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9/9/2016 Central Nervous System or CNS Some Basic Neuroanatomy The Central Nervous System Figure 3.3: Central Nervous System Development • Brain develops from a fluid-filled, tubular structure • Upper tube develops into • • • • Forebrain Midbrain Hindbrain At 3 weeks: all equal in size • At 11 weeks: forebrain becomes the largest part The Forebrain • Right & left cerebral hemispheres (seen from above) • The surface of hemispheres is the very folded cerebral cortex • Lower tube becomes the spinal cord Copyright © 2009 Allyn & Bacon 1 9/9/2016 Corpus Callosum Side View Central Sulcus Lateral fissure The Forebrain – Cortex. Figure 3.8: Lobes and Cortical Areas Garrett: Brain & Behavior 4e 11 2 9/9/2016 Beyond the Motor Areas: Prefrontal Cortex Humans: Well-developed prefrontal cortex Frontal Lobe “Executive Functions” • Mental representation of the world; working memory & temporal memory (order of events in time) • Forming goals, anticipating consequences • Considering options; applying knowledge & past emotions & consequences to making choices/decisions • Choosing & initiating goal-directed behaviors • Self-monitoring your responses • Correcting/adapting behavior in response to feedback or changes in context; inhibiting responses • Attention & persistence towards goal despite distraction The Case of Phineas Gage • Phineas had been a responsible, mild mannered, church-going family man before his accident. • After afterwards he not only lost executive functions but his behavior & emotions were disinhibited. • Prefrontal lobotomy cut the connections between this executive area and the rest of the brain/spinal cord • https://www.youtube.com/watch?v=_0aNILW6ILk MRI Reconstructions of Damage • Phineas as well as many modern day frontal patients are also likely to lose their social sensitivity to others (lack of tact, empathy, conscience, caring about others) • https://www.youtube.com/watch?v=jK1sj4JEJ2o&list=U U943UnajVxe9SpFJpwxpLsQ&index=1 3 9/9/2016 Neocortex Has 6 Layers With Regional Variations in Thickness A “Processing Unit” Within the Cortex is a Column of Cells The Brain is Like a Tootsie Pop • Note: as we cover the “subcortical” parts of the forebrain, I’m including a few brain areas our chapter skips Some forebrain areas are hidden beneath the cortex See 235-236 4 9/9/2016 The Basal Ganglia Motor System (see 361) 3 2 1 Hypothalamus • Plays a role in lots of different basic behaviors/motivations necessary for survival of individual & survival of the species • The “four F’s” • • • • Means “beneath the thalamus” The Hypothalamus Feeding Fighting (aggression & rage) Fleeing (fear behaviors) Mating : ) • But also primitive parenting behaviors, temperature regulation, hormone regulation, biorhythms & sleep, mood/emotions The Brainstem Areas Again The Thalamus works closely with regions of cortex • Best known for partially processing all incoming sensations except smell before passing input on to cortex • Also has some motor, memory and emotional functions. 5 9/9/2016 In Front of Hypothalamus is the “Basal Forebrain” • Activates cortex for consciousness and cognitive/memory function. Another component of the basal forebrain is the nucleus accumbens, a hub of our pleasure/reward pathway Ventricles Filled With CSF CSF is continually produced in all ventricles the heads towards the hindbrain to exit thru the 4th ventricle roof to circulate around the outer surface of cord and brain. It is finally reabsorbed into bloodstream at the center top of the brain 6 9/9/2016 Enlarged Ventricles Due to Hydrocephalus Enlarged Skull (bones not yet fused in infants) https://www.youtube.com/watch?v=WU HdkP278q0&list=PLJG4HdSoAx23j8Ev hgzuJ3sEtCiMsqNJg&index=6 Go to 20 A Shunt Tube Drains Away Excess CSF “Setting sun” eyes http://www.youtube.com/watch?v=7b2JsLRanmk The Reptilian Brain Middle layer added emotion & memory capabilities. Newest outer layer added judgment, reasoning, planning and self-control. • The brain stem, especially its core, is the most primitive portion of our brain, relatively unchanged from the time that dinosaurs roamed the earth. Most reptile behavior is reflexive response to stimuli. 7 9/9/2016 The Brain Stem Reticular Activating System Thalamus Hypothalamus • The cells of the “reticular formation” have many other functions as well. Midbrain Cerebellum Pons Medulla 2 and 3 on the “dorsal” surface of midbrain are the primitive visual (2) and auditory (3) processing centers, the superior (2) and inferior (3) colliculus. Substantia Nigra Dopamine Neurons Colliculi Primarily Handle Visual & Auditory Reflexes The Brainstem Thalamus Hypothalamus Midbrain Cerebellum Pons Medulla 8 9/9/2016 A Sadder Example Mike, the Headless Chicken • Anencephaly – forebrain fails to develop. Baby has a flattened, open skull. Baby shows basic reflexive behaviors (can nurse, grasp, etc.) but with only hindbrain & midbrain structures intact, survival is brief (hours-days). • An example of such reflexive behaviors in a normal infant • Survived 18 months • Could still stand, sit on a perch, walk clumsily, and attempt to crow and preen. • These basic behaviors are like reflexes – built into the brainstem. http://en.wikipedia.org/wiki/Mike_the_Headless_Chicken Afferent Spinal Reflexes Are Triggered Before Brain Experiences Sensation Efferent CNS is Protected by: • Bone • Meninges • Layer of cerebrospinal fluid (CSF) • Blood-brain Barrier The Meninges completely enclose the CNS and help protect it. Dura Arachnoid Pia 9 9/9/2016 “-itis” = inflammation Meningitis= inflammation of meninges Peripheral Nervous System (PNS) All the nerves outside of brain & spinal cord Book 4.6 Divisions of the Nervous System Structures Controlled by the ANS 10