Originates in ependymal cells of choroid plexus • http://www.sickkids.ca/childphysiology/cpwp/Brain/csf.htm • http://www.cnl.salk.edu/~fellous/courses/cogs17f2/csf.mov

  5. http://www.stanford.edu/group/hopes/basics/braintut/brain.swfhttp://www.stanford.edu/group/hopes/basics/braintut/brain.swf

  6. Hydrocephalus- caused when CSF formation increases, or reabsorption decreases

  7. Divisions of Brain • Brain Stem • Midbrain/Mesencephalon -processes basic visual and audio data -reflexive responses -maintenance of consciousness b. Pons -relays sensory info -Subconscious center • Medulla -relays sensory info -autonomic center for regulation basic life functions

  8. Divisions of Brain • Dicephalon- sits on top of brain stem • Thalamus-final relay point for ascending sensory info • Hypothalamus-controls emotions • Epiphalamus (pineal body)- secretes melatonin http://outreach.mcb.harvard.edu/animations/brainanatomy.swf

  9. Divisions of Brain • Cerebellum- “little brain”, 2nd largest part • Outer crust= cortex= made of gray matter, contains large neurons called Purkinje cells • Inside= white matter= braches like tree, called arbor vitae • Peduncles- 3 large nerves masses that connect cerebellum to other parts of brain

  10. Functions of Cerebellum • Promotes smooth muscle movement • Maintains muscle tone and posture • Receives impulses from middle ear to maintain equilibrium -affected by alcohol- produces ataxia= uncoordinated motions -damage to Purkinje cells can result in permanent loss of coordination http://outreach.mcb.harvard.edu/animations/brainanatomy.swf

  11. Divisions of Brain 4. Cerebrum

  12. 4. Cerebrum • Largest and most prominent brain part -Contains 12 billion neurons -And 50 billion glial cells • Covered by 2-5 mm of gray matter • Features; gyri, sulci, fissures

  13. Longitudinal- divides left & right hemispheres Transverse- separates cerebrum from cerebellum Fissures of Cerebrum

  14. http://outreach.mcb.harvard.edu/animations/brainanatomy.swf

  15. Cerebrum “Connections” • Areas of the brain lead to other parts of the brain via tracts/fibers made of white matter • 3 types • Association- transmit impulses b/t/w neurons in same hemisphere • Commisural- connect cooresponding areas of left and right hemispheres • Projection- extend from cortex to descending pathways out of cerebrum

  16. Areas of Cerebrum • Cerebral Cortex- outermost portion, white matter • Cerebral Nuclei- inner portion, gray matter - function in subconscious control of skeletal muscle, and learned muscle patterns

  17. Areas of Cerebral Cortex • Motor/sensory a. Frontal lobe/primary motor cortex voluntary control of skeletal muscle b. Parietal Lobe/primary sensory cortex conscious perception through skin+ taste c. Occipital-/visual cortex conscious perception of visual stimuli d. Temporal/ auditory and olfactory cortex conscious perception of sound and smells

  18. Areas of Cerebrum • Association Areas- interpret info and coordinate a response a. Somatic sensory- touch b. Somatic motor- learned movements b. Visual- C+A+R c. Auditory- word recognition

  19. Areas of Cerebrum • Integrative Centers-complex motor functions, and analysis • Wernicke’s area-receives info from all sensory association areas, plays role in personality • Broca’s/Speech area- regulates breathing for speech • Prefrontal cortex-time sequencing

  20. Cranial Nerves • PNS components that connect directly to brain rather than spinal cord • 12 cranial nerves- I-XII • # by position (beginning at cerebrum) • Classified as sensory, special sensory, motor, or mixed • See p466-474 • “On old Olympic towering top a Fin and German viewed some hops”

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