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Brain Structure and Function

Brain Structure and Function

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Brain Structure and Function

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  1. Brain Structure and Function

  2. “If the human brain were so simple that we could understand it, we would be so simple that we couldn’t” • -Emerson Pugh, The Biological Origin of Human Values (1977)

  3. Phineas Gage • September 13th, 1848 • Phineas 25 years old • Rutland & Burlington Railroad, Cavendish, VT • Paving the way for new RR tracks • “Tamping Iron” • 1.25in x 3ft

  4. Phineas Gage • Accident • Quick Recovery • Months later: “No longer Gage” • Before: capable, efficient, best foreman, well-balanced mind • After: extravagant, anti-social, liar, grossly profane • Stint with P.T Barnum • Died 12 years later

  5. Evolution of the Brain • Reptilian  Paleomammalian  Neomammalian

  6. The Brain • Brainstem • responsible for automatic survival functions • Medulla • controls heartbeat and breathing

  7. Parts of the Brain • BRAINSTEM Heart rate and breathing THALAMUS Relays messages amygdala hippocampus pituitary CEREBELLUM  Coordination and balance

  8. Reticular Formation • Widespread connections • Arousal of the brain as a whole • Reticular activating system (RAS) • Maintains consciousness and alertness • Functions in sleep and arousal from sleep

  9. The Cerebellum • helps coordinate voluntary movement and balance

  10. The Limbic System • Hypothalamus, pituitary, amygdala, and hippocampus all deal with basic drives, emotions, and memory • Hippocampus  Memory processing • Amygdala  Aggression (fight) and fear (flight) • Hypothalamus  Hunger, thirst, body temperature, pleasure; regulates pituitary gland (hormones)

  11. The Limbic System • Hypothalamus • neural structure lying below (hypo) the thalamus; directs several maintenance activities • eating • drinking • body temperature • helps govern the endocrine system via the pituitary gland • linked to emotion

  12. The Limbic System • Amygdala • two almond-shaped neural clusters that are components of the limbic system and are linked to emotion and fear

  13. The Brain • Thalamus • the brain’s sensory switchboard, located on top of the brainstem • it directs messages to the sensory receiving areas in the cortex and transmits replies to the cerebellum and medulla

  14. The Cerebral Cortex • Cerebral Cortex • the body’s ultimate control and information processing center

  15. The lobes of the cerebral hemispheres

  16. The lobes of the cerebral hemispheres Planning, decision making speech Sensory Vision Auditory

  17. The Cerebral Cortex • Frontal Lobes • involved in speaking and muscle movements and in making plans and judgments • the “executive” • Parietal Lobes • include the sensory cortex

  18. The Cerebral Cortex • Occipital Lobes • include the visual areas, which receive visual information from the opposite visual field • Temporal Lobes • include the auditory areas, each of which receives auditory information primarily from the opposite ear

  19. The Cerebral Cortex • Frontal (Forehead to top) Motor Cortex • Parietal (Top to rear) Sensory Cortex • Occipital (Back) Visual Cortex • Temporal (Above ears) Auditory Cortex

  20. Motor/Sensory Cortex • Contralateral • Homunculus • Unequal representation

  21. Sensory Areas – Sensory Homunculus Figure 13.10

  22. The Cerebral Cortex • Aphasia • impairment of language, usually caused by left hemisphere damage either to Broca’s area (impairing speaking) or to Wernicke’s area (impairing understanding) –see clips • Broca’s Area • an area of the left frontal lobe that directs the muscle movements involved in speech • Wernicke’s Area • an area of the left temporal lobe involved in language comprehension and expression

  23. Language Areas • Broca  Expression • Wernicke  Comprehensionand reception • Aphasias LEFT HEMISPHERE

  24. Paul Broca [1800s] • Suggested localization

  25. Techniques to examine functions of the brain 1. Remove part of the brain & see what effect it has on behavior 2. Examine humans who have suffered brain damage

  26. 3. Stimulate the brain 4. Record brain activity

  27. Brain Lateralization

  28. Our Divided Brains • Corpus collosum – large bundle of neural fibers (myelinated axons, or white matter) connecting the two hemispheres

  29. Hemispheric Specialization • LEFT • Symbolic thinking • (Language) • Detail • Literal meaning RIGHT Spatial perception Overall picture Context, metaphor

  30. Contra-lateral division of labor • Right hemisphere controls left side of body and visual field • Left hemisphere controls right side of body and visual field

  31. Split Brain Patients • Epileptic patients had corpus callosum cut to reduce seizures in the brain • Lives largely unaffected, seizures reduced • Affected abilities related to naming objects in the left visual field

  32. Brain Plasticity

  33. Brain Plasticity • The ability of the brain to reorganize neural pathways based on new experiences • Persistent functional changes in the brain represent new knowledge • Age dependent component • Brain injuries

  34. Impoverished environment Enriched environment Environmental influences on neuroplasticity

  35. Sensation and Perception

  36. Sensation • The process by which the central nervous system receives input from the environment via sensory neurons • Bottom up processing

  37. Perception • The process by which the brain interprets and organizes sensory information • Top-down processing

  38. The psychophysics of sensation • Absolute threshold the minimum stimulation needed to detect a stimulus with 50% accuracy • Subliminal stimulation below the absolute threshold for conscious awareness • May affect behavior without conscious awareness • Sensory adaptation/habituationdiminished sensitivity to an unchanging stimulus

  39. The five major senses • Vision – electromagnetic • Occipital lobe • Hearing – mechanical • Temporal lobe • Touch – mechanical • Sensory cortex • Taste – chemical • Gustatory insular cortex • Smell – chemical • Olfactory bulb • Orbitofrontal cortex • Vomeronasal organ?

  40. The sixth sense And the seventh…and eighth…and ninth… • Vestibular  balance and motion • Inner ear • Proprioceptive  relative position of body parts • Parietal lobe • Temperature  heat • Thermoreceptors throughout the body, sensory cortex • Nociception  pain • Nociceptors throughout the body, sensory cortex

  41. Thresholds of the five major senses

  42. The Retina • The retina at the back of the eye is actually part of the brain! Rods – brightness Cones – color